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Label Element Value
Prospectus [Line Items] rr_ProspectusLineItems  
Document Type dei_DocumentType 497
Document Period End Date dei_DocumentPeriodEndDate Sep. 30, 2024
Entity Registrant Name dei_EntityRegistrantName THORNBURG INVESTMENT TRUST
Entity Central Index Key dei_EntityCentralIndexKey 0000816153
Entity Inv Company Type dei_EntityInvCompanyType N-1A
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Jan. 31, 2025
Document Effective Date dei_DocumentEffectiveDate Feb. 01, 2025
Prospectus Date rr_ProspectusDate Feb. 01, 2025
Retail | Thornburg Global Opportunities Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Global Opportunities Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks long-term capital appreciation by investing in equity and debt securities of all types from issuers around the world.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 14.91% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 14.91%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment goal by investing primarily in a broad range of equity securities, including common stocks, preferred stocks and publicly traded real estate investment trusts. The Fund may invest in any stock or other equity security which its investment advisor, Thornburg Investment Management, Inc. (“Thornburg”), believes may assist the Fund in pursuing its goal, including smaller companies with market capitalizations less than $500 million.

The Fund portfolio includes investments in both domestic securities and securities of issuers domiciled in or economically tied to countries outside the United States, including developing countries. Relative proportions of each will vary from time to time, depending upon Thornburg’s view of specific investment opportunities and macro-economic factors. Under normal market conditions, the Fund invests a significant portion of its assets in issuers domiciled in or economically tied to countries outside the United States.

The Fund’s investments are determined by individual issuer and industry analysis. Investment decisions are based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for securities, and analysis of specific issuers.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Global Opportunities Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C and Class I share performance to the MSCI All Country World Net Total Return USD Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The index is not actively managed and is not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Global Opportunities Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown on the bar chart, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 21.72%

6/30/2020

Lowest Quarterly Results

-24.82%

3/31/2020

The sales charge for Class A shares is not reflected in the returns shown on the bar chart, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Retail | Thornburg Global Opportunities Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retail | Thornburg Global Opportunities Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Global Opportunities Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Retail | Thornburg Global Opportunities Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Global Opportunities Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retail | Thornburg Global Opportunities Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retail | Thornburg Global Opportunities Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retail | Thornburg Global Opportunities Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection.
Retail | Thornburg Global Opportunities Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices. This risk may be more pronounced for the Fund’s investments in developing countries.
Retail | Thornburg Global Opportunities Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Global Opportunities Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retail | Thornburg Global Opportunities Fund | Real Estate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Real Estate Risk – The Fund’s investments in publicly traded real estate investment trusts (“REITs”) are subject to risks affecting real estate investments generally (including market conditions, competition, property obsolescence, changes in interest rates and casualty to real estate), as well as risks specifically affecting REITs (the quality and skill of REIT management and the internal expenses of the REIT).
Retail | Thornburg Global Opportunities Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Global Opportunities Fund | Risks Affecting Specific Countries or Regions [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Countries or Regions – If a significant portion of the Fund’s assets is invested in issuers that are economically exposed to one country or region, the Fund’s share value may be more susceptible to the conditions and developments in that country or region, and potentially more volatile than the share value of a more geographically diversified fund. A specific country or region could also be adversely affected by conditions or developments arising in other countries. For example, the U.S. government could take actions to prohibit or restrict individuals or companies within the U.S. from purchasing or holding the shares of issuers in another country, which may limit the Fund’s ability to invest in that country or cause the Fund to have to sell investments in that country at less than desired prices. The nature and degree of the risks affecting a given country or region, and the extent of the Fund’s exposure to any such country or region, is expected to vary over time.
Retail | Thornburg Global Opportunities Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a security may decline in response to developments affecting the specific issuer of the security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retail | Thornburg Global Opportunities Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments.
Retail | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THOAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [1]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.84%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.25%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.34%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.34%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 580
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 855
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,151
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,990
Annual Return 2015 rr_AnnualReturn2015 1.12%
Annual Return 2016 rr_AnnualReturn2016 3.64%
Annual Return 2017 rr_AnnualReturn2017 21.64%
Annual Return 2018 rr_AnnualReturn2018 (20.92%)
Annual Return 2019 rr_AnnualReturn2019 28.35%
Annual Return 2020 rr_AnnualReturn2020 22.32%
Annual Return 2021 rr_AnnualReturn2021 14.42%
Annual Return 2022 rr_AnnualReturn2022 (10.35%)
Annual Return 2023 rr_AnnualReturn2023 15.91%
Annual Return 2024 rr_AnnualReturn2024 12.67%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 21.72%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (24.82%)
1 Year rr_AverageAnnualReturnYear01 7.60%
5 Years rr_AverageAnnualReturnYear05 9.37%
10 Years rr_AverageAnnualReturnYear10 7.31%
Retail | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.76%
5 Years rr_AverageAnnualReturnYear05 7.26%
10 Years rr_AverageAnnualReturnYear10 6.08%
Retail | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.93%
5 Years rr_AverageAnnualReturnYear05 6.82%
10 Years rr_AverageAnnualReturnYear10 5.51%
Retail | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class A | MSCI All Country World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 17.49%
5 Years rr_AverageAnnualReturnYear05 10.06%
10 Years rr_AverageAnnualReturnYear10 9.23%
Retail | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THOCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00% [2]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.84%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.33%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.17%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.17%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 320
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 679
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,164
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,503
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 220
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 679
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,164
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,503
1 Year rr_AverageAnnualReturnYear01 10.74%
5 Years rr_AverageAnnualReturnYear05 9.52%
10 Years rr_AverageAnnualReturnYear10 6.98%
Retail | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class C | MSCI All Country World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 17.49%
5 Years rr_AverageAnnualReturnYear05 10.06%
10 Years rr_AverageAnnualReturnYear10 9.23%
Retail | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THOIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.84%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.24%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.08%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.09%) [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 101
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 335
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 587
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,309
1 Year rr_AverageAnnualReturnYear01 13.08%
5 Years rr_AverageAnnualReturnYear05 10.72%
10 Years rr_AverageAnnualReturnYear10 8.15%
Retail | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class I | MSCI All Country World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 17.49%
5 Years rr_AverageAnnualReturnYear05 10.06%
10 Years rr_AverageAnnualReturnYear10 9.23%
Retail | Thornburg International Equity Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading International Equity Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The Fund seeks long-term capital appreciation by investing in equity and debt securities of all types.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock The secondary, non-fundamental goal of the Fund is to seek some current income.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 45.47% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 45.47%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests primarily in common stocks of non-U.S. companies and in depositary receipts associated with such stocks. The Fund may invest in developing countries. Under normal conditions, the Fund will invest at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in common stocks or depositary receipts.

The Fund’s investment advisor, Thornburg Investment Management, Inc. (“Thornburg”), intends to invest on an opportunistic basis where the Fund’s portfolio managers believe intrinsic value is not recognized by the marketplace. The Fund seeks to identify value in a broad or different context by investing in a diversified portfolio of stocks the Fund categorizes as basic values, consistent earners, and emerging franchises, when the portfolio managers believe these issues are value priced. The relative proportions of securities invested in each of those categories will vary over time. The Fund seeks to invest in promising companies, and may invest in stocks that reflect unfavorable market perceptions of the company or industry fundamentals. The Fund may invest in companies of any size, but invests primarily in the large and middle capitalization range of publicly traded companies.

The Fund’s investments are determined by individual issuer and industry analysis. Investment decisions are based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for securities, and analysis of specific issuers.

The Fund categorizes its equity investments in the following three categories:

Basic Value: Companies generally operating in mature or cyclical industries and which generally exhibit more economic sensitivity and/or higher volatility in earnings and cash flow.

Consistent Earner: Companies which generally exhibit predictable growth, profitability, cash flow and/or dividends.

Emerging Franchise: Companies with the potential to grow at an above average rate because of a product or service that is establishing a new market and/or taking share from existing participants.

Inclusion of any investment in any of the three described categories represents the opinion of Thornburg concerning the characteristics and prospects of the investment. There is no assurance that any company selected for investment will, once categorized in one of the three described investment categories, continue to have the positive characteristics or fulfill the

expectations that Thornburg had for the company when it was selected for investment, and any such company may not grow or may decline in earnings and size.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in common stocks or depositary receipts may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the International Equity Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C and Class I share performance to the MSCI All Country World ex USA Net Total Return USD Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The MSCI EAFE (Europe, Australasia, Far East) Net Total Return USD Index was removed as the Funds’ secondary index effective September 30, 2024. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the International Equity Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 18.62%

12/31/2022

Lowest Quarterly Results

-19.54%

3/31/2020

The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Retail | Thornburg International Equity Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retail | Thornburg International Equity Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg International Equity Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Retail | Thornburg International Equity Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg International Equity Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retail | Thornburg International Equity Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retail | Thornburg International Equity Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retail | Thornburg International Equity Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection.
Retail | Thornburg International Equity Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices.
Retail | Thornburg International Equity Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg International Equity Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retail | Thornburg International Equity Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg International Equity Fund | Risks Affecting Specific Countries or Regions [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Countries or Regions – If a significant portion of the Fund’s assets is invested in issuers that are economically exposed to one country or region, the Fund’s share value may be more susceptible to the conditions and developments in that country or region, and potentially more volatile than the share value of a more geographically diversified fund. A specific country or region could also be adversely affected by conditions or developments arising in other countries. For example, the U.S. government could take actions to prohibit or restrict individuals or companies within the U.S. from purchasing or holding the shares of issuers in another country, which may limit the Fund’s ability to invest in that country or cause the Fund to have to sell investments in that country at less than desired prices. The nature and degree of the risks affecting a given country or region, and the extent of the Fund’s exposure to any such country or region, is expected to vary over time.
Retail | Thornburg International Equity Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a security may decline in response to developments affecting the specific issuer of the security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retail | Thornburg International Equity Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments.
Retail | Thornburg International Equity Fund | Depositary Receipts Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Depositary Receipts Risk – An investment in American Depositary Receipts (“ADRs”), European Depositary Receipts (“EDRs”) or Global Depositary Receipts (“GDRs”) is an alternative to the purchase of the underlying securities in their national markets and/or currencies. However, ADRs, EDRs, and GDRs remain subject to many of the risks associated with investing directly in foreign securities, including the political and economic risks associated with the underlying issuer’s country. Certain countries may limit the ability to convert a depositary receipt into the underlying foreign security and vice versa, which may cause the securities of the foreign company to trade at a discount or premium to the market price of the related depositary receipts. Moreover, EDRs and GDRs can involve currency risk since, unlike ADRs, they may not be U.S. dollar denominated.
Retail | Thornburg International Equity Fund | Risks Affecting Investments in China [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Investments in China – A significant portion of the Fund’s assets may be invested in companies exposed to China. Risks affecting investments in China include a potential downturn in the Chinese economy, reduced liquidity or increased price volatility in the Chinese securities markets as a result of trading suspensions affecting Chinese issuers or other factors, the potential that the Chinese government may expand restrictions on foreign investments or the repatriation of capital, and the implementation of new tariffs or other trade barriers by China or its trading partners. A lack of transparency respecting Chinese companies may also reduce the Fund’s ability to conduct diligence respecting those companies’ accounting and governance standards, which may in turn reduce the Fund’s ability to detect fraudulent practices that may adversely affect the companies’ stock prices.
Retail | Thornburg International Equity Fund | Thornburg International Equity Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TGVAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [4]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.77%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.26%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.28%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.28%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 575
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 838
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,121
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,926
Annual Return 2015 rr_AnnualReturn2015 6.26%
Annual Return 2016 rr_AnnualReturn2016 (2.74%)
Annual Return 2017 rr_AnnualReturn2017 24.98%
Annual Return 2018 rr_AnnualReturn2018 (20.05%)
Annual Return 2019 rr_AnnualReturn2019 28.66%
Annual Return 2020 rr_AnnualReturn2020 22.36%
Annual Return 2021 rr_AnnualReturn2021 7.26%
Annual Return 2022 rr_AnnualReturn2022 (17.01%)
Annual Return 2023 rr_AnnualReturn2023 15.77%
Annual Return 2024 rr_AnnualReturn2024 11.24%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2022
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 18.62%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (19.54%)
1 Year rr_AverageAnnualReturnYear01 6.24%
5 Years rr_AverageAnnualReturnYear05 6.02%
10 Years rr_AverageAnnualReturnYear10 5.94%
Retail | Thornburg International Equity Fund | Thornburg International Equity Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.25%
5 Years rr_AverageAnnualReturnYear05 4.26%
10 Years rr_AverageAnnualReturnYear10 3.89%
Retail | Thornburg International Equity Fund | Thornburg International Equity Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.53%
5 Years rr_AverageAnnualReturnYear05 4.19%
10 Years rr_AverageAnnualReturnYear10 4.06%
Retail | Thornburg International Equity Fund | Thornburg International Equity Fund - Class A | MSCI All Country World ex USA Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retail | Thornburg International Equity Fund | Thornburg International Equity Fund - Class A | MSCI EAFE (Europe, Australasia, Far East) Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.82%
5 Years rr_AverageAnnualReturnYear05 4.73%
10 Years rr_AverageAnnualReturnYear10 5.20%
Retail | Thornburg International Equity Fund | Thornburg International Equity Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THGCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00% [5]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.77%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.40%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.17%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.17%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 320
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 679
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,164
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,503
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 220
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 679
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,164
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,503
1 Year rr_AverageAnnualReturnYear01 9.28%
5 Years rr_AverageAnnualReturnYear05 6.19%
10 Years rr_AverageAnnualReturnYear10 5.62%
Retail | Thornburg International Equity Fund | Thornburg International Equity Fund - Class C | MSCI All Country World ex USA Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retail | Thornburg International Equity Fund | Thornburg International Equity Fund - Class C | MSCI EAFE (Europe, Australasia, Far East) Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.82%
5 Years rr_AverageAnnualReturnYear05 4.73%
10 Years rr_AverageAnnualReturnYear10 5.20%
Retail | Thornburg International Equity Fund | Thornburg International Equity Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TGVIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.77%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.21%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.98%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.08%) [6]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.90%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 92
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 304
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 534
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,194
1 Year rr_AverageAnnualReturnYear01 11.60%
5 Years rr_AverageAnnualReturnYear05 7.33%
10 Years rr_AverageAnnualReturnYear10 6.77%
Retail | Thornburg International Equity Fund | Thornburg International Equity Fund - Class I | MSCI All Country World ex USA Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retail | Thornburg International Equity Fund | Thornburg International Equity Fund - Class I | MSCI EAFE (Europe, Australasia, Far East) Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.82%
5 Years rr_AverageAnnualReturnYear05 4.73%
10 Years rr_AverageAnnualReturnYear10 5.20%
Retail | Thornburg Better World International Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Better World International Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks long-term capital appreciation.

Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 60.57% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 60.57%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year) your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment goal by investing primarily in a broad range of foreign equity securities or depositary receipts of foreign equity securities. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in issuers that the Fund’s investment advisor, Thornburg Investment Management, Inc. (‘Thornburg’), has determined exhibit one or more significant and positive environmental, social and governance (“ESG”) characteristics. For this purpose, Thornburg considers an ESG factor to be significant if it is likely to materially affect the issuer’s risk and return profile and, accordingly, the issuer’s long-term investment performance.

The Fund may invest in any stock or other equity security which Thornburg believes may assist the Fund in pursuing its goal, including common stocks, preferred stocks and publicly traded real estate investment trusts. The Fund may invest in companies of any size, but invests primarily in the large and middle capitalization range of publicly traded companies. The Fund may also invest in developing country companies.

Thornburg intends to invest on an opportunistic basis where the Fund’s portfolio managers believe intrinsic value is not recognized by the marketplace. The Fund seeks to identify value in a broad or different context by investing in a diversified portfolio of stocks the Fund categorizes as basic values, consistent earners, and emerging franchises, when the portfolio managers believe these issues are value priced. The relative proportions of securities invested in each of those categories will vary over time.

The Fund categorizes its equity investments in the following three categories:

Basic Value: Companies generally operating in mature or cyclical industries and which generally exhibit more economic sensitivity and/or higher volatility in earnings and cash flow.

Consistent Earner: Companies which generally exhibit predictable growth, profitability, cash flow and/or dividends.

Emerging Franchise: Companies with the potential to grow at an above average rate because of a product or service that is establishing a new market and/or taking share from existing participants.

Inclusion of any investment in any of the three described categories represents the opinion of Thornburg concerning the characteristics and prospects of the investment. There is no assurance that any company selected for investment will, once categorized in one of the three described investment categories, continue to have the positive characteristics or fulfill the expectations that Thornburg had for the company when it was selected for investment, and any such company may not grow or may decline in earnings and size.

The Fund’s investments are determined by individual issuer and industry analysis. Investment decisions also include consideration of domestic and international economic developments, outlooks for securities markets, interest rates and inflation, and the supply and demand for securities. The Fund seeks to invest in companies which in Thornburg’s view are trading at discount to their intrinsic value and also demonstrate one or more significant positive ESG characteristics. Through Thornburg’s fundamental research process, Thornburg evaluates each potential investment based on a variety of factors, including traditional investment criteria such as the company’s ability to effectively allocate capital, willingness to pay dividends and repurchase shares, ability to sustain a competitive advantage, and ability to grow its core business. As part of its research process for the Fund’s investments, Thornburg also assesses each issuer’s ESG characteristics, focusing on those ESG characteristics which Thornburg believes are significant insofar as they are expected to materially affect the issuer’s investment performance. The specific ESG characteristics which Thornburg determines to be significant will vary over time and among different financial sectors and industries, but will generally include the following:

•Environmental characteristics, such as an issuer’s emissions and energy management practices;

•Social capital characteristics, such as an issuer’s data security and privacy practices;

•Human capital characteristics, such as an issuer’s labor practices;

•Business model and innovation characteristics, such as an issuer’s supply chain management practices; and

•Leadership and governance characteristics, such as an issuer’s practices toward managing legal and regulatory risks.

While Thornburg makes its own judgments about the ESG characteristics of each investment, Thornburg’s approach may be informed by third party data and other research tools, including consideration of the list of material ESG factors established by the Sustainability Accounting Standards Board.

Market observers differ in their perspectives and understanding of the importance of ESG factors to investment decisions. In its evaluation of potential investments, Thornburg may identify as significant certain ESG characteristics that are different from the characteristics that other investors may consider significant. Thornburg consequently may not consider the same ESG characteristics that other investors might consider in evaluating a potential investment. Similarly, Thornburg may assess the significance of ESG characteristics differently than some other investors, assigning either greater or lesser emphasis to a characteristic than another investor might assign.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in issuers that exhibit one or more significant and positive ESG characteristics may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Better World International Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C and Class I share performance to the MSCI All Country World ex USA Net Total Return USD Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The index is not actively managed and is not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Better World International Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown on the bar chart, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 22.85%

6/30/2020

Lowest Quarterly Results

-19.58%

3/31/2020

The sales charge for Class A shares is not reflected in the returns shown on the bar chart, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.

The performance information shown above may include gains attributable to the Fund’s investments in shares of companies through initial public offerings (“IPOs”). There can be no assurance that the Fund will have continued access to profitable IPOs and, as the Fund’s assets grow, the impact of the Fund’s investment in IPOs on the performance of the Fund may decline.
Retail | Thornburg Better World International Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retail | Thornburg Better World International Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Better World International Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Retail | Thornburg Better World International Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Better World International Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retail | Thornburg Better World International Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retail | Thornburg Better World International Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retail | Thornburg Better World International Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection.
Retail | Thornburg Better World International Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices. This risk may be more pronounced for the Fund’s investments in developing countries.
Retail | Thornburg Better World International Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Better World International Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retail | Thornburg Better World International Fund | Real Estate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Real Estate Risk – The Fund’s investments in publicly traded real estate investment trusts (“REITs”) are subject to risks affecting real estate investments generally (including market conditions, competition, property obsolescence, changes in interest rates and casualty to real estate), as well as risks specifically affecting REITs (the quality and skill of REIT management and the internal expenses of the REIT).

Retail | Thornburg Better World International Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Better World International Fund | Risks Affecting Specific Countries or Regions [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Countries or Regions – If a significant portion of the Fund’s assets is invested in issuers that are economically exposed to one country or region, the Fund’s share value may be more susceptible to the conditions and developments in that country or region, and potentially more volatile than the share value of a more geographically diversified fund. A specific country or region could also be adversely affected by conditions or developments arising in other countries. For example, the U.S. government could take actions to prohibit or restrict individuals or companies within the U.S. from purchasing or holding the shares of issuers in another country, which may limit the Fund’s ability to invest in that country or cause the Fund to have to sell investments in that country at less than desired prices. The nature and degree of the risks affecting a given country or region, and the extent of the Fund’s exposure to any such country or region, is expected to vary over time.
Retail | Thornburg Better World International Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a security may decline in response to developments affecting the specific issuer of the security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retail | Thornburg Better World International Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments.
Retail | Thornburg Better World International Fund | Depositary Receipts Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Depositary Receipts Risk – An investment in American Depositary Receipts (“ADRs”), European Depositary Receipts (“EDRs”) or Global Depositary Receipts (“GDRs”) is an alternative to the purchase of the underlying securities in their national markets and/or currencies. However, ADRs, EDRs, and GDRs remain subject to many of the risks associated with investing directly in foreign securities, including the political and economic risks associated with the underlying issuer’s country. Certain

countries may limit the ability to convert a depositary receipt into the underlying foreign security and vice versa, which may cause the securities of the foreign company to trade at a discount or premium to the market price of the related depositary receipts. Moreover, EDRs and GDRs can involve currency risk since, unlike ADRs, they may not be U.S. dollar denominated.
Retail | Thornburg Better World International Fund | Risks Affecting Investments in China [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Investments in China – A significant portion of the Fund’s assets may be invested in companies exposed to China. Risks affecting investments in China include a potential downturn in the Chinese economy, reduced liquidity or increased price volatility in the Chinese securities markets as a result of trading suspensions affecting Chinese issuers or other factors, the potential that the Chinese government may expand restrictions on foreign investments or the repatriation of capital, and the implementation of new tariffs or other trade barriers by China or its trading partners. A lack of transparency respecting Chinese companies may also reduce the Fund’s ability to conduct diligence respecting those companies’ accounting and governance standards, which may in turn reduce the Fund’s ability to detect fraudulent practices that may adversely affect the companies’ stock prices.
Retail | Thornburg Better World International Fund | ESG Investing Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

ESG Investing Risk – Thornburg’s assessments of company ESG characteristics may result in decisions not to purchase, or to sell, investments which are otherwise consistent with the Fund’s investment goal and subsequently produce attractive investment performance, and Thornburg’s assessments of these characteristics may at times reduce the Fund’s exposure to market sectors or types of investments that produce positive investment performance. The application of ESG principles and the perceptions of the commitment of a given company to ESG principles vary among investors, analysts and other market observers. Consequently, Thornburg’s assessments respecting the ESG characteristics associated with any company may differ from the perceptions of other persons, including other mutual funds. Additionally, it may be difficult in certain instances for Thornburg to evaluate correctly a company’s commitment to positive ESG practices, and a failure to do so may result in investment in companies with practices that are not consistent with the Fund’s aspirations.
Retail | Thornburg Better World International Fund | Thornburg Better World International Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TBWAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [7]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.97%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.36%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.58%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.58%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 603
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 926
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,272
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,244
Annual Return 2016 rr_AnnualReturn2016 6.76%
Annual Return 2017 rr_AnnualReturn2017 21.88%
Annual Return 2018 rr_AnnualReturn2018 (14.28%)
Annual Return 2019 rr_AnnualReturn2019 23.72%
Annual Return 2020 rr_AnnualReturn2020 25.85%
Annual Return 2021 rr_AnnualReturn2021 (18.48%)
Annual Return 2022 rr_AnnualReturn2022 20.39%
Annual Return 2023 rr_AnnualReturn2023 12.13%
Annual Return 2024 rr_AnnualReturn2024 6.53%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 22.85%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (19.58%)
1 Year rr_AverageAnnualReturnYear01 1.72%
5 Years rr_AverageAnnualReturnYear05 7.10%
Since Inception rr_AverageAnnualReturnSinceInception 7.92%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 01, 2015
Retail | Thornburg Better World International Fund | Thornburg Better World International Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.39%
5 Years rr_AverageAnnualReturnYear05 5.94%
Since Inception rr_AverageAnnualReturnSinceInception 6.48%
Retail | Thornburg Better World International Fund | Thornburg Better World International Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.02%
5 Years rr_AverageAnnualReturnYear05 5.21%
Since Inception rr_AverageAnnualReturnSinceInception 5.73%
Retail | Thornburg Better World International Fund | Thornburg Better World International Fund - Class A | MSCI All Country World ex USA Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
Since Inception rr_AverageAnnualReturnSinceInception 6.23%
Retail | Thornburg Better World International Fund | Thornburg Better World International Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TBWCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00% [8]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.97%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.58%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.55%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.36%) [9]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.19%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 322
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 759
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,323
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,858
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 222
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 759
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,323
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,858
1 Year rr_AverageAnnualReturnYear01 4.73%
5 Years rr_AverageAnnualReturnYear05 7.32%
Since Inception rr_AverageAnnualReturnSinceInception 7.76%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 01, 2015
Retail | Thornburg Better World International Fund | Thornburg Better World International Fund - Class C | MSCI All Country World ex USA Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
Since Inception rr_AverageAnnualReturnSinceInception 6.23%
Retail | Thornburg Better World International Fund | Thornburg Better World International Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TBWIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.97%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.27%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.24%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.34%) [9]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.90%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 92
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 360
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 648
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,470
1 Year rr_AverageAnnualReturnYear01 7.11%
5 Years rr_AverageAnnualReturnYear05 8.69%
Since Inception rr_AverageAnnualReturnSinceInception 9.17%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 01, 2015
Retail | Thornburg Better World International Fund | Thornburg Better World International Fund - Class I | MSCI All Country World ex USA Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
Since Inception rr_AverageAnnualReturnSinceInception 6.23%
Retail | Thornburg International Growth Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading International Growth Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks long-term growth of capital by investing in equity securities selected for their growth potential.

Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 44.57% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 44.57%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in growth companies and invests at least 75% of its net assets, plus the amount of any borrowings for investment purposes, in foreign securities or depositary receipts of foreign securities. For this purpose, the Fund currently considers a company to be a growth company if it meets any of the following criteria:

•It is a constituent of the MSCI All Country World Growth Index; or

•It has, over the last five years, grown its revenues or earnings per share at an average annual rate which exceeds the median growth rate of revenues or earnings per share, as applicable, for companies in the MSCI All Country World ex-U.S. Index; or

•It is projected by consensus estimates as compiled by FactSet Research Systems, over the next two years, to grow its revenues or earnings per share at an average annual rate which exceeds the median growth rate of revenues or earnings per share, as applicable, for companies in the MSCI All Country World ex-U.S. Index.

While the Fund expects to invest primarily in foreign equity securities (primarily common stocks), the Fund may own a variety of securities, including domestic equity securities. The Fund may invest in developing countries.

The Fund’s investment advisor, Thornburg Investment Management, Inc. (“Thornburg”) intends to invest in companies that it believes will have growing revenues and earnings. The Fund can invest in companies of any size, from larger, well-established companies to smaller, emerging growth companies.

The Fund’s investments are determined by individual issuer and industry analysis. Investment decisions are based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for securities, and analysis of specific issuers.

The Fund typically makes equity investments in the following three types of companies:

Growth Industry Leader: Companies in this category often have leadership positions in growing markets. In some cases these companies may have dominant market share. These companies tend to be larger and more established.

Consistent Grower: Companies in this category generally exhibit steady earnings or revenue growth, or both. These companies may have subscription or other recurring revenue profiles. Given their business models, these companies may outperform in weak markets.

Emerging Growth: Companies often addressing a new market or carving out a niche in an existing market. Companies in this category may experience rapid growth, and tend to be smaller, earlier stage companies. These companies may exhibit high volatility.

Inclusion of any investment in any of the three described categories represents the opinion of Thornburg concerning the characteristics and prospects of the investment. There is no assurance that any company selected for investment will, once categorized in one of the three described investment categories, continue to have the positive characteristics or fulfill the expectations that Thornburg had for the company when it was selected for investment, and any such company may not grow or may decline in earnings and size.

In conjunction with individual issuer analysis, Thornburg may identify and invest at times with a greater emphasis in industries or economic sectors it expects to experience growth. The Fund does not have a strategy to invest in particular industry or economic sectors, and its exposures to particular industries or economic sectors are expected to vary over time. Investment decisions are also based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, and the supply and demand for securities.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in growth companies may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders. Additionally, the Fund may change its definition of what constitutes a “growth company” at any time without advance notice to shareholders.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the International Growth Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares vary in each full year shown. The average annual total return figures compare Class A, Class C and Class I share performance to the MSCI All Country World ex USA Net Total Return, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the MSCI All Country World ex USA Growth Net Total Return USD Index, an additional index that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the International Growth Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown on the bar chart, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 25.93%

6/30/2020

Lowest Quarterly Results

-17.74%

12/31/2018

The sales charge for Class A shares is not reflected in the returns shown on the bar chart, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Retail | Thornburg International Growth Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retail | Thornburg International Growth Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg International Growth Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Retail | Thornburg International Growth Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg International Growth Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries

ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retail | Thornburg International Growth Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retail | Thornburg International Growth Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retail | Thornburg International Growth Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection.
Retail | Thornburg International Growth Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices. This risk may be more pronounced for the Fund’s investments in developing countries.
Retail | Thornburg International Growth Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg International Growth Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retail | Thornburg International Growth Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg International Growth Fund | Risks Affecting Specific Countries or Regions [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Countries or Regions – If a significant portion of the Fund’s assets is invested in issuers that are economically exposed to one country or region, the Fund’s share value may be more susceptible to the conditions and developments in that country or region, and potentially more volatile than the share value of a more geographically diversified fund. A specific country or region could also be adversely affected by conditions or developments arising in other countries. For example, the U.S. government could take actions to prohibit or restrict individuals or companies within the U.S. from purchasing or holding the shares of issuers in another country, which may limit the Fund’s ability to invest in that country or cause the Fund to have to sell investments in that country at less than desired prices. The nature and degree of the risks affecting a given country or region, and the extent of the Fund’s exposure to any such country or region, is expected to vary over time.
Retail | Thornburg International Growth Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a security may decline in response to developments affecting the specific issuer of the security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retail | Thornburg International Growth Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies, including smaller, earlier stage companies, may involve additional risks. These risks may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments.
Retail | Thornburg International Growth Fund | Depositary Receipts Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Depositary Receipts Risk – An investment in American Depositary Receipts (“ADRs”), European Depositary Receipts (“EDRs”) or Global Depositary Receipts (“GDRs”) is an alternative to the purchase of the underlying securities in their national markets and/or currencies. However, ADRs, EDRs, and GDRs remain subject to many of the risks associated with investing directly in foreign securities, including the political and economic risks associated with the underlying issuer’s country. Certain countries may limit the ability to convert a depositary receipt into the underlying foreign security and vice versa, which may cause the securities of the foreign company to trade at a discount or premium to the market price of the related depositary receipts. Moreover, EDRs and GDRs can involve currency risk since, unlike ADRs, they may not be U.S. dollar denominated.
Retail | Thornburg International Growth Fund | Growth Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Growth Company Risk – Growth company stocks may trade at higher multiples of current earnings than other equity securities and, therefore, may be more sensitive to changes in current or expected earnings than other equity securities and may be more volatile. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can cushion stock prices in market downturns. These risks may be more pronounced in companies that are in the earlier stages of their growth cycle.
Retail | Thornburg International Growth Fund | Information Technology Securities Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Information Technology Securities Risk – Information technology companies may at times be more vulnerable to product obsolescence caused by rapid technology changes, the failure to obtain or maintain intellectual property rights, the inability to develop new products, competition from new and existing market entrants, and changes in consumer preferences. Information technology stocks may also be more volatile than the overall market.
Retail | Thornburg International Growth Fund | Thornburg International Growth Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TIGAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [10]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.85%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.28%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.38%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.38%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 584
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 867
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,171
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,033
Annual Return 2015 rr_AnnualReturn2015 6.33%
Annual Return 2016 rr_AnnualReturn2016 (5.05%)
Annual Return 2017 rr_AnnualReturn2017 34.33%
Annual Return 2018 rr_AnnualReturn2018 (17.01%)
Annual Return 2019 rr_AnnualReturn2019 25.87%
Annual Return 2020 rr_AnnualReturn2020 33.94%
Annual Return 2021 rr_AnnualReturn2021 (4.46%)
Annual Return 2022 rr_AnnualReturn2022 (26.33%)
Annual Return 2023 rr_AnnualReturn2023 17.96%
Annual Return 2024 rr_AnnualReturn2024 2.04%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 25.93%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2018
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (17.74%)
1 Year rr_AverageAnnualReturnYear01 (2.56%)
5 Years rr_AverageAnnualReturnYear05 1.62%
10 Years rr_AverageAnnualReturnYear10 4.38%
Retail | Thornburg International Growth Fund | Thornburg International Growth Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (4.33%)
5 Years rr_AverageAnnualReturnYear05 0.80%
10 Years rr_AverageAnnualReturnYear10 3.76%
Retail | Thornburg International Growth Fund | Thornburg International Growth Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (0.23%)
5 Years rr_AverageAnnualReturnYear05 1.24%
10 Years rr_AverageAnnualReturnYear10 3.43%
Retail | Thornburg International Growth Fund | Thornburg International Growth Fund - Class A | MSCI All Country World ex USA Net Total Return (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retail | Thornburg International Growth Fund | Thornburg International Growth Fund - Class A | MSCI All Country World ex USA Growth Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.07%
5 Years rr_AverageAnnualReturnYear05 3.44%
10 Years rr_AverageAnnualReturnYear10 5.35%
Retail | Thornburg International Growth Fund | Thornburg International Growth Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TIGCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00% [11]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.85%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.52%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.37%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.37%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 340
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 739
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,265
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,706
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 240
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 739
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,265
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,706
1 Year rr_AverageAnnualReturnYear01 0.07%
5 Years rr_AverageAnnualReturnYear05 1.65%
10 Years rr_AverageAnnualReturnYear10 4.00%
Retail | Thornburg International Growth Fund | Thornburg International Growth Fund - Class C | MSCI All Country World ex USA Net Total Return (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retail | Thornburg International Growth Fund | Thornburg International Growth Fund - Class C | MSCI All Country World ex USA Growth Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.07%
5 Years rr_AverageAnnualReturnYear05 3.44%
10 Years rr_AverageAnnualReturnYear10 5.35%
Retail | Thornburg International Growth Fund | Thornburg International Growth Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TINGX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.85%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.19%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.04%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [12]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 101
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 326
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 569
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,266
1 Year rr_AverageAnnualReturnYear01 2.43%
5 Years rr_AverageAnnualReturnYear05 2.91%
10 Years rr_AverageAnnualReturnYear10 5.25%
Retail | Thornburg International Growth Fund | Thornburg International Growth Fund - Class I | MSCI All Country World ex USA Net Total Return (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retail | Thornburg International Growth Fund | Thornburg International Growth Fund - Class I | MSCI All Country World ex USA Growth Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.07%
5 Years rr_AverageAnnualReturnYear05 3.44%
10 Years rr_AverageAnnualReturnYear10 5.35%
Retail | Thornburg Developing World Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Developing World Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund’s primary investment goal is long-term capital appreciation.

Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charge applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 90.88% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 90.88%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charge applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund pursues its objective by investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of issuers which Thornburg views as having substantial economic ties to one or more developing countries. Developing countries are considered by Thornburg generally to be those countries which are not included in the MSCI World Index. The material factors that Thornburg considers when determining whether an issuer has substantial economic ties to a developing country include whether the issuer:

•is included in the MSCI Emerging Markets Index;

•is organized or headquartered in an developing country, or maintains most of its assets in one or more such countries;

•has equity securities that are traded principally on a stock exchange of a developing country; or

•derives, or is expected to derive, a majority of its profits, revenues, sales, or income from one or more developing countries.

The Fund may invest in issuers of any size of capitalization, including small companies, and expects that under normal conditions its assets will be invested in issuers domiciled in or tied economically to a variety of different developing countries.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in developing country issuers may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders.

Among the specific factors considered in identifying securities for inclusion in the Fund are domestic and international economic developments, outlooks for securities markets, the supply and demand for equity securities, and analysis of specific issuers. The Fund typically makes its equity investments in the following three types of issuers:

Basic Value: Companies generally operating in mature or cyclical industries and which generally exhibit more economic sensitivity and/or higher volatility in earnings and cash flow.

Consistent Earner: Companies which generally exhibit predictable growth, profitability, cash flow and/or dividends.

Emerging Franchise: Companies with the potential to grow at an above average rate because of a product or service that is establishing a new market and/or taking share from existing participants.

Inclusion of any investment in any of the three described categories represents the opinion of Thornburg concerning the characteristics and prospects of the investment. There is no assurance that any company selected for investment will, once categorized in one of the three described investment categories, continue to have the positive characteristics or fulfill the expectations that Thornburg had for the company when it was selected for investment, and any such company may not grow or may decline in earnings and size.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Developing World Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C and Class I share performance to the MSCI Emerging Markets Net Total Return USD Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The index is not actively managed and is not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Developing World Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown on the bar chart, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 21.64%

12/31/2020

Lowest Quarterly Results

-24.81%

3/31/2020

The sales charge for Class A shares is not reflected in the returns shown on the bar chart, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Retail | Thornburg Developing World Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retail | Thornburg Developing World Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Developing World Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Retail | Thornburg Developing World Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Developing World Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retail | Thornburg Developing World Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retail | Thornburg Developing World Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retail | Thornburg Developing World Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protections.
Retail | Thornburg Developing World Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices. This risk may be more pronounced for the Fund’s investments in developing countries.
Retail | Thornburg Developing World Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Developing World Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility. These risks may be more pronounced for the Fund’s investments in developing countries.
Retail | Thornburg Developing World Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Developing World Fund | Risks Affecting Specific Countries or Regions [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Countries or Regions – If a significant portion of the Fund’s assets is invested in issuers that are economically exposed to one country or region, the Fund’s share value may be more susceptible to the conditions and developments in that country or region, and potentially more volatile than the share value of a more geographically diversified fund. A specific country or region could also be adversely affected by conditions or developments arising in other countries. For example, the U.S. government could take actions to prohibit or restrict individuals or companies within the U.S. from purchasing or holding the shares of issuers in another country, which may limit the Fund’s ability to invest in that country or cause the Fund to have to sell investments in that country at less than desired prices. The nature and degree of the risks affecting a given country or region, and the extent of the Fund’s exposure to any such country or region, is expected to vary over time.
Retail | Thornburg Developing World Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of an equity security may decline in response to developments affecting the specific issuer of the security or obligation, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retail | Thornburg Developing World Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments.
Retail | Thornburg Developing World Fund | Risks Affecting Investments in China [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Investments in China – A significant portion of the Fund’s assets may be invested in companies exposed to China. Risks affecting investments in China include a potential downturn in the Chinese economy, reduced liquidity or increased price volatility in the Chinese securities markets as a result of trading suspensions affecting Chinese issuers or other factors, the potential that the Chinese government may expand restrictions on foreign investments or the repatriation of capital, and the implementation of new tariffs or other trade barriers by China or its trading partners. A lack of transparency respecting Chinese companies may also reduce the Fund’s ability to conduct diligence respecting those companies’ accounting and governance standards, which may in turn reduce the Fund’s ability to detect fraudulent practices that may adversely affect the companies’ stock prices.
Retail | Thornburg Developing World Fund | Thornburg Developing World Fund Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THDAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [13]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.95%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.42%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.62%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.62%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 607
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 938
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,292
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,285
Annual Return 2015 rr_AnnualReturn2015 (15.34%)
Annual Return 2016 rr_AnnualReturn2016 2.55%
Annual Return 2017 rr_AnnualReturn2017 35.31%
Annual Return 2018 rr_AnnualReturn2018 (15.18%)
Annual Return 2019 rr_AnnualReturn2019 29.03%
Annual Return 2020 rr_AnnualReturn2020 22.66%
Annual Return 2021 rr_AnnualReturn2021 (3.01%)
Annual Return 2022 rr_AnnualReturn2022 (25.78%)
Annual Return 2023 rr_AnnualReturn2023 6.13%
Annual Return 2024 rr_AnnualReturn2024 5.30%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 21.64%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (24.81%)
1 Year rr_AverageAnnualReturnYear01 0.58%
5 Years rr_AverageAnnualReturnYear05 (1.18%)
10 Years rr_AverageAnnualReturnYear10 1.94%
Retail | Thornburg Developing World Fund | Thornburg Developing World Fund Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (0.39%)
5 Years rr_AverageAnnualReturnYear05 (1.61%)
10 Years rr_AverageAnnualReturnYear10 1.60%
Retail | Thornburg Developing World Fund | Thornburg Developing World Fund Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.35%
5 Years rr_AverageAnnualReturnYear05 (1.08%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Developing World Fund | Thornburg Developing World Fund Class A | MSCI Emerging Markets Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 7.50%
5 Years rr_AverageAnnualReturnYear05 1.70%
10 Years rr_AverageAnnualReturnYear10 3.64%
Retail | Thornburg Developing World Fund | Thornburg Developing World Fund Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THDCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00% [14]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.95%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.59%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.54%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.21%) [15]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.33%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 336
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 771
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,332
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,860
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 236
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 771
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,332
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,860
1 Year rr_AverageAnnualReturnYear01 3.38%
5 Years rr_AverageAnnualReturnYear05 (1.06%)
10 Years rr_AverageAnnualReturnYear10 1.61%
Retail | Thornburg Developing World Fund | Thornburg Developing World Fund Class C | MSCI Emerging Markets Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 7.50%
5 Years rr_AverageAnnualReturnYear05 1.70%
10 Years rr_AverageAnnualReturnYear10 3.64%
Retail | Thornburg Developing World Fund | Thornburg Developing World Fund Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THDIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.95%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.34%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.29%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.25%) [15]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.04%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 106
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 384
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 684
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,535
1 Year rr_AverageAnnualReturnYear01 5.80%
5 Years rr_AverageAnnualReturnYear05 0.14%
10 Years rr_AverageAnnualReturnYear10 2.83%
Retail | Thornburg Developing World Fund | Thornburg Developing World Fund Class I | MSCI Emerging Markets Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 7.50%
5 Years rr_AverageAnnualReturnYear05 1.70%
10 Years rr_AverageAnnualReturnYear10 3.64%
Retail | Thornburg Small/Mid Cap Core Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Small/Mid Cap Core Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks long-term capital appreciation by investing in equity and debt securities of all types.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

The secondary, non-fundamental goal of the Fund is to seek some current income.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 32.79% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 32.79%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal conditions, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in small- and mid-capitalization companies. The Fund currently defines small- and mid-capitalization companies to be those within the market capitalization range comprised by the Russell 2500 Index – Total Return. As of November 30, 2024, the market capitalization range of the Russell 2500 Index – Total Return was approximately $12.46 million to $53.31 billion. The Russell 2500 Index – Total Return is completely reconstituted on an annual basis each June by the index provider, which generally results in updates to the capitalization range of the index and to the companies included in the index. The capitalization range of companies in which the Fund invests will in general also change annually to reflect the reconstitution of the index. The Fund may change the definition of what constitutes “small- and mid-capitalization companies” without advance notice to shareholders.

The Fund expects to invest primarily in domestic common stocks. However, the Fund may own foreign common stocks which, in the opinion of the Fund’s investment advisor, Thornburg Investment Management, Inc. (“Thornburg”), offer prospects for meeting the Fund’s investment goals.

With its core approach to stock selection, the Fund seeks to invest in a broadly diversified portfolio of companies the Fund categorizes as basic values, consistent earners, and emerging franchises, as described in more detail below. The relative proportions of securities invested in each of those categories will vary over time.

Thornburg primarily takes a bottom-up, fundamental view in determining the attractiveness of individual securities and in making investment decisions. Among the specific factors considered by Thornburg in identifying securities for inclusion in the Fund are:

•earnings growth potential

•durable business model

•industry growth potential

•innovation driving the potential to disrupt entrenched competitors

•intrinsic value appreciation potential

•potential size of addressable market

•management strength

•leverage

•return on invested capital

•valuation metrics, including: price/earnings (“PE”) ratio; enterprise value/revenue ratio; PE/growth rate ratio, enterprise value/EBITDA (earnings before interest, taxes, depreciation and amortization) ratio; and free cash flow yield.

The Fund categorizes its investments in the following three categories:

Basic Value: Companies generally operating in mature or cyclical industries and which generally exhibit more economic sensitivity and/or higher volatility in earnings and cash flow.

Consistent Earner: Companies which generally exhibit predictable growth and profitability, and consistent cash flow and/or dividends.

Emerging Franchise: Companies with the potential to grow at an above average rate because of a product or service that is establishing a new market and/or taking share from existing participants.

Inclusion of any investment in any of the three described categories represents the opinion of Thornburg concerning the characteristics and prospects of the investment. There is no assurance that any company selected for investment will, once categorized in one of the three described investment categories, continue to have the positive characteristics or fulfill the expectations that Thornburg had for the company when it was selected for investment, and any such company may not grow or may decline in earnings and size.

The Fund selects foreign securities issued by companies domiciled in countries whose currencies are freely convertible into U.S. dollars, or in companies in other countries whose business is conducted primarily in U.S. dollars.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in small- and mid-capitalization companies may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Small/Mid Cap Core Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C and Class I share performance to the Russell 3000 Index – Total Return, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the Russell 2500 Index—Total Return, an additional index that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.

Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Small/Mid Cap Core Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 18.89%

6/30/2020

Lowest Quarterly Results

-26.30%

3/31/2020

The sales charge for Class A shares is not reflected in the returns shown in the bar chart, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.

The performance information shown above may include gains attributable to the Fund’s investments in shares of companies through initial public offerings (“IPOs”). There can be no assurance that the Fund will have continued access to profitable IPOs and, as the Fund’s assets grow, the impact of the Fund’s investment in IPOs on the performance of the Fund may decline.
Retail | Thornburg Small/Mid Cap Core Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retail | Thornburg Small/Mid Cap Core Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Small/Mid Cap Core Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Small/Mid Cap Core Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retail | Thornburg Small/Mid Cap Core Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection.
Retail | Thornburg Small/Mid Cap Core Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices.
Retail | Thornburg Small/Mid Cap Core Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Small/Mid Cap Core Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retail | Thornburg Small/Mid Cap Core Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Small/Mid Cap Core Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a security may decline in response to developments affecting the specific issuer of the security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retail | Thornburg Small/Mid Cap Core Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, earlier stages of development and lack of well-established businesses, more limited access to markets and financial resources, greater vulnerability to competition and market risks and fluctuations, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments. Relative to the stocks of large capitalization companies, the stocks of small- and mid-capitalization companies may be thinly traded and sales may result in higher transaction costs. Also, small- and mid-capitalization companies may perform poorly during times of economic stress.
Retail | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TVAFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [16]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.87%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.26% [17]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.38%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.38%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 584
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 867
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,171
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,033
Annual Return 2015 rr_AnnualReturn2015 3.41%
Annual Return 2016 rr_AnnualReturn2016 6.60%
Annual Return 2017 rr_AnnualReturn2017 23.33%
Annual Return 2018 rr_AnnualReturn2018 (9.69%)
Annual Return 2019 rr_AnnualReturn2019 28.88%
Annual Return 2020 rr_AnnualReturn2020 11.71%
Annual Return 2021 rr_AnnualReturn2021 13.83%
Annual Return 2022 rr_AnnualReturn2022 (19.55%)
Annual Return 2023 rr_AnnualReturn2023 13.14%
Annual Return 2024 rr_AnnualReturn2024 19.42%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 18.89%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (26.30%)
1 Year rr_AverageAnnualReturnYear01 14.04%
5 Years rr_AverageAnnualReturnYear05 5.71%
10 Years rr_AverageAnnualReturnYear10 7.64%
Retail | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 14.04%
5 Years rr_AverageAnnualReturnYear05 4.03%
10 Years rr_AverageAnnualReturnYear10 6.71%
Retail | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 8.31%
5 Years rr_AverageAnnualReturnYear05 4.09%
10 Years rr_AverageAnnualReturnYear10 5.98%
Retail | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class A | Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
Retail | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class A | Russell 2500 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 12.00%
5 Years rr_AverageAnnualReturnYear05 8.77%
10 Years rr_AverageAnnualReturnYear10 8.85%
Retail | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TVCFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00% [18]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.87%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.10% [17]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.97%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.63%) [17]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.34%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 337
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 859
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,507
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 3,245
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 237
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 859
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,507
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 3,245
1 Year rr_AverageAnnualReturnYear01 17.25%
5 Years rr_AverageAnnualReturnYear05 5.73%
10 Years rr_AverageAnnualReturnYear10 7.23%
Retail | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class C | Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
Retail | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class C | Russell 2500 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 12.00%
5 Years rr_AverageAnnualReturnYear05 8.77%
10 Years rr_AverageAnnualReturnYear10 8.85%
Retail | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TVIFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.87%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.21% [17]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.08%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.13%) [17]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.95%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 97
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 331
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 583
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,305
1 Year rr_AverageAnnualReturnYear01 19.92%
5 Years rr_AverageAnnualReturnYear05 7.10%
10 Years rr_AverageAnnualReturnYear10 8.55%
Retail | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class I | Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
Retail | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class I | Russell 2500 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 12.00%
5 Years rr_AverageAnnualReturnYear05 8.77%
10 Years rr_AverageAnnualReturnYear10 8.85%
Retail | Thornburg Small/Mid Cap Growth Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Small/Mid Cap Growth Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks long-term growth of capital by investing in equity securities selected for their growth potential.

Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 32.58% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 32.58%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal conditions, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in small- and mid-capitalization companies and at least 80% of its net assets in growth companies. The Fund currently defines small- and mid-capitalization companies to be those within the market capitalization range comprised by the Russell 2500 Growth Index – Total Return. As of November 30, 2024, the market capitalization range of the Russell 2500 Growth Index – Total Return was approximately $12.46 million to $53.31 billion. The Russell 2500 Growth Index – Total Return is completely reconstituted on an annual basis each June by the index provider, which generally results in updates to the capitalization range of the index and to the companies included in the index. The capitalization range of companies in which the Fund invests will in general also change annually to reflect the reconstitution of the index. The Fund may change the definition of what constitutes “small- and mid-capitalization companies” without advance notice to shareholders. The Fund currently considers a company to be a growth company if it meets any of the following criteria:

•It is a constituent of the Russell 2500 Growth Index; or

•It has, over the last five years, grown its revenues or earnings per share at an average annual rate which exceeds the median growth rate of revenues or earnings per share, as applicable, for companies in the Russell 2500 Index; or

•It is projected by consensus estimates as compiled by FactSet Research Systems, over the next two years, to grow its revenues or earnings per share at an average annual rate which exceeds the median growth rate of revenues or earnings per share, as applicable, for companies in the Russell 2500 Index.

The Fund expects to invest primarily in domestic common stocks. However, the Fund may own foreign common stocks which, in the opinion of the Fund’s investment advisor, Thornburg Investment Management, Inc. (“Thornburg”), offer prospects for meeting the Fund’s investment goal.

The Fund seeks to invest in a diversified portfolio of companies the Fund categorizes as consistent growers, disruptors, and emerging franchises, as described in more detail below. The relative proportions of securities invested in each of those categories will vary over time.

Thornburg primarily takes a bottom-up, fundamental view in determining the attractiveness of individual securities and in making investment decisions. Among the specific factors considered by Thornburg in identifying securities for inclusion in the Fund are:

•earnings growth potential

•durable business model

•industry growth potential

•innovation driving the potential to disrupt entrenched competitors

•intrinsic value appreciation potential

•potential size of addressable market

•management strength

•leverage

•return on invested capital

•valuation metrics, including: price/earnings (“PE”) ratio; enterprise value/revenue ratio; PE/growth rate ratio, enterprise value/EBITDA (earnings before interest, taxes, depreciation and amortization) ratio; and free cash flow yield.

The Fund categorizes its equity investments in the following three categories:

Consistent Grower: Companies in this category generally exhibit steady earnings or revenue growth, or both. These companies may have subscription or other recurring revenue profiles. Given their business models, these companies may outperform in weak markets.

Disruptor: Companies which are at the early stages of growth; which usually possess highly innovative or differentiated products and services, but which may require substantial additional time or investment to capitalize on market opportunities and achieve profitability.

Emerging Franchise: Companies with the potential to grow at an above average rate because of a product or service that is establishing a new market and/or taking share from existing participants.

Inclusion of any investment in any of the three described categories represents the opinion of Thornburg concerning the characteristics and prospects of the investment. There is no assurance that any company selected for investment will, once categorized in one of the three described investment categories, continue to have the positive characteristics or fulfill the expectations that Thornburg had for the company when it was selected for investment, and any such company may not grow or may decline in earnings and size.

In conjunction with individual issuer analysis, Thornburg may identify and invest at times with a greater emphasis in industries or economic sectors it expects to experience growth. The Fund does not have a strategy to invest in particular industry or economic sectors, and its exposures to particular industries or economic sectors are expected to vary over time.

The Fund selects foreign securities issued by companies domiciled in countries whose currencies are freely convertible into U.S. dollars, or in companies in other countries whose business is conducted primarily in U.S. dollars.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in small- and mid-capitalization companies may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders. The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in growth companies may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders. Additionally, the Fund may change its definition of what constitutes a “growth company” at any time without advance notice to shareholders.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Small/Mid Cap Growth Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C and Class I share performance to the Russell 3000 Index – Total Return, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the Russell 2500 Index—Total Return, an additional index that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.

Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Small/Mid Cap Growth Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 30.93%

6/30/2020

Lowest Quarterly Results

-24.94%

6/30/2022

The sales charge for Class A shares is not reflected in the returns shown in the bar chart, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Retail | Thornburg Small/Mid Cap Growth Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retail | Thornburg Small/Mid Cap Growth Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Small/Mid Cap Growth Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Small/Mid Cap Growth Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retail | Thornburg Small/Mid Cap Growth Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations,taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection.
Retail | Thornburg Small/Mid Cap Growth Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices.
Retail | Thornburg Small/Mid Cap Growth Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Small/Mid Cap Growth Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retail | Thornburg Small/Mid Cap Growth Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Small/Mid Cap Growth Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a security may decline in response to developments affecting the specific issuer of the security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retail | Thornburg Small/Mid Cap Growth Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, earlier stages of development and lack of well-established businesses, more limited access to markets and financial resources, greater vulnerability to competition and market risks and fluctuations, lack of management depth,

increased volatility in share price, and possible difficulties in valuing or selling these investments. Relative to the stocks of large capitalization companies, the stocks of small- and mid-capitalization companies may be thinly traded and sales may result in higher transaction costs. Also, small- and mid-capitalization companies may perform poorly during times of economic stress.
Retail | Thornburg Small/Mid Cap Growth Fund | Growth Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Growth Company Risk – Growth company stocks may trade at higher multiples of current earnings than other equity securities and, therefore, may be more sensitive to changes in current or expected earnings than other equity securities and may be more volatile. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can cushion stock prices in market downturns. These risks may be more pronounced in companies that are in the earlier stages of their growth cycle.
Retail | Thornburg Small/Mid Cap Growth Fund | Information Technology Securities Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Information Technology Securities Risk – Information technology companies may at times be more vulnerable to product obsolescence caused by rapid technology changes, the failure to obtain or maintain intellectual property rights, the inability to develop new products, competition from new and existing market entrants, and changes in consumer preferences. Information technology stocks may also be more volatile than the overall market.
Retail | Thornburg Small/Mid Cap Growth Fund | Biotechnology Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Biotechnology Company Risk – The Fund may invest in biotechnology companies, which may at times be more vulnerable to product obsolescence, failures to develop successful products despite significant investments in research and development, the failure to obtain or maintain intellectual property rights, competition from new and existing market entrants, and product liability claims from consumers. Biotechnology companies may also be adversely affected by changes in government regulations and restrictions. Additionally, biotechnology companies may be more reliant on capital markets to invest in and support their business operations, and biotechnology companies’ valuations, especially those of smaller, less-seasoned companies, tend to be more volatile than the overall market.
Retail | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THCGX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [19]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.87%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.30%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.42%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.42%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 588
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 879
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,191
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,075
Annual Return 2015 rr_AnnualReturn2015 2.78%
Annual Return 2016 rr_AnnualReturn2016 (2.35%)
Annual Return 2017 rr_AnnualReturn2017 23.91%
Annual Return 2018 rr_AnnualReturn2018 (2.56%)
Annual Return 2019 rr_AnnualReturn2019 28.91%
Annual Return 2020 rr_AnnualReturn2020 41.65%
Annual Return 2021 rr_AnnualReturn2021 (4.32%)
Annual Return 2022 rr_AnnualReturn2022 (34.19%)
Annual Return 2023 rr_AnnualReturn2023 19.56%
Annual Return 2024 rr_AnnualReturn2024 19.67%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 30.93%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (24.94%)
1 Year rr_AverageAnnualReturnYear01 14.30%
5 Years rr_AverageAnnualReturnYear05 4.03%
10 Years rr_AverageAnnualReturnYear10 6.65%
Retail | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 14.30%
5 Years rr_AverageAnnualReturnYear05 1.95%
10 Years rr_AverageAnnualReturnYear10 5.35%
Retail | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 8.47%
5 Years rr_AverageAnnualReturnYear05 3.26%
10 Years rr_AverageAnnualReturnYear10 5.40%
Retail | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class A | Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
Retail | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class A | Russell 2500 Growth Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 13.90%
5 Years rr_AverageAnnualReturnYear05 8.08%
10 Years rr_AverageAnnualReturnYear10 9.45%
Retail | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TCGCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00% [20]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.87%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.25%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 3.12%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.78%) [21]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.34%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 337
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 890
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,567
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 3,076
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 237
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 890
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,567
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 3,076
1 Year rr_AverageAnnualReturnYear01 17.51%
5 Years rr_AverageAnnualReturnYear05 4.09%
10 Years rr_AverageAnnualReturnYear10 6.26%
Retail | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class C | Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
Retail | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class C | Russell 2500 Growth Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 13.90%
5 Years rr_AverageAnnualReturnYear05 8.08%
10 Years rr_AverageAnnualReturnYear10 9.45%
Retail | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THIGX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.87%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.21%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.08%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.13%) [21]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.95%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 97
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 331
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 583
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,305
1 Year rr_AverageAnnualReturnYear01 20.20%
5 Years rr_AverageAnnualReturnYear05 5.43%
10 Years rr_AverageAnnualReturnYear10 7.57%
Retail | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class I | Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
Retail | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class I | Russell 2500 Growth Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 13.90%
5 Years rr_AverageAnnualReturnYear05 8.08%
10 Years rr_AverageAnnualReturnYear10 9.45%
Retail | Thornburg Investment Income Builder Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Investment Income Builder Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund’s primary investment goal is to provide a level of current income which exceeds the average yield on U.S. stocks generally, and which will generally grow, subject to periodic fluctuations, over the years on a per share basis.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

The Fund’s secondary investment goal is long-term capital appreciation.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 24.81% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 24.81%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text] rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees The Total Annual Fund Operating Expenses do not match the Ratios to Average Net Assets shown in the Financial Highlights section of the Prospectus, which reflect the operating expenses of the Fund and do not include acquired fund fees and expenses (‘AFFE’). AFFE are expenses incurred indirectly by other investment companies in which the Fund holds shares, are not direct costs paid by Fund shareholders, and are not used to calculate the Fund’s net asset value.
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment goals by investing in a broad range of income producing securities, primarily including stocks and bonds, as described below. The Fund will under normal conditions invest at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in income-producing securities, and at least 50% of its net assets, plus the amount of any borrowings for investment purposes, in common stocks.

The Fund may invest in any stock or other equity security which the Fund’s investment advisor, Thornburg Investment Management, Inc. (“Thornburg”), believes may assist the Fund in pursuing its investment goals (including smaller companies with market capitalization of less than $500 million and companies in developing countries), including preferred stock and publicly traded real estate investment trusts. The Fund expects that equity investments in the Fund’s portfolio normally will be weighted in favor of companies which pay dividends or other current income.

The Fund may invest in debt obligations of any kind, including corporate bonds and other obligations, mortgage- and other asset-backed securities and government obligations. The Fund may purchase debt obligations of any maturity and of any credit quality, including “high yield” or “junk” bonds. There is no minimum credit quality or rating of debt obligation the Fund may purchase. The Fund also may invest in debt obligations which have a combination of equity and debt characteristics, such as convertible bonds.

The Fund may invest a significant portion of its assets in securities of issuers domiciled in or economically tied to countries outside the United States, including developing countries.

The Fund’s investments are determined by individual issuer and industry analysis. Investment decisions are based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for debt and equity securities, and analysis of specific issuers. The Fund ordinarily acquires and holds debt obligations for investment rather than for realization of gains by short-term trading on market fluctuations. However, the Fund may dispose of any such security prior to its scheduled maturity to enhance income or reduce loss, to change the portfolio’s average maturity, or otherwise to respond to market conditions.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Investment Income Builder Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares vary in each full year shown. The average annual total return figures compare Class A, Class C and Class I share performance to the MSCI World Net Total Return USD Index and the Bloomberg U.S. Aggregate Total Return Index Value USD, each a broad-based securities market index that represents the overall applicable market in which the Fund invests, and a Blended Benchmark, comprised of 25% Bloomberg U.S. Aggregate Bond Total Return Value USD, and 75% MSCI World Net Total Return USD Index, an additional benchmark that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Investment Income Builder Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown on the bar chart, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 15.96%

12/31/2020

Lowest Quarterly Results

-25.98%

3/31/2020

The sales charge for Class A shares is not reflected in the returns shown on the bar chart, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Retail | Thornburg Investment Income Builder Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retail | Thornburg Investment Income Builder Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Investment Income Builder Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If debt obligations held by the Fund are downgraded by ratings agencies or go into default, or if management action, legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Because the ability of an issuer of a lower-rated or unrated obligation to pay principal and interest when due is typically less certain than for an issuer of a higher-rated obligation, lower-rated and unrated obligations are generally more vulnerable than higher-rated obligations to default, to ratings downgrades, and to liquidity risk. The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Retail | Thornburg Investment Income Builder Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Investment Income Builder Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities or debt obligations of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retail | Thornburg Investment Income Builder Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retail | Thornburg Investment Income Builder Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retail | Thornburg Investment Income Builder Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection. In addition, some foreign government debt obligations may be subject to default, delays in payment, adverse legislation or government action, or could be downgraded by ratings agencies.
Retail | Thornburg Investment Income Builder Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices.
Retail | Thornburg Investment Income Builder Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Investment Income Builder Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retail | Thornburg Investment Income Builder Fund | Real Estate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Real Estate Risk – The Fund’s investments in publicly traded real estate investment trusts (“REITs”) are subject to risks affecting real estate investments generally (including market conditions, competition, property obsolescence, changes in interest rates and casualty to real estate), as well as risks specifically affecting REITs (the quality and skill of REIT management and the internal expenses of the REIT).
Retail | Thornburg Investment Income Builder Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Investment Income Builder Fund | Risks Affecting Specific Countries or Regions [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Countries or Regions – If a significant portion of the Fund’s assets is invested in issuers that are economically exposed to one country or region, the Fund’s share value may be more susceptible to the conditions and developments in that country or region, and potentially more volatile than the share value of a more geographically diversified fund. A specific country or region could also be adversely affected by conditions or developments arising in other countries. For example, the U.S. government could take actions to prohibit or restrict individuals or companies within the U.S. from purchasing or holding the shares of issuers in another country, which may limit the Fund’s ability to invest in that country or cause the Fund to have to sell investments in that country at less than desired prices. The nature and degree of the risks affecting a given country or region, and the extent of the Fund’s exposure to any such country or region, is expected to vary over time.
Retail | Thornburg Investment Income Builder Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of an equity security or debt obligation may decline in response to developments affecting the specific issuer of the security or obligation, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retail | Thornburg Investment Income Builder Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulty in valuing or selling these investments.
Retail | Thornburg Investment Income Builder Fund | Convertible Debt Obligation Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Convertible Debt Obligation Risk – The market value of a convertible debt obligation may vary with changes in prevailing interest rates and changing evaluations of the ability of the issuer to meet principal and interest payments. The market value of a convertible debt obligation may also vary in accordance with the market value of the underlying stock. As a result, convertible debt obligations held by the Fund will tend to perform more like equity securities when the underlying stock price is high (because it is assumed that the Fund will convert the obligation), and more like non-convertible debt obligations when the underlying stock price is low (because it is assumed that the Fund will not convert the obligation). Because its market value can be influenced by several factors, a convertible debt obligation will not be as sensitive to interest rate changes as a similar non-convertible debt obligation, and generally will have less potential for gain or loss than the underlying stock.
Retail | Thornburg Investment Income Builder Fund | Foreign Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Government Obligations Risk – Debt obligations may be issued by foreign governments and their agencies and instrumentalities, including the governments of developing countries and “supra-national” entities such as the International Bank for Reconstruction and Development. The Fund’s investments in these foreign debt obligations may be denominated in U.S. dollars or in foreign currencies. These securities, even if denominated in U.S. dollars, may be affected significantly by fluctuations in the value of foreign currencies, and the value of these securities in U.S. dollars may decline even if the securities increase in value in their home country. The governmental issuers of these debt obligations may be less willing or able than the U.S. to repay principal and interest when due, and they may require that the terms for payment be renegotiated. In some countries there may be political instability or insufficient government supervision of markets, and the legal protections for the

Fund’s investments could be subject to unfavorable judicial or administrative changes. These risks may be more pronounced for the Fund’s investments in debt obligations issued by developing countries.
Retail | Thornburg Investment Income Builder Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retail | Thornburg Investment Income Builder Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments in debt obligations may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. This effect is also typically more pronounced for mortgage- and other asset-backed securities, the value of which may fluctuate more significantly in response to interest rate changes. When interest rates decrease, the Fund’s dividends may decline.
Retail | Thornburg Investment Income Builder Fund | Prepayment and Extension Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Prepayment and Extension Risk – When market interest rates decline, certain debt obligations held by the Fund may be repaid more quickly than anticipated, requiring the Fund to reinvest the proceeds of those repayments in obligations which bear a lower interest rate. Conversely, when market interest rates increase, certain debt obligations held by the Fund may be repaid more slowly than anticipated, causing assets of the Fund to remain invested in relatively lower yielding obligations. These risks may be more pronounced for the Fund’s investments in mortgage-backed and asset-backed securities.
Retail | Thornburg Investment Income Builder Fund | U.S. Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

U.S. Government Obligations Risk – U.S. government obligations are subject to the same risks affecting other debt obligations. Although securities backed by the full faith credit of the U.S. government are commonly regarded as having relatively less risk of default, it is possible that the U.S. government may be unwilling or unable to repay principal and interest when due and may require that the terms for payment be renegotiated. Further obligations that are backed by the full faith and credit of the U.S. government remain subject to the other general risks applicable to debt obligations, such as market risks, liquidity risks, and interest rate risks, and may be subject to ratings downgrades. U.S. government obligations also include obligations of U.S. government agencies, instrumentalities, and government-sponsored enterprises, commonly referred to as “agency obligations.” Some agency obligations are backed by the full faith and credit of the U.S. government, but other agency obligations have no specific backing or only limited support from the agency’s authority to borrow from the U.S. government or the discretionary authority of the Treasury to purchase obligations of the issuing agency.
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TIBAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [22]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.69%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.19%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.17% [23]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 564
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 805
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,065
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,806
Annual Return 2015 rr_AnnualReturn2015 (5.37%)
Annual Return 2016 rr_AnnualReturn2016 9.50%
Annual Return 2017 rr_AnnualReturn2017 14.78%
Annual Return 2018 rr_AnnualReturn2018 (4.62%)
Annual Return 2019 rr_AnnualReturn2019 17.66%
Annual Return 2020 rr_AnnualReturn2020 (0.65%)
Annual Return 2021 rr_AnnualReturn2021 20.02%
Annual Return 2022 rr_AnnualReturn2022 (8.27%)
Annual Return 2023 rr_AnnualReturn2023 17.90%
Annual Return 2024 rr_AnnualReturn2024 13.13%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 15.96%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (25.98%)
1 Year rr_AverageAnnualReturnYear01 8.06%
5 Years rr_AverageAnnualReturnYear05 6.86%
10 Years rr_AverageAnnualReturnYear10 6.40%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.84%
5 Years rr_AverageAnnualReturnYear05 4.71%
10 Years rr_AverageAnnualReturnYear10 4.40%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.87%
5 Years rr_AverageAnnualReturnYear05 4.30%
10 Years rr_AverageAnnualReturnYear10 4.03%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class A | MSCI World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 18.67%
5 Years rr_AverageAnnualReturnYear05 11.17%
10 Years rr_AverageAnnualReturnYear10 9.95%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class A | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class A | Blended Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 14.12%
5 Years rr_AverageAnnualReturnYear05 8.42%
10 Years rr_AverageAnnualReturnYear10 7.93%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TIBCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00% [24]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.69%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.20%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.93% [23]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 296
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 606
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,042
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,254
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 196
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 606
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,042
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,254
1 Year rr_AverageAnnualReturnYear01 11.27%
5 Years rr_AverageAnnualReturnYear05 7.04%
10 Years rr_AverageAnnualReturnYear10 6.10%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class C | MSCI World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 18.67%
5 Years rr_AverageAnnualReturnYear05 11.17%
10 Years rr_AverageAnnualReturnYear10 9.95%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class C | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class C | Blended Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 14.12%
5 Years rr_AverageAnnualReturnYear05 8.42%
10 Years rr_AverageAnnualReturnYear10 7.93%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TIBIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.69%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.20%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.93% [23]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 95
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 296
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 515
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,143
1 Year rr_AverageAnnualReturnYear01 13.38%
5 Years rr_AverageAnnualReturnYear05 8.10%
10 Years rr_AverageAnnualReturnYear10 7.17%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class I | MSCI World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 18.67%
5 Years rr_AverageAnnualReturnYear05 11.17%
10 Years rr_AverageAnnualReturnYear10 9.95%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class I | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class I | Blended Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 14.12%
5 Years rr_AverageAnnualReturnYear05 8.42%
10 Years rr_AverageAnnualReturnYear10 7.93%
Retail | Thornburg Summit Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Summit Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks to grow real wealth over time.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 66.54% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 66.54%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text] rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees The Total Annual Fund Operating Expenses and Total Annual Fund Operating Expenses After Fee Waiver/Expense Reimbursement do not match the Ratios to Average Net Assets shown in the Financial Highlights section of the Prospectus, which reflect the operating expenses of the Fund and do not include acquired fund fees and expenses (‘AFFE’). AFFE are expenses incurred indirectly by other investment companies in which the Fund holds shares, are not direct costs paid by Fund shareholders, and are not used to calculate the Fund’s net asset value.
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year) your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund seeks to grow real wealth over time. “Real wealth” for this purpose is a mix of capital appreciation and current income that is intended to exceed the rate of inflation. While the Fund seeks to achieve its goal over a variety of different market environments by selecting investments from a range of asset classes, the value of an investment in the Fund will fluctuate and the Fund may not achieve its goal in every environment or in all environments. Under normal conditions the Fund’s investments are expected to emphasize long positions in equity securities and fixed income obligations, though the Fund may also invest a significant amount of its assets in short positions in equity securities and fixed income obligations, in commodities-related investments, in derivative instruments, in currencies, and in cash or cash equivalents. There are no specific percentage limitations on the amount of the Fund’s portfolio that may be invested in a particular asset class, and the proportions of the Fund’s assets that are invested in the respective asset classes are expected to vary over time and from time to time depending upon Thornburg Investment Management, Inc.’s (“Thornburg”) perceptions of which types of investments represent better values and opportunities to achieve the Fund’s investment goal.

With respect to its equity investments, the Fund may invest in any stock or equity security, including common stocks, preferred stocks, convertible securities, warrants, depositary receipts, publicly traded real estate investment trusts, and shares in exchange traded funds. The Fund may invest in companies of any size. The Fund’s portfolio may include investments in United States issuers and the securities of issuers domiciled outside the United States, including developing countries. The relative proportions of the Fund’s U.S. and foreign investments will vary over time depending upon Thornburg’s view of specific investment opportunities and macroeconomic factors.

With respect to its fixed income investments, the Fund expects that under normal market conditions its investments will include the following types of obligations, which may be of any quality and of any maturity:

•bonds and other debt obligations issued by domestic and foreign companies of any size (including lower-rated “high yield” or “junk” bonds);

•mortgage-backed securities and other asset-backed securities;

•convertible debt obligations;

•obligations issued by foreign governments (including developing countries);

•collateralized mortgage obligations (“CMOs”), collateralized debt obligations (“CDOs”), collateralized bond obligations (“CBOs”), and collateralized loan obligations (“CLOs”);

•obligations of the U.S. government and its agencies and sponsored enterprises;

•zero coupon bonds and “stripped” securities (including both income only and principal only securities); and

•taxable municipal obligations and participations in municipal obligations.

The Fund’s investments may include both long and short positions. A short sale involves the sale by the Fund of a security that the Fund does not own. The Fund borrows the security that it intends to sell from a broker or other institution, and at a later date the Fund completes the short sale by purchasing that same security on the open market and delivering it to the lending institution. The Fund may also seek to achieve short exposure to an investment through the use of derivative instruments, Allocating the Fund’s portfolio among long and short positions is intended to permit the Fund to pursue its investment goal with lower volatility relative to broad-based securities market indices. While the Fund expects under normal conditions to invest a larger portion of its portfolio in long positions than short positions, the relative proportions of long and short equity investments will vary, and its short positions may represent a significant portion of the Fund’s portfolio during some periods.

With respect to its commodities-related investments, the Fund may invest in exchange traded funds or in other, similar investment vehicles that invest in commodities, and the Fund may invest in commodity-linked derivative instruments whose value is based on the value of an underlying commodity or commodity index, such as commodity futures contracts, commodity forward contracts, and commodity options contracts. The Fund may also seek to obtain exposure to the investment returns of commodities markets by investing in equity and debt securities of companies that operate commodities-based businesses.

The Fund’s investments are determined by individual issuer and industry analysis. Investment decisions are based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for equity and debt securities, and analysis of specific issuers. The Fund ordinarily acquires and holds debt obligations for investment rather than for realization of gains by short-term trading on market fluctuations. However, the Fund may dispose of any such security prior to its scheduled maturity to enhance income or reduce loss or to change the portfolio’s average maturity, and the Fund may dispose of any of its investments if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.

The Fund may also purchase or sell futures contracts or purchase or sell interest rate swaps or credit default swaps to hedge against a decline in the value of the Fund’s other investments, to obtain investment exposure to a particular asset class, or to establish a short position with respect to an investment.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Summit Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares of the Fund for each full year shown. The average annual total return figures compare Class A and Class I share performance to the MSCI All Country World Net Total Return USD Index and the Bloomberg Global-Aggregate Total Return Index Value Unhedged USD, each a broad-based securities market index that represents the overall applicable market in which the Fund invests, and a Blended Benchmark, comprised of 60% MSCI All Country World Index and 40% Bloomberg Global Aggregate Bond Index, an additional index that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Summit Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 7.58%

12/31/2023

Lowest Quarterly Results

-9.62%

6/30/2022
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Retail | Thornburg Summit Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retail | Thornburg Summit Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Summit Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If debt obligations held by the Fund are downgraded by ratings agencies or go into default, or if management action, legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and any dividends paid by the Fund may be reduced. Because

the ability of an issuer of a lower-rated or unrated debt obligation to pay principal and interest when due is typically less certain than for an issuer of a higher-rated debt obligation, lower-rated and unrated debt obligations are generally more vulnerable than higher-rated debt obligations to default, to ratings downgrades, and to liquidity risk. Debt obligations backed by so-called “subprime” mortgages may also be subject to a greater risk of default or downgrade. Debt obligations issued by the U.S. government or its agencies, instrumentalities and government sponsored enterprises are also subject to credit risk. Securities backed by the full faith and credit of the U.S. government, such as U.S. Treasury obligations, are commonly regarded as having small exposure to credit risk. Obligations of certain U.S. agencies, instrumentalities and enterprises (sometimes referred to as “agency obligations”) are not direct obligations of the U.S. government, may not be backed by the full faith and credit of the U.S. government, and may have a greater exposure to credit risk. The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Retail | Thornburg Summit Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Summit Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities or debt obligations of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts a significant percentage of its business in developing countries.
Retail | Thornburg Summit Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retail | Thornburg Summit Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retail | Thornburg Summit Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers and in depositary receipts may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection. In addition, some foreign government debt obligations may be subject to default, delays in payment, adverse legislation or government action, or could be downgraded by ratings agencies.
Retail | Thornburg Summit Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of the investments promptly, or may only be able to sell investments at less than desired prices. This risk may be more pronounced for the Fund’s investments in developing countries. Additionally, the market for lower-rated and unrated debt obligations (including particularly “junk” or “high yield” bonds) and debt obligations backed by so-called “subprime” mortgages may be less liquid than the market for other obligations, making it difficult for the Fund to value its investment in a lower-rated or unrated obligation or to sell the investment in a timely manner or at an acceptable price.
Retail | Thornburg Summit Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced or the Fund may otherwise be unsuccessful in pursuing its investment goal if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Summit Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility. This effect is typically more pronounced for lower-rated and unrated debt obligations (including particularly “junk” or “high yield” bonds), the value of which may fluctuate more significantly in response to poor economic growth or other changes in market conditions, political, economic and legal developments. Additionally, because the Fund has to accrue income on zero coupon bonds on a current basis even though the Fund does not receive the income from those bonds currently in cash, zero coupon bonds subject the Fund to the risk of having to generate cash from other sources (including through the sale of portfolio securities) in order to make required distributions of the income accrued from its investments in zero coupon bonds.
Retail | Thornburg Summit Fund | Real Estate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Real Estate Risk – The Fund’s investments in publicly traded real estate investment trusts (“REITs”) are subject to risks affecting real estate investments generally (including market conditions, competition, property obsolescence, changes in interest rates and casualty to real estate), as well as risks specifically affecting REITs (the quality and skill of REIT management and the internal expenses of the REIT).
Retail | Thornburg Summit Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Summit Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of an equity security or debt obligation may decline in response to developments affecting the specific issuer of the security or obligation, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retail | Thornburg Summit Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulty in valuing or selling these investments.
Retail | Thornburg Summit Fund | Depositary Receipts Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Depositary Receipts Risk – An investment in American Depositary Receipts (“ADRs”), European Depositary Receipts (“EDRs”) or Global Depositary Receipts (“GDRs”) is an alternative to the purchase of the underlying securities in their national markets and/or currencies. However, ADRs, EDRs, and GDRs remain subject to many of the risks associated with investing directly in foreign securities, including the political and economic risks associated with the underlying issuer’s country. Certain countries may limit the ability to convert a depositary receipt into the underlying foreign security and vice versa, which may cause the securities of the foreign company to trade at a discount or premium to the market price of the related depositary receipts. Moreover, EDRs and GDRs can involve currency risk since, unlike ADRs, they may not be U.S. dollar denominated.
Retail | Thornburg Summit Fund | Convertible Debt Obligation Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Convertible Debt Obligation Risk – The market value of a convertible debt obligation may vary with changes in prevailing interest rates and changing evaluations of the ability of the issuer to meet principal and interest payments. The market value of a convertible debt obligation may also vary in accordance with the market value of the underlying stock. As a result, convertible debt obligations held by the Fund will tend to perform more like equity securities when the underlying stock price is high (because it is assumed that the Fund will convert the obligation), and more like non-convertible debt obligations when the underlying stock price is low (because it is assumed that the Fund will not convert the obligation). Because its market value can be influenced by several factors, a convertible debt obligation will not be as sensitive to interest rate changes as a similar non-convertible debt obligation, and generally will have less potential for gain or loss than the underlying stock.
Retail | Thornburg Summit Fund | Foreign Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Government Obligations Risk – Debt obligations may be issued by foreign governments and their agencies and instrumentalities, including the governments of developing countries and “supra-national” entities such as the International Bank for Reconstruction and Development. The Fund’s investments in these foreign debt obligations may be denominated in U.S. dollars or in foreign currencies. These securities, even if denominated in U.S. dollars, may be affected significantly by fluctuations in the value of foreign currencies, and the value of these securities in U.S. dollars may decline even if the securities

increase in value in their home country. The governmental issuers of these debt obligations may be less willing or able than the U.S. to repay principal and interest when due, and they may require that the terms for payment be renegotiated. In some countries there may be political instability or insufficient government supervision of markets, and the legal protections for the Fund’s investments could be subject to unfavorable judicial or administrative changes. These risks may be more pronounced for the Fund’s investments in debt obligations issued by developing countries.
Retail | Thornburg Summit Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retail | Thornburg Summit Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments in debt obligations may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term debt obligations. This effect is also typically more pronounced for zero coupon bonds and mortgage- and other asset-backed securities, the value of which may fluctuate more significantly in response to interest rate changes. When interest rates decrease, the Fund’s dividends, if any, may decline.
Retail | Thornburg Summit Fund | Prepayment and Extension Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Prepayment and Extension Risk – When market interest rates decline, certain debt obligations held by the Fund may be repaid more quickly than anticipated, requiring the Fund to reinvest the proceeds of those repayments in obligations which bear a lower interest rate. Conversely, when market interest rates increase, certain debt obligations held by the Fund may be repaid more slowly than anticipated, causing assets of the Fund to remain invested in relatively lower yielding obligations. These risks may be more pronounced for the Fund’s investments in mortgage-backed and asset-backed securities.
Retail | Thornburg Summit Fund | U.S. Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

U.S. Government Obligations Risk – U.S. government obligations are subject to the same risks affecting other debt obligations. Although securities backed by the full faith credit of the U.S. government are commonly regarded as having relatively less risk of default, it is possible that the U.S. government may be unwilling or unable to repay principal and interest when due and may require that the terms for payment be renegotiated. Further obligations that are backed by the full faith and credit of the U.S. government remain subject to the other general risks applicable to debt obligations, such as market risks, liquidity risks, and interest rate risks, and may be subject to ratings downgrades. U.S. government obligations also include obligations of U.S. government agencies, instrumentalities, and government-sponsored enterprises, commonly referred to as “agency obligations.” Some agency obligations are backed by the full faith and credit of the U.S. government, but other agency obligations have no specific backing or only limited support from the agency’s authority to borrow from the U.S. government or the discretionary authority of the Treasury to purchase obligations of the issuing agency.
Retail | Thornburg Summit Fund | Commodities-Related Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Commodities-Related Investment Risk – Investments that expose the Fund to the commodities market, such as commodity-linked derivatives instruments or exchange traded funds or other investment vehicles that invest in commodities, may subject the Fund to greater volatility than investments in other securities. The value of a commodity-related investment may be affected by changes in overall market movements, commodity index volatility, changes in interest rates, risks affecting derivatives when used to obtain commodities exposure, or factors affecting a particular industry or commodity.
Retail | Thornburg Summit Fund | Derivatives Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Derivatives Risk – The Fund’s investments in futures, interest rate swaps, and credit default swaps involve the risks associated with the securities or other assets underlying those derivatives, including the risk of changes in the value of the underlying assets between the date that the Fund enters into the derivatives transaction and the date that the Fund closes out that transaction. The Fund’s investments in futures, interest rate swaps, and credit default swaps also involve the risk that the other party to the transaction will be unable or unwilling to perform its obligations to the Fund, that the Fund will be unable to sell or close its positions in such derivatives or will be delayed in doing so, and that the Fund will have difficulty valuing such derivatives.
Retail | Thornburg Summit Fund | Inflation Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Inflation Risk – Although the Fund seeks to generate capital appreciation and current income that exceeds the rate of inflation over a variety of different market environments, there is no guarantee that the Fund will be able to do so at all times. If at any time the rate of inflation exceeds Thornburg’s expectations, or if for other reasons the Fund’s portfolio is unsuccessful in producing a mix of capital appreciation and current income that exceeds the rate of inflation, the Fund may not achieve its goal.
Retail | Thornburg Summit Fund | Short Sale Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Short Sale Risk – A short sale involves the sale by the Fund of a security that the Fund has borrowed, but does not own, in anticipation of purchasing that same security at a lower price in the future in order to close the short position. If the value of the borrowed security increases between the date the Fund enters into the short sale and the date that the Fund buys that security to cover its short position, the Fund may experience a loss.
Retail | Thornburg Summit Fund | Structured Products Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Structured Products Risk – Investments in securities that are backed by, or represent interests in, an underlying pool of securities or other assets, including investments in mortgage- and asset-backed securities and in CMOs, CDOs and CLOS, involve risks associated with the underlying assets (e.g., the risks of default by mortgagors whose mortgages are included in a mortgage-backed security or CMO), and may also involve different or greater risks, including the risk that distributions from the underlying assets will be inadequate to make interest or other payments to the Fund, the risk that the issuer of the securities will fail to administer the underlying assets properly or become insolvent, prepayment and extension risk, and the risk that the securities will be less liquid than other Fund investments.
Retail | Thornburg Summit Fund | Zero Coupon Bonds and Stripped Securities Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Zero Coupon Bonds and Stripped Securities Risk – Zero coupon bonds are corporate or government-issued debt obligations that do not provide for periodic or “coupon” payments of interest, and that are issued at a substantial discount to their face value. The buyer of a zero coupon bond realizes a stated rate of return determined by the gradual accretion in the value of the security. A “stripped” security is a debt obligation that has been transformed into a zero coupon bond by creating a separate, new security comprised of the separate income component of the debt obligation (commonly referred to as an “income only” or “I/O” security) or the separate principal component of the debt obligation (commonly referred to as a “principal only” or “P/O” security). Because zero coupon bonds do not provide for periodic payments of interest, their value is generally more volatile than the value of a comparable, interest-paying bond. The Fund may also have to recognize income on the bond and make distributions to shareholders before it has received any cash payments on the bond. To generate the cash necessary to satisfy such distributions, the Fund may have to sell portfolio securities that it otherwise might have continued to hold or use cash flows from other sources, including the proceeds from the sale of Fund shares.
Retail | Thornburg Summit Fund | Thornburg Summit Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TSAMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [25]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none [26]
Component2 Other Expenses rr_Component2OtherExpensesOverAssets none [26]
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.79% [26]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.02%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.81% [27]
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.85%) [28]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.96% [27]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 544
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 915
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,310
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,414
Annual Return 2023 rr_AnnualReturn2023 12.49%
Annual Return 2024 rr_AnnualReturn2024 11.15%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 7.58%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (9.62%)
1 Year rr_AverageAnnualReturnYear01 6.15%
Since Inception rr_AverageAnnualReturnSinceInception 3.82%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 26, 2022
Retail | Thornburg Summit Fund | Thornburg Summit Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.56%
Since Inception rr_AverageAnnualReturnSinceInception 2.62%
Retail | Thornburg Summit Fund | Thornburg Summit Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.99%
Since Inception rr_AverageAnnualReturnSinceInception 2.46%
Retail | Thornburg Summit Fund | Thornburg Summit Fund - Class A | Blended Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 9.49%
Since Inception rr_AverageAnnualReturnSinceInception 3.27%
Retail | Thornburg Summit Fund | Thornburg Summit Fund - Class A | MSCI All Country World Net Total Return USD Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 17.49%
Since Inception rr_AverageAnnualReturnSinceInception 8.25%
Retail | Thornburg Summit Fund | Thornburg Summit Fund - Class A | Bloomberg Global-Aggregate Total Return Index Value Unhedged USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (1.69%)
Since Inception rr_AverageAnnualReturnSinceInception (4.11%)
Retail | Thornburg Summit Fund | Thornburg Summit Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TSUMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none [26]
Component2 Other Expenses rr_Component2OtherExpensesOverAssets none [26]
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.40% [26]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.02%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.17% [27]
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.46%) [28]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.71% [27]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 73
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 326
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 599
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,379
1 Year rr_AverageAnnualReturnYear01 11.41%
5 Years rr_AverageAnnualReturnYear05 10.69%
Since Inception rr_AverageAnnualReturnSinceInception 10.85%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2019
Retail | Thornburg Summit Fund | Thornburg Summit Fund - Class I | Blended Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 9.49%
5 Years rr_AverageAnnualReturnYear05 5.32%
Since Inception rr_AverageAnnualReturnSinceInception 6.40%
Retail | Thornburg Summit Fund | Thornburg Summit Fund - Class I | MSCI All Country World Net Total Return USD Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 17.49%
5 Years rr_AverageAnnualReturnYear05 10.06%
Since Inception rr_AverageAnnualReturnSinceInception 10.99%
Retail | Thornburg Summit Fund | Thornburg Summit Fund - Class I | Bloomberg Global-Aggregate Total Return Index Value Unhedged USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (1.69%)
5 Years rr_AverageAnnualReturnYear05 (1.96%)
Since Inception rr_AverageAnnualReturnSinceInception (0.68%)
Retail | Thornburg Ultra Short Income Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Ultra Short Income Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks current income, consistent with preservation of capital.

Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 44.59% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 44.59%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year) your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Thornburg Investment Management Inc. (“Thornburg”) actively manages the Fund’s holdings in pursuing the Fund’s investment goal. While Thornburg follows domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for debt obligations, and other factors, the Fund’s investments are determined by individual security analysis. The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may dispose of any security prior to its scheduled maturity to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, or to otherwise respond to current market conditions.

Under normal conditions, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in (i) obligations of the U.S. government, its agencies and instrumentalities, and (ii) debt obligations rated at the time of purchase in one of the four highest ratings of S&P Global Ratings (AAA, AA, A, or BBB) or Moody’s Investors Services, Inc. (Aaa, Aa, A, or Baa) or, if no credit rating is available, judged to be of comparable quality by Thornburg. The Fund may purchase corporate debt, municipal securities, and short-term commercial paper and bankers’ acceptances, and the Fund may also purchase securities backed by an underlying pool of debt obligations, including mortgage-backed securities, asset-backed securities, collateralized mortgage obligations, and collateralized debt obligations (sometimes referred to collectively as “structured products”). The Fund may purchase foreign securities of the same types and quality as the domestic securities it purchases when Thornburg anticipates foreign securities offer more investment potential. The Fund may invest in debt obligations which are rated by S&P Global Ratings or Moody’s Investors Services, Inc. at the time of purchase as below investment grade (commonly referred to as “junk” or “high yield” bonds) or, if no credit rating is available, are judged to be of comparable quality by Thornburg, but such investments will be less than 20% of the Fund’s net assets under normal conditions.

The Fund may also purchase or sell futures contracts or purchase or sell interest rate swaps or credit default swaps to hedge against a decline in the value of the Fund’s other investments or to manage portfolio duration.

Because the magnitude of changes in the value of interest-bearing obligations is greater for obligations with longer durations given an equivalent change in interest rates, the Fund seeks to reduce changes in its share value compared to longer duration fixed income portfolios by maintaining a portfolio of investments with a dollar-weighted average duration of normally no more than one half (0.5) of a year. Duration is a measure of estimated sensitivity to interest rate changes, and a debt obligation or a portfolio of obligations with a higher duration will typically be more sensitive to interest rate changes than an obligation or a portfolio with a lower duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example, an obligation with a duration of 0.5 would be expected to change in price by approximately 0.5% in response to a 1% change in interest rates. There is no limitation on the duration or maturity of any specific security the Fund may purchase, and the Fund may sell any security before it matures. The Fund also attempts to reduce changes in share value through credit analysis, selection, and diversification.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.  The objective of preserving capital may prevent the Fund from obtaining the highest yields available.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Ultra Short Income Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A and Class I share performance to the Bloomberg U.S. Aggregate Total Return Index Value USD, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the ICE BofA U.S. Treasury Bill Index, an additional index that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.

Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Ultra Short Income Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 3.80%

6/30/2020

Lowest Quarterly Results

-1.66%

3/31/2020

The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation, and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation, and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Retail | Thornburg Ultra Short Income Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retail | Thornburg Ultra Short Income Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Ultra Short Income Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – All securities owned by the Fund may be subject to default, delays in payment, adverse legislation or other government action, or could be downgraded by ratings agencies, reducing the value of the Fund’s shares. Securities backed by the full faith and credit of the U.S. government, such as U.S. Treasury obligations, are commonly regarded as having small exposure to credit risk. Obligations of certain U.S. government agencies, instrumentalities and government sponsored enterprises (sometimes referred to as “agency obligations”) are not direct obligations of the United States, may not be backed by the full faith and credit of the U.S. government, and may have a greater exposure to credit risk. Although the U.S. government is required by law to provide credit support for some agency obligations, there is no assurance that the U.S. government would provide financial support for any such obligation on a default by the issuing agency, instrumentality or enterprise in the absence of a legal requirement to do so. As of the date of this Prospectus, securities backed by the U.S. government, and the securities of U.S. government agencies, instrumentalities and enterprises that may be purchased by the Fund are rated “Aaa” by Moody’s Investors Services or “AA+” by S&P Global Ratings. Ratings agencies may reduce the ratings of any securities in the future.
Retail | Thornburg Ultra Short Income Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Ultra Short Income Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in the debt obligations of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes, or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection. These risks may be more pronounced for investments in developing countries. In addition, some foreign government debt obligations may be subject to default, delays in payment, adverse legislation or government action, or could be downgraded by ratings agencies.
Retail | Thornburg Ultra Short Income Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices.
Retail | Thornburg Ultra Short Income Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Ultra Short Income Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. For example, a fall in worldwide demand for U.S. government securities or general economic decline could lower the value of those securities.
Retail | Thornburg Ultra Short Income Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Ultra Short Income Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a debt obligation may decline in response to developments affecting the specific issuer of the obligation, even if other issuers or the overall economy are unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retail | Thornburg Ultra Short Income Fund | Foreign Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Government Obligations Risk – Debt obligations may be issued by foreign governments and their agencies and instrumentalities, including the governments of developing countries and “supra-national” entities such as the International Bank for Reconstruction and Development. The Fund’s investments in these foreign debt obligations may be denominated in U.S. dollars or in foreign currencies. These securities, even if denominated in U.S. dollars, may be affected significantly by fluctuations in the value of foreign currencies, and the value of these securities in U.S. dollars may decline even if the securities increase in value in their home country. The governmental issuers of these debt obligations may be less willing or able than the U.S. to repay principal and interest when due, and they may require that the terms for payment be renegotiated. In some countries there may be political instability or insufficient government supervision of markets, and the legal protections for the

Fund’s investments could be subject to unfavorable judicial or administrative changes. These risks may be more pronounced for the Fund’s investments in debt obligations issued by developing countries.
Retail | Thornburg Ultra Short Income Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retail | Thornburg Ultra Short Income Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. When interest rates decrease, the Fund’s dividends may decline.
Retail | Thornburg Ultra Short Income Fund | Prepayment and Extension Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Prepayment and Extension Risk – When market interest rates decline, certain debt obligations held by the Fund may be repaid more quickly than anticipated, requiring the Fund to reinvest the proceeds of those repayments in obligations which bear a lower interest rate. Conversely, when market interest rates increase, certain debt obligations held by the Fund may be repaid more slowly than anticipated, causing assets of the Fund to remain invested in relatively lower yielding obligations. These risks may be more pronounced for the Fund’s investments in mortgage-backed and asset-backed securities.
Retail | Thornburg Ultra Short Income Fund | U.S. Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

U.S. Government Obligations Risk – U.S. government obligations are subject to the same risks affecting other debt obligations. Although securities backed by the full faith credit of the U.S. government are commonly regarded as having relatively less risk of default, it is possible that the U.S. government may be unwilling or unable to repay principal and interest when due and may require that the terms for payment be renegotiated. Further obligations that are backed by the full faith and credit of the U.S. government remain subject to the other general risks applicable to debt obligations, such as market risks, liquidity risks, and interest rate risks, and may be subject to ratings downgrades. U.S. government obligations also include obligations of U.S. government agencies, instrumentalities, and government-sponsored enterprises, commonly referred to as “agency obligations.” Some agency obligations are backed by the full faith and credit of the U.S. government, but other agency obligations have no specific backing or only limited support from the agency’s authority to borrow from the U.S. government or the discretionary authority of the Treasury to purchase obligations of the issuing agency.
Retail | Thornburg Ultra Short Income Fund | Derivatives Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Derivatives Risk – The Fund’s investments in futures, interest rate swaps, and credit default swaps involve the risks associated with the securities or other assets underlying those derivatives, including the risk of changes in the value of the underlying assets between the date that the Fund enters into the derivatives transaction and the date that the Fund closes out that transaction. The Fund’s investments in futures, interest rate swaps, and credit default swaps also involve the risk that the other party to the transaction will be unable or unwilling to perform its obligations to the Fund, that the Fund will be unable to sell or close its positions in such derivatives or will be delayed in doing so, and that the Fund will have difficulty valuing such derivatives.
Retail | Thornburg Ultra Short Income Fund | Structured Products Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Structured Products Risk – Investments in securities that are backed by, or represent interests in, an underlying pool of securities or other assets, including investments in mortgage- and asset-backed securities and in collateralized mortgage obligations and collateralized debt obligations, involve the risks associated with the underlying assets (e.g., the risk of default by mortgagors whose mortgages are included in a mortgage-backed security or collateralized mortgage obligation), and may also involve the risk that distributions from the underlying assets will be inadequate to make interest or other payments to the Fund, the risk that the issuer of the securities will fail to administer the underlying assets properly or become insolvent, and the risk that the securities will be less liquid than other Fund investments.
Retail | Thornburg Ultra Short Income Fund | Thornburg Ultra Short Income Fund Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TLDAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.25%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [29]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.20%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.43%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.88%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.38%) [30]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 275
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 462
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 665
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,251
Annual Return 2015 rr_AnnualReturn2015 0.28%
Annual Return 2016 rr_AnnualReturn2016 1.69%
Annual Return 2017 rr_AnnualReturn2017 1.31%
Annual Return 2018 rr_AnnualReturn2018 1.41%
Annual Return 2019 rr_AnnualReturn2019 3.74%
Annual Return 2020 rr_AnnualReturn2020 3.05%
Annual Return 2021 rr_AnnualReturn2021 0.12%
Annual Return 2022 rr_AnnualReturn2022 0.02%
Annual Return 2023 rr_AnnualReturn2023 5.57%
Annual Return 2024 rr_AnnualReturn2024 5.65%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 3.80%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (1.66%)
1 Year rr_AverageAnnualReturnYear01 3.28%
5 Years rr_AverageAnnualReturnYear05 2.54%
10 Years rr_AverageAnnualReturnYear10 2.11%
Retail | Thornburg Ultra Short Income Fund | Thornburg Ultra Short Income Fund Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.03%
5 Years rr_AverageAnnualReturnYear05 1.24%
10 Years rr_AverageAnnualReturnYear10 1.13%
Retail | Thornburg Ultra Short Income Fund | Thornburg Ultra Short Income Fund Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.91%
5 Years rr_AverageAnnualReturnYear05 1.38%
10 Years rr_AverageAnnualReturnYear10 1.19%
Retail | Thornburg Ultra Short Income Fund | Thornburg Ultra Short Income Fund Class A | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Ultra Short Income Fund | Thornburg Ultra Short Income Fund Class A | ICE BofA U.S. Treasury Bill Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.30%
5 Years rr_AverageAnnualReturnYear05 2.48%
10 Years rr_AverageAnnualReturnYear10 1.79%
Retail | Thornburg Ultra Short Income Fund | Thornburg Ultra Short Income Fund Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TLDIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.29%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.54%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.24%) [30]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.30%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 31
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 149
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 278
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 654
1 Year rr_AverageAnnualReturnYear01 5.79%
5 Years rr_AverageAnnualReturnYear05 3.04%
10 Years rr_AverageAnnualReturnYear10 2.45%
Retail | Thornburg Ultra Short Income Fund | Thornburg Ultra Short Income Fund Class I | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Ultra Short Income Fund | Thornburg Ultra Short Income Fund Class I | ICE BofA U.S. Treasury Bill Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.30%
5 Years rr_AverageAnnualReturnYear05 2.48%
10 Years rr_AverageAnnualReturnYear10 1.79%
Retail | Thornburg Limited Term U.S. Government Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Limited Term U.S. Government Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The primary goal of Limited Term U.S. Government Fund is to provide as high a level of current income as is consistent, in the view of the Fund’s investment advisor, with safety of capital.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

As a secondary goal, the Fund seeks to reduce changes in its share price compared to longer term portfolios.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 32.26% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 32.26%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s portfolio in pursuing the Fund’s investment goals. While Thornburg follows domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for debt obligations, and other factors, the Fund’s investments are determined by individual security analysis. The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may dispose of any security before its scheduled maturity to enhance income or reduce loss, to change the portfolio’s average maturity, or to otherwise respond to market conditions.

Limited Term U.S. Government Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in U.S. Government Securities. For this purpose, “U.S. Government Securities” means:

Securities backed by the full faith and credit of the U.S. government, including direct obligations of the U.S. Treasury (such as U.S. Treasury Bonds) and obligations of U.S. government agencies and instrumentalities which are guaranteed by the U.S. Treasury (such as “Ginnie Mae” mortgage-backed certificates issued by the Government National Mortgage Association).

Securities issued or guaranteed by U.S. government agencies, instrumentalities or sponsored enterprises, but which are not backed by the full faith and credit of the U.S. government. These securities include mortgage-backed certificates, collateralized mortgage obligations (“CMOs”), and debentures issued by “Freddie Mac” (Federal Home Loan Mortgage Corporation) and “Fannie Mae” (Federal National Mortgage Association).

U.S. Government Securities include for this purpose repurchase agreements secured by the securities described above, and participations having economic characteristics similar to those securities. “Participations” are undivided interests in pools of securities where the underlying credit support passes through to the participants.

Because the magnitude of changes in the value of interest-bearing obligations is greater for obligations with longer terms given an equivalent change in interest rates, the Fund seeks to reduce changes in its share value by maintaining a portfolio of investments with a dollar-weighted average maturity or expected life of normally less than five years. There is no limitation on the maturity of any specific security the Fund may purchase, and the Fund may sell any security before it matures. The Fund also attempts to reduce changes in share value through credit analysis, selection and diversification.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.  The objective of preserving capital may prevent the Fund from obtaining the highest yields available.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Limited Term U.S. Government Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C, Class C2 and Class I share performance to the Bloomberg U.S. Aggregate Total Return Index Value USD, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the Bloomberg U.S. Government Intermediate Total Return Index Value Unhedged, an additional benchmark that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Limited Term U.S. Government Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 4.26%

9/30/2024

Lowest Quarterly Results

-3.63%

3/31/2022

The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Retail | Thornburg Limited Term U.S. Government Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retail | Thornburg Limited Term U.S. Government Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Limited Term U.S. Government Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – All securities owned by the Fund may be subject to default, delays in payment, adverse legislation or other government action, or could be downgraded by ratings agencies, reducing the value of the Fund’s shares. Securities backed by the full faith and credit of the U.S. government, such as U.S. Treasury obligations, are commonly regarded as having small exposure to credit risk. Obligations of certain U.S. government agencies, instrumentalities and government-sponsored enterprises (sometimes referred to as “agency obligations”) are not direct obligations of the United States, may not be backed by the full faith and credit of the U.S. government, and may have a greater exposure to credit risk. Although the U.S. government is required by law to provide credit support for some agency obligations, there is no assurance that the U.S. government would provide financial support for any such obligation on a default by the issuing agency, instrumentality or enterprise in the absence of a legal requirement to do so. As of the date of this Prospectus, securities backed by the full faith and credit of the U.S. government, and securities of U.S. government agencies, instrumentalities and enterprises which may be purchased by the Fund are rated “Aaa” by Moody’s Investors Services or “AA+” by S&P Global Ratings. Ratings agencies may reduce the ratings of any securities in the future.

Retail | Thornburg Limited Term U.S. Government Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Limited Term U.S. Government Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices.
Retail | Thornburg Limited Term U.S. Government Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Limited Term U.S. Government Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. For example, a fall in worldwide demand for U.S. government securities or general economic decline could lower the value of those securities.
Retail | Thornburg Limited Term U.S. Government Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Limited Term U.S. Government Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. This effect is also typically more pronounced for the Fund’s investment in mortgage-backed securities, the value of which may fluctuate more significantly in response to interest rate changes. When interest rates decrease, the Fund’s dividends may decline.
Retail | Thornburg Limited Term U.S. Government Fund | Prepayment and Extension Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Prepayment and Extension Risk – When market interest rates decline, certain debt obligations held by the Fund may be repaid more quickly than anticipated, requiring the Fund to reinvest the proceeds of those repayments in obligations which bear a lower interest rate. Conversely, when market interest rates increase, certain debt obligations held by the Fund may be repaid more slowly than anticipated, causing assets of the Fund to remain invested in relatively lower yielding obligations. These risks may be more pronounced for the Fund’s investments in mortgage-backed securities.
Retail | Thornburg Limited Term U.S. Government Fund | U.S. Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

U.S. Government Obligations Risk – U.S. government obligations are subject to the same risks affecting other debt obligations. Although securities backed by the full faith credit of the U.S. government are commonly regarded as having relatively less risk of default, it is possible that the U.S. government may be unwilling or unable to repay principal and interest when due and may require that the terms for payment be renegotiated. Further obligations that are backed by the full faith and credit of the U.S. government remain subject to the other general risks applicable to debt obligations, such as market risks, liquidity risks, and interest rate risks, and may be subject to ratings downgrades. U.S. government obligations also include obligations of U.S. government agencies, instrumentalities, and government-sponsored enterprises, commonly referred to as “agency obligations.” Some agency obligations are backed by the full faith and credit of the U.S. government, but other agency obligations have no specific backing or only limited support from the agency’s authority to borrow from the U.S. government or the discretionary authority of the Treasury to purchase obligations of the issuing agency.
Retail | Thornburg Limited Term U.S. Government Fund | Structured Products Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Structured Products Risk – Investments in securities that are backed by, or represent interests in, an underlying pool of securities or other assets, including investments in mortgage-backed securities and in CMOs, involve the risks associated with the underlying assets (e.g., the risk of default by mortgagors whose mortgages are included in a mortgage-backed security or CMO), and may also involve different or greater risks, including the risk that distributions from the underlying assets will be inadequate to make interest or other payments to the Fund, the risk that the issuer of the securities will fail to administer the underlying assets properly or become insolvent, and the risk that the securities will be less liquid than other Fund investments.
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTUSX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.25%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [31]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.37%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.38%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.00%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.01%) [32]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 324
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 535
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 764
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,421
Annual Return 2015 rr_AnnualReturn2015 0.34%
Annual Return 2016 rr_AnnualReturn2016 0.90%
Annual Return 2017 rr_AnnualReturn2017 0.60%
Annual Return 2018 rr_AnnualReturn2018 0.83%
Annual Return 2019 rr_AnnualReturn2019 3.61%
Annual Return 2020 rr_AnnualReturn2020 3.77%
Annual Return 2021 rr_AnnualReturn2021 (1.83%)
Annual Return 2022 rr_AnnualReturn2022 (7.97%)
Annual Return 2023 rr_AnnualReturn2023 3.85%
Annual Return 2024 rr_AnnualReturn2024 2.40%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2024
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.26%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.63%)
1 Year rr_AverageAnnualReturnYear01 0.12%
5 Years rr_AverageAnnualReturnYear05 (0.36%)
10 Years rr_AverageAnnualReturnYear10 0.44%
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (0.94%)
5 Years rr_AverageAnnualReturnYear05 (1.11%)
10 Years rr_AverageAnnualReturnYear10 (0.27%)
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.07%
5 Years rr_AverageAnnualReturnYear05 (0.59%)
10 Years rr_AverageAnnualReturnYear10 0.03%
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class A | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class A | Bloomberg U.S. Government Intermediate Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.44%
5 Years rr_AverageAnnualReturnYear05 0.49%
10 Years rr_AverageAnnualReturnYear10 1.24%
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTUCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 0.50% [32]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.37%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.97%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.84%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.60%) [33]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.24%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 176
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 520
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 940
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,109
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 126
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 520
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 940
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,109
1 Year rr_AverageAnnualReturnYear01 1.57%
5 Years rr_AverageAnnualReturnYear05 (0.38%)
10 Years rr_AverageAnnualReturnYear10 0.28%
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class C | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class C | Bloomberg U.S. Government Intermediate Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.44%
5 Years rr_AverageAnnualReturnYear05 0.49%
10 Years rr_AverageAnnualReturnYear10 1.24%
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class C2  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTUQX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 0.65% [32]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.37%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.65%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 2.47%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 3.49%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (2.25%) [33]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.24%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 191
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 862
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,619
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 3,616
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 126
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 862
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,619
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 3,616
1 Year rr_AverageAnnualReturnYear01 1.42%
Since Inception rr_AverageAnnualReturnSinceInception (1.23%)
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 01, 2020
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class C2 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
Since Inception rr_AverageAnnualReturnSinceInception (1.91%)
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class C2 | Bloomberg U.S. Government Intermediate Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.44%
Since Inception rr_AverageAnnualReturnSinceInception (0.78%)
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTUIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.37%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.28%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.65%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.65%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 66
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 208
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 362
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 810
1 Year rr_AverageAnnualReturnYear01 2.65%
5 Years rr_AverageAnnualReturnYear05 0.22%
10 Years rr_AverageAnnualReturnYear10 0.89%
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class I | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class I | Bloomberg U.S. Government Intermediate Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.44%
5 Years rr_AverageAnnualReturnYear05 0.49%
10 Years rr_AverageAnnualReturnYear10 1.24%
Retail | Thornburg Limited Term Income Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Limited Term Income Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The primary goal of Limited Term Income Fund is to provide as high a level of current income as is consistent, in the view of the Fund’s investment advisor, with safety of capital.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

As a secondary goal, the Fund seeks to reduce changes in its share prices compared to longer term portfolios.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 59.42% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 59.42%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s portfolio in pursuing the Fund’s investment goals. While Thornburg follows domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for debt obligations, and other factors, the Fund’s investments are determined by individual security analysis. The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may dispose of any security prior to its scheduled maturity to enhance income or reduce loss, to change the portfolio’s average maturity, or to otherwise respond to current market conditions.

The Fund invests at least 65% of its net assets, plus the amount of any borrowings for investment purposes, in (i) obligations of the U.S. government, its agencies and instrumentalities, and (ii) debt obligations rated at the time of purchase in one of the three highest principal long term rating categories of S&P Global Ratings (AAA, AA or A) or Moody’s Investors Services, Inc. (Aaa, Aa or A), or the equivalent three highest short term ratings of those ratings agencies, or, if no credit rating is available, judged to be of comparable quality as determined by Thornburg. The Fund will not invest in any debt obligation rated at the time of purchase lower than BBB by S&P, Baa by Moody’s, of the equivalent short term ratings of those ratings agencies, or, if no credit rating is available, judged to be of comparable quality as determined by Thornburg. The Fund may purchase corporate debt obligations, municipal securities, and commercial paper and bankers’ acceptances, and the Fund may also purchase securities backed by an underlying pool of debt obligations, including mortgage-backed securities, asset-backed securities, collateralized mortgage obligations, and collateralized debt obligations (sometimes referred to collectively as “structured products”). The Fund may purchase foreign securities of the same types and quality as the domestic securities it purchases when Thornburg believes these investments are consistent with the Fund’s objectives.

Because the magnitude of changes in the value of interest-bearing obligations is greater for obligations with longer terms given an equivalent change in interest rates, the Fund seeks to reduce changes in its share value by maintaining a portfolio of investments with a dollar-weighted average maturity or expected life of normally less than five years. As a result, the Fund also maintains a portfolio of investments having a dollar-weighted average effective duration of normally no more than five years. Duration is a measure of estimated sensitivity to interest rate changes. A portfolio with a longer average effective duration will typically be more sensitive to interest rate changes than a portfolio with a shorter average effective duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example,

an obligation with a duration of 5 would be expected to change in price by approximately 5% in response to a 1% change in interest rates. During temporary periods the Fund’s portfolio maturity and average effective duration may be reduced for defensive purposes. There is no limitation on the maturity of any specific security the Fund may purchase, and the Fund may sell any security before it matures. The Fund also attempts to reduce changes in share value through credit analysis, selection and diversification.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.  The objective of preserving capital may prevent the Fund from obtaining the highest yields available.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Limited Term Income Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C, Class C2 and Class I share performance to the Bloomberg U.S. Aggregate Total Return Index Value USD, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the Bloomberg Intermediate U.S. Government/

Credit Total Return Index Value Unhedged, an additional benchmark that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Limited Term Income Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart above and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 5.71%

6/30/2020

Lowest Quarterly Results

-3.89%

3/31/2022

The sales charge for Class A shares is not reflected in the returns shown in the bar chart above and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Retail | Thornburg Limited Term Income Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retail | Thornburg Limited Term Income Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Limited Term Income Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – All securities owned by the Fund may be subject to default, delays in payment, adverse legislation or other government action, or could be downgraded by ratings agencies, reducing the value of the Fund’s shares. Securities backed by the full faith and credit of the U.S. government, such as U.S. Treasury obligations, are commonly regarded as having small exposure to credit risk. Obligations of certain U.S. government agencies, instrumentalities and government sponsored enterprises (sometimes referred to as “agency obligations”) are not direct obligations of the United States, may not be backed by the full faith and credit of the U.S. government, and may have a greater exposure to credit risk. Although the U.S. government is required by law to provide credit support for some agency obligations, there is no assurance that the U.S. government would provide financial support for any such obligation on a default by the issuing agency, instrumentality or enterprise in the absence of a legal requirement to do so. As of the date of this Prospectus, securities backed by the full faith and credit of the U.S. government, and securities of U.S. government agencies, instrumentalities and enterprises which may be purchased by the Fund, are rated “Aaa” by Moody’s Investors Services or “AA+” by S&P Global Ratings. Ratings agencies may reduce the ratings of any securities in the future. Lower-rated or unrated obligations in which the Fund is permitted to invest may have, or may be perceived to have, greater risk of default and ratings downgrades.
Retail | Thornburg Limited Term Income Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Limited Term Income Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in the debt obligations of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection. These risks may be more pronounced for investments in developing countries. In addition, some foreign government debt obligations may be subject to default, delays in payment, adverse legislation or government action, or could be downgraded by ratings agencies.
Retail | Thornburg Limited Term Income Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices.
Retail | Thornburg Limited Term Income Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Limited Term Income Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. For example, a fall in worldwide demand for U.S. government securities or general economic decline could lower the value of those securities.
Retail | Thornburg Limited Term Income Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Limited Term Income Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a debt obligation may decline in response to developments affecting the specific issuer of the obligation, even if other issuers or the overall economy are unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retail | Thornburg Limited Term Income Fund | Foreign Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Government Obligations Risk – Debt obligations may be issued by foreign governments and their agencies and instrumentalities, including the governments of developing countries and “supra-national” entities such as the International Bank for Reconstruction and Development. The Fund’s investments in these foreign debt obligations may be denominated in U.S. dollars or in foreign currencies. These securities, even if denominated in U.S. dollars, may be affected significantly by fluctuations in the value of foreign currencies, and the value of these securities in U.S. dollars may decline even if the securities increase in value in their home country. The governmental issuers of these debt obligations may be less willing or able than the U.S. to repay principal and interest when due, and they may require that the terms for payment be renegotiated. In some countries there may be political instability or insufficient government supervision of markets, and the legal protections for the Fund’s investments could be subject to unfavorable judicial or administrative changes. These risks may be more pronounced for the Fund’s investments in debt obligations issued by developing countries.
Retail | Thornburg Limited Term Income Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. This effect is also typically more pronounced for the Fund’s investment in mortgage- and other asset-backed securities, the value of which may fluctuate more significant in response to interest rate changes. When interest rates decrease, the Fund’s dividends may decline.
Retail | Thornburg Limited Term Income Fund | Prepayment and Extension Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Prepayment and Extension Risk – When market interest rates decline, certain debt obligations held by the Fund may be repaid more quickly than anticipated, requiring the Fund to reinvest the proceeds of those repayments in obligations which bear a lower interest rate. Conversely, when market interest rates increase, certain debt obligations held by the Fund may be repaid more slowly than anticipated, causing assets of the Fund to remain invested in relatively lower yielding obligations. These risks may be more pronounced for the Fund’s investments in mortgage-backed and asset-backed securities.
Retail | Thornburg Limited Term Income Fund | U.S. Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

U.S. Government Obligations Risk – U.S. government obligations are subject to the same risks affecting other debt obligations. Although securities backed by the full faith credit of the U.S. government are commonly regarded as having relatively less risk of default, it is possible that the U.S. government may be unwilling or unable to repay principal and interest when due and may require that the terms for payment be renegotiated. Further obligations that are backed by the full faith and credit of the U.S. government remain subject to the other general risks applicable to debt obligations, such as market risks, liquidity risks, and interest rate risks, and may be subject to ratings downgrades. U.S. government obligations also include obligations of U.S. government agencies, instrumentalities, and government-sponsored enterprises, commonly referred to as “agency obligations.” Some agency obligations are backed by the full faith and credit of the U.S. government, but other agency obligations have no specific backing or only limited support from the agency’s authority to borrow from the U.S. government or the discretionary authority of the Treasury to purchase obligations of the issuing agency.
Retail | Thornburg Limited Term Income Fund | Structured Products Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Structured Products Risk – Investments in securities that are backed by, or represent interests in, an underlying pool of securities or other assets, including investments in mortgage- and asset-backed securities and in collateralized mortgage obligations and collateralized debt obligations, involve the risks associated with the underlying assets (e.g., the risk of default by mortgagors whose mortgages are included in a mortgage-backed security or collateralized mortgage obligation), and may also involve different or greater risks, including the risk that distributions from the underlying assets will be inadequate to make interest or other payments to the Fund, the risk that the issuer of the securities will fail to administer the underlying assets properly or become insolvent, and the risk that the securities will be less liquid than other Fund investments.
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THIFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.25%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [34]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.32%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.19%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.76%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.76%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 301
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 462
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 638
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,146
Annual Return 2015 rr_AnnualReturn2015 0.47%
Annual Return 2016 rr_AnnualReturn2016 3.12%
Annual Return 2017 rr_AnnualReturn2017 2.27%
Annual Return 2018 rr_AnnualReturn2018 0.99%
Annual Return 2019 rr_AnnualReturn2019 5.37%
Annual Return 2020 rr_AnnualReturn2020 7.37%
Annual Return 2021 rr_AnnualReturn2021 (1.07%)
Annual Return 2022 rr_AnnualReturn2022 (7.33%)
Annual Return 2023 rr_AnnualReturn2023 6.27%
Annual Return 2024 rr_AnnualReturn2024 4.34%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 5.71%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.89%)
1 Year rr_AverageAnnualReturnYear01 1.96%
5 Years rr_AverageAnnualReturnYear05 1.45%
10 Years rr_AverageAnnualReturnYear10 1.95%
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.40%
5 Years rr_AverageAnnualReturnYear05 0.36%
10 Years rr_AverageAnnualReturnYear10 0.92%
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.14%
5 Years rr_AverageAnnualReturnYear05 0.64%
10 Years rr_AverageAnnualReturnYear10 1.04%
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class A | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class A | Bloomberg Intermediate U.S. Government/Credit Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.00%
5 Years rr_AverageAnnualReturnYear05 0.86%
10 Years rr_AverageAnnualReturnYear10 1.71%
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THICX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 0.50% [35]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.32%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.19%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.01%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.01%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 153
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 322
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 558
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,236
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 103
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 322
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 558
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,236
1 Year rr_AverageAnnualReturnYear01 3.59%
5 Years rr_AverageAnnualReturnYear05 1.53%
10 Years rr_AverageAnnualReturnYear10 1.87%
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class C | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class C | Bloomberg Intermediate U.S. Government/Credit Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.00%
5 Years rr_AverageAnnualReturnYear05 0.86%
10 Years rr_AverageAnnualReturnYear10 1.71%
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class C2  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THIQX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 0.65% [35]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.32%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.65%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.45%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.42%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.18%) [36]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.24%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 191
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 432
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 759
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,686
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 126
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 432
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 759
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,686
1 Year rr_AverageAnnualReturnYear01 3.29%
Since Inception rr_AverageAnnualReturnSinceInception 0.15%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 01, 2020
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class C2 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
Since Inception rr_AverageAnnualReturnSinceInception (1.91%)
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class C2 | Bloomberg Intermediate U.S. Government/Credit Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.00%
Since Inception rr_AverageAnnualReturnSinceInception (0.35%)
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THIIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.32%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.20%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.52%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [36]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.49%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 50
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 164
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 288
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 650
1 Year rr_AverageAnnualReturnYear01 4.72%
5 Years rr_AverageAnnualReturnYear05 2.05%
10 Years rr_AverageAnnualReturnYear10 2.42%
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class I | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class I | Bloomberg Intermediate U.S. Government/Credit Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.00%
5 Years rr_AverageAnnualReturnYear05 0.86%
10 Years rr_AverageAnnualReturnYear10 1.71%
Retail | Thornburg Core Plus Bond Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Core Plus Bond Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks to maximize total return, consistent with the long-term preservation of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in this Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 159, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 212, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 39.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 73.32% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 73.32%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year) your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s portfolio in pursuing the Fund’s investment goal. Under normal conditions, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in debt obligations. The Fund may invest up to 25% of its net assets, plus the amount of any borrowings for investment purposes, in debt obligations which, at the time of purchase, are rated by a nationally recognized statistical rating organization as below investment grade (sometimes called “junk” bonds or “high yield” bonds) or, if unrated, are issued by obligors which Thornburg determines to have comparable below investment grade obligations outstanding or to be comparable to obligors with outstanding below investment grade obligations. The Fund may not, at the time of purchase, invest more than 25% of its net assets, plus the amount of any borrowings for investment purposes, in debt obligations denominated in non-U.S. currencies, but this limitation does not apply to debt obligations issued by foreign issuers and denominated in U.S. dollars. Additionally, the Fund may not, at the time of purchase, invest more than 15% of its net assets, plus the amount of any borrowings for investment purposes, in debt obligations issued by issuers in emerging markets, also known as developing countries.

There is no limitation on the duration or maturity of any specific debt obligation the Fund may purchase. The Fund will, however, generally seek to maintain a portfolio of investments with a dollar-weighted average duration that falls within two years of the dollar-weighted average duration of the Fund’s benchmark index, the Bloomberg U.S. Aggregate Bond Index. Duration is a measure of estimated sensitivity to interest rate changes, and a debt obligation or a portfolio of obligations with a higher duration will typically be more sensitive to interest rate changes than an obligation or a portfolio with a lower duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example, an obligation with a duration of 0.5 would be expected to change in price by approximately 0.5% in response to a 1% change in interest rates.

While the Fund may invest in debt obligations of any type, the Fund will typically invest in the following types of debt obligations:

•corporate debt obligations from domestic and foreign issuers of any market capitalization;

•obligations issued or guaranteed by U.S. and non-U.S. governments and their agencies or instrumentalities; and

•mortgage-backed and asset-backed securities, including residential or commercial mortgage-backed securities, or collateralized mortgage obligations, issued by agencies of the U.S. government or issued by private entities.

Each of the Fund’s investments is determined by individual issuer and industry analysis, including Thornburg’s evaluation of domestic and international economic developments, outlooks for securities markets, interest rates and inflation, and the supply and demand for debt obligations.

The Fund may also invest in futures contracts, options, swaps, and forward contracts to hedge against the decline in the value of certain of the Fund’s investments, to manage portfolio duration, or to enhance the Fund’s investment returns.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.  Because the Fund seeks to maximize total return while also preserving capital, the Fund may not always obtain the highest yields available.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in debt obligations may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Core Plus Bond Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C and Class I share performance to the Bloomberg U.S. Aggregate Total Return Index Value USD, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The index is not actively managed and is not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Core Plus Bond Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 5.06%

9/30/2024

Lowest Quarterly Results

-3.13%

12/31/2024
Retail | Thornburg Core Plus Bond Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retail | Thornburg Core Plus Bond Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Core Plus Bond Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If obligations held by the Fund are downgraded by ratings agencies or go into default, or if management action, legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Because the ability of an issuer of a lower-rated or unrated obligation to pay principal and interest when due is typically less certain than for an issuer of a higher-rated obligation, lower-rated and unrated obligations are generally more vulnerable than higher- rated obligations to default, to ratings downgrades, and to liquidity risk. Debt obligations backed by so-called “subprime” mortgages may also be subject to a greater risk of default or downgrade. Debt obligations issued by the U.S. government or its agencies, instrumentalities and government sponsored enterprises are also subject to credit risk. Securities backed by the full faith and credit of the U.S. government, such as U.S. Treasury obligations, are commonly regarded as having small exposure to credit risk. Obligations of certain U.S. agencies, instrumentalities and enterprises (sometimes referred to as “agency obligations”) are not direct obligations of the U.S. government, may not be backed by the full faith and credit of the U.S. government, and may have a greater exposure to credit risk.
Retail | Thornburg Core Plus Bond Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants, or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Core Plus Bond Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retail | Thornburg Core Plus Bond Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in the debt obligations of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection. In addition, some foreign government debt obligations may be subject to default, delays in payment, adverse legislation or government action, or could be downgraded by ratings agencies.
Retail | Thornburg Core Plus Bond Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices. The market for lower-rated and unrated debt obligations (including particularly “junk” or “high yield” bonds) and debt obligations backed by so-called “subprime” mortgages may be less liquid than the market for other obligations, making it difficult for the Fund to value its investment in a lower-rated or unrated obligation or to sell the investment in a timely manner or at an acceptable price.
Retail | Thornburg Core Plus Bond Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Core Plus Bond Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. This effect is typically more pronounced for lower-rated and unrated debt obligations (including particularly “junk” or “high yield” bonds), the value of which may fluctuate more significantly in response to poor economic growth or other changes in market conditions, political, economic, and legal developments, and developments affecting specific issuers.

Retail | Thornburg Core Plus Bond Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell

securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Core Plus Bond Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a debt obligation may decline in response to developments affecting the specific issuer of the obligation or security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.

Retail | Thornburg Core Plus Bond Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Debt obligations of small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility, and possible difficulties in valuing or selling these investments.

Retail | Thornburg Core Plus Bond Fund | Foreign Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Government Obligations Risk – Debt obligations may be issued by foreign governments and their agencies and instrumentalities, including the governments of developing countries and “supra-national” entities such as the International Bank for Reconstruction and Development. The Fund’s investments in these foreign debt obligations may be denominated in U.S. dollars or in foreign currencies. These securities, even if denominated in U.S. dollars, may be affected significantly by fluctuations in the value of foreign currencies, and the value of these securities in U.S. dollars may decline even if the securities increase in value in their home country. The governmental issuers of these debt obligations may be less willing or able than the U.S. to repay principal and interest when due, and they may require that the terms for payment be renegotiated. In some countries there may be political instability or insufficient government supervision of markets, and the legal protections for the Fund’s investments could be subject to unfavorable judicial or administrative changes. These risks may be more pronounced for the Fund’s investments in debt obligations issued by developing countries.
Retail | Thornburg Core Plus Bond Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retail | Thornburg Core Plus Bond Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. This effect is also typically more pronounced for mortgage- and other asset-backed securities, the value of which may fluctuate more significantly in response to interest rate changes. When interest rates decrease, the Fund’s dividends may decline.
Retail | Thornburg Core Plus Bond Fund | Prepayment and Extension Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Prepayment and Extension Risk – When market interest rates decline, certain debt obligations held by the Fund may be repaid more quickly than anticipated, requiring the Fund to reinvest the proceeds of those repayments in obligations which bear a lower interest rate. Conversely, when market interest rates increase, certain debt obligations held by the Fund may be repaid more slowly than anticipated, causing assets of the Fund to remain invested in relatively lower yielding obligations. These risks may be more pronounced for the Fund’s investments in mortgage-backed and asset-backed securities.
Retail | Thornburg Core Plus Bond Fund | U.S. Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

U.S. Government Obligations Risk – U.S. government obligations are subject to the same risks affecting other debt obligations. Although securities backed by the full faith credit of the U.S. government are commonly regarded as having relatively less risk of default, it is possible that the U.S. government may be unwilling or unable to repay principal and interest when due and may require that the terms for payment be renegotiated. Further obligations that are backed by the full faith and credit of the U.S. government remain subject to the other general risks applicable to debt obligations, such as market risks, liquidity risks, and interest rate risks, and may be subject to ratings downgrades. U.S. government obligations also include obligations of U.S. government agencies, instrumentalities, and government-sponsored enterprises, commonly referred to as “agency obligations.” Some agency obligations are backed by the full faith and credit of the U.S. government, but other agency obligations have no specific backing or only limited support from the agency’s authority to borrow from the U.S. government or the discretionary authority of the Treasury to purchase obligations of the issuing agency.
Retail | Thornburg Core Plus Bond Fund | Derivatives Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Derivatives Risk – The Fund’s investments in futures contracts, options, swaps, forward contracts, and other derivative instruments involve the risks associated with the securities or other assets underlying those derivatives, and also may involve risks different or greater than the risks affecting the underlying assets, including the inability or unwillingness of the other party to a derivative to perform its obligations to the Fund, the Fund’s inability or delays in selling or closing positions in derivatives, and difficulties in valuing derivatives.
Retail | Thornburg Core Plus Bond Fund | Structured Products Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Structured Products Risk – Investments in securities that are backed by, or represent interests in, an underlying pool of securities or other assets, including investments in mortgage- and asset-backed securities and in collateralized mortgage obligations, involve the risks associated with the underlying assets (e.g., the risk of default by mortgagors whose mortgages are included in a mortgage-backed security or collateralized mortgage obligation), and may also involve different or greater risks, including the risk that distributions from the underlying assets will be inadequate to make interest or other payments to the Fund, the risk that the issuer of the securities will fail to administer the underlying assets properly or become insolvent, and the risk that the securities will be less liquid than other Fund investments.

Retail | Thornburg Core Plus Bond Fund | Emerging Markets Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Emerging Markets Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in emerging markets, also known as developing countries, because the economies of those markets are usually less diversified, communications, transportation and economic infrastructures are less developed, and emerging markets ordinarily have less established legal, political, business and social frameworks. At times the prices of debt obligations of an issuer in an emerging market may be extremely volatile. An issuer in a developed country may be similarly affected by these emerging markets risks to the extent that the issuer conducts its business in emerging markets.
Retail | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THCAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [37]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.49%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 10.18%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 10.92%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (10.17%) [38]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.75%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 523
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 2,571
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 4,383
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 8,054
Annual Return 2024 rr_AnnualReturn2024 1.36%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2024
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 5.06%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2024
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.13%)
1 Year rr_AverageAnnualReturnYear01 (3.19%)
Since Inception rr_AverageAnnualReturnSinceInception 3.26%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 02, 2023
Retail | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (5.10%)
Since Inception rr_AverageAnnualReturnSinceInception 1.25%
Retail | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (1.90%)
Since Inception rr_AverageAnnualReturnSinceInception 1.65%
Retail | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class A | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
Since Inception rr_AverageAnnualReturnSinceInception 7.08%
Retail | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THCCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00% [39]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.49%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.96%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 3.45%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (1.95%) [38]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 253
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 878
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,626
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 3,599
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 153
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 878
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,626
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 3,599
1 Year rr_AverageAnnualReturnYear01 (0.34%)
Since Inception rr_AverageAnnualReturnSinceInception 6.36%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 02, 2023
Retail | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class C | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
Since Inception rr_AverageAnnualReturnSinceInception 7.08%
Retail | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THCIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.49%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.62%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.11%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.61%) [38]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 51
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 292
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 552
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,297
1 Year rr_AverageAnnualReturnYear01 1.66%
Since Inception rr_AverageAnnualReturnSinceInception 7.46%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 02, 2023
Retail | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class I | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
Since Inception rr_AverageAnnualReturnSinceInception 7.08%
Retail | Thornburg Strategic Income Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Strategic Income Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund’s primary investment goal is to seek a high level of current income.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

The Fund’s secondary investment goal is some long-term capital appreciation.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 60.47% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 60.47%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment goals by investing in a broad range of income-producing investments from throughout the world, primarily including debt obligations. The Fund expects, under normal conditions, to invest a majority of its assets in the debt obligations described below.

The Fund may invest in debt obligations of any kind, of any quality, and of any maturity. The Fund expects, under normal conditions, to select a majority of its investments from among the following types of debt obligations:

•bonds and other debt obligations issued by domestic and foreign companies of any size (including lower-rated “high yield” or “junk” bonds)

•mortgage-backed securities and other asset-backed securities, including commercial mortgage-backed securities

•convertible debt obligations

•obligations issued by foreign governments (including developing countries)

•collateralized mortgage obligations (“CMOs”), collateralized debt obligations (“CDOs”), collateralized bond obligations (“CBOs”), and collateralized loan obligations (“CLOs”)

•obligations of the U.S. government and its agencies and sponsored enterprises

•structured notes

•zero coupon bonds and “stripped” securities

•taxable municipal obligations and participations in municipal obligations

The Fund’s investments are determined by individual issuer and industry analysis. Investment decisions are based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for debt securities, and analysis of specific issuers.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.  The objective of preserving capital may prevent the Fund from obtaining the highest yields available.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Strategic Income Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows the annual total return for Class A shares in the one full year shown. The average annual total return figures compare Class A, Class C and Class I share performance to the Bloomberg U.S. Aggregate Total Return Index Value USD, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the Bloomberg U.S. Universal Total Return Index Value Unhedged, an additional benchmark that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. The Blended Benchmark, comprised of 80% Bloomberg U.S. Aggregate Bond Total Return Value USD and 20% MSCI World Net Total Return USD Index, was removed as the Fund’s secondary index effective September 30, 2024. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Strategic Income Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 7.98%

6/30/2020

Lowest Quarterly Results

-5.71%

3/31/2020

The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Retail | Thornburg Strategic Income Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retail | Thornburg Strategic Income Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Strategic Income Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If obligations held by the Fund are downgraded by ratings agencies or go into default, or if management action, legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Because the ability of an issuer of a lower-rated or unrated obligation to pay principal and interest when due is typically less certain than for an issuer of a higher-rated obligation, lower-rated and unrated obligations are generally more vulnerable than higher- rated obligations to default, to ratings downgrades, and to liquidity risk. Debt obligations backed by so-called “subprime” mortgages may also be subject to a greater risk of default or downgrade. Debt obligations issued by the U.S. government or its agencies, instrumentalities and government sponsored enterprises are also subject to credit risk. Securities backed by the full faith and credit of the U.S. government, such as U.S. Treasury obligations, are commonly regarded as having small exposure to credit risk. Obligations of certain U.S. agencies, instrumentalities and enterprises (sometimes referred to as “agency obligations”) are not direct obligations of the U.S. government, may not be backed by the full faith and credit of the U.S. government, and may have a greater exposure to credit risk.
Retail | Thornburg Strategic Income Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Strategic Income Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of debt obligations of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retail | Thornburg Strategic Income Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retail | Thornburg Strategic Income Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in the debt obligations of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection. In addition, some foreign government debt obligations may be subject to default, delays in payment, adverse legislation or government action, or could be downgraded by ratings agencies.
Retail | Thornburg Strategic Income Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices. The market for lower-rated and unrated debt obligations (including particularly “junk” or “high yield” bonds) and debt obligations backed by so-called “subprime” mortgages may be less liquid than the market for other obligations, making it difficult for the Fund to value its investment in a lower-rated or unrated obligation or to sell the investment in a timely manner or at an acceptable price.
Retail | Thornburg Strategic Income Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Strategic Income Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. This effect is typically more pronounced for lower-rated and unrated debt obligations (including particularly “junk” or “high yield” bonds), the value of which may fluctuate more significantly in response to poor economic growth or other changes in market conditions, political, economic and legal developments. The market value of any zero coupon bonds or “stripped” securities that the Fund may purchase will typically be more volatile than the value of a comparable, interest-paying bond. Additionally, zero coupon bonds and “stripped” securities are subject to the risk that the Fund may have to recognize income on its investment and make distributions to shareholders before it has received any cash payments on its investment.
Retail | Thornburg Strategic Income Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Strategic Income Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a debt obligation may decline in response to developments affecting the specific issuer of the obligation or security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retail | Thornburg Strategic Income Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments.
Retail | Thornburg Strategic Income Fund | Convertible Debt Obligation Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Convertible Debt Obligation Risk – The market value of a convertible debt obligation may vary with changes in prevailing interest rates and changing evaluations of the ability of the issuer to meet principal and interest payments. The market value of a convertible debt obligation may also vary in accordance with the market value of the underlying stock. As a result, convertible debt obligations held by the Fund will tend to perform more like equity securities when the underlying stock price is high (because it is assumed that the Fund will convert the obligation), and more like non-convertible debt obligations when the underlying stock price is low (because it is assumed that the Fund will not convert the obligation). Because its market value can be influenced by several factors, a convertible debt obligation will not be as sensitive to interest rate changes as a similar non-convertible debt obligation, and generally will have less potential for gain or loss than the underlying stock.
Retail | Thornburg Strategic Income Fund | Foreign Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Government Obligations Risk – Debt obligations may be issued by foreign governments and their agencies and instrumentalities, including the governments of developing countries and “supra-national” entities such as the International Bank for Reconstruction and Development. The Fund’s investments in these foreign debt obligations may be denominated in U.S. dollars or in foreign currencies. These securities, even if denominated in U.S. dollars, may be affected significantly by fluctuations in the value of foreign currencies, and the value of these securities in U.S. dollars may decline even if the securities increase in value in their home country. The governmental issuers of these debt obligations may be less willing or able than the U.S. to repay principal and interest when due, and they may require that the terms for payment be renegotiated. In some countries there may be political instability or insufficient government supervision of markets, and the legal protections for the

Fund’s investments could be subject to unfavorable judicial or administrative changes. These risks may be more pronounced for the Fund’s investments in debt obligations issued by developing countries.
Retail | Thornburg Strategic Income Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retail | Thornburg Strategic Income Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. This effect is also typically more pronounced for mortgage- and other asset-backed securities, the value of which may fluctuate more significantly in response to interest rate changes. When interest rates decrease, the Fund’s dividends may decline.
Retail | Thornburg Strategic Income Fund | Prepayment and Extension Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Prepayment and Extension Risk – When market interest rates decline, certain debt obligations held by the Fund may be repaid more quickly than anticipated, requiring the Fund to reinvest the proceeds of those repayments in obligations which bear a lower interest rate. Conversely, when market interest rates increase, certain debt obligations held by the Fund may be repaid more slowly than anticipated, causing assets of the Fund to remain invested in relatively lower yielding obligations. These risks may be more pronounced for the Fund’s investments in mortgage-backed and asset-backed securities.
Retail | Thornburg Strategic Income Fund | U.S. Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

U.S. Government Obligations Risk – U.S. government obligations are subject to the same risks affecting other debt obligations. Although securities backed by the full faith credit of the U.S. government are commonly regarded as having relatively less risk of default, it is possible that the U.S. government may be unwilling or unable to repay principal and interest when due and may require that the terms for payment be renegotiated. Further obligations that are backed by the full faith and credit of the U.S. government remain subject to the other general risks applicable to debt obligations, such as market risks, liquidity risks, and interest rate risks, and may be subject to ratings downgrades. U.S. government obligations also include obligations of U.S. government agencies, instrumentalities, and government-sponsored enterprises, commonly referred to as “agency obligations.” Some agency obligations are backed by the full faith and credit of the U.S. government, but other agency obligations have no specific backing or only limited support from the agency’s authority to borrow from the U.S. government or the discretionary authority of the Treasury to purchase obligations of the issuing agency.
Retail | Thornburg Strategic Income Fund | Structured Products Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Structured Products Risk – Investments in securities that are backed by, or represent interests in, an underlying pool of securities or other assets, including investments in mortgage- and asset-backed securities and in collateralized mortgage obligations and collateralized debt obligations, involve the risks associated with the underlying assets (e.g., the risk of default by mortgagors whose mortgages are included in a mortgage-backed security or collateralized mortgage obligation), and may also involve different or greater risks, including the risk that distributions from the underlying assets will be inadequate to make interest or other payments to the Fund, the risk that the issuer of the securities will fail to administer the underlying assets properly or become insolvent, and the risk that the securities will be less liquid than other Fund investments.
Retail | Thornburg Strategic Income Fund | Zero Coupon Bonds and Stripped Securities Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Zero Coupon Bonds and Stripped Securities Risk – Zero coupon bonds are corporate or government-issued debt obligations that do not provide for periodic or “coupon” payments of interest, and that are issued at a substantial discount to their face value. The buyer of a zero coupon bond realizes a stated rate of return determined by the gradual accretion in the value of the security. A “stripped” security is a debt obligation that has been transformed into a zero coupon bond by creating a separate, new security comprised of the separate income component of the debt obligation (commonly referred to as an “income only” or “I/O” security) or the separate principal component of the debt obligation (commonly referred to as a “principal only” or “P/O” security). Because zero coupon bonds do not provide for periodic payments of interest, their value is generally more volatile than the value of a comparable, interest-paying bond. The Fund may also have to recognize income on the bond and make distributions to shareholders before it has received any cash payments on the bond. To generate the cash necessary to satisfy such distributions, the Fund may have to sell portfolio securities that it otherwise might have continued to hold or use cash flows from other sources, including the proceeds from the sale of Fund shares.
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TSIAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [40]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.21%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.00%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.00%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 547
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 754
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 978
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,620
Annual Return 2015 rr_AnnualReturn2015 (2.34%)
Annual Return 2016 rr_AnnualReturn2016 7.69%
Annual Return 2017 rr_AnnualReturn2017 6.01%
Annual Return 2018 rr_AnnualReturn2018 0.30%
Annual Return 2019 rr_AnnualReturn2019 7.55%
Annual Return 2020 rr_AnnualReturn2020 7.86%
Annual Return 2021 rr_AnnualReturn2021 2.43%
Annual Return 2022 rr_AnnualReturn2022 (6.62%)
Annual Return 2023 rr_AnnualReturn2023 7.28%
Annual Return 2024 rr_AnnualReturn2024 4.45%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 7.98%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (5.71%)
1 Year rr_AverageAnnualReturnYear01 (0.27%)
5 Years rr_AverageAnnualReturnYear05 2.00%
10 Years rr_AverageAnnualReturnYear10 2.88%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (2.17%)
5 Years rr_AverageAnnualReturnYear05 0.40%
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (0.18%)
5 Years rr_AverageAnnualReturnYear05 0.83%
10 Years rr_AverageAnnualReturnYear10 1.51%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class A | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class A | Bloomberg U.S. Universal Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.04%
5 Years rr_AverageAnnualReturnYear05 0.06%
10 Years rr_AverageAnnualReturnYear10 1.73%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class A | Blended Benchmark (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.57%
5 Years rr_AverageAnnualReturnYear05 2.07%
10 Years rr_AverageAnnualReturnYear10 3.17%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TSICX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00% [41]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.21%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.75%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.75%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 278
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 551
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 949
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,062
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 178
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 551
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 949
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,062
1 Year rr_AverageAnnualReturnYear01 2.59%
5 Years rr_AverageAnnualReturnYear05 2.19%
10 Years rr_AverageAnnualReturnYear10 2.62%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class C | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class C | Bloomberg U.S. Universal Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.04%
5 Years rr_AverageAnnualReturnYear05 0.06%
10 Years rr_AverageAnnualReturnYear10 1.73%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class C | Blended Benchmark (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.57%
5 Years rr_AverageAnnualReturnYear05 2.07%
10 Years rr_AverageAnnualReturnYear10 3.17%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TSIIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.20%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.74%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.14%) [42]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.60%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 61
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 222
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 398
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 905
1 Year rr_AverageAnnualReturnYear01 4.83%
5 Years rr_AverageAnnualReturnYear05 3.33%
10 Years rr_AverageAnnualReturnYear10 3.73%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class I | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class I | Bloomberg U.S. Universal Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.04%
5 Years rr_AverageAnnualReturnYear05 0.06%
10 Years rr_AverageAnnualReturnYear10 1.73%
Retail | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class I | Blended Benchmark (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.57%
5 Years rr_AverageAnnualReturnYear05 2.07%
10 Years rr_AverageAnnualReturnYear10 3.17%
Retail | Thornburg Short Duration Municipal Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Short Duration Municipal Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks current income exempt from federal income tax, consistent with preservation of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 63.53% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 63.53%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year) your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its primary goal by investing principally in a laddered maturity portfolio of municipal obligations issued by states and state agencies, local governments and their agencies and by United States territories and possessions. Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s portfolio. Investment decisions are based upon outlooks for interest rates and securities markets, the supply of municipal debt obligations, and analysis of specific securities. The Fund invests primarily in obligations and participations in obligations which are rated by a nationally recognized statistical rating organization at the time of purchase as investment grade or, if unrated, are issued by obligors which Thornburg determines have comparable investment grade obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding investment grade obligations. The Fund may invest up to 20 percent of its net assets, plus the amount of any borrowings for investment purposes, in lower-quality municipal debt obligations rated by a nationally recognized statistical rating organization at the time of purchase as below investment grade (sometimes called “junk” bonds or “high yield” bonds) or, if unrated, issued by obligors which Thornburg determines have comparable below investment grade municipal obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding below investment grade obligations. “Participations” are undivided interests in pools of securities where the underlying credit support passes through to the participants. The Fund’s portfolio is “laddered” by investing in obligations of different maturities so that some obligations mature during each of the coming years.

Because the magnitude of changes in value of interest-bearing obligations is greater for obligations with longer durations given an equivalent change in interest rates, the Fund seeks to reduce changes in its share value compared to longer duration fixed income portfolios by maintaining a portfolio of investments with a dollar-weighted average duration of normally no more than three years. Duration is a measure of estimated sensitivity to interest rate changes, and a debt obligation or a portfolio of obligations with a higher duration will typically be more sensitive to interest rate changes than an obligation or a portfolio with a lower duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example, an obligation with a duration of 3 would be expected to change in price by approximately 3% in response to a 1% change in interest rates. During temporary periods the Fund’s average duration and average portfolio maturity may be further reduced for defensive purposes. There is no limitation on the duration or maturity of any specific security the Fund may purchase. The Fund may dispose of any security before it matures. The Fund also attempts to reduce changes in its share value through credit analysis, selection and diversification.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.  The objective of preserving capital may prevent the Fund from obtaining the highest yields available.

The Fund normally invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in municipal obligations the income from which is exempt from the regular federal income tax, though the income on those investments may still be subject to the federal alternative minimum tax (“AMT”). Gains realized on investments held by the Fund and not offset by realized losses will be subject to federal income tax.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Short Duration Municipal Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A and Class I share performance to the ICE BofA U.S. Municipal Securities Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the ICE BofA 1-3 Year U.S. Municipal Securities Index, an additional index that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Short Duration Municipal Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter ended

Highest Quarterly Results

 2.46%

12/31/2023

Lowest Quarterly Results

-2.50%

3/31/2022

The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation, and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation, and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Retail | Thornburg Short Duration Municipal Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retail | Thornburg Short Duration Municipal Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Short Duration Municipal Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If obligations held by the Fund are downgraded by ratings agencies or go into default, or if legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and any dividends paid by the Fund may be reduced. For example, municipal leases held by the Fund may be subject to non-appropriation provisions which permit governmental agencies or issuers to discontinue payments to the Fund under the municipal leases.
Retail | Thornburg Short Duration Municipal Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Short Duration Municipal Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices.
Retail | Thornburg Short Duration Municipal Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Short Duration Municipal Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. This effect is typically more pronounced for the Fund’s investments in lower rated and unrated municipal obligations, the value of which may fluctuate more significant in response to poor economic growth or other changes in market conditions, political, economic and legal developments, and developments affecting specific issuers.
Retail | Thornburg Short Duration Municipal Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Short Duration Municipal Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retail | Thornburg Short Duration Municipal Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. When interest rates decrease, the Fund’s dividends may decline. Decreases in market interest rates may also result in prepayments of obligations the Fund acquires, requiring the Fund to reinvest at lower interest rates.
Retail | Thornburg Short Duration Municipal Fund | Tax Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Tax Risk – The income on the Fund’s municipal obligations could become subject to federal income or state income tax due to noncompliant conduct by issuers, unfavorable legislation or litigation or adverse interpretations by regulatory authorities. All or a portion of the Fund’s distributions that are exempt from regular federal income tax may nevertheless be taken into account for purposes of the federal AMT and state income tax.
Retail | Thornburg Short Duration Municipal Fund | Thornburg Short Duration Municipal Fund Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TLMAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.25%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [43]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.40%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.20%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.63%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.23%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.53%) [44]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.70%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 295
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 555
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 836
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,634
Annual Return 2015 rr_AnnualReturn2015 0.14%
Annual Return 2016 rr_AnnualReturn2016 0.01%
Annual Return 2017 rr_AnnualReturn2017 0.89%
Annual Return 2018 rr_AnnualReturn2018 0.84%
Annual Return 2019 rr_AnnualReturn2019 1.91%
Annual Return 2020 rr_AnnualReturn2020 0.87%
Annual Return 2021 rr_AnnualReturn2021 (0.25%)
Annual Return 2022 rr_AnnualReturn2022 (2.52%)
Annual Return 2023 rr_AnnualReturn2023 3.46%
Annual Return 2024 rr_AnnualReturn2024 2.53%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 2.46%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (2.50%)
1 Year rr_AverageAnnualReturnYear01 0.19%
5 Years rr_AverageAnnualReturnYear05 0.49%
10 Years rr_AverageAnnualReturnYear10 0.62%
Retail | Thornburg Short Duration Municipal Fund | Thornburg Short Duration Municipal Fund Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.18%
5 Years rr_AverageAnnualReturnYear05 0.49%
10 Years rr_AverageAnnualReturnYear10 0.62%
Retail | Thornburg Short Duration Municipal Fund | Thornburg Short Duration Municipal Fund Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.35%
5 Years rr_AverageAnnualReturnYear05 0.74%
10 Years rr_AverageAnnualReturnYear10 0.74%
Retail | Thornburg Short Duration Municipal Fund | Thornburg Short Duration Municipal Fund Class A | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg Short Duration Municipal Fund | Thornburg Short Duration Municipal Fund Class A | ICE BofA 1-3 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.63%
5 Years rr_AverageAnnualReturnYear05 1.27%
10 Years rr_AverageAnnualReturnYear10 1.30%
Retail | Thornburg Short Duration Municipal Fund | Thornburg Short Duration Municipal Fund Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TLMIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.40%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.23%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.63%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.13%) [44]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 51
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 189
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 338
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 774
1 Year rr_AverageAnnualReturnYear01 2.74%
5 Years rr_AverageAnnualReturnYear05 1.00%
10 Years rr_AverageAnnualReturnYear10 0.98%
Retail | Thornburg Short Duration Municipal Fund | Thornburg Short Duration Municipal Fund Class I | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg Short Duration Municipal Fund | Thornburg Short Duration Municipal Fund Class I | ICE BofA 1-3 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.63%
5 Years rr_AverageAnnualReturnYear05 1.27%
10 Years rr_AverageAnnualReturnYear10 1.30%
Retail | Thornburg Limited Term Municipal Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Limited Term Municipal Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The primary investment goal of Limited Term Municipal Fund is to obtain as high a level of current income exempt from federal individual income tax as is consistent, in the view of the Fund’s investment advisor, with preservation of capital.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

The secondary goal of the Fund is to reduce expected changes in its share price compared to longer intermediate and long-term bond portfolios.

Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 39.61% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 39.61%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its primary goal by investing principally in a laddered maturity portfolio of municipal obligations issued by states and state agencies, local governments and their agencies and by United States territories and possessions. Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s portfolio. Investment decisions are based upon outlooks for interest rates and securities markets, the supply of municipal debt obligations, and analysis of specific securities. The Fund invests primarily in obligations and participations in obligations which are rated by a nationally recognized statistical rating organization at the time of purchase as investment grade or, if unrated, are issued by obligors which Thornburg determines have comparable investment grade obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding investment grade obligations. The Fund may invest up to 20 percent of its net assets, plus the amount of any borrowings for investment purposes, in lower-quality municipal debt obligations rated by a nationally recognized statistical rating organization at the time of purchase as below investment grade (sometimes called “junk” bonds or “high yield” bonds) or, if unrated, issued by obligors which Thornburg determines have comparable below investment grade municipal obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding below investment grade obligations. “Participations” are undivided interests in pools of securities where the underlying credit support passes through to the participants. The Fund’s portfolio is “laddered” by investing in obligations of different maturities so that some obligations mature during each of the coming years.

Because the magnitude of changes in value of interest-bearing obligations is greater for obligations with longer terms given an equivalent change in interest rates, the Fund seeks to reduce changes in its share value by maintaining a portfolio of investments with a dollar-weighted average maturity normally less than five years. As a result, the Fund also maintains a portfolio of investments having a dollar-weighted average effective duration of normally no more than five years. Duration is a measure of estimated sensitivity to interest rate changes. A portfolio with a longer average effective duration will typically be more sensitive to interest rate changes than a portfolio with a shorter average effective duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example, an obligation with a duration of 5 would be expected to change in price by approximately 5% in response to a 1% change in interest rates. During temporary periods the Fund’s portfolio maturity and average effective duration may be reduced for defensive purposes. There is no limitation on the maturity of any specific security the Fund may purchase. The Fund may dispose of any security before it matures. The Fund also attempts to reduce changes in its share value through credit analysis, selection and diversification.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.  The objective of preserving capital may prevent the Fund from obtaining the highest yields available.

The Fund normally invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in municipal obligations the income from which is exempt from the regular federal income tax, though the income on those investments may still be subject to the federal alternative minimum tax (“AMT”). Gains realized on investments held by the Fund and not offset by realized losses will be subject to federal income tax.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Limited Term Municipal Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C, Class C2 and Class I share performance to the ICE BofA U.S. Municipal Securities Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the ICE BofA 1-10 Year U.S. Municipal Securities Index, an additional index that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Limited Term Municipal Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results 

 4.61%

12/31/2023

Lowest Quarterly Results

-4.32%

3/31/2022

The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.

Retail | Thornburg Limited Term Municipal Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retail | Thornburg Limited Term Municipal Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Limited Term Municipal Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If obligations held by the Fund are downgraded by ratings agencies or go into default, or if legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Lower-rated or unrated obligations held by the Fund may have, or may be perceived to have, greater risk of default and ratings downgrades. For example, municipal leases held by the Fund may be subject to non-appropriation provisions which permit governmental agencies or issuers to discontinue payments to the Fund under the municipal leases.
Retail | Thornburg Limited Term Municipal Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Limited Term Municipal Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices. The market for lower- rated and unrated obligations may be less liquid than the market for other obligations, making it difficult for the Fund to value its investment in a lower-rated or unrated obligation or to sell the investment in a timely manner or at an acceptable price.
Retail | Thornburg Limited Term Municipal Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Limited Term Municipal Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. This effect is typically more pronounced for the Fund’s investments in lower- rated and unrated municipal obligations, the value of which may fluctuate more significantly in response to poor economic growth or other changes in market conditions, political, economic and legal developments, and developments affecting specific issuers.
Retail | Thornburg Limited Term Municipal Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Limited Term Municipal Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retail | Thornburg Limited Term Municipal Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. When interest rates decrease, the Fund’s dividends may decline. Decreases in market interest rates may also result in prepayments of obligations the Fund acquires, requiring the Fund to reinvest at lower interest rates.
Retail | Thornburg Limited Term Municipal Fund | Tax Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Tax Risk – The income on the Fund’s municipal obligations could become subject to federal income or state income tax due to noncompliant conduct by issuers, unfavorable legislation or litigation or adverse interpretations by regulatory authorities. All or a portion of the Fund’s distributions that are exempt from regular federal income tax may nevertheless be taken into account for purposes of the federal AMT and state income tax.
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTMFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.25%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [45]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.33%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.19%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.77%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.77%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 302
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 465
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 643
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,158
Annual Return 2015 rr_AnnualReturn2015 1.50%
Annual Return 2016 rr_AnnualReturn2016 (0.69%)
Annual Return 2017 rr_AnnualReturn2017 2.29%
Annual Return 2018 rr_AnnualReturn2018 0.88%
Annual Return 2019 rr_AnnualReturn2019 3.81%
Annual Return 2020 rr_AnnualReturn2020 2.96%
Annual Return 2021 rr_AnnualReturn2021 (0.19%)
Annual Return 2022 rr_AnnualReturn2022 (5.11%)
Annual Return 2023 rr_AnnualReturn2023 4.29%
Annual Return 2024 rr_AnnualReturn2024 1.30%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.61%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (4.32%)
1 Year rr_AverageAnnualReturnYear01 (1.01%)
5 Years rr_AverageAnnualReturnYear05 0.29%
10 Years rr_AverageAnnualReturnYear10 0.92%
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (1.01%)
5 Years rr_AverageAnnualReturnYear05 0.29%
10 Years rr_AverageAnnualReturnYear10 0.92%
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.63%
5 Years rr_AverageAnnualReturnYear05 0.70%
10 Years rr_AverageAnnualReturnYear10 1.13%
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class A | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class A | ICE BofA 1-10 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.58%
5 Years rr_AverageAnnualReturnYear05 1.06%
10 Years rr_AverageAnnualReturnYear10 1.71%
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTMCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 0.50% [46]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.33%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.21%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.04%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.04%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 156
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 331
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 574
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,271
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 106
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 331
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 574
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,271
1 Year rr_AverageAnnualReturnYear01 0.60%
5 Years rr_AverageAnnualReturnYear05 0.34%
10 Years rr_AverageAnnualReturnYear10 0.82%
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class C | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class C | ICE BofA 1-10 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.58%
5 Years rr_AverageAnnualReturnYear05 1.06%
10 Years rr_AverageAnnualReturnYear10 1.71%
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class C2  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTMQX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 0.65% [46]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.33%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.65%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.74%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.72%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.48%) [47]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.24%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 191
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 495
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 888
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,990
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 126
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 495
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 888
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,990
1 Year rr_AverageAnnualReturnYear01 0.26%
Since Inception rr_AverageAnnualReturnSinceInception (0.35%)
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 01, 2020
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class C2 | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
Since Inception rr_AverageAnnualReturnSinceInception 0.54%
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class C2 | ICE BofA 1-10 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.58%
Since Inception rr_AverageAnnualReturnSinceInception 0.57%
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTMIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.33%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.18%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.51%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.51%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 52
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 164
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 285
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 640
1 Year rr_AverageAnnualReturnYear01 1.56%
5 Years rr_AverageAnnualReturnYear05 0.83%
10 Years rr_AverageAnnualReturnYear10 1.33%
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class I | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg Limited Term Municipal Fund | Thornburg Limited Term Municipal Fund - Class I | ICE BofA 1-10 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.58%
5 Years rr_AverageAnnualReturnYear05 1.06%
10 Years rr_AverageAnnualReturnYear10 1.71%
Retail | Thornburg Intermediate Municipal Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Intermediate Municipal Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The primary investment goal of Intermediate Municipal Fund is to obtain as high a level of current income exempt from federal individual income tax as is consistent, in the view of the Fund’s investment advisor, with preservation of capital.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

The secondary goal of the Fund is to reduce expected changes in its share price compared to long-term bond portfolios.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 29.65% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 29.65%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its primary goal by investing principally in a laddered maturity portfolio of municipal obligations issued by states and state agencies, local governments and their agencies, and by United States territories and possessions. Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s portfolio. Investment decisions are based upon outlooks for interest rates and securities markets, the supply of municipal debt obligations, and analysis of specific securities. The Fund invests primarily in obligations and participations in obligations which are rated by a nationally recognized statistical rating organization at the time of purchase as investment grade or, if unrated, are issued by obligors which Thornburg determines have comparable investment grade obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding investment grade obligations. The Fund may invest up to 20 percent of its net assets, plus the amount of any borrowings for investment purposes, in lower-quality municipal debt obligations rated by a nationally recognized statistical rating organization at the time of purchase as below investment grade (sometimes called “junk” bonds or “high yield” bonds) or, if unrated, issued by obligors which Thornburg determines have comparable below investment grade municipal obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding below investment grade obligations. “Participations” are undivided interests in pools of securities where the underlying credit support passes through to the participants. The Fund’s portfolio is “laddered” by investing in obligations of different maturities so that some obligations mature during each of the coming years.

The Fund seeks to maintain a portfolio of investments having a dollar-weighted average effective duration of normally three to ten years. Duration is a measure of estimated sensitivity to interest rate changes. A portfolio with a longer average effective duration will typically be more sensitive to interest rate changes than a portfolio with a shorter average effective duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example, an obligation with a duration of 10 would be expected to change in price by approximately 10% in response to a 1% change in interest rates. During temporary periods the Fund’s average effective duration may be reduced for defensive purposes. There is no limitation on the duration or maturity of any specific security the Fund may purchase. The Fund may dispose of any security before it matures. The Fund also attempts to reduce changes in its share value through credit analysis, selection and diversification.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals. The objective of preserving capital may prevent the Fund from obtaining the highest yields available.

The Fund normally invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in municipal obligations the income from which is exempt from the regular federal income tax, though the income on those investments may still be subject to the federal alternative minimum tax (“AMT”). Gains realized on investments held by the Fund and not offset by realized losses will be subject to federal income tax.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Intermediate Municipal Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C, Class C2 and Class I share performance to the ICE BofA U.S. Municipal Securities Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the ICE BofA 3-15 Year U.S. Municipal Securities Index, an additional index that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Intermediate Municipal Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 5.69%

12/31/2023

Lowest Quarterly Results

-5.27%

3/31/2022

The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.

Retail | Thornburg Intermediate Municipal Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retail | Thornburg Intermediate Municipal Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Intermediate Municipal Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If obligations held by the Fund are downgraded by ratings agencies or go into default, or if legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Lower-rated or unrated obligations held by the Fund may have, or may be perceived to have, greater risk of default and ratings downgrades. For example, municipal leases held by the Fund may be subject to non-appropriation provisions which permit governmental agencies or issuers to discontinue payments to the Fund under the municipal leases.
Retail | Thornburg Intermediate Municipal Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Intermediate Municipal Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices. The market for lower-rated and unrated obligations may be less liquid than the market for other obligations, making it difficult for the Fund to value its investment in a lower-rated or unrated obligation or to sell the investment in a timely manner or at an acceptable price.
Retail | Thornburg Intermediate Municipal Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Intermediate Municipal Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. This effect is typically more pronounced for the Fund’s investments in lower- rated and unrated municipal obligations, the value of which may fluctuate more significantly in response to poor economic growth or other changes in market conditions, political, economic and legal developments, and developments affecting specific issuers.
Retail | Thornburg Intermediate Municipal Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Intermediate Municipal Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retail | Thornburg Intermediate Municipal Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. When interest rates decrease, the Fund’s dividends may decline. Decreases in market interest rates may also result in prepayments of obligations the Fund acquires, requiring the Fund to reinvest at lower interest rates.
Retail | Thornburg Intermediate Municipal Fund | Tax Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Tax Risk – The income on the Fund’s municipal obligations could become subject to federal income or state income tax due to noncompliant conduct by issuers, unfavorable legislation or litigation or adverse interpretations by regulatory authorities. All or a portion of the Fund’s distributions that are exempt from regular federal income tax may nevertheless be taken into account for purposes of the federal AMT and state income tax.
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THIMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.00%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [48]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.48%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.20%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.93%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.21%) [49]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.72%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 272
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 470
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 684
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,301
Annual Return 2015 rr_AnnualReturn2015 2.11%
Annual Return 2016 rr_AnnualReturn2016 (0.50%)
Annual Return 2017 rr_AnnualReturn2017 3.61%
Annual Return 2018 rr_AnnualReturn2018 0.56%
Annual Return 2019 rr_AnnualReturn2019 5.64%
Annual Return 2020 rr_AnnualReturn2020 3.81%
Annual Return 2021 rr_AnnualReturn2021 0.99%
Annual Return 2022 rr_AnnualReturn2022 (6.41%)
Annual Return 2023 rr_AnnualReturn2023 5.45%
Annual Return 2024 rr_AnnualReturn2024 1.84%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 5.69%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (5.27%)
1 Year rr_AverageAnnualReturnYear01 (0.18%)
5 Years rr_AverageAnnualReturnYear05 0.65%
10 Years rr_AverageAnnualReturnYear10 1.45%
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (0.18%)
5 Years rr_AverageAnnualReturnYear05 0.65%
10 Years rr_AverageAnnualReturnYear10 1.45%
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.27%
5 Years rr_AverageAnnualReturnYear05 1.13%
10 Years rr_AverageAnnualReturnYear10 1.68%
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class A | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class A | ICE BofA 3-15 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.99%
5 Years rr_AverageAnnualReturnYear05 1.04%
10 Years rr_AverageAnnualReturnYear10 2.12%
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THMCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 0.60% [50]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.48%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.60%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.31%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.39%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.30%) [49]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.09%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 171
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 411
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 732
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,643
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 111
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 411
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 732
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,643
1 Year rr_AverageAnnualReturnYear01 0.88%
5 Years rr_AverageAnnualReturnYear05 0.68%
10 Years rr_AverageAnnualReturnYear10 1.30%
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class C | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class C | ICE BofA 3-15 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.99%
5 Years rr_AverageAnnualReturnYear05 1.04%
10 Years rr_AverageAnnualReturnYear10 2.12%
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class C2  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THMQX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 0.65% [50]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.48%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.65%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.93%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.06%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.97%) [49]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.09%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 176
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 552
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,019
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,312
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 111
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 552
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,019
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,312
1 Year rr_AverageAnnualReturnYear01 0.83%
Since Inception rr_AverageAnnualReturnSinceInception 0.31%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 01, 2020
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class C2 | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
Since Inception rr_AverageAnnualReturnSinceInception 0.54%
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class C2 | ICE BofA 3-15 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.99%
Since Inception rr_AverageAnnualReturnSinceInception 0.44%
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THMIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.48%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.19%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.67%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.19%) [49]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.48%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 49
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 195
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 354
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 817
1 Year rr_AverageAnnualReturnYear01 2.01%
5 Years rr_AverageAnnualReturnYear05 1.29%
10 Years rr_AverageAnnualReturnYear10 1.91%
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class I | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg Intermediate Municipal Fund | Thornburg Intermediate Municipal Fund - Class I | ICE BofA 3-15 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.99%
5 Years rr_AverageAnnualReturnYear05 1.04%
10 Years rr_AverageAnnualReturnYear10 2.12%
Retail | Thornburg Strategic Municipal Income Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Strategic Municipal Income Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks a high level of current income exempt from federal individual income tax.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 23.43% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 23.43%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s investments in pursuing the Fund’s investment goal. The Fund invests principally in a portfolio of municipal obligations issued by states and state agencies, local governments and their agencies, and by United States territories and possessions. Investment decisions are based upon outlooks for interest rates and securities markets, the supply of municipal debt obligations, the difference in yields between higher and lower-rated obligations, and analysis of specific obligations. The Fund invests in obligations and participations in obligations of any credit quality. The Fund may invest up to 50 percent of its net assets, plus the amount of any borrowings for investment purposes, in lower-quality debt obligations rated by a nationally recognized statistical rating organization at the time of purchase as below investment grade (sometimes called “junk” bonds or “high yield” bonds) or, if unrated, issued by obligors which Thornburg determines have comparable below investment grade obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding below investment grade obligations. The Fund may also invest in obligations that are in default at the time of purchase. “Participations” are undivided interests in pools of securities where the underlying credit support passes through to the participants.

The Fund may invest in municipal obligations of any maturity, but seeks to maintain a portfolio of investments having a dollar-weighted average effective duration of normally one to ten years. Duration is a measure of estimated sensitivity to interest rate changes. A portfolio with a longer average effective duration will typically be more sensitive to interest rate changes than a portfolio with a shorter average effective duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example, an obligation with a duration of 10 would be expected to change in price by approximately 10% in response to a 1% change in interest rates. During temporary periods the Fund’s average effective duration and average portfolio maturity may be reduced for defensive purposes. There is no limitation on the duration or maturity of any specific security the Fund may purchase. The Fund may dispose of any security before it matures. The Fund attempts to reduce changes in its share value through credit analysis, selection and diversification.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to

changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.  The objective of preserving capital may prevent the Fund from obtaining the highest yields available.

The Fund normally invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in municipal obligations the income from which is exempt from the regular federal income tax, though the income on those investments may still be subject to the federal alternative minimum tax (“AMT”). Gains realized on investments held by the Fund and not offset by realized losses will be subject to federal income tax.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Strategic Municipal Income Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C and Class I share performance to the ICE BofA U.S. Municipal Securities Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. This index is not actively managed and is not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Strategic Municipal Income Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 6.46%

12/31/2023

Lowest Quarterly Results

-5.52%

3/31/2022

The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Retail | Thornburg Strategic Municipal Income Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retail | Thornburg Strategic Municipal Income Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg Strategic Municipal Income Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If obligations held by the Fund are downgraded by ratings agencies or go into default, or if legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Because the ability of an issuer of a lower-rated or unrated obligation to pay principal and interest when due is typically less certain than for an issuer of a higher- rated obligation, lower-rated and unrated obligations are generally more vulnerable than higher-rated obligations to default, to ratings downgrades, and to liquidity risk. For example, municipal leases held by the Fund may be subject to non-appropriation provisions which permit governmental agencies or issuers to discontinue payments to the Fund under the municipal leases.
Retail | Thornburg Strategic Municipal Income Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg Strategic Municipal Income Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices. The market for lower-rated and unrated obligations (including particularly “junk” or “high yield” bonds) may be less liquid than the market for other obligations, making it difficult for the Fund to value its investment in a lower-rated or unrated obligation or to sell the investment in a timely manner or at an acceptable price.
Retail | Thornburg Strategic Municipal Income Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg Strategic Municipal Income Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. This effect is typically more pronounced for the Fund’s investments in lower-rated and unrated municipal obligations (including particularly “junk” or “high yield” bonds), the value of which may

fluctuate more significantly in response to poor economic growth or other changes in market conditions, political, economic and legal developments, and developments affecting specific issuers.
Retail | Thornburg Strategic Municipal Income Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg Strategic Municipal Income Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retail | Thornburg Strategic Municipal Income Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. When interest rates decrease, the Fund’s dividends may decline. Decreases in market interest rates may also result in prepayments of obligations the Fund acquires, requiring the Fund to reinvest at lower interest rates.
Retail | Thornburg Strategic Municipal Income Fund | Tax Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Tax Risk – The income on the Fund’s municipal obligations could become subject to federal income or state income tax due to noncompliant conduct by issuers, unfavorable legislation or litigation or adverse interpretations by regulatory authorities. All or a portion of the Fund’s distributions that are exempt from regular federal income tax may nevertheless be taken into account for purposes of the federal AMT and state income tax.
Retail | Thornburg Strategic Municipal Income Fund | Thornburg Strategic Municipal Income Fund Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TSSAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.00%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [51]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.27%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.27%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.46%) [52]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.81%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 281
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 550
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 840
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,664
Annual Return 2015 rr_AnnualReturn2015 2.23%
Annual Return 2016 rr_AnnualReturn2016 (0.38%)
Annual Return 2017 rr_AnnualReturn2017 4.04%
Annual Return 2018 rr_AnnualReturn2018 0.74%
Annual Return 2019 rr_AnnualReturn2019 5.59%
Annual Return 2020 rr_AnnualReturn2020 3.79%
Annual Return 2021 rr_AnnualReturn2021 1.22%
Annual Return 2022 rr_AnnualReturn2022 (8.23%)
Annual Return 2023 rr_AnnualReturn2023 5.89%
Annual Return 2024 rr_AnnualReturn2024 2.87%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 6.46%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (5.52%)
1 Year rr_AverageAnnualReturnYear01 0.81%
5 Years rr_AverageAnnualReturnYear05 0.58%
10 Years rr_AverageAnnualReturnYear10 1.50%
Retail | Thornburg Strategic Municipal Income Fund | Thornburg Strategic Municipal Income Fund Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.81%
5 Years rr_AverageAnnualReturnYear05 0.58%
10 Years rr_AverageAnnualReturnYear10 1.50%
Retail | Thornburg Strategic Municipal Income Fund | Thornburg Strategic Municipal Income Fund Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.91%
5 Years rr_AverageAnnualReturnYear05 1.06%
10 Years rr_AverageAnnualReturnYear10 1.73%
Retail | Thornburg Strategic Municipal Income Fund | Thornburg Strategic Municipal Income Fund Class A | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg Strategic Municipal Income Fund | Thornburg Strategic Municipal Income Fund Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TSSCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 0.60% [53]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.60%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.62%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.97%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.69%) [52]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.28%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 190
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 552
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 999
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,240
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 130
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 552
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 999
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,240
1 Year rr_AverageAnnualReturnYear01 1.72%
5 Years rr_AverageAnnualReturnYear05 0.51%
10 Years rr_AverageAnnualReturnYear10 1.25%
Retail | Thornburg Strategic Municipal Income Fund | Thornburg Strategic Municipal Income Fund Class C | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg Strategic Municipal Income Fund | Thornburg Strategic Municipal Income Fund Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TSSIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.26%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.01%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.42%) [52]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.59%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 60
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 280
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 517
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,198
1 Year rr_AverageAnnualReturnYear01 3.10%
5 Years rr_AverageAnnualReturnYear05 1.21%
10 Years rr_AverageAnnualReturnYear10 1.94%
Retail | Thornburg Strategic Municipal Income Fund | Thornburg Strategic Municipal Income Fund Class I | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg California Limited Term Municipal Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Limited Term California Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The primary investment goal of Limited Term California Fund is to obtain as high a level of current income exempt from federal and California state individual income taxes as is consistent, in the view of the Fund’s investment advisor, with preservation of capital.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

The secondary goal of the Fund is to reduce expected changes in its share price compared to longer intermediate and long-term bond portfolios.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 46.36% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 46.36%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock

You would pay the following expenses if you did not redeem your Class C shares:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its primary goal by investing principally in a laddered maturity portfolio of municipal obligations issued by the State of California and its agencies, and by California local governments and their agencies. Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s portfolio. Investment decisions are based upon outlooks for interest rates and securities markets, the supply of municipal debt obligations, and analysis of specific securities. The Fund invests primarily in obligations and participations in obligations which are rated by a nationally recognized statistical rating organization at the time of purchase as investment grade or, if unrated, are issued by obligors which Thornburg determines have comparable investment grade obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding investment grade obligations. The Fund may invest up to 20 percent of its net assets, plus the amount of any borrowings for investment purposes, in lower-quality municipal debt obligations rated by a nationally recognized statistical rating organization at the time of purchase as below investment grade (sometimes called “junk” bonds or “high yield” bonds) or, if unrated, issued by obligors which Thornburg determines have comparable below investment grade municipal obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding below investment grade obligations. “Participations” are undivided interests in pools of securities where the underlying credit support passes through to the participants. The Fund may invest in obligations issued by United States territories and possessions. The Fund’s portfolio is “laddered” by investing in obligations of different maturities so that some obligations mature during each of the coming years.

Because the magnitude of changes in value of interest-bearing obligations is greater for obligations with longer terms given an equivalent change in interest rates, the Fund seeks to reduce changes in its share value by maintaining a portfolio of investments with a dollar-weighted average maturity normally less than five years. As a result, the Fund also maintains a portfolio of investments having a dollar-weighted average effective duration of normally no more than five years. Duration is a measure of estimated sensitivity to interest rate changes. A portfolio with a longer average effective duration will typically be more sensitive to interest rate changes than a portfolio with a shorter average effective duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example, an obligation with a duration of 5 would be expected to change in price by approximately 5% in response to a 1% change in interest rates. During temporary periods the Fund’s portfolio maturity and average effective duration may be

reduced for defensive purposes. There is no limitation on the maturity of any specific security the Fund may purchase. The Fund may dispose of any security before it matures. The Fund also attempts to reduce changes in its share value through credit analysis, selection and diversification.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals. The objective of preserving capital may prevent the Fund from obtaining the highest yields available.

The Fund normally invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in municipal obligations originating in California, the income from which is exempt from regular federal or California income taxes, though the income on those investments may still be subject to the federal alternative minimum tax (“AMT”). Gains realized on investments held by the Fund and not offset by realized losses will be subject to federal income tax.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Limited Term California Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class C, Class C2 and Class I share performance to the ICE BofA U.S. Municipal Securities Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The ICE BofA 1-10 Year U.S. Municipal Securities Index was removed as the Fund’s benchmark index effective September 30, 2024. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Limited Term California Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 4.30%

12/31/2023

Lowest Quarterly Results

-3.99%

3/31/2022

The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.

Retail | Thornburg California Limited Term Municipal Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retail | Thornburg California Limited Term Municipal Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg California Limited Term Municipal Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If obligations held by the Fund are downgraded by ratings agencies or go into default, or if legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Lower-rated or unrated obligations held by the Fund may have, or may be perceived to have, greater risk of default and ratings downgrades. For example, municipal leases held by the Fund may be subject to non-appropriation provisions which permit governmental agencies or issuers to discontinue payments to the Fund under the municipal leases.
Retail | Thornburg California Limited Term Municipal Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg California Limited Term Municipal Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices. The market for lower- rated and unrated obligations may be less liquid than the market for other obligations, making it difficult for the Fund to value its investment in a lower-rated or unrated obligation or to sell the investment in a timely manner or at an acceptable price.
Retail | Thornburg California Limited Term Municipal Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg California Limited Term Municipal Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. This effect is typically more pronounced for the Fund’s investments in lower- rated and unrated municipal obligations, the value of which may fluctuate more significant in response to poor economic growth or other changes in market conditions, political, economic and legal developments, and developments affecting specific issuers.
Retail | Thornburg California Limited Term Municipal Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg California Limited Term Municipal Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retail | Thornburg California Limited Term Municipal Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. When interest rates decrease, the Fund’s dividends may decline. Decreases in market interest rates may also result in prepayments of obligations the Fund acquires, requiring the Fund to reinvest at lower interest rates.
Retail | Thornburg California Limited Term Municipal Fund | Tax Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Tax Risk – The income on the Fund’s municipal obligations could become subject to federal income or state income tax due to noncompliant conduct by issuers, unfavorable legislation or litigation or adverse interpretations by regulatory authorities. All or a portion of the Fund’s distributions that are exempt from regular federal income tax may nevertheless be taken into account for purposes of the federal AMT and state income tax.
Retail | Thornburg California Limited Term Municipal Fund | Single State Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Single State Risk – Because the Fund invests primarily in obligations originating in California, the Fund’s share value may be more sensitive to adverse economic, political or regulatory developments in that state. Budgetary concerns, decreased revenues, and adverse conditions significant to a sector of the state, municipalities within the state, or local economies may negatively affect the ability of state and local issuers to make full and timely principal or interest payments on their debt obligations.
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTCAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.25%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [54]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.50%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.21%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.96%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.22%) [55]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.74%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 299
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 503
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 723
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,357
Annual Return 2015 rr_AnnualReturn2015 1.66%
Annual Return 2016 rr_AnnualReturn2016 (0.99%)
Annual Return 2017 rr_AnnualReturn2017 2.05%
Annual Return 2018 rr_AnnualReturn2018 0.52%
Annual Return 2019 rr_AnnualReturn2019 3.20%
Annual Return 2020 rr_AnnualReturn2020 1.91%
Annual Return 2021 rr_AnnualReturn2021 (0.41%)
Annual Return 2022 rr_AnnualReturn2022 (4.46%)
Annual Return 2023 rr_AnnualReturn2023 4.17%
Annual Return 2024 rr_AnnualReturn2024 1.32%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.30%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.99%)
1 Year rr_AverageAnnualReturnYear01 (0.96%)
5 Years rr_AverageAnnualReturnYear05 0.16%
10 Years rr_AverageAnnualReturnYear10 0.72%
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (0.96%)
5 Years rr_AverageAnnualReturnYear05 0.16%
10 Years rr_AverageAnnualReturnYear10 0.72%
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.58%
5 Years rr_AverageAnnualReturnYear05 0.55%
10 Years rr_AverageAnnualReturnYear10 0.93%
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class A | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class A | ICE BofA 1-10 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.58%
5 Years rr_AverageAnnualReturnYear05 1.06%
10 Years rr_AverageAnnualReturnYear10 1.71%
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTCCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 0.50% [56]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.50%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.70%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.70%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.68%) [55]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.02%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 154
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 469
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 859
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,952
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 104
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 469
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 859
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,952
1 Year rr_AverageAnnualReturnYear01 0.54%
5 Years rr_AverageAnnualReturnYear05 0.18%
10 Years rr_AverageAnnualReturnYear10 0.59%
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class C | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class C | ICE BofA 1-10 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.58%
5 Years rr_AverageAnnualReturnYear05 1.06%
10 Years rr_AverageAnnualReturnYear10 1.71%
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class C2  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTCQX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 0.65% [56]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.50%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.65%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.74%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.89%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (1.87%) [55]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.02%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 169
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 718
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,358
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 3,079
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 104
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 718
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,358
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 3,079
1 Year rr_AverageAnnualReturnYear01 0.40%
Since Inception rr_AverageAnnualReturnSinceInception (0.08%)
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 01, 2020
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class C2 | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
Since Inception rr_AverageAnnualReturnSinceInception 0.54%
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class C2 | ICE BofA 1-10 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.58%
Since Inception rr_AverageAnnualReturnSinceInception 0.57%
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTCIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.50%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.21%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.71%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.22%) [55]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.49%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 50
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 205
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 373
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 862
1 Year rr_AverageAnnualReturnYear01 1.58%
5 Years rr_AverageAnnualReturnYear05 0.72%
10 Years rr_AverageAnnualReturnYear10 1.13%
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class I | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg California Limited Term Municipal Fund | Thornburg California Limited Term Municipal Fund - Class I | ICE BofA 1-10 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.58%
5 Years rr_AverageAnnualReturnYear05 1.06%
10 Years rr_AverageAnnualReturnYear10 1.71%
Retail | Thornburg New Mexico Intermediate Municipal Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Intermediate New Mexico Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The primary investment goal of Intermediate New Mexico Fund is to obtain as high a level of current income exempt from federal and New Mexico state individual income taxes as is consistent, in the view of the Fund’s investment advisor, with preservation of capital.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

The secondary goal of the Fund is to reduce expected changes in its share price compared to long-term bond portfolios.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 19.49% of the average value of its portfolio.

Portfolio Turnover, Rate rr_PortfolioTurnoverRate 19.49%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year) your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its primary goal by investing principally in a laddered maturity portfolio of municipal obligations issued by the State of New Mexico and its agencies, and by New Mexico local governments and their agencies. Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s portfolio. Investment decisions are based upon outlooks for interest rates and securities markets, the supply of municipal debt obligations, and analysis of specific securities. The Fund invests primarily in obligations and participations in obligations which are rated by a nationally recognized statistical rating organization at the time of purchase as investment grade or, if unrated, are issued by obligors which Thornburg determines have comparable investment grade obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding investment grade obligations. The Fund may invest up to 20 percent of its net assets, plus the amount of any borrowings for investment purposes, in lower-quality municipal debt obligations rated by a nationally recognized statistical rating organization at the time of purchase as below investment grade (sometimes called “junk” bonds or “high yield” bonds) or, if unrated, issued by obligors which Thornburg determines have comparable below investment grade municipal obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding below investment grade obligations. “Participations” are undivided interests in pools of securities where the underlying credit support passes through to the participants. The Fund may invest in obligations issued by United States territories and possessions. The Fund’s portfolio is “laddered” by investing in obligations of different maturities so that some obligations mature during each of the coming years.

The Fund seeks to maintain a portfolio of investments having a dollar-weighted average effective duration of normally three to ten years. Duration is a measure of estimated sensitivity to interest rate changes. A portfolio with a longer average effective duration will typically be more sensitive to interest rate changes than a portfolio with a shorter average effective duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example, an obligation with a duration of 10 would be expected to change in price by approximately 10% in response to a 1% change in interest rates. During temporary periods the Fund’s average effective duration may be reduced for defensive purposes. There is no limitation on the duration or maturity of any specific security the Fund may purchase. The Fund may dispose of any security before it matures. The Fund also attempts to reduce changes in its share value through credit analysis, selection and diversification.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals. The objective of preserving capital may prevent the Fund from obtaining the highest yields available.

The Fund normally invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in municipal obligations originating in New Mexico, the income from which is exempt from regular federal or New Mexico income taxes, though the income on those investments may still be subject to the federal alternative minimum tax (“AMT”). Gains realized on investments held by the Fund and not offset by realized losses will be subject to federal income tax.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Intermediate New Mexico Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A, Class D and Class I share performance to the ICE BofA U.S. Municipal Securities Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The ICE BofA 3-15 Year U.S. Municipal Securities Index was removed as the Fund’s benchmark index effective September 30, 2024. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Intermediate New Mexico Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 5.24%

12/31/2023

Lowest Quarterly Results

-4.97%

3/31/2022

The sales charge for Class A shares is not reflected in the returns shown in the bar chart above, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.

Retail | Thornburg New Mexico Intermediate Municipal Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retail | Thornburg New Mexico Intermediate Municipal Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg New Mexico Intermediate Municipal Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If obligations held by the Fund are downgraded by ratings agencies or go into default, or if legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Lower-rated or unrated obligations held by the Fund may have, or may be perceived to have, greater risk of default and ratings downgrades. For example, municipal leases held by the Fund may be subject to non-appropriation provisions which permit governmental agencies or issuers to discontinue payments to the Fund under the municipal leases.
Retail | Thornburg New Mexico Intermediate Municipal Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg New Mexico Intermediate Municipal Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices. The market for lower- rated and unrated obligations may be less liquid than the market for other obligations, making it difficult for the Fund to value its investment in a lower-rated or unrated obligation or to sell the investment in a timely manner or at an acceptable price.
Retail | Thornburg New Mexico Intermediate Municipal Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg New Mexico Intermediate Municipal Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. This effect is typically more pronounced for the Fund’s investments in lower- rated and unrated municipal obligations, the value of which may fluctuate more significant in response to poor economic growth or other changes in market conditions, political, economic and legal developments, and developments affecting specific issuers.
Retail | Thornburg New Mexico Intermediate Municipal Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg New Mexico Intermediate Municipal Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retail | Thornburg New Mexico Intermediate Municipal Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. When interest rates decrease, the Fund’s dividends may decline. Decreases in market interest rates may also result in prepayments of obligations the Fund acquires, requiring the Fund to reinvest at lower interest rates.
Retail | Thornburg New Mexico Intermediate Municipal Fund | Tax Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Tax Risk – The income on the Fund’s municipal obligations could become subject to federal income or state income tax due to noncompliant conduct by issuers, unfavorable legislation or litigation or adverse interpretations by regulatory authorities. All or a portion of the Fund’s distributions that are exempt from regular federal income tax may nevertheless be taken into account for purposes of the federal AMT and state income tax.
Retail | Thornburg New Mexico Intermediate Municipal Fund | Single State Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Single State Risk – Because the Fund invests primarily in obligations originating in New Mexico, the Fund’s share value may be more sensitive to adverse economic, political or regulatory developments in that state. Budgetary concerns, decreased revenues, and adverse conditions significant to a sector of the state, municipalities within the state, or local economies may negatively affect the ability of state and local issuers to make full and timely principal or interest payments on their debt obligations.
Retail | Thornburg New Mexico Intermediate Municipal Fund | Risk Nondiversified Status [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Non-diversification Risk – The Fund is a non-diversified investment company, which means that it may invest a greater proportion of its assets in the securities of a single issuer. This may be riskier, because a default or other adverse condition affecting such an issuer could cause the Fund’s share price to decline to a greater degree.
Retail | Thornburg New Mexico Intermediate Municipal Fund | Thornburg New Mexico Intermediate Municipal Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THNMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.00%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [57]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.50%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.31%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.06%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.07%) [58]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 299
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 524
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 766
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,462
Annual Return 2015 rr_AnnualReturn2015 2.16%
Annual Return 2016 rr_AnnualReturn2016 (0.41%)
Annual Return 2017 rr_AnnualReturn2017 2.03%
Annual Return 2018 rr_AnnualReturn2018 1.40%
Annual Return 2019 rr_AnnualReturn2019 4.49%
Annual Return 2020 rr_AnnualReturn2020 3.46%
Annual Return 2021 rr_AnnualReturn2021 0.10%
Annual Return 2022 rr_AnnualReturn2022 (6.27%)
Annual Return 2023 rr_AnnualReturn2023 3.93%
Annual Return 2024 rr_AnnualReturn2024 0.64%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 5.24%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (4.97%)
1 Year rr_AverageAnnualReturnYear01 (1.41%)
5 Years rr_AverageAnnualReturnYear05 (0.10%)
10 Years rr_AverageAnnualReturnYear10 0.90%
Retail | Thornburg New Mexico Intermediate Municipal Fund | Thornburg New Mexico Intermediate Municipal Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (1.41%)
5 Years rr_AverageAnnualReturnYear05 (0.10%)
10 Years rr_AverageAnnualReturnYear10 0.90%
Retail | Thornburg New Mexico Intermediate Municipal Fund | Thornburg New Mexico Intermediate Municipal Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.22%
5 Years rr_AverageAnnualReturnYear05 0.36%
10 Years rr_AverageAnnualReturnYear10 1.18%
Retail | Thornburg New Mexico Intermediate Municipal Fund | Thornburg New Mexico Intermediate Municipal Fund - Class A | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg New Mexico Intermediate Municipal Fund | Thornburg New Mexico Intermediate Municipal Fund - Class A | ICE BofA 3-15 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.99%
5 Years rr_AverageAnnualReturnYear05 1.04%
10 Years rr_AverageAnnualReturnYear10 2.12%
Retail | Thornburg New Mexico Intermediate Municipal Fund | Thornburg New Mexico Intermediate Municipal Fund - Class D  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THNDX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.50%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.36%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.36%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.12%) [58]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.24%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 126
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 419
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 733
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,625
1 Year rr_AverageAnnualReturnYear01 0.46%
5 Years rr_AverageAnnualReturnYear05 0.05%
10 Years rr_AverageAnnualReturnYear10 0.87%
Retail | Thornburg New Mexico Intermediate Municipal Fund | Thornburg New Mexico Intermediate Municipal Fund - Class D | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg New Mexico Intermediate Municipal Fund | Thornburg New Mexico Intermediate Municipal Fund - Class D | ICE BofA 3-15 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.99%
5 Years rr_AverageAnnualReturnYear05 1.04%
10 Years rr_AverageAnnualReturnYear10 2.12%
Retail | Thornburg New Mexico Intermediate Municipal Fund | Thornburg New Mexico Intermediate Municipal Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THNIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.50%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.25%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.75%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.08%) [58]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.67%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 68
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 232
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 409
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 923
1 Year rr_AverageAnnualReturnYear01 1.04%
5 Years rr_AverageAnnualReturnYear05 0.62%
10 Years rr_AverageAnnualReturnYear10 1.44%
Retail | Thornburg New Mexico Intermediate Municipal Fund | Thornburg New Mexico Intermediate Municipal Fund - Class I | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg New Mexico Intermediate Municipal Fund | Thornburg New Mexico Intermediate Municipal Fund - Class I | ICE BofA 3-15 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.99%
5 Years rr_AverageAnnualReturnYear05 1.04%
10 Years rr_AverageAnnualReturnYear10 2.12%
Retail | Thornburg New York Intermediate Municipal Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Intermediate New York Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The primary investment goal of Intermediate New York Fund is to obtain as high a level of current income exempt from federal, New York State and New York City individual income taxes as is consistent, in the view of the Fund’s investment advisor, with preservation of capital.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

The secondary goal of the Fund is to reduce expected changes in its share price compared to long-term bond portfolios.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds. More information about this and other discounts and sales charge waivers is available from your financial intermediary, in the Prospectus under the captions “Class A Sales Charge Waivers,” beginning on page 165, and “Appendix A – Sales Charge Waivers Offered by Financial Intermediaries,” beginning on page 220, and in the Statement of Additional Information under the caption “Additional Information Respecting Purchase and Redemption of Shares,” beginning on page 92.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was ­20.23% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 20.23%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for discounts from the sales charges applicable to Class A shares if you or other qualifying account holders invest, or agree to invest in the future, at least $50,000 in the Thornburg Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its primary goal by investing principally in a laddered maturity portfolio of municipal obligations issued by New York State and its agencies, and by New York State local governments and their agencies. Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s portfolio. Investment decisions are based upon outlooks for interest rates and securities markets, the supply of municipal debt obligations, and analysis of specific securities. The Fund invests primarily in obligations and participations in obligations which are rated by a nationally recognized statistical rating organization at the time of purchase as investment grade or, if unrated, are issued by obligors which Thornburg determines have comparable investment grade obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding investment grade obligations. The Fund may invest up to 20 percent of its net assets, plus the amount of any borrowings for investment purposes, in lower-quality municipal debt obligations rated by a nationally recognized statistical rating organization at the time of purchase as below investment grade (sometimes called “junk” bonds or “high yield” bonds) or, if unrated, issued by obligors which Thornburg determines have comparable below investment grade municipal obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding below investment grade obligations. “Participations” are undivided interests in pools of securities where the underlying credit support passes through to the participants. The Fund may invest in obligations issued by United States territories and possessions. The Fund’s portfolio is “laddered” by investing in obligations of different maturities so that some obligations mature during each of the coming years.

The Fund seeks to maintain a portfolio of investments having a dollar-weighted average effective duration of normally three to ten years. Duration is a measure of estimated sensitivity to interest rate changes. A portfolio with a longer average effective duration will typically be more sensitive to interest rate changes than a portfolio with a shorter average effective duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example, an obligation with a duration of 10 would be expected to change in price by approximately 10% in response to a 1% change in interest rates. During temporary periods the Fund’s average effective duration may be reduced for defensive purposes. There is no limitation on the duration or maturity of any specific security the Fund may purchase. The Fund may dispose of any security before it matures. The Fund also attempts to reduce changes in its share value through credit analysis, selection and diversification.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.  The objective of preserving capital may prevent the Fund from obtaining the highest yields available.

The Fund normally invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in municipal obligations originating in New York, the income from which is exempt from regular federal or New York income taxes, though the income on those investments may still be subject to the federal alternative minimum tax (“AMT”). Gains realized on investments held by the Fund and not offset by realized losses will be subject to federal income tax.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Intermediate New York Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class A shares have been different in each full year shown. The average annual total return figures compare Class A and Class I share performance to the ICE BofA U.S. Municipal Securities Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The ICE BofA 3-15 Year U.S. Municipal Securities Index was removed as the Fund’s benchmark index effective September 30, 2024. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Intermediate New York Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The sales charge for Class A shares is not reflected in the returns shown in the bar chart, and the returns would be less if the charge was taken into account.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Total
Returns

Quarter
ended

Highest Quarterly Results

 5.30%

12/31/2023

Lowest Quarterly Results

-4.83%

3/31/2022

The sales charge for Class A shares is not reflected in the returns shown in the bar chart, and the returns would be less if the charge was taken into account.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class A shares, and after-tax returns for other share classes will vary.

Retail | Thornburg New York Intermediate Municipal Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retail | Thornburg New York Intermediate Municipal Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retail | Thornburg New York Intermediate Municipal Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If obligations held by the Fund are downgraded by ratings agencies or go into default, or if legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Lower-rated or unrated obligations held by the Fund may have, or may be perceived to have, greater risk of default and ratings downgrades. For example, municipal leases held by the Fund may be subject to non-appropriation provisions which permit governmental agencies or issuers to discontinue payments to the Fund under the municipal leases.
Retail | Thornburg New York Intermediate Municipal Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retail | Thornburg New York Intermediate Municipal Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices. The market for lower- rated and unrated obligations may be less liquid than the market for other obligations, making it difficult for the Fund to value its investment in a lower-rated or unrated obligation or to sell the investment in a timely manner or at an acceptable price.
Retail | Thornburg New York Intermediate Municipal Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retail | Thornburg New York Intermediate Municipal Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. This effect is typically more pronounced for the Fund’s investments in lower- rated and unrated municipal obligations, the value of which may fluctuate more significantly in response to poor economic growth or other changes in market conditions, political, economic and legal developments, and developments affecting specific issuers.
Retail | Thornburg New York Intermediate Municipal Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retail | Thornburg New York Intermediate Municipal Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retail | Thornburg New York Intermediate Municipal Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. When interest rates decrease, the Fund’s dividends may decline. Decreases in market interest rates may also result in prepayments of obligations the Fund acquires, requiring the Fund to reinvest at lower interest rates.
Retail | Thornburg New York Intermediate Municipal Fund | Tax Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Tax Risk – The income on the Fund’s municipal obligations could become subject to federal income or state income tax due to noncompliant conduct by issuers, unfavorable legislation or litigation or adverse interpretations by regulatory authorities. All or a portion of the Fund’s distributions that are exempt from regular federal income tax may nevertheless be taken into account for purposes of the federal AMT and state income tax.
Retail | Thornburg New York Intermediate Municipal Fund | Single State Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Single State Risk – Because the Fund invests primarily in obligations originating in New York, the Fund’s share value may be more sensitive to adverse economic, political or regulatory developments in that state. Budgetary concerns, decreased revenues, and adverse conditions significant to a sector of the state, municipalities within the state, or local economies may negatively affect the ability of state and local issuers to make full and timely principal or interest payments on their debt obligations.
Retail | Thornburg New York Intermediate Municipal Fund | Risk Nondiversified Status [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Non-diversification Risk – The Fund is a non-diversified investment company, which means that it may invest a greater proportion of its assets in the securities of a single issuer. This may be riskier, because a default or other adverse condition affecting such an issuer could cause the Fund’s share price to decline to a greater degree.
Retail | Thornburg New York Intermediate Municipal Fund | Thornburg New York Intermediate Municipal Fund - Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THNYX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.00%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [59]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.50%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.64%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.39%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.40%) [60]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 299
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 593
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 908
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,801
Annual Return 2015 rr_AnnualReturn2015 2.18%
Annual Return 2016 rr_AnnualReturn2016 (0.51%)
Annual Return 2017 rr_AnnualReturn2017 2.67%
Annual Return 2018 rr_AnnualReturn2018 0.16%
Annual Return 2019 rr_AnnualReturn2019 4.56%
Annual Return 2020 rr_AnnualReturn2020 2.99%
Annual Return 2021 rr_AnnualReturn2021 0.32%
Annual Return 2022 rr_AnnualReturn2022 (5.64%)
Annual Return 2023 rr_AnnualReturn2023 4.75%
Annual Return 2024 rr_AnnualReturn2024 1.03%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 5.30%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (4.83%)
1 Year rr_AverageAnnualReturnYear01 (1.00%)
5 Years rr_AverageAnnualReturnYear05 0.23%
10 Years rr_AverageAnnualReturnYear10 1.01%
Retail | Thornburg New York Intermediate Municipal Fund | Thornburg New York Intermediate Municipal Fund - Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (1.01%)
5 Years rr_AverageAnnualReturnYear05 0.23%
10 Years rr_AverageAnnualReturnYear10 1.01%
Retail | Thornburg New York Intermediate Municipal Fund | Thornburg New York Intermediate Municipal Fund - Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.55%
5 Years rr_AverageAnnualReturnYear05 0.69%
10 Years rr_AverageAnnualReturnYear10 1.29%
Retail | Thornburg New York Intermediate Municipal Fund | Thornburg New York Intermediate Municipal Fund - Class A | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg New York Intermediate Municipal Fund | Thornburg New York Intermediate Municipal Fund - Class A | ICE BofA 3-15 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.99%
5 Years rr_AverageAnnualReturnYear05 1.04%
10 Years rr_AverageAnnualReturnYear10 2.12%
Retail | Thornburg New York Intermediate Municipal Fund | Thornburg New York Intermediate Municipal Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TNYIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.50%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.62%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.12%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.45%) [60]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.67%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 68
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 311
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 573
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,323
1 Year rr_AverageAnnualReturnYear01 1.36%
5 Years rr_AverageAnnualReturnYear05 0.95%
10 Years rr_AverageAnnualReturnYear10 1.53%
Retail | Thornburg New York Intermediate Municipal Fund | Thornburg New York Intermediate Municipal Fund - Class I | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 2.34%
Retail | Thornburg New York Intermediate Municipal Fund | Thornburg New York Intermediate Municipal Fund - Class I | ICE BofA 3-15 Year U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.99%
5 Years rr_AverageAnnualReturnYear05 1.04%
10 Years rr_AverageAnnualReturnYear10 2.12%
Retirement | Thornburg Global Opportunities Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Global Opportunities Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks long-term capital appreciation by investing in equity and debt securities of all types from issuers around the world.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 14.91% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 14.91%
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment goal by investing primarily in a broad range of equity securities, including common stocks, preferred stocks and publicly traded real estate investment trusts. The Fund may invest in any stock or other equity security which its investment advisor, Thornburg Investment Management, Inc. (“Thornburg”), believes may assist the Fund in pursuing its goal, including smaller companies with market capitalizations of less than $500 million.

The Fund portfolio includes investments in both domestic securities and securities of issuers domiciled in or economically tied to countries outside the United States, including developing countries. Relative proportions of each will vary from time to time, depending upon Thornburg’s view of specific investment opportunities and macro-economic factors. Under normal market conditions, the Fund invests a significant portion of its assets in issuers domiciled in or economically tied to countries outside the United States.

The Fund’s investments are determined by individual issuer and industry analysis. Investment decisions are based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for securities, and analysis of specific issuers.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Global Opportunities Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class R3 shares have been different in each full year shown. The average annual total return figures Class R3, Class R4, Class R5 and Class R6 share performance to the MSCI All Country World Net Total Return USD Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The index is not actively managed and is not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Global Opportunities Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class R3 Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 21.70%

6/30/2020

Lowest Quarterly Results

-24.86%

3/31/2020
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Retirement | Thornburg Global Opportunities Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retirement | Thornburg Global Opportunities Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retirement | Thornburg Global Opportunities Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Retirement | Thornburg Global Opportunities Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retirement | Thornburg Global Opportunities Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retirement | Thornburg Global Opportunities Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retirement | Thornburg Global Opportunities Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retirement | Thornburg Global Opportunities Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection.
Retirement | Thornburg Global Opportunities Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices. This risk may be more pronounced for the Fund’s investments in developing countries.
Retirement | Thornburg Global Opportunities Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retirement | Thornburg Global Opportunities Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retirement | Thornburg Global Opportunities Fund | Real Estate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Real Estate Risk – The Fund’s investments in publicly traded real estate investment trusts (“REITs”) are subject to risks affecting real estate investments generally (including market conditions, competition, property obsolescence, changes in interest rates and casualty to real estate), as well as risks specifically affecting REITs (the quality and skill of REIT management and the internal expenses of the REIT).
Retirement | Thornburg Global Opportunities Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retirement | Thornburg Global Opportunities Fund | Risks Affecting Specific Countries or Regions [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Countries or Regions – If a significant portion of the Fund’s assets is invested in issuers that are economically exposed to one country or region, the Fund’s share value may be more susceptible to the conditions and developments in that country or region, and potentially more volatile than the share value of a more geographically diversified fund. A specific country or region could also be adversely affected by conditions or developments arising in other countries. For example, the U.S. government could take actions to prohibit or restrict individuals or companies within the U.S. from purchasing or holding the shares of issuers in another country, which may limit the Fund’s ability to invest in that country or cause the Fund to have to sell investments in that country at less than desired prices. The nature and degree of the risks affecting a given country or region, and the extent of the Fund’s exposure to any such country or region, is expected to vary over time.
Retirement | Thornburg Global Opportunities Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a security may decline in response to developments affecting the specific issuer of the security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retirement | Thornburg Global Opportunities Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments.
Retirement | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class R3  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THORX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.84%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.15%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.49%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.99%) [61]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 153
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 681
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,236
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,751
Annual Return 2015 rr_AnnualReturn2015 0.95%
Annual Return 2016 rr_AnnualReturn2016 3.49%
Annual Return 2017 rr_AnnualReturn2017 21.37%
Annual Return 2018 rr_AnnualReturn2018 (21.07%)
Annual Return 2019 rr_AnnualReturn2019 28.09%
Annual Return 2020 rr_AnnualReturn2020 22.05%
Annual Return 2021 rr_AnnualReturn2021 14.18%
Annual Return 2022 rr_AnnualReturn2022 (10.52%)
Annual Return 2023 rr_AnnualReturn2023 15.69%
Annual Return 2024 rr_AnnualReturn2024 12.55%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 21.70%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (24.86%)
1 Year rr_AverageAnnualReturnYear01 12.55%
5 Years rr_AverageAnnualReturnYear05 10.18%
10 Years rr_AverageAnnualReturnYear10 7.61%
Retirement | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class R3 | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 10.68%
5 Years rr_AverageAnnualReturnYear05 8.12%
10 Years rr_AverageAnnualReturnYear10 6.44%
Retirement | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class R3 | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 7.88%
5 Years rr_AverageAnnualReturnYear05 7.52%
10 Years rr_AverageAnnualReturnYear10 5.81%
Retirement | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class R3 | MSCI All Country World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 17.49%
5 Years rr_AverageAnnualReturnYear05 10.06%
10 Years rr_AverageAnnualReturnYear10 9.23%
Retirement | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class R4  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THOVX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.84%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.06%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.15%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.75%) [61]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.40%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 143
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 601
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,086
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,424
1 Year rr_AverageAnnualReturnYear01 12.60%
5 Years rr_AverageAnnualReturnYear05 10.27%
10 Years rr_AverageAnnualReturnYear10 7.70%
Retirement | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class R4 | MSCI All Country World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 17.49%
5 Years rr_AverageAnnualReturnYear05 10.06%
10 Years rr_AverageAnnualReturnYear10 9.23%
Retirement | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class R5  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THOFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.84%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.51%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.35%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.36%) [61]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 101
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 392
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 705
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,593
1 Year rr_AverageAnnualReturnYear01 13.04%
5 Years rr_AverageAnnualReturnYear05 10.71%
10 Years rr_AverageAnnualReturnYear10 8.14%
Retirement | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class R5 | MSCI All Country World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 17.49%
5 Years rr_AverageAnnualReturnYear05 10.06%
10 Years rr_AverageAnnualReturnYear10 9.23%
Retirement | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class R6  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THOGX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.84%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.17%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.01%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.16%) [61]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.85%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 87
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 306
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 542
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,222
1 Year rr_AverageAnnualReturnYear01 13.21%
5 Years rr_AverageAnnualReturnYear05 10.87%
Since Inception rr_AverageAnnualReturnSinceInception 8.98%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 10, 2017
Retirement | Thornburg Global Opportunities Fund | Thornburg Global Opportunities Fund - Class R6 | MSCI All Country World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 17.49%
5 Years rr_AverageAnnualReturnYear05 10.06%
Since Inception rr_AverageAnnualReturnSinceInception 10.44%
Retirement | Thornburg International Equity Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading International Equity Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The Fund seeks long-term capital appreciation by investing in equity and debt securities of all types.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock The secondary, non-fundamental goal of the Fund is to seek some current income.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 45.47% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 45.47%
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund invests primarily in common stocks of non-U.S. companies and depositary receipts associated with such stocks. The Fund may invest in developing countries. Under normal conditions, the Fund will invest at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in common stocks or depositary receipts.

The Fund’s investment advisor, Thornburg Investment Management, Inc. (“Thornburg”), intends to invest on an opportunistic basis where the Fund’s portfolio managers believe intrinsic value is not recognized by the marketplace. The Fund seeks to identify value in a broad or different context by investing in a diversified portfolio of stocks the Fund categorizes as basic values, consistent earners, and emerging franchises, when the portfolio managers believe these issues are value priced. The relative proportions of securities invested in each of those categories will vary over time. The Fund seeks to invest in promising companies, and may invest in stocks that reflect unfavorable market perceptions of the company or industry fundamentals. The Fund may invest in companies of any size, but invests primarily in the large and middle capitalization range of publicly traded companies.

The Fund’s investments are determined by individual issuer and industry analysis. Investment decisions are based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for securities, and analysis of specific issuers.

Thornburg typically categorizes the Fund’s equity investments in one of the following three categories:

Basic Value: Companies generally operating in mature or cyclical industries and which generally exhibit more economic sensitivity and/or higher volatility in earnings and cash flow.

Consistent Earner: Companies which generally exhibit predictable growth, profitability, cash flow and/or dividends.

Emerging Franchise: Companies with the potential to grow at an above average rate because of a product or service that is establishing a new market and/or taking share from existing participants.

Inclusion of any investment in any of the three described categories represents Thornburg’s opinion concerning the characteristics and prospects of the investment. There is no assurance that any company selected for investment will, once categorized in one of the three described investment categories, continue to have the positive characteristics or fulfill the expectations that Thornburg had for the company when it was selected for investment, and any such company may not grow or may decline in earnings and size.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in common stocks or depositary receipts may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the International Equity Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class R3 shares have been different in each full year shown. The average annual total return figures compare Class R3, Class R4, Class R5 and Class R6 share performance to the MSCI All Country World ex USA Net Total Return USD Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The MSCI EAFE (Europe, Australasia, Far East) Net Total Return USD Index was removed as the Funds’ secondary index effective September 30, 2024. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the International Equity Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class R3 Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 18.53%

12/31/2022

Lowest Quarterly Results

-19.56%

3/31/2020
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.

 
Retirement | Thornburg International Equity Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retirement | Thornburg International Equity Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retirement | Thornburg International Equity Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Retirement | Thornburg International Equity Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retirement | Thornburg International Equity Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retirement | Thornburg International Equity Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retirement | Thornburg International Equity Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retirement | Thornburg International Equity Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection.
Retirement | Thornburg International Equity Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices.
Retirement | Thornburg International Equity Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retirement | Thornburg International Equity Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retirement | Thornburg International Equity Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retirement | Thornburg International Equity Fund | Risks Affecting Specific Countries or Regions [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Countries or Regions – If a significant portion of the Fund’s assets is invested in issuers that are economically exposed to one country or region, the Fund’s share value may be more susceptible to the conditions and developments in that country or region, and potentially more volatile than the share value of a more geographically diversified fund. A specific country or region could also be adversely affected by conditions or developments arising in other countries. For example, the U.S. government could take actions to prohibit or restrict individuals or companies within the U.S. from purchasing or holding the shares of issuers in another country, which may limit the Fund’s ability to invest in that country or cause the Fund to have to sell investments in that country at less than desired prices. The nature and degree of the risks affecting a given country or region, and the extent of the Fund’s exposure to any such country or region, is expected to vary over time.
Retirement | Thornburg International Equity Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a security may decline in response to developments affecting the specific issuer of the security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retirement | Thornburg International Equity Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments.
Retirement | Thornburg International Equity Fund | Depositary Receipts Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Depositary Receipts Risk – An investment in American Depositary Receipts (“ADRs”), European Depositary Receipts (“EDRs”) or Global Depositary Receipts (“GDRs”) is an alternative to the purchase of the underlying securities in their national markets and/or currencies. However, ADRs, EDRs, and GDRs remain subject to many of the risks associated with investing directly in foreign securities, including the political and economic risks associated with the underlying issuer’s country. Certain countries may limit the ability to convert a depositary receipt into the underlying foreign security and vice versa, which may cause the securities of the foreign company to trade at a discount or premium to the market price of the related depositary receipts. Moreover, EDRs and GDRs can involve currency risk since, unlike ADRs, they may not be U.S. dollar denominated.
Retirement | Thornburg International Equity Fund | Risks Affecting Investments in China [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Investments in China – A significant portion of the Fund’s assets may be invested in companies exposed to China. Risks affecting investments in China include a potential downturn in the Chinese economy, reduced liquidity or increased price volatility in the Chinese securities markets as a result of trading suspensions affecting Chinese issuers or other factors, the potential that the Chinese government may expand restrictions on foreign investments or the repatriation of capital, and the implementation of new tariffs or other trade barriers by China or its trading partners. A lack of transparency respecting Chinese companies may also reduce the Fund’s ability to conduct diligence respecting those companies’ accounting and governance standards, which may in turn reduce the Fund’s ability to detect fraudulent practices that may adversely affect the companies’ stock prices.
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R3  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TGVRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.77%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.40%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.67%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.31%) [62]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.36%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 138
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 496
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 878
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,950
Annual Return 2015 rr_AnnualReturn2015 6.07%
Annual Return 2016 rr_AnnualReturn2016 (2.88%)
Annual Return 2017 rr_AnnualReturn2017 24.78%
Annual Return 2018 rr_AnnualReturn2018 (20.22%)
Annual Return 2019 rr_AnnualReturn2019 28.39%
Annual Return 2020 rr_AnnualReturn2020 22.12%
Annual Return 2021 rr_AnnualReturn2021 7.10%
Annual Return 2022 rr_AnnualReturn2022 (17.13%)
Annual Return 2023 rr_AnnualReturn2023 15.45%
Annual Return 2024 rr_AnnualReturn2024 11.05%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2022
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 18.53%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (19.56%)
1 Year rr_AverageAnnualReturnYear01 11.05%
5 Years rr_AverageAnnualReturnYear05 6.80%
10 Years rr_AverageAnnualReturnYear10 6.23%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R3 | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 9.05%
5 Years rr_AverageAnnualReturnYear05 5.10%
10 Years rr_AverageAnnualReturnYear10 4.25%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R3 | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 7.42%
5 Years rr_AverageAnnualReturnYear05 4.84%
10 Years rr_AverageAnnualReturnYear10 4.35%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R3 | MSCI EAFE (Europe, Australasia, Far East) Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.82%
5 Years rr_AverageAnnualReturnYear05 4.73%
10 Years rr_AverageAnnualReturnYear10 5.20%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R3 | MSCI All Country World ex-U.S. Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R4  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THVRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.77%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.47%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.49%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.33%) [62]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.16%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 118
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 439
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 782
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,751
1 Year rr_AverageAnnualReturnYear01 11.27%
5 Years rr_AverageAnnualReturnYear05 7.02%
10 Years rr_AverageAnnualReturnYear10 6.44%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R4 | MSCI EAFE (Europe, Australasia, Far East) Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.82%
5 Years rr_AverageAnnualReturnYear05 4.73%
10 Years rr_AverageAnnualReturnYear10 5.20%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R4 | MSCI All Country World ex-U.S. Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R5  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TIVRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.77%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.41%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.18%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.28%) [62]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.90%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 92
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 347
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 622
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,407
1 Year rr_AverageAnnualReturnYear01 11.54%
5 Years rr_AverageAnnualReturnYear05 7.29%
10 Years rr_AverageAnnualReturnYear10 6.72%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R5 | MSCI EAFE (Europe, Australasia, Far East) Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.82%
5 Years rr_AverageAnnualReturnYear05 4.73%
10 Years rr_AverageAnnualReturnYear10 5.20%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R5 | MSCI All Country World ex-U.S. Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R6  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TGIRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.77%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.14%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.91%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.21%) [62]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.70%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 72
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 269
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 483
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,100
1 Year rr_AverageAnnualReturnYear01 11.78%
5 Years rr_AverageAnnualReturnYear05 7.51%
10 Years rr_AverageAnnualReturnYear10 6.94%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R6 | MSCI EAFE (Europe, Australasia, Far East) Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.82%
5 Years rr_AverageAnnualReturnYear05 4.73%
10 Years rr_AverageAnnualReturnYear10 5.20%
Retirement | Thornburg International Equity Fund | Thornburg International Equity Fund - Class R6 | MSCI All Country World ex-U.S. Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retirement | Thornburg International Growth Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading International Growth Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks long-term growth of capital by investing in equity securities selected for their growth potential.

Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2025
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 44.57% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 44.57%
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in growth companies and invests at least 75% of its net assets, plus the amount of any borrowings for investment purposes, in foreign securities or depositary receipts of foreign securities. For this purpose, the Fund currently considers a company to be a growth company if it meets any of the following criteria:

•It is a constituent of the MSCI All Country World Growth Index; or

•It has, over the last five years, grown its revenues or earnings per share at an average annual rate which exceeds the median growth rate of revenues or earnings per share, as applicable, for companies in the MSCI All Country World ex-U.S. Index; or

•It is projected by consensus estimates as compiled by FactSet Research Systems, over the next two years, to grow its revenues or earnings per share at an average annual rate which exceeds the median growth rate of revenues or earnings per share, as applicable, for companies in the MSCI All Country World ex-U.S. Index.

While the Fund expects to invest primarily in foreign equity securities (primarily common stocks), the Fund may own a variety of securities, including domestic equity securities. The Fund may invest in developing countries.

The Fund’s investment advisor, Thornburg Investment Management, Inc. (“Thornburg”) intends to invest in companies that it believes will have growing revenues and earnings. The Fund can invest in companies of any size, from larger, well-established companies to smaller, emerging growth companies.

The Fund’s investments are determined by individual issuer and industry analysis. Investment decisions are based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for securities, and analysis of specific issuers.

Thornburg typically categorizes the Fund’s equity investments in one of the following three categories:

Growth Industry Leader: Companies in this category often have leadership positions in growing markets. In some cases these companies may have dominant market share. These companies tend to be larger and more established.

Consistent Grower: Companies in this category generally exhibit steady earnings or revenue growth, or both. These companies may have subscription or other recurring revenue profiles. Given their business models, these companies may outperform in weak markets.

Emerging Growth: Companies often addressing a new market or carving out a niche in an existing market. Companies in this category may experience rapid growth, and tend to be smaller, earlier stage companies. These companies may exhibit high volatility.

Inclusion of any investment in any of the three described categories represents Thornburg’s opinion concerning the characteristics and prospects of the investment. There is no assurance that any company selected for investment will, once categorized in one of the three described investment categories, continue to have the positive characteristics or fulfill the expectations that Thornburg had for the company when it was selected for investment, and any such company may not grow or may decline in earnings and size.

In conjunction with individual issuer analysis, Thornburg may identify and invest at times with a greater emphasis in industries or economic sectors it expects to experience growth. The Fund does not have a strategy to invest in particular industry or economic sectors, and its exposures to particular industries or economic sectors are expected to vary over time. Investment decisions are also based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, and the supply and demand for securities.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in growth companies may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders. Additionally, the Fund may change its definition of what constitutes a “growth company” at any time without advance notice to shareholders.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in International Growth Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class R3 shares vary in each full year shown. The average annual total return figures compare Class R3, Class R4, Class R5 and Class R6 share

performance to the MSCI All Country World ex USA Net Total Return, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the MSCI All Country World ex USA Growth Net Total Return USD Index, an additional index that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in International Growth Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class R3 Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 25.89%

6/30/2020

Lowest Quarterly Results

-17.77%

12/31/2018
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Retirement | Thornburg International Growth Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retirement | Thornburg International Growth Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retirement | Thornburg International Growth Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Retirement | Thornburg International Growth Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retirement | Thornburg International Growth Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retirement | Thornburg International Growth Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retirement | Thornburg International Growth Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retirement | Thornburg International Growth Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection.
Retirement | Thornburg International Growth Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices. This risk may be more pronounced for the Fund’s investments in developing countries.
Retirement | Thornburg International Growth Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retirement | Thornburg International Growth Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retirement | Thornburg International Growth Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retirement | Thornburg International Growth Fund | Risks Affecting Specific Countries or Regions [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Countries or Regions – If a significant portion of the Fund’s assets is invested in issuers that are economically exposed to one country or region, the Fund’s share value may be more susceptible to the conditions and developments in that country or region, and potentially more volatile than the share value of a more geographically diversified fund. A specific country or region could also be adversely affected by conditions or developments arising in other countries. For example, the U.S. government could take actions to prohibit or restrict individuals or companies within the U.S. from purchasing or holding the shares of issuers in another country, which may limit the Fund’s ability to invest in that country or cause the Fund to have to sell investments in that country at less than desired prices. The nature and degree of the risks affecting a given country or region, and the extent of the Fund’s exposure to any such country or region, is expected to vary over time.
Retirement | Thornburg International Growth Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a security may decline in response to developments affecting the specific issuer of the security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retirement | Thornburg International Growth Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies, including smaller, earlier stage companies, may involve additional risks. These risks may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments.
Retirement | Thornburg International Growth Fund | Depositary Receipts Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Depositary Receipts Risk – An investment in American Depositary Receipts (“ADRs”), European Depositary Receipts (“EDRs”) or Global Depositary Receipts (“GDRs”) is an alternative to the purchase of the underlying securities in their national markets and/or currencies. However, ADRs, EDRs, and GDRs remain subject to many of the risks associated with investing directly in foreign securities, including the political and economic risks associated with the underlying issuer’s country. Certain countries may limit the ability to convert a depositary receipt into the underlying foreign security and vice versa, which may cause the securities of the foreign company to trade at a discount or premium to the market price of the related depositary receipts. Moreover, EDRs and GDRs can involve currency risk since, unlike ADRs, they may not be U.S. dollar denominated.
Retirement | Thornburg International Growth Fund | Growth Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Growth Company Risk – Growth company stocks may trade at higher multiples of current earnings than other equity securities and, therefore, may be more sensitive to changes in current or expected earnings than other equity securities and may be more volatile. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can cushion stock prices in market downturns. These risks may be more pronounced in companies that are in the earlier stages of their growth cycle.
Retirement | Thornburg International Growth Fund | Information Technology Securities Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Information Technology Securities Risk – Information technology companies may at times be more vulnerable to product obsolescence caused by rapid technology changes, the failure to obtain or maintain intellectual property rights, the inability to develop new products, competition from new and existing market entrants, and changes in consumer preferences. Information technology stocks may also be more volatile than the overall market.
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R3  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TIGVX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.85%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.83%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.18%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.68%) [63]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 153
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 617
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,107
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,460
Annual Return 2015 rr_AnnualReturn2015 6.25%
Annual Return 2016 rr_AnnualReturn2016 (5.16%)
Annual Return 2017 rr_AnnualReturn2017 34.22%
Annual Return 2018 rr_AnnualReturn2018 (17.18%)
Annual Return 2019 rr_AnnualReturn2019 25.66%
Annual Return 2020 rr_AnnualReturn2020 33.64%
Annual Return 2021 rr_AnnualReturn2021 (4.69%)
Annual Return 2022 rr_AnnualReturn2022 (26.36%)
Annual Return 2023 rr_AnnualReturn2023 17.80%
Annual Return 2024 rr_AnnualReturn2024 1.93%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 25.89%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2018
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (17.77%)
1 Year rr_AverageAnnualReturnYear01 1.93%
5 Years rr_AverageAnnualReturnYear05 2.41%
10 Years rr_AverageAnnualReturnYear10 4.72%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R3 | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.05%
5 Years rr_AverageAnnualReturnYear05 1.58%
10 Years rr_AverageAnnualReturnYear10 4.10%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R3 | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.50%
5 Years rr_AverageAnnualReturnYear05 1.85%
10 Years rr_AverageAnnualReturnYear10 3.72%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R3 | MSCI All Country World ex USA Net Total Return (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R3 | MSCI All Country World ex U.S. Growth Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.07%
5 Years rr_AverageAnnualReturnYear05 3.44%
10 Years rr_AverageAnnualReturnYear10 5.35%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R4  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TINVX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.85%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.94%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.04%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.64%) [63]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.40%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 143
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 578
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,039
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,318
1 Year rr_AverageAnnualReturnYear01 2.02%
5 Years rr_AverageAnnualReturnYear05 2.50%
10 Years rr_AverageAnnualReturnYear10 4.82%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R4 | MSCI All Country World ex USA Net Total Return (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R4 | MSCI All Country World ex U.S. Growth Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.07%
5 Years rr_AverageAnnualReturnYear05 3.44%
10 Years rr_AverageAnnualReturnYear10 5.35%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R5  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TINFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.85%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.72%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.57%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.58%) [63]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 101
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 439
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 800
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,818
1 Year rr_AverageAnnualReturnYear01 2.38%
5 Years rr_AverageAnnualReturnYear05 2.91%
10 Years rr_AverageAnnualReturnYear10 5.24%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R5 | MSCI All Country World ex USA Net Total Return (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R5 | MSCI All Country World ex U.S. Growth Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.07%
5 Years rr_AverageAnnualReturnYear05 3.44%
10 Years rr_AverageAnnualReturnYear10 5.35%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R6  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THGIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.85%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.17%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.02%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.13%) [63]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.89%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 91
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 312
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 551
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,236
1 Year rr_AverageAnnualReturnYear01 2.52%
5 Years rr_AverageAnnualReturnYear05 3.02%
10 Years rr_AverageAnnualReturnYear10 5.35%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R6 | MSCI All Country World ex USA Net Total Return (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 4.10%
10 Years rr_AverageAnnualReturnYear10 4.80%
Retirement | Thornburg International Growth Fund | Thornburg International Growth Fund - Class R6 | MSCI All Country World ex U.S. Growth Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.07%
5 Years rr_AverageAnnualReturnYear05 3.44%
10 Years rr_AverageAnnualReturnYear10 5.35%
Retirement | Thornburg Developing World Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Developing World Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund’s primary investment goal is long-term capital appreciation.

Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 90.88% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 90.88%
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund pursues its objective by investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of issuers which Thornburg views as having substantial economic ties to one or more developing countries. Developing countries are considered by Thornburg generally to be those countries which are not included in the MSCI World Index. The material factors that Thornburg considers when determining whether an issuer has substantial economic ties to a developing country include whether the issuer:

•is included in the MSCI Emerging Markets Index;

•is organized or headquartered in a developing country, or maintains most of its assets in one or more such countries;

•has equity securities that are traded principally on a stock exchange of a developing country; or

•derives, or is expected to derive, a majority of its profits, revenues, sales, or income from one or more developing countries.

The Fund may invest in issuers of any size of capitalization, including small companies, and expects that under normal conditions its assets will be invested in issuers domiciled in or tied economically to a variety of different developing countries.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in developing country issuers may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders.

Among the specific factors considered in identifying securities for inclusion in the Fund are domestic and international economic developments, outlooks for securities markets, the supply and demand for equity securities, and analysis of specific issuers. Thornburg typically categorizes the Fund’s equity investments in one of the following three categories:

Basic Value: Companies generally operating in mature or cyclical industries and which generally exhibit more economic sensitivity and/or higher volatility in earnings and cash flow.

Consistent Earner: Companies which generally exhibit predictable growth, profitability, cash flow and/or dividends.

Emerging Franchise: Companies with the potential to grow at an above average rate because of a product or service that is establishing a new market and/or taking share from existing participants.

Inclusion of any investment in any of the three described categories represents Thornburg’s opinion concerning the characteristics and prospects of the investment. There is no assurance that any company selected for investment will, once categorized in one of the three described investment categories, continue to have the positive characteristics or fulfill the expectations that Thornburg had for the company when it was selected for investment, and any such company may not grow or may decline in earnings and size.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Developing World Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class R5 shares have been different in each full year shown. The average annual total return figures compare Class R5 and Class R6 share performance to the MSCI Emerging Markets Net Total Return USD Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The index is not actively managed and is not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Developing World Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class R5 Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 21.77%

6/30/2020

Lowest Quarterly Results

-24.75%

3/31/2020
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class R5 shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class R5 shares, and after-tax returns for other share classes will vary.
Retirement | Thornburg Developing World Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retirement | Thornburg Developing World Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retirement | Thornburg Developing World Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Retirement | Thornburg Developing World Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retirement | Thornburg Developing World Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retirement | Thornburg Developing World Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retirement | Thornburg Developing World Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retirement | Thornburg Developing World Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protections.
Retirement | Thornburg Developing World Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices. This risk may be more pronounced for the Fund’s investments in developing countries.
Retirement | Thornburg Developing World Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retirement | Thornburg Developing World Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility. These risks may be more pronounced for the Fund’s investments in developing countries.
Retirement | Thornburg Developing World Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retirement | Thornburg Developing World Fund | Risks Affecting Specific Countries or Regions [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Countries or Regions – If a significant portion of the Fund’s assets is invested in issuers that are economically exposed to one country or region, the Fund’s share value may be more susceptible to the conditions and developments in that country or region, and potentially more volatile than the share value of a more geographically diversified fund. A specific country or region could also be adversely affected by conditions or developments arising in other countries. For example, the U.S. government could take actions to prohibit or restrict individuals or companies within the U.S. from purchasing or holding the shares of issuers in another country, which may limit the Fund’s ability to invest in that country or cause the Fund to have to sell investments in that country at less than desired prices. The nature and degree of the risks affecting a given country or region, and the extent of the Fund’s exposure to any such country or region, is expected to vary over time.
Retirement | Thornburg Developing World Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of an equity security may decline in response to developments affecting the specific issuer of the security or obligation, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retirement | Thornburg Developing World Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments.
Retirement | Thornburg Developing World Fund | Risks Affecting Investments in China [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Investments in China – A significant portion of the Fund’s assets may be invested in companies exposed to China. Risks affecting investments in China include a potential downturn in the Chinese economy, reduced liquidity or increased price volatility in the Chinese securities markets as a result of trading suspensions affecting Chinese issuers or other factors, the potential that the Chinese government may expand restrictions on foreign investments or the repatriation of capital, and the implementation of new tariffs or other trade barriers by China or its trading partners. A lack of transparency respecting Chinese companies may also reduce the Fund’s ability to conduct diligence respecting those companies’ accounting and governance standards, which may in turn reduce the Fund’s ability to detect fraudulent practices that may adversely affect the companies’ stock prices.
Retirement | Thornburg Developing World Fund | Thornburg Developing World Fund Class R5  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THDRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.95%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.09%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.04%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (1.00%) [64]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.04%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 106
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 543
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,006
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,289
Annual Return 2015 rr_AnnualReturn2015 (14.94%)
Annual Return 2016 rr_AnnualReturn2016 3.08%
Annual Return 2017 rr_AnnualReturn2017 35.84%
Annual Return 2018 rr_AnnualReturn2018 (14.88%)
Annual Return 2019 rr_AnnualReturn2019 29.53%
Annual Return 2020 rr_AnnualReturn2020 23.08%
Annual Return 2021 rr_AnnualReturn2021 (2.65%)
Annual Return 2022 rr_AnnualReturn2022 (25.51%)
Annual Return 2023 rr_AnnualReturn2023 6.60%
Annual Return 2024 rr_AnnualReturn2024 5.75%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 21.77%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (24.75%)
1 Year rr_AverageAnnualReturnYear01 5.75%
5 Years rr_AverageAnnualReturnYear05 0.13%
10 Years rr_AverageAnnualReturnYear10 2.83%
Retirement | Thornburg Developing World Fund | Thornburg Developing World Fund Class R5 | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.55%
5 Years rr_AverageAnnualReturnYear05 (0.43%)
10 Years rr_AverageAnnualReturnYear10 2.34%
Retirement | Thornburg Developing World Fund | Thornburg Developing World Fund Class R5 | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.41%
5 Years rr_AverageAnnualReturnYear05 (0.14%)
10 Years rr_AverageAnnualReturnYear10 1.98%
Retirement | Thornburg Developing World Fund | Thornburg Developing World Fund Class R5 | MSCI Emerging Markets Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 7.50%
5 Years rr_AverageAnnualReturnYear05 1.70%
10 Years rr_AverageAnnualReturnYear10 3.64%
Retirement | Thornburg Developing World Fund | Thornburg Developing World Fund Class R6  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TDWRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.95%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.29%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.24%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.30%) [64]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.94%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 96
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 364
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 652
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,474
1 Year rr_AverageAnnualReturnYear01 5.88%
5 Years rr_AverageAnnualReturnYear05 0.23%
10 Years rr_AverageAnnualReturnYear10 2.93%
Retirement | Thornburg Developing World Fund | Thornburg Developing World Fund Class R6 | MSCI Emerging Markets Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 7.50%
5 Years rr_AverageAnnualReturnYear05 1.70%
10 Years rr_AverageAnnualReturnYear10 3.64%
Retirement | Thornburg Small/Mid Cap Core Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Small/Mid Cap Core Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks long-term capital appreciation by investing in equity and debt securities of all types.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

The secondary, non-fundamental goal of the Fund is to seek some current income.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 32.79% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 32.79%
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal conditions, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in small- and mid-capitalization companies. The Fund currently defines small- and mid-capitalization companies to be those within the market capitalization range comprised by the Russell 2500 Index – Total Return. As of November 30, 2024, the market capitalization range of the Russell 2500 Index – Total Return was approximately $12.46 million to $53.31 billion. The Russell 2500 Index – Total Return is completely reconstituted on an annual basis each June by the index provider, which generally results in updates to the capitalization range of the index and to the companies included in the index. The capitalization range of companies in which the Fund invests will in general also change annually to reflect the reconstitution of the index. The Fund may change the definition of what constitutes “small- and mid-capitalization companies” without advance notice to shareholders.

The Fund expects to invest primarily in domestic common stocks. However, the Fund may own foreign common stocks which, in the opinion of the Fund’s investment advisor, Thornburg Investment Management, Inc. (“Thornburg”), offer prospects for meeting the Fund’s investment goals.

With its core approach to stock selection, the Fund seeks to invest in a broadly diversified portfolio of companies the Fund categorizes as basic values, consistent earners, and emerging franchises, as described in more detail below. The relative proportions of securities invested in each of those categories will vary over time.

Thornburg primarily takes a bottom-up, fundamental view in determining the attractiveness of individual securities and in making investment decisions. Among the specific factors considered by Thornburg in identifying securities for inclusion in the Fund are:

•earnings growth potential

•durable business model

•industry growth potential

•innovation driving the potential to disrupt entrenched competitors

•intrinsic value appreciation potential

•potential size of addressable market

•management strength

•leverage

•return on invested capital

•valuation metrics, including: price/earnings (“PE”) ratio; enterprise value/revenue ratio; PE/growth rate ratio, enterprise value/EBITDA (earnings before interest, taxes, depreciation and amortization) ratio; and free cash flow yield.

Thornburg typically categorizes the Fund’s equity investments in one of the following three categories:

Basic Value: Companies generally operating in mature or cyclical industries and which generally exhibit more economic sensitivity and/or higher volatility in earnings and cash flow.

Consistent Earner: Companies which generally exhibit predictable growth and profitability, and consistent cash flow and/or dividends.

Emerging Franchise: Companies with the potential to grow at an above average rate because of a product or service that is establishing a new market and/or taking share from existing participants.

Inclusion of any investment in any of the three described categories represents Thornburg’s opinion concerning the characteristics and prospects of the investment. There is no assurance that any company selected for investment will, once categorized in one of the three described investment categories, continue to have the positive characteristics or fulfill the expectations that Thornburg had for the company when it was selected for investment, and any such company may not grow or may decline in earnings and size.

The Fund selects foreign securities issued by companies domiciled in countries whose currencies are freely convertible into U.S. dollars, or in companies in other countries whose business is conducted primarily in U.S. dollars.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in small- and mid-capitalization companies may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Small/Mid Cap Core Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class R3 shares have been different in each full year shown. The average annual total return figures compare Class R3, Class R4 and Class R5 share performance to the Russell 3000 Index—Total Return, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the Russell 2500 Index—Total Return, an additional index that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Small/Mid Cap Core Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class R3 Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 18.90%

6/30/2020

Lowest Quarterly Results

-26.31%

3/31/2020
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.

The performance information shown above may include gains attributable to the Fund’s investments in shares of companies through initial public offerings (“IPOs”). There can be no assurance that the Fund will have continued access to profitable IPOs and, as the Fund’s assets grow, the impact of the Fund’s investment in IPOs on the performance of the Fund may decline.
Retirement | Thornburg Small/Mid Cap Core Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retirement | Thornburg Small/Mid Cap Core Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retirement | Thornburg Small/Mid Cap Core Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retirement | Thornburg Small/Mid Cap Core Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retirement | Thornburg Small/Mid Cap Core Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection.
Retirement | Thornburg Small/Mid Cap Core Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices.
Retirement | Thornburg Small/Mid Cap Core Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retirement | Thornburg Small/Mid Cap Core Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retirement | Thornburg Small/Mid Cap Core Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retirement | Thornburg Small/Mid Cap Core Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a security may decline in response to developments affecting the specific issuer of the security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retirement | Thornburg Small/Mid Cap Core Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, earlier stages of development and lack of well-established businesses, more limited access to markets and financial resources, greater vulnerability to competition and market risks and fluctuations, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments. Relative to the stocks of large capitalization companies, the stocks of small- and mid-capitalization companies may be thinly traded and sales may result in higher transaction costs. Also, small- and mid-capitalization companies may perform poorly during times of economic stress.
Retirement | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class R3  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TVRFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.87%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.51%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.88%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.57%) [65]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.31%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 133
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 536
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 963
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,155
Annual Return 2015 rr_AnnualReturn2015 3.45%
Annual Return 2016 rr_AnnualReturn2016 6.65%
Annual Return 2017 rr_AnnualReturn2017 23.35%
Annual Return 2018 rr_AnnualReturn2018 (9.72%)
Annual Return 2019 rr_AnnualReturn2019 28.86%
Annual Return 2020 rr_AnnualReturn2020 11.70%
Annual Return 2021 rr_AnnualReturn2021 13.78%
Annual Return 2022 rr_AnnualReturn2022 (19.49%)
Annual Return 2023 rr_AnnualReturn2023 13.19%
Annual Return 2024 rr_AnnualReturn2024 19.48%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 18.90%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (26.31%)
1 Year rr_AverageAnnualReturnYear01 19.48%
5 Years rr_AverageAnnualReturnYear05 6.71%
10 Years rr_AverageAnnualReturnYear10 8.16%
Retirement | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class R3 | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 19.48%
5 Years rr_AverageAnnualReturnYear05 5.01%
10 Years rr_AverageAnnualReturnYear10 7.23%
Retirement | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class R3 | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 11.53%
5 Years rr_AverageAnnualReturnYear05 4.88%
10 Years rr_AverageAnnualReturnYear10 6.42%
Retirement | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class R3 | Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
Retirement | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class R3 | Russell 2500 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 12.00%
5 Years rr_AverageAnnualReturnYear05 8.77%
10 Years rr_AverageAnnualReturnYear10 8.85%
Retirement | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class R4  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TVIRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.87%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.16%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.95%) [65]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.21%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 123
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 584
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,072
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,418
1 Year rr_AverageAnnualReturnYear01 19.61%
5 Years rr_AverageAnnualReturnYear05 6.82%
10 Years rr_AverageAnnualReturnYear10 8.27%
Retirement | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class R4 | Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
Retirement | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class R4 | Russell 2500 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 12.00%
5 Years rr_AverageAnnualReturnYear05 8.77%
10 Years rr_AverageAnnualReturnYear10 8.85%
Retirement | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class R5  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TVRRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.87%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.00%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.87%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.92%) [65]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.95%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 97
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 498
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 925
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,115
1 Year rr_AverageAnnualReturnYear01 19.91%
5 Years rr_AverageAnnualReturnYear05 7.10%
10 Years rr_AverageAnnualReturnYear10 8.55%
Retirement | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class R5 | Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
Retirement | Thornburg Small/Mid Cap Core Fund | Thornburg Small/Mid Cap Core Fund - Class R5 | Russell 2500 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 12.00%
5 Years rr_AverageAnnualReturnYear05 8.77%
10 Years rr_AverageAnnualReturnYear10 8.85%
Retirement | Thornburg Small/Mid Cap Growth Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Small/Mid Cap Growth Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks long-term growth of capital by investing in equity securities selected for their growth potential.

Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 32.58% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 32.58%
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal conditions, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in small- and mid-capitalization companies and at least 80% of its net assets in growth companies. The Fund currently defines small- and mid-capitalization companies to be those within the market capitalization range comprised by the Russell 2500 Growth Index – Total Return. As of November 30, 2024, the market capitalization range of the Russell 2500 Growth Index – Total Return was approximately $12.46 million to $53.31 billion. The Russell 2500 Growth Index – Total Return is completely reconstituted on an annual basis each June by the index provider, which generally results in updates to the capitalization range of the index and to the companies included in the index. The capitalization range of companies in which the Fund invests will in general also change annually to reflect the reconstitution of the index. The Fund may change the definition of what constitutes “small- and mid-capitalization companies” without advance notice to shareholders. The Fund currently considers a company to be a growth company if it meets any of the following criteria:

•It is a constituent of the Russell 2500 Growth Index; or

•It has, over the last five years, grown its revenues or earnings per share at an average annual rate which exceeds the median growth rate of revenues or earnings per share, as applicable, for companies in the Russell 2500 Index; or

•It is projected by consensus estimates as compiled by FactSet Research Systems, over the next two years, to grow its revenues or earnings per share at an average annual rate which exceeds the median growth rate of revenues or earnings per share, as applicable, for companies in the Russell 2500 Index.

The Fund expects to invest primarily in domestic common stocks. However, the Fund may own foreign common stocks which, in the opinion of the Fund’s investment advisor, Thornburg Investment Management, Inc. (“Thornburg”), offer prospects for meeting the Fund’s investment goal.

The Fund seeks to invest in a diversified portfolio of companies the Fund categorizes as consistent growers, disruptors, and emerging franchises, as described in more detail below. The relative proportions of securities invested in each of those categories will vary over time.

Thornburg primarily takes a bottom-up, fundamental view in determining the attractiveness of individual securities and in making investment decisions. Among the specific factors considered by Thornburg in identifying securities for inclusion in the Fund are:

•earnings growth potential

•durable business model

•industry growth potential

•innovation driving the potential to disrupt entrenched competitors

•intrinsic value appreciation potential

•potential size of addressable market

•management strength

•leverage

•return on invested capital

•valuation metrics, including: price/earnings (“PE”) ratio; enterprise value/revenue ratio; PE/growth rate ratio, enterprise value/EBITDA (earnings before interest, taxes, depreciation and amortization) ratio; and free cash flow yield.

Thornburg typically categorizes the Fund’s equity investments in one of the following three categories:

Consistent Grower: Companies in this category generally exhibit steady earnings or revenue growth, or both. These companies may have subscription or other recurring revenue profiles. Given their business models, these companies may outperform in weak markets.

Disruptor: Companies which are at the early stages of growth; which usually possess highly innovative or differentiated products and services, but which may require substantial additional time or investment to capitalize on market opportunities and achieve profitability. Companies in this category often are in leadership positions in growing markets. These companies may operate in niche markets with large or dominant share.

Emerging Franchise: Companies with the potential to grow at an above average rate because of a product or service that is establishing a new market and/or taking share from existing participants.

Inclusion of any investment in any of the three described categories represents Thornburg’s opinion concerning the characteristics and prospects of the investment. There is no assurance that any company selected for investment will, once categorized in one of the three described investment categories, continue to have the positive characteristics or fulfill the expectations that Thornburg had for the company when it was selected for investment, and any such company may not grow or may decline in earnings and size.

In conjunction with individual issuer analysis, Thornburg may identify and invest at times with a greater emphasis in industries or economic sectors it expects to experience growth. The Fund does not have a strategy to invest in particular industry or economic sectors, and its exposures to particular industries or economic sectors are expected to vary over time.

The Fund selects foreign securities issued by companies domiciled in countries whose currencies are freely convertible into U.S. dollars, or in companies in other countries whose business is conducted primarily in U.S. dollars.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in small- and mid-capitalization companies may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders. The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in growth companies may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders. Additionally, the Fund may change its definition of what constitutes a “growth company” at any time without advance notice to shareholders.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Small/Mid Cap Growth Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class R3 shares have been different in each full year shown. The average annual total return figures compare Class R3, Class R4 and Class R5 share performance to the Russell 3000 Index—Total Return, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the Russell 2500 Index—Total Return, an additional index that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Small/Mid Cap Growth Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class R3 Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 30.91%

6/30/2020

Lowest Quarterly Results

-24.91%

6/30/2022
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Retirement | Thornburg Small/Mid Cap Growth Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retirement | Thornburg Small/Mid Cap Growth Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retirement | Thornburg Small/Mid Cap Growth Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retirement | Thornburg Small/Mid Cap Growth Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retirement | Thornburg Small/Mid Cap Growth Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection.
Retirement | Thornburg Small/Mid Cap Growth Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices.
Retirement | Thornburg Small/Mid Cap Growth Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retirement | Thornburg Small/Mid Cap Growth Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retirement | Thornburg Small/Mid Cap Growth Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retirement | Thornburg Small/Mid Cap Growth Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a security may decline in response to developments affecting the specific issuer of the security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retirement | Thornburg Small/Mid Cap Growth Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, earlier stages of development and lack of well-established businesses, more limited access to markets and financial resources, greater vulnerability to competition and market risks and fluctuations, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments. Relative to the stocks of large capitalization companies, the stocks of small- and mid-capitalization companies may be thinly traded and sales may result in higher transaction costs. Also, small- and mid-capitalization companies may perform poorly during times of economic stress.
Retirement | Thornburg Small/Mid Cap Growth Fund | Growth Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Growth Company Risk – Growth company stocks may trade at higher multiples of current earnings than other equity securities and, therefore, may be more sensitive to changes in current or expected earnings than other equity securities and may be more volatile. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can cushion stock prices in market downturns. These risks may be more pronounced in companies that are in the earlier stages of their growth cycle.
Retirement | Thornburg Small/Mid Cap Growth Fund | Information Technology Securities Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Information Technology Securities Risk – Information technology companies may at times be more vulnerable to product obsolescence caused by rapid technology changes, the failure to obtain or maintain intellectual property rights, the inability to develop new products, competition from new and existing market entrants, and changes in consumer preferences. Information technology stocks may also be more volatile than the overall market.
Retirement | Thornburg Small/Mid Cap Growth Fund | Biotechnology Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Biotechnology Company Risk – The Fund may invest in biotechnology companies, which may at times be more vulnerable to product obsolescence, failures to develop successful products despite significant investments in research and development, the failure to obtain or maintain intellectual property rights, competition from new and existing market entrants, and product liability claims from consumers. Biotechnology companies may also be adversely affected by changes in government regulations and restrictions. Additionally, biotechnology companies may be more reliant on capital markets to invest in and support their business operations, and biotechnology companies’ valuations, especially those of smaller, less-seasoned companies, tend to be more volatile than the overall market.
Retirement | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class R3  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THCRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.87%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.51%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.88%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.42%) [66]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.46%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 149
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 550
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 977
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,167
Annual Return 2015 rr_AnnualReturn2015 2.68%
Annual Return 2016 rr_AnnualReturn2016 (2.46%)
Annual Return 2017 rr_AnnualReturn2017 23.79%
Annual Return 2018 rr_AnnualReturn2018 (2.72%)
Annual Return 2019 rr_AnnualReturn2019 28.72%
Annual Return 2020 rr_AnnualReturn2020 41.38%
Annual Return 2021 rr_AnnualReturn2021 (4.47%)
Annual Return 2022 rr_AnnualReturn2022 (34.21%)
Annual Return 2023 rr_AnnualReturn2023 19.54%
Annual Return 2024 rr_AnnualReturn2024 19.61%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 30.91%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (24.91%)
1 Year rr_AverageAnnualReturnYear01 19.61%
5 Years rr_AverageAnnualReturnYear05 4.90%
10 Years rr_AverageAnnualReturnYear10 7.03%
Retirement | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class R3 | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 19.61%
5 Years rr_AverageAnnualReturnYear05 2.77%
10 Years rr_AverageAnnualReturnYear10 5.71%
Retirement | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class R3 | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 11.61%
5 Years rr_AverageAnnualReturnYear05 3.95%
10 Years rr_AverageAnnualReturnYear10 5.72%
Retirement | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class R3 | Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
Retirement | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class R3 | Russell 2500 Growth Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 13.90%
5 Years rr_AverageAnnualReturnYear05 8.08%
10 Years rr_AverageAnnualReturnYear10 9.45%
Retirement | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class R4  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TCGRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.87%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 2.37%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 3.49%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (2.13%) [66]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.36%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 138
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 873
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,630
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 3,624
1 Year rr_AverageAnnualReturnYear01 19.70%
5 Years rr_AverageAnnualReturnYear05 5.00%
10 Years rr_AverageAnnualReturnYear10 7.13%
Retirement | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class R4 | Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
Retirement | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class R4 | Russell 2500 Growth Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 13.90%
5 Years rr_AverageAnnualReturnYear05 8.08%
10 Years rr_AverageAnnualReturnYear10 9.45%
Retirement | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class R5  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THGRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.87%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.47%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.34%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.39%) [66]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.95%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 97
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 386
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 697
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,579
1 Year rr_AverageAnnualReturnYear01 20.20%
5 Years rr_AverageAnnualReturnYear05 5.44%
10 Years rr_AverageAnnualReturnYear10 7.57%
Retirement | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class R5 | Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
Retirement | Thornburg Small/Mid Cap Growth Fund | Thornburg Small/Mid Cap Growth Fund - Class R5 | Russell 2500 Growth Index-Total Return (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 13.90%
5 Years rr_AverageAnnualReturnYear05 8.08%
10 Years rr_AverageAnnualReturnYear10 9.45%
Retirement | Thornburg Investment Income Builder Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Investment Income Builder Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund’s primary investment goal is to provide a level of current income which exceeds the average yield on U.S. stocks generally, and which will generally grow, subject to periodic fluctuations, over the years on a per share basis.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

The Fund’s secondary investment goal is long-term capital appreciation.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 24.81% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 24.81%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text] rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees The Total Annual Fund Operating Expenses and Total Annual Fund Operating Expenses After Fee Waiver/Expense Reimbursement do not match the Ratios to Average Net Assets shown in the Financial Highlights section of the Prospectus, which reflect the operating expenses of the Fund and do not include acquired fund fees and expenses (‘AFFE’). AFFE are expenses incurred indirectly by other investment companies in which the Fund holds shares, are not direct costs paid by Fund shareholders, and are not used to calculate the Fund’s net asset value.
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment goals by investing in a broad range of income producing securities, primarily including stocks and bonds, as described below. The Fund will under normal conditions invest at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in income-producing securities, and at least 50% of its net assets, plus the amount of any borrowings for investment purposes, in common stocks.

The Fund may invest in any stock or other equity security which Thornburg believes may assist the Fund in pursuing its investment goals (including smaller companies with market capitalization of less than $500 million and companies in developing countries), including preferred stock and publicly traded real estate investment trusts. The Fund expects that equity investments in the Fund’s portfolio normally will be weighted in favor of companies which pay dividends or other current income.

The Fund may invest in debt obligations of any kind, including corporate bonds and other obligations, mortgage- and other asset-backed securities and government obligations. The Fund may purchase debt obligations of any maturity and of any credit quality, including “high yield” or “junk” bonds. There is no minimum credit quality or rating of debt obligation the Fund may purchase. The Fund also may invest in debt obligations which have a combination of equity and debt characteristics, such as convertible bonds.

The Fund may invest a significant portion of its assets in securities of issuers domiciled in or economically tied to countries outside the United States, including developing countries.

The Fund’s investments are determined by individual issuer and industry analysis. Investment decisions are based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for debt and equity securities, and analysis of specific issuers. The Fund ordinarily acquires and holds debt obligations for investment rather than for realization of gains by short-term trading on market fluctuations. However, the Fund may dispose of any such security prior to its scheduled maturity to enhance income or reduce loss, to change the portfolio’s average maturity, or otherwise to respond to market conditions.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in Investment Income Builder Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class R3 shares vary in each full year shown. The average annual total return figures compare Class R3, Class R4, Class R5 and Class R6 share performance to the MSCI World Net Total Return USD Index and the Bloomberg U.S. Aggregate Total Return Index Value USD, each a broad-based securities market index that represents the overall applicable market in which the Fund invests, and a Blended Benchmark, comprised of 25% Bloomberg U.S. Aggregate Bond Total Return Value USD, and 75% MSCI World Net Total Return USD Index, an additional benchmark that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in Investment Income Builder Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class R3 Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 15.81%

12/31/2020

Lowest Quarterly Results

-26.02%

3/31/2020
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Retirement | Thornburg Investment Income Builder Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retirement | Thornburg Investment Income Builder Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retirement | Thornburg Investment Income Builder Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If debt obligations held by the Fund are downgraded by ratings agencies or go into default, or if management action, legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Because the ability of an issuer of a lower-rated or unrated obligation to pay principal and interest when due is typically less certain than for an issuer of a higher-rated obligation, lower-rated and unrated obligations are generally more vulnerable than higher-rated obligations to default, to ratings downgrades, and to liquidity risk. The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Retirement | Thornburg Investment Income Builder Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retirement | Thornburg Investment Income Builder Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities or debt obligations of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retirement | Thornburg Investment Income Builder Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Retirement | Thornburg Investment Income Builder Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retirement | Thornburg Investment Income Builder Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection. In addition, some foreign government debt obligations may be subject to default, delays in payment, adverse legislation or government action, or could be downgraded by ratings agencies.
Retirement | Thornburg Investment Income Builder Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices.
Retirement | Thornburg Investment Income Builder Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retirement | Thornburg Investment Income Builder Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility.
Retirement | Thornburg Investment Income Builder Fund | Real Estate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Real Estate Risk – The Fund’s investments in publicly traded real estate investment trusts (“REITs”) are subject to risks affecting real estate investments generally (including market conditions, competition, property obsolescence, changes in interest rates and casualty to real estate), as well as risks specifically affecting REITs (the quality and skill of REIT management and the internal expenses of the REIT).
Retirement | Thornburg Investment Income Builder Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retirement | Thornburg Investment Income Builder Fund | Risks Affecting Specific Countries or Regions [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Countries or Regions – If a significant portion of the Fund’s assets is invested in issuers that are economically exposed to one country or region, the Fund’s share value may be more susceptible to the conditions and developments in that country or region, and potentially more volatile than the share value of a more geographically diversified fund. A specific country or region could also be adversely affected by conditions or developments arising in other countries. For example, the U.S. government could take actions to prohibit or restrict individuals or companies within the U.S. from purchasing or holding the shares of issuers in another country, which may limit the Fund’s ability to invest in that country or cause the Fund to have to sell investments in that country at less than desired prices. The nature and degree of the risks affecting a given country or region, and the extent of the Fund’s exposure to any such country or region, is expected to vary over time.
Retirement | Thornburg Investment Income Builder Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of an equity security or debt obligation may decline in response to developments affecting the specific issuer of the security or obligation, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retirement | Thornburg Investment Income Builder Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulty in valuing or selling these investments.
Retirement | Thornburg Investment Income Builder Fund | Convertible Debt Obligation Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Convertible Debt Obligation Risk – The market value of a convertible debt obligation may vary with changes in prevailing interest rates and changing evaluations of the ability of the issuer to meet principal and interest payments. The market value of a convertible debt obligation may also vary in accordance with the market value of the underlying stock. As a result, convertible debt obligations held by the Fund will tend to perform more like equity securities when the underlying stock price is high (because it is assumed that the Fund will convert the obligation), and more like non-convertible debt obligations when the underlying stock price is low (because it is assumed that the Fund will not convert the obligation). Because its market value can be influenced by several factors, a convertible debt obligation will not be as sensitive to interest rate changes as a similar non-convertible debt obligation, and generally will have less potential for gain or loss than the underlying stock.
Retirement | Thornburg Investment Income Builder Fund | Foreign Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Government Obligations Risk – Debt obligations may be issued by foreign governments and their agencies and instrumentalities, including the governments of developing countries and “supra-national” entities such as the International Bank for Reconstruction and Development. The Fund’s investments in these foreign debt obligations may be denominated in U.S. dollars or in foreign currencies. These securities, even if denominated in U.S. dollars, may be affected significantly by fluctuations in the value of foreign currencies, and the value of these securities in U.S. dollars may decline even if the securities increase in value in their home country. The governmental issuers of these debt obligations may be less willing or able than the U.S. to repay principal and interest when due, and they may require that the terms for payment be renegotiated. In some countries there may be political instability or insufficient government supervision of markets, and the legal protections for the Fund’s investments could be subject to unfavorable judicial or administrative changes. These risks may be more pronounced for the Fund’s investments in debt obligations issued by developing countries.
Retirement | Thornburg Investment Income Builder Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retirement | Thornburg Investment Income Builder Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments in debt obligations may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. This effect is also typically more pronounced for mortgage- and other asset-backed securities, the value of which may fluctuate more significantly in response to interest rate changes. When interest rates decrease, the Fund’s dividends may decline.
Retirement | Thornburg Investment Income Builder Fund | Prepayment and Extension Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Prepayment and Extension Risk – When market interest rates decline, certain debt obligations held by the Fund may be repaid more quickly than anticipated, requiring the Fund to reinvest the proceeds of those repayments in obligations which bear a lower interest rate. Conversely, when market interest rates increase, certain debt obligations held by the Fund may be repaid more slowly than anticipated, causing assets of the Fund to remain invested in relatively lower yielding obligations. These risks may be more pronounced for the Fund’s investments in mortgage-backed and asset-backed securities.
Retirement | Thornburg Investment Income Builder Fund | U.S. Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

U.S. Government Obligations Risk – U.S. government obligations are subject to the same risks affecting other debt obligations. Although securities backed by the full faith credit of the U.S. government are commonly regarded as having relatively less risk of default, it is possible that the U.S. government may be unwilling or unable to repay principal and interest when due and may require that the terms for payment be renegotiated. Further obligations that are backed by the full faith and credit of the U.S. government remain subject to the other general risks applicable to debt obligations, such as market risks, liquidity risks, and interest rate risks, and may be subject to ratings downgrades. U.S. government obligations also include obligations of U.S. government agencies, instrumentalities, and government-sponsored enterprises, commonly referred to as “agency obligations.” Some agency obligations are backed by the full faith and credit of the U.S. government, but other agency obligations have no specific backing or only limited support from the agency’s authority to borrow from the U.S. government or the discretionary authority of the Treasury to purchase obligations of the issuing agency.
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R3  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TIBRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.69%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.49%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.72% [67]
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.18%) [68]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.54% [67]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 157
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 524
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 917
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,015
Annual Return 2015 rr_AnnualReturn2015 (5.72%)
Annual Return 2016 rr_AnnualReturn2016 9.17%
Annual Return 2017 rr_AnnualReturn2017 14.49%
Annual Return 2018 rr_AnnualReturn2018 (5.01%)
Annual Return 2019 rr_AnnualReturn2019 17.28%
Annual Return 2020 rr_AnnualReturn2020 (1.02%)
Annual Return 2021 rr_AnnualReturn2021 19.59%
Annual Return 2022 rr_AnnualReturn2022 (8.62%)
Annual Return 2023 rr_AnnualReturn2023 17.49%
Annual Return 2024 rr_AnnualReturn2024 12.68%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 15.81%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (26.02%)
1 Year rr_AverageAnnualReturnYear01 12.68%
5 Years rr_AverageAnnualReturnYear05 7.45%
10 Years rr_AverageAnnualReturnYear10 6.52%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R3 | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 10.53%
5 Years rr_AverageAnnualReturnYear05 5.44%
10 Years rr_AverageAnnualReturnYear10 4.66%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R3 | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 7.61%
5 Years rr_AverageAnnualReturnYear05 4.85%
10 Years rr_AverageAnnualReturnYear10 4.22%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R3 | MSCI World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 18.67%
5 Years rr_AverageAnnualReturnYear05 11.17%
10 Years rr_AverageAnnualReturnYear10 9.95%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R3 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R3 | Blended Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 14.12%
5 Years rr_AverageAnnualReturnYear05 8.42%
10 Years rr_AverageAnnualReturnYear10 7.93%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R4  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TIBGX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.69%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.63%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.61% [67]
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.17%) [68]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.44% [67]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 147
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 491
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 860
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,897
1 Year rr_AverageAnnualReturnYear01 12.84%
5 Years rr_AverageAnnualReturnYear05 7.56%
10 Years rr_AverageAnnualReturnYear10 6.62%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R4 | MSCI World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 18.67%
5 Years rr_AverageAnnualReturnYear05 11.17%
10 Years rr_AverageAnnualReturnYear10 9.95%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R4 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R4 | Blended Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 14.12%
5 Years rr_AverageAnnualReturnYear05 8.42%
10 Years rr_AverageAnnualReturnYear10 7.93%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R5  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TIBMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.69%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.56%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.29% [67]
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.26%) [68]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.03% [67]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 105
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 383
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 683
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,534
1 Year rr_AverageAnnualReturnYear01 13.26%
5 Years rr_AverageAnnualReturnYear05 7.99%
10 Years rr_AverageAnnualReturnYear10 7.05%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R5 | MSCI World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 18.67%
5 Years rr_AverageAnnualReturnYear05 11.17%
10 Years rr_AverageAnnualReturnYear10 9.95%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R5 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R5 | Blended Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 14.12%
5 Years rr_AverageAnnualReturnYear05 8.42%
10 Years rr_AverageAnnualReturnYear10 7.93%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R6  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TIBOX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.69%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.14%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.87% [67]
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [68]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.84% [67]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 86
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 275
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 479
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,070
1 Year rr_AverageAnnualReturnYear01 13.44%
5 Years rr_AverageAnnualReturnYear05 8.20%
Since Inception rr_AverageAnnualReturnSinceInception 8.41%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 10, 2017
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R6 | MSCI World Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 18.67%
5 Years rr_AverageAnnualReturnYear05 11.17%
Since Inception rr_AverageAnnualReturnSinceInception 11.28%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R6 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
Since Inception rr_AverageAnnualReturnSinceInception 1.19%
Retirement | Thornburg Investment Income Builder Fund | Thornburg Investment Income Builder Fund - Class R6 | Blended Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 14.12%
5 Years rr_AverageAnnualReturnYear05 8.42%
Since Inception rr_AverageAnnualReturnSinceInception 8.88%
Retirement | Thornburg Limited Term U.S. Government Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Limited Term U.S. Government Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The primary goal of Limited Term U.S. Government Fund is to provide as high a level of current income as is consistent, in the view of the Fund’s investment advisor, with safety of capital.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

As a secondary goal, the Fund seeks to reduce changes in its share price compared to longer term portfolios.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 32.26% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 32.26%
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s portfolio in pursuing the Fund’s investment goals. While Thornburg follows domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for debt obligations, and other factors, the Fund’s investments are determined by individual security analysis. The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may dispose of any security before its scheduled maturity to enhance income or reduce loss, to change the portfolio’s average maturity, or to otherwise respond to market conditions.

Limited Term U.S. Government Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in U.S. Government Securities. For this purpose, “U.S. Government Securities” means:

Securities backed by the full faith and credit of the U.S. government, including direct obligations of the U.S. Treasury (such as U.S. Treasury Bonds) and obligations of U.S. government agencies and instrumentalities which are guaranteed by the U.S. Treasury (such as “Ginnie Mae” mortgage-backed certificates issued by the Government National Mortgage Association).

Securities issued or guaranteed by U.S. government agencies, instrumentalities or sponsored enterprises, but which are not backed by the full faith and credit of the U.S. government. These securities include mortgage-backed certificates, collateralized mortgage obligations (“CMOs”), and debentures issued by “Freddie Mac” (Federal Home Loan Mortgage Corporation) and “Fannie Mae” (Federal National Mortgage Association).

U.S. Government Securities include for this purpose repurchase agreements secured by the securities described above, and participations having economic characteristics similar to those securities. “Participations” are undivided interests in pools of securities where the underlying credit support passes through to the participants.

Because the magnitude of changes in the value of interest-bearing obligations is greater for obligations with longer terms given an equivalent change in interest rates, the Fund seeks to reduce changes in its share value by maintaining a portfolio of investments with a dollar-weighted average maturity or expected life of normally less than five years. There is no limitation on the maturity of any specific security the Fund may purchase, and the Fund may sell any security before it matures. The Fund also attempts to reduce changes in share value through credit analysis, selection and diversification.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals. The objective of preserving capital may prevent the Fund from obtaining the highest yields available.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in Limited Term U.S. Government Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class R3 shares have been different in each full year shown. The average annual total return figures compare Class R3, Class R4, and Class R5 share performance to the Bloomberg U.S. Aggregate Total Return Index Value USD, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the Bloomberg U.S. Government Intermediate Total Return Index Value Unhedged, an additional benchmark that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in Limited Term U.S. Government Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class R3 Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 4.33%

12/31/2023

Lowest Quarterly Results

-3.65%

3/31/2022
 
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Retirement | Thornburg Limited Term U.S. Government Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retirement | Thornburg Limited Term U.S. Government Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retirement | Thornburg Limited Term U.S. Government Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – All securities owned by the Fund may be subject to default, delays in payment, adverse legislation or other government action, or could be downgraded by ratings agencies, reducing the value of the Fund’s shares. Securities backed by the full faith and credit of the U.S. government, such as U.S. Treasury obligations, are commonly regarded as having small exposure to credit risk. Obligations of certain U.S. government agencies, instrumentalities and government-sponsored enterprises (sometimes referred to as “agency obligations”) are not direct obligations of the United States, may not be backed by the full faith and credit of the U.S. government, and may have a greater exposure to credit risk. Although the U.S. government is required by law to provide credit support for some agency obligations, there is no assurance that the U.S. government would provide financial support for any such obligation on a default by the issuing agency, instrumentality or enterprise in the absence of a legal requirement to do so. As of the date of this Prospectus, securities backed by the full faith and credit of the U.S. government, and securities of U.S. government agencies, instrumentalities and enterprises which may be purchased by the Fund are rated “Aaa” by Moody’s Investors Services or “AA+” by S&P Global Ratings. Ratings agencies may reduce the ratings of any securities in the future.

Retirement | Thornburg Limited Term U.S. Government Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retirement | Thornburg Limited Term U.S. Government Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices.
Retirement | Thornburg Limited Term U.S. Government Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retirement | Thornburg Limited Term U.S. Government Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. For example, a fall in worldwide demand for U.S. government securities or general economic decline could lower the value of those securities.
Retirement | Thornburg Limited Term U.S. Government Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retirement | Thornburg Limited Term U.S. Government Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. This effect is also typically more pronounced for the Fund’s investment in mortgage-backed securities, the value of which may fluctuate more significantly in response to interest rate changes. When interest rates decrease, the Fund’s dividends may decline.
Retirement | Thornburg Limited Term U.S. Government Fund | Prepayment and Extension Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Prepayment and Extension Risk – When market interest rates decline, certain debt obligations held by the Fund may be repaid more quickly than anticipated, requiring the Fund to reinvest the proceeds of those repayments in obligations which bear a lower interest rate. Conversely, when market interest rates increase, certain debt obligations held by the Fund may be repaid more slowly than anticipated, causing assets of the Fund to remain invested in relatively lower yielding obligations. These risks may be more pronounced for the Fund’s investments in mortgage-backed securities.
Retirement | Thornburg Limited Term U.S. Government Fund | U.S. Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

U.S. Government Obligations Risk – U.S. government obligations are subject to the same risks affecting other debt obligations. Although securities backed by the full faith credit of the U.S. government are commonly regarded as having relatively less risk of default, it is possible that the U.S. government may be unwilling or unable to repay principal and interest when due and may require that the terms for payment be renegotiated. Further obligations that are backed by the full faith and credit of the U.S. government remain subject to the other general risks applicable to debt obligations, such as market risks, liquidity risks, and interest rate risks, and may be subject to ratings downgrades. U.S. government obligations also include obligations of U.S. government agencies, instrumentalities, and government-sponsored enterprises, commonly referred to as “agency obligations.” Some agency obligations are backed by the full faith and credit of the U.S. government, but other agency obligations have no specific backing or only limited support from the agency’s authority to borrow from the U.S. government or the discretionary authority of the Treasury to purchase obligations of the issuing agency.
Retirement | Thornburg Limited Term U.S. Government Fund | Structured Products Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Structured Products Risk – Investments in securities that are backed by, or represent interests in, an underlying pool of securities or other assets, including investments in mortgage-backed securities and in CMOs, involve the risks associated with the underlying assets (e.g., the risk of default by mortgagors whose mortgages are included in a mortgage-backed security or CMO), and may also involve different or greater risks, including the risk that distributions from the underlying assets will be inadequate to make interest or other payments to the Fund, the risk that the issuer of the securities will fail to administer the underlying assets properly or become insolvent, and the risk that the securities will be less liquid than other Fund investments.
Retirement | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class R3  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTURX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.37%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.05%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.92%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.93%) [69]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 101
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 513
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 950
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,168
Annual Return 2015 rr_AnnualReturn2015 0.27%
Annual Return 2016 rr_AnnualReturn2016 0.91%
Annual Return 2017 rr_AnnualReturn2017 0.56%
Annual Return 2018 rr_AnnualReturn2018 0.73%
Annual Return 2019 rr_AnnualReturn2019 3.52%
Annual Return 2020 rr_AnnualReturn2020 3.66%
Annual Return 2021 rr_AnnualReturn2021 (1.94%)
Annual Return 2022 rr_AnnualReturn2022 (8.01%)
Annual Return 2023 rr_AnnualReturn2023 3.90%
Annual Return 2024 rr_AnnualReturn2024 2.32%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.33%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.65%)
1 Year rr_AverageAnnualReturnYear01 2.32%
5 Years rr_AverageAnnualReturnYear05 (0.12%)
10 Years rr_AverageAnnualReturnYear10 0.53%
Retirement | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class R3 | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.23%
5 Years rr_AverageAnnualReturnYear05 (0.84%)
10 Years rr_AverageAnnualReturnYear10 (0.15%)
Retirement | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class R3 | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.37%
5 Years rr_AverageAnnualReturnYear05 (0.39%)
10 Years rr_AverageAnnualReturnYear10 0.11%
Retirement | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class R3 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retirement | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class R3 | Bloomberg U.S. Government Intermediate Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.44%
5 Years rr_AverageAnnualReturnYear05 0.49%
10 Years rr_AverageAnnualReturnYear10 1.24%
Retirement | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class R4  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTUGX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.37%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 2.03%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.65%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (1.66%) [69]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 101
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 665
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,256
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,860
1 Year rr_AverageAnnualReturnYear01 2.32%
5 Years rr_AverageAnnualReturnYear05 (0.14%)
Since Inception rr_AverageAnnualReturnSinceInception 0.52%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 01, 2014
Retirement | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class R4 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
Since Inception rr_AverageAnnualReturnSinceInception 1.35%
Retirement | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class R4 | Bloomberg U.S. Government Intermediate Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.44%
5 Years rr_AverageAnnualReturnYear05 0.49%
Since Inception rr_AverageAnnualReturnSinceInception 1.24%
Retirement | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class R5  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol LTGRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.37%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.87%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.24%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (1.57%) [69]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.67%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 68
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 549
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,056
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,452
1 Year rr_AverageAnnualReturnYear01 2.65%
5 Years rr_AverageAnnualReturnYear05 0.18%
10 Years rr_AverageAnnualReturnYear10 0.85%
Retirement | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class R5 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retirement | Thornburg Limited Term U.S. Government Fund | Thornburg Limited Term U.S. Government Fund - Class R5 | Bloomberg U.S. Government Intermediate Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.44%
5 Years rr_AverageAnnualReturnYear05 0.49%
10 Years rr_AverageAnnualReturnYear10 1.24%
Retirement | Thornburg Limited Term Income Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Limited Term Income Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The primary goal of Limited Term Income Fund is to provide as high a level of current income as is consistent, in the view of the Fund’s investment advisor, with safety of capital.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

As a secondary goal, the Fund seeks to reduce changes in its share prices compared to longer term portfolios.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 59.42% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 59.42%
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s portfolio in pursuing the Fund’s investment goals. While Thornburg follows domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for debt obligations, and other factors, the Fund’s investments are determined by individual security analysis. The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may dispose of any security prior to its scheduled maturity to enhance income or reduce loss, to change the portfolio’s average maturity, or to otherwise respond to current market conditions.

The Fund invests at least 65% of its net assets, plus the amount of any borrowings for investment purposes, in (i) obligations of the U.S. government, its agencies and instrumentalities, and (ii) debt obligations rated at the time of purchase in one of the three highest principal long term rating categories of S&P Global Ratings (AAA, AA or A) or Moody’s Investors Services, Inc. (Aaa, Aa or A), or the equivalent three highest short term ratings of those ratings agencies, or, if no credit rating is available, judged to be of comparable quality as determined by Thornburg. The Fund will not invest in any debt obligation rated at the time of purchase lower than BBB by S&P, Baa by Moody’s, the of equivalent short term ratings of those ratings agencies, or, if no credit rating is available, judged to be of comparable quality as determined by Thornburg. The Fund may purchase debt obligations such as corporate debt obligations, mortgage-backed securities, other asset-backed securities, municipal securities, and commercial paper and bankers’ acceptances. The Fund may purchase foreign securities of the same types and quality as the domestic securities it purchases when Thornburg believes these investments are consistent with the Fund’s objectives.

Because the magnitude of changes in the value of interest-bearing obligations is greater for obligations with longer terms given an equivalent change in interest rates, the Fund seeks to reduce changes in its share value by maintaining a portfolio of investments with a dollar-weighted average maturity or expected life normally of less than five years. As a result, the Fund also maintains a portfolio of investments having a dollar-weighted average effective duration of normally no more than five years. Duration is a measure of estimated sensitivity to interest rate changes. A portfolio with a longer average effective duration will typically be more sensitive to interest rate changes than a portfolio with a shorter average effective duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example, an obligation with a duration of 5 would be expected to change in price by approximately 5% in response to a 1% change in interest rates. During temporary periods the Fund’s portfolio maturity and average effective duration may be reduced for defensive purposes. There is no limitation on the maturity of any specific security the Fund may purchase, and the Fund may sell any security before it matures. The Fund also attempts to reduce changes in share value through credit analysis, selection and diversification.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals. The objective of preserving capital may prevent the Fund from obtaining the highest yields available.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in Limited Term Income Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class R3 shares have been different in each full year shown. The average annual total return figures compare Class R3, Class R4, Class R5 and Class R6 share performance to the Bloomberg U.S. Aggregate Total Return Index Value USD, a broad-based securities

market index that represents the overall applicable market in which the Fund invests, and the Bloomberg Intermediate U.S. Government/Credit Total Return Index Value Unhedged, an additional benchmark that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in Limited Term Income Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class R3 Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 5.66%

6/30/2020

Lowest Quarterly Results

-3.94%

3/31/2022
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Retirement | Thornburg Limited Term Income Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retirement | Thornburg Limited Term Income Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retirement | Thornburg Limited Term Income Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – All securities owned by the Fund may be subject to default, delays in payment, adverse legislation or other government action, or could be downgraded by ratings agencies, reducing the value of the Fund’s shares. Securities backed by the full faith and credit of the U.S. government, such as U.S. Treasury obligations, are commonly regarded as having small exposure to credit risk. Obligations of certain U.S. government agencies, instrumentalities and government sponsored enterprises (sometimes referred to as “agency obligations”) are not direct obligations of the United States, may not be backed by the full faith and credit of the U.S. government, and may have a greater exposure to credit risk. Although the U.S. government is required by law to provide credit support for some agency obligations, there is no assurance that the U.S. government would provide financial support for any such obligation on a default by the issuing agency, instrumentality or enterprise in the absence of a legal requirement to do so. As of the date of this Prospectus, securities backed by the full faith and credit of the U.S. government, and securities of U.S. government agencies, instrumentalities and enterprises which may be purchased by the Fund, are rated “Aaa” by Moody’s Investors Services or “AA+” by S&P Global Ratings. Ratings agencies may reduce the ratings of any securities in the future. Lower-rated or unrated obligations in which the Fund is permitted to invest may have, or may be perceived to have, greater risk of default and ratings downgrades.
Retirement | Thornburg Limited Term Income Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retirement | Thornburg Limited Term Income Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in the debt obligations of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection. These risks may be more pronounced for investments in developing countries. In addition, some foreign government debt obligations may be subject to default, delays in payment, adverse legislation or government action, or could be downgraded by ratings agencies.
Retirement | Thornburg Limited Term Income Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices.
Retirement | Thornburg Limited Term Income Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retirement | Thornburg Limited Term Income Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. For example, a fall in worldwide demand for U.S. government securities or general economic decline could lower the value of those securities.
Retirement | Thornburg Limited Term Income Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retirement | Thornburg Limited Term Income Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a debt obligation may decline in response to developments affecting the specific issuer of the obligation, even if other issuers or the overall economy are unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retirement | Thornburg Limited Term Income Fund | Foreign Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Government Obligations Risk – Debt obligations may be issued by foreign governments and their agencies and instrumentalities, including the governments of developing countries and “supra-national” entities such as the International Bank for Reconstruction and Development. The Fund’s investments in these foreign debt obligations may be denominated in U.S. dollars or in foreign currencies. These securities, even if denominated in U.S. dollars, may be affected significantly by fluctuations in the value of foreign currencies, and the value of these securities in U.S. dollars may decline even if the securities increase in value in their home country. The governmental issuers of these debt obligations may be less willing or able than the U.S. to repay principal and interest when due, and they may require that the terms for payment be renegotiated. In some countries there may be political instability or insufficient government supervision of markets, and the legal protections for the Fund’s investments could be subject to unfavorable judicial or administrative changes. These risks may be more pronounced for the Fund’s investments in debt obligations issued by developing countries.
Retirement | Thornburg Limited Term Income Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. This effect is also typically

more pronounced for the Fund’s investment in mortgage- and other asset-backed securities, the value of which may fluctuate more significant in response to interest rate changes. When interest rates decrease, the Fund’s dividends may decline.
Retirement | Thornburg Limited Term Income Fund | Prepayment and Extension Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Prepayment and Extension Risk – When market interest rates decline, certain debt obligations held by the Fund may be repaid more quickly than anticipated, requiring the Fund to reinvest the proceeds of those repayments in obligations which bear a lower interest rate. Conversely, when market interest rates increase, certain debt obligations held by the Fund may be repaid more slowly than anticipated, causing assets of the Fund to remain invested in relatively lower yielding obligations. These risks may be more pronounced for the Fund’s investments in mortgage-backed and asset-backed securities.
Retirement | Thornburg Limited Term Income Fund | U.S. Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

U.S. Government Obligations Risk – U.S. government obligations are subject to the same risks affecting other debt obligations. Although securities backed by the full faith credit of the U.S. government are commonly regarded as having relatively less risk of default, it is possible that the U.S. government may be unwilling or unable to repay principal and interest when due and may require that the terms for payment be renegotiated. Further obligations that are backed by the full faith and credit of the U.S. government remain subject to the other general risks applicable to debt obligations, such as market risks, liquidity risks, and interest rate risks, and may be subject to ratings downgrades. U.S. government obligations also include obligations of U.S. government agencies, instrumentalities, and government-sponsored enterprises, commonly referred to as “agency obligations.” Some agency obligations are backed by the full faith and credit of the U.S. government, but other agency obligations have no specific backing or only limited support from the agency’s authority to borrow from the U.S. government or the discretionary authority of the Treasury to purchase obligations of the issuing agency.
Retirement | Thornburg Limited Term Income Fund | Structured Products Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Structured Products Risk – Investments in securities that are backed by, or represent interests in, an underlying pool of securities or other assets, including investments in mortgage- and asset-backed securities and in collateralized mortgage obligations and collateralized debt obligations, involve the risks associated with the underlying assets (e.g., the risk of default by mortgagors whose mortgages are included in a mortgage-backed security or collateralized mortgage obligation), and may also involve different or greater risks, including the risk that distributions from the underlying assets will be inadequate to make interest or other payments to the Fund, the risk that the issuer of the securities will fail to administer the underlying assets properly or become insolvent, and the risk that the securities will be less liquid than other Fund investments.
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R3  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THIRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.32%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.26%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.08%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.09%) [70]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 101
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 335
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 587
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,309
Annual Return 2015 rr_AnnualReturn2015 0.35%
Annual Return 2016 rr_AnnualReturn2016 3.00%
Annual Return 2017 rr_AnnualReturn2017 2.15%
Annual Return 2018 rr_AnnualReturn2018 0.82%
Annual Return 2019 rr_AnnualReturn2019 5.15%
Annual Return 2020 rr_AnnualReturn2020 7.13%
Annual Return 2021 rr_AnnualReturn2021 (1.30%)
Annual Return 2022 rr_AnnualReturn2022 (7.52%)
Annual Return 2023 rr_AnnualReturn2023 6.04%
Annual Return 2024 rr_AnnualReturn2024 4.12%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 5.66%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.94%)
1 Year rr_AverageAnnualReturnYear01 4.12%
5 Years rr_AverageAnnualReturnYear05 1.54%
10 Years rr_AverageAnnualReturnYear10 1.91%
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R3 | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.61%
5 Years rr_AverageAnnualReturnYear05 0.54%
10 Years rr_AverageAnnualReturnYear10 0.96%
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R3 | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.42%
5 Years rr_AverageAnnualReturnYear05 0.75%
10 Years rr_AverageAnnualReturnYear10 1.05%
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R3 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R3 | Bloomberg Intermediate U.S. Government/Credit Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.00%
5 Years rr_AverageAnnualReturnYear05 0.86%
10 Years rr_AverageAnnualReturnYear10 1.71%
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R4  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THRIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.32%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.64%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.21%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.22%) [70]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 101
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 362
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 644
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,446
1 Year rr_AverageAnnualReturnYear01 4.19%
5 Years rr_AverageAnnualReturnYear05 1.54%
Since Inception rr_AverageAnnualReturnSinceInception 1.92%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 01, 2014
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R4 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
Since Inception rr_AverageAnnualReturnSinceInception 1.35%
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R4 | Bloomberg Intermediate U.S. Government/Credit Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.00%
5 Years rr_AverageAnnualReturnYear05 0.86%
Since Inception rr_AverageAnnualReturnSinceInception 1.71%
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R5  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THRRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.32%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.34%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.66%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.17%) [70]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.49%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 50
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 194
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 351
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 806
1 Year rr_AverageAnnualReturnYear01 4.64%
5 Years rr_AverageAnnualReturnYear05 2.05%
10 Years rr_AverageAnnualReturnYear10 2.35%
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R5 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R5 | Bloomberg Intermediate U.S. Government/Credit Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.00%
5 Years rr_AverageAnnualReturnYear05 0.86%
10 Years rr_AverageAnnualReturnYear10 1.71%
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R6  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THRLX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.32%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.15%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.47%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [70]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.42%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 43
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 146
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 258
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 587
1 Year rr_AverageAnnualReturnYear01 4.79%
5 Years rr_AverageAnnualReturnYear05 2.13%
Since Inception rr_AverageAnnualReturnSinceInception 2.58%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 10, 2017
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R6 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
Since Inception rr_AverageAnnualReturnSinceInception 1.19%
Retirement | Thornburg Limited Term Income Fund | Thornburg Limited Term Income Fund - Class R6 | Bloomberg Intermediate U.S. Government/Credit Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.00%
5 Years rr_AverageAnnualReturnYear05 0.86%
Since Inception rr_AverageAnnualReturnSinceInception 1.68%
Retirement | Thornburg Core Plus Bond Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Core Plus Bond Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks to maximize total return, consistent with the long-term preservation of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 73.32% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 73.32%
Expense Example [Heading] rr_ExpenseExampleHeading Example.higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year) your costs would be:
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be

higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year) your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s portfolio in pursuing the Fund’s investment goal. Under normal conditions, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in debt obligations. The Fund may invest up to 25% of its net assets, plus the amount of any borrowings for investment purposes, in debt obligations which, at the time of purchase, are rated by a nationally recognized statistical rating organization as below investment grade (sometimes called “junk” bonds or “high yield” bonds) or, if unrated, are issued by obligors which Thornburg determines to have comparable below investment grade obligations outstanding or to be comparable to obligors with outstanding below investment grade obligations. The Fund may not, at the time of purchase, invest more than 25% of its net assets, plus the amount of any borrowings for investment purposes, in debt obligations denominated in non-U.S. currencies, but this limitation does not apply to debt obligations issued by foreign issuers and denominated in U.S. dollars. Additionally, the Fund may not, at the time of purchase, invest more than 15% of its net assets, plus the amount of any borrowings for investment purposes, in debt obligations issued by issuers in emerging markets, also known as developing countries.

There is no limitation on the duration or maturity of any specific debt obligation the Fund may purchase. The Fund will, however, generally seek to maintain a portfolio of investments with a dollar-weighted average duration that falls within two years of the dollar-weighted average duration of the Fund’s benchmark index, the Bloomberg U.S. Aggregate Bond Index. Duration is a measure of estimated sensitivity to interest rate changes, and a debt obligation or a portfolio of obligations with a higher duration will typically be more sensitive to interest rate changes than an obligation or a portfolio with a lower duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example, an obligation with a duration of 0.5 would be expected to change in price by approximately 0.5% in response to a 1% change in interest rates.

While the Fund may invest in debt obligations of any type, the Fund will typically invest in the following types of debt obligations:

•corporate debt obligations from domestic and foreign issuers of any market capitalization;

•obligations issued or guaranteed by U.S. and non-U.S. governments and their agencies or instrumentalities; and

•mortgage-backed and asset-backed securities, including residential or commercial mortgage-backed securities, or collateralized mortgage obligations, issued by agencies of the U.S. government or issued by private entities.

Each of the Fund’s investments is determined by individual issuer and industry analysis, including Thornburg’s evaluation of domestic and international economic developments, outlooks for securities markets, interest rates and inflation, and the supply and demand for debt obligations.

The Fund may also invest in futures contracts, options, swaps, and forward contracts to hedge against the decline in the value of certain of the Fund’s investments, to manage portfolio duration, or to enhance the Fund’s investment returns.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to

changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.  Because the Fund seeks to maximize total return while also preserving capital, the Fund may not always obtain the highest yields available.

The Fund’s policy of investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in debt obligations may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Core Plus Bond Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class R3 shares have been different in each full year shown. The average annual total return figures compare Class R3, Class R4, Class R5 and Class R6 share performance to the Bloomberg U.S. Aggregate Total Return Index Value USD, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The index is not actively managed and is not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Core Plus Bond Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class R3 Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 5.00%

9/30/2024

Lowest Quarterly Results

-3.30%

12/31/2024
Retirement | Thornburg Core Plus Bond Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Retirement | Thornburg Core Plus Bond Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retirement | Thornburg Core Plus Bond Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If obligations held by the Fund are downgraded by ratings agencies or go into default, or if management action, legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Because the ability of an issuer of a lower-rated or unrated obligation to pay principal and interest when due is typically less certain than for an issuer of a higher-rated obligation, lower-rated and unrated obligations are generally more vulnerable than higher- rated obligations to default, to ratings downgrades, and to liquidity risk. Debt obligations backed by so-called “subprime” mortgages may also be subject to a greater risk of default or downgrade. Debt obligations issued by the U.S. government or its agencies, instrumentalities and government sponsored enterprises are also subject to credit risk. Securities backed by the full faith and credit of the U.S. government, such as U.S. Treasury obligations, are commonly regarded as having small exposure to credit risk. Obligations of certain U.S. agencies, instrumentalities and enterprises (sometimes referred to as “agency obligations”) are not direct obligations of the U.S. government, may not be backed by the full faith and credit of the U.S. government, and may have a greater exposure to credit risk.
Retirement | Thornburg Core Plus Bond Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants, or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retirement | Thornburg Core Plus Bond Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retirement | Thornburg Core Plus Bond Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in the debt obligations of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection. In addition, some foreign government debt obligations may be subject to default, delays in payment, adverse legislation or government action, or could be downgraded by ratings agencies.
Retirement | Thornburg Core Plus Bond Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices. The market for lower-rated and unrated debt obligations (including particularly “junk” or “high yield” bonds) and debt obligations backed by so-called “subprime” mortgages may be less liquid than the market for other obligations, making it difficult for the Fund to value its investment in a lower-rated or unrated obligation or to sell the investment in a timely manner or at an acceptable price.
Retirement | Thornburg Core Plus Bond Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retirement | Thornburg Core Plus Bond Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. This effect is typically more pronounced for lower-rated and unrated debt obligations (including particularly “junk” or “high yield” bonds), the value of which may fluctuate more significantly in response to poor economic growth or other changes in market conditions, political, economic, and legal developments, and developments affecting specific issuers.

Retirement | Thornburg Core Plus Bond Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retirement | Thornburg Core Plus Bond Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a debt obligation may decline in response to developments affecting the specific issuer of the obligation or security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.

Retirement | Thornburg Core Plus Bond Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Debt obligations of small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility, and possible difficulties in valuing or selling these investments.
Retirement | Thornburg Core Plus Bond Fund | Foreign Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Government Obligations Risk – Debt obligations may be issued by foreign governments and their agencies and instrumentalities, including the governments of developing countries and “supra-national” entities such as the International Bank for Reconstruction and Development. The Fund’s investments in these foreign debt obligations may be denominated in U.S. dollars or in foreign currencies. These securities, even if denominated in U.S. dollars, may be affected significantly by fluctuations in the value of foreign currencies, and the value of these securities in U.S. dollars may decline even if the securities

increase in value in their home country. The governmental issuers of these debt obligations may be less willing or able than the U.S. to repay principal and interest when due, and they may require that the terms for payment be renegotiated. In some countries there may be political instability or insufficient government supervision of markets, and the legal protections for the Fund’s investments could be subject to unfavorable judicial or administrative changes. These risks may be more pronounced for the Fund’s investments in debt obligations issued by developing countries.
Retirement | Thornburg Core Plus Bond Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retirement | Thornburg Core Plus Bond Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. This effect is also typically more pronounced for mortgage- and other asset-backed securities, the value of which may fluctuate more significantly in response to interest rate changes. When interest rates decrease, the Fund’s dividends may decline.
Retirement | Thornburg Core Plus Bond Fund | Prepayment and Extension Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Prepayment and Extension Risk – When market interest rates decline, certain debt obligations held by the Fund may be repaid more quickly than anticipated, requiring the Fund to reinvest the proceeds of those repayments in obligations which bear a lower interest rate. Conversely, when market interest rates increase, certain debt obligations held by the Fund may be repaid more slowly than anticipated, causing assets of the Fund to remain invested in relatively lower yielding obligations. These risks may be more pronounced for the Fund’s investments in mortgage-backed and asset-backed securities.
Retirement | Thornburg Core Plus Bond Fund | U.S. Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

U.S. Government Obligations Risk – U.S. government obligations are subject to the same risks affecting other debt obligations. Although securities backed by the full faith credit of the U.S. government are commonly regarded as having relatively less risk of default, it is possible that the U.S. government may be unwilling or unable to repay principal and interest when due and may require that the terms for payment be renegotiated. Further obligations that are backed by the full faith and credit of the U.S. government remain subject to the other general risks applicable to debt obligations, such as market risks, liquidity risks, and interest rate risks, and may be subject to ratings downgrades. U.S. government obligations also include obligations of U.S. government agencies, instrumentalities, and government-sponsored enterprises, commonly referred to as “agency obligations.” Some agency obligations are backed by the full faith and credit of the U.S. government, but other agency obligations have no specific backing or only limited support from the agency’s authority to borrow from the U.S. government or the discretionary authority of the Treasury to purchase obligations of the issuing agency.
Retirement | Thornburg Core Plus Bond Fund | Derivatives Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Derivatives Risk – The Fund’s investments in futures contracts, options, swaps, forward contracts, and other derivative instruments involve the risks associated with the securities or other assets underlying those derivatives, and also may involve risks different or greater than the risks affecting the underlying assets, including the inability or unwillingness of the other party to a derivative to perform its obligations to the Fund, the Fund’s inability or delays in selling or closing positions in derivatives, and difficulties in valuing derivatives.
Retirement | Thornburg Core Plus Bond Fund | Structured Products Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Structured Products Risk – Investments in securities that are backed by, or represent interests in, an underlying pool of securities or other assets, including investments in mortgage- and asset-backed securities and in collateralized mortgage obligations, involve the risks associated with the underlying assets (e.g., the risk of default by mortgagors whose mortgages are included in a mortgage-backed security or collateralized mortgage obligation), and may also involve different or greater risks, including the risk that distributions from the underlying assets will be inadequate to make interest or other payments to the Fund, the risk that the issuer of the securities will fail to administer the underlying assets properly or become insolvent, and the risk that the securities will be less liquid than other Fund investments.

Retirement | Thornburg Core Plus Bond Fund | Emerging Markets Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Emerging Markets Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in emerging markets, also known as developing countries, because the economies of those markets are usually less diversified, communications, transportation and economic infrastructures are less developed, and emerging markets ordinarily have less established legal, political, business and social frameworks. At times the prices of debt obligations of an issuer in an emerging market may be extremely volatile. An issuer in a developed country may be similarly affected by these emerging markets risks to the extent that the issuer conducts its business in emerging markets.
Retirement | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class R3  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THCHX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.49%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 5.61%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 6.60%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (5.60%) [71]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.00%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 102
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,453
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 2,761
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 5,852
Annual Return 2024 rr_AnnualReturn2024 1.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2024
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 5.00%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2024
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.30%)
1 Year rr_AverageAnnualReturnYear01 1.01%
Since Inception rr_AverageAnnualReturnSinceInception 6.79%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 02, 2023
Retirement | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class R3 | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (0.89%)
Since Inception rr_AverageAnnualReturnSinceInception 4.81%
Retirement | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class R3 | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 0.59%
Since Inception rr_AverageAnnualReturnSinceInception 4.35%
Retirement | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class R3 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
Since Inception rr_AverageAnnualReturnSinceInception 7.08%
Retirement | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class R4  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THCEX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.49%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 3.91%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 4.65%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (3.90%) [71]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.75%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 77
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,050
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 2,029
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 4,509
1 Year rr_AverageAnnualReturnYear01 1.26%
Since Inception rr_AverageAnnualReturnSinceInception 7.05%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 02, 2023
Retirement | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class R4 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
Since Inception rr_AverageAnnualReturnSinceInception 7.08%
Retirement | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class R5  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THCFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.49%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 5.60%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 6.09%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (5.59%) [71]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 51
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,310
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 2,542
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 5,505
1 Year rr_AverageAnnualReturnYear01 1.51%
Since Inception rr_AverageAnnualReturnSinceInception 7.32%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 02, 2023
Retirement | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class R5 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
Since Inception rr_AverageAnnualReturnSinceInception 7.08%
Retirement | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class R6  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THCSX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.49%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.74%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.23%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (1.74%) [71]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.49%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 50
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 529
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,035
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,428
1 Year rr_AverageAnnualReturnYear01 1.65%
Since Inception rr_AverageAnnualReturnSinceInception 7.44%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 02, 2023
Retirement | Thornburg Core Plus Bond Fund | Thornburg Core Plus Bond Fund - Class R6 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
Since Inception rr_AverageAnnualReturnSinceInception 7.08%
Retirement | Thornburg Strategic Income Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Strategic Income Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund’s primary investment goal is to seek a high level of current income.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

The Fund’s secondary investment goal is some long-term capital appreciation.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 1, 2026
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 60.47% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 60.47%
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements in the first year), your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund pursues its investment goals by investing in a broad range of income-producing investments from throughout the world, primarily including debt obligations. The Fund expects, under normal conditions, to invest a majority of its assets in the debt obligations described below.

The Fund may invest in debt obligations of any kind, of any quality, and of any maturity. The Fund expects, under normal conditions, to select a majority of its investments from among the following types of debt obligations:

•bonds and other debt obligations issued by domestic and foreign companies of any size (including lower-rated “high yield” or “junk” bonds)

•mortgage-backed securities and other asset-backed securities, including commercial mortgage-backed securities

•convertible debt obligations

•obligations issued by foreign governments (including developing countries)

•collateralized mortgage obligations (“CMOs”), collateralized debt obligations (“CDOs”), collateralized bond obligations (“CBOs”), and collateralized loan obligations (“CLOs”)

•obligations of the U.S. government and its agencies and sponsored enterprises

•structured notes

•zero coupon bonds and “stripped” securities

•taxable municipal obligations and participations in municipal obligations

The Fund’s investments are determined by individual issuer and industry analysis. Investment decisions are based on domestic and international economic developments, outlooks for securities markets, interest rates and inflation, the supply and demand for debt securities, and analysis of specific issuers.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals. The objective of preserving capital may prevent the Fund from obtaining the highest yields available.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in Strategic Income Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows the annual total return for Class R3 shares in the one full year shown. The average annual total return figures compare Class R3, Class R4, Class R5 and Class R6 share performance to the Bloomberg U.S. Aggregate Total Return Index Value USD, a broad-based securities market index that represents the overall applicable market in which the Fund invests, and the Bloomberg U.S. Universal Total Return Index Value Unhedged, an additional benchmark that represents the market sectors which Thornburg believes are more representative of the Fund’s investment universe. The Blended Benchmark, comprised of 80% Bloomberg U.S. Aggregate Bond Total Return Value USD and 20% MSCI World Net Total Return USD Index, was removed as the Fund’s secondary index effective September 30, 2024. These indexes are not actively managed and are not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown below is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in Strategic Income Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns – Class R3 Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

7.85%

6/30/2020

Lowest Quarterly Results

-5.71%

3/31/2020
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the highest historical individual federal marginal income tax rates, and do not reflect state or local income taxes. Actual after-tax returns depend on an investor’s own tax situation and may differ from the returns shown, and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns shown relate only to Class R3 shares, and after-tax returns for other share classes will vary.
Retirement | Thornburg Strategic Income Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Retirement | Thornburg Strategic Income Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Retirement | Thornburg Strategic Income Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If obligations held by the Fund are downgraded by ratings agencies or go into default, or if management action, legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Because the ability of an issuer of a lower-rated or unrated obligation to pay principal and interest when due is typically less certain than for an issuer of a higher-rated obligation, lower-rated and unrated obligations are generally more vulnerable than higher- rated obligations to default, to ratings downgrades, and to liquidity risk. Debt obligations backed by so-called “subprime” mortgages may also be subject to a greater risk of default or downgrade. Debt obligations issued by the U.S. government or its agencies, instrumentalities and government sponsored enterprises are also subject to credit risk. Securities backed by the full faith and credit of the U.S. government, such as U.S. Treasury obligations, are commonly regarded as having small exposure to credit risk. Obligations of certain U.S. agencies, instrumentalities and enterprises (sometimes referred to as “agency obligations”) are not direct obligations of the U.S. government, may not be backed by the full faith and credit of the U.S. government, and may have a greater exposure to credit risk.
Retirement | Thornburg Strategic Income Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Retirement | Thornburg Strategic Income Fund | Developing Country Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in developing countries because the economies of those countries are usually less diversified, communications, transportation and economic infrastructures are less developed, and developing countries ordinarily have less established legal, political, business and social frameworks. At times the prices of debt obligations of a developing country issuer may be extremely volatile. An issuer domiciled in a developed country may be similarly affected by these developing country risks to the extent that the issuer conducts its business in developing countries.
Retirement | Thornburg Strategic Income Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Retirement | Thornburg Strategic Income Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in the debt obligations of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protection. In addition, some foreign government debt obligations may be subject to default, delays in payment, adverse legislation or government action, or could be downgraded by ratings agencies.
Retirement | Thornburg Strategic Income Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices. The market for lower-rated and unrated debt obligations (including particularly “junk” or “high yield” bonds) and debt obligations backed by so-called “subprime” mortgages may be less liquid than the market for other obligations, making it difficult for the Fund to value its investment in a lower-rated or unrated obligation or to sell the investment in a timely manner or at an acceptable price.
Retirement | Thornburg Strategic Income Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Retirement | Thornburg Strategic Income Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. This effect is typically more pronounced for lower-rated and unrated debt obligations (including particularly “junk” or “high yield” bonds), the value of which may fluctuate more significantly in response to poor economic growth or other changes in market conditions, political, economic and legal developments, and developments affecting specific issuers. The market value of any zero coupon bonds or “stripped” securities that the Fund may purchase will typically be more volatile than the value of a comparable, interest-paying bond. Additionally, zero coupon bonds and “stripped” securities are subject to the risk that the Fund may have to recognize income on its investment and make distributions to shareholders before it has received any cash payments on its investment.
Retirement | Thornburg Strategic Income Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – If a significant percentage of the Fund’s shares is owned or controlled by a single shareholder, the Fund is subject to the risk that a redemption by that shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity.
Retirement | Thornburg Strategic Income Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of a debt obligation may decline in response to developments affecting the specific issuer of the obligation or security, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Retirement | Thornburg Strategic Income Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from

limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments.
Retirement | Thornburg Strategic Income Fund | Convertible Debt Obligation Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Convertible Debt Obligation Risk – The market value of a convertible debt obligation may vary with changes in prevailing interest rates and changing evaluations of the ability of the issuer to meet principal and interest payments. The market value of a convertible debt obligation may also vary in accordance with the market value of the underlying stock. As a result, convertible debt obligations held by the Fund will tend to perform more like equity securities when the underlying stock price is high (because it is assumed that the Fund will convert the obligation), and more like non-convertible debt obligations when the underlying stock price is low (because it is assumed that the Fund will not convert the obligation). Because its market value can be influenced by several factors, a convertible debt obligation will not be as sensitive to interest rate changes as a similar non-convertible debt obligation, and generally will have less potential for gain or loss than the underlying stock.
Retirement | Thornburg Strategic Income Fund | Foreign Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Government Obligations Risk – Debt obligations may be issued by foreign governments and their agencies and instrumentalities, including the governments of developing countries and “supra-national” entities such as the International Bank for Reconstruction and Development. The Fund’s investments in these foreign debt obligations may be denominated in U.S. dollars or in foreign currencies. These securities, even if denominated in U.S. dollars, may be affected significantly by fluctuations in the value of foreign currencies, and the value of these securities in U.S. dollars may decline even if the securities increase in value in their home country. The governmental issuers of these debt obligations may be less willing or able than the U.S. to repay principal and interest when due, and they may require that the terms for payment be renegotiated. In some countries there may be political instability or insufficient government supervision of markets, and the legal protections for the

Fund’s investments could be subject to unfavorable judicial or administrative changes. These risks may be more pronounced for the Fund’s investments in debt obligations issued by developing countries.
Retirement | Thornburg Strategic Income Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Retirement | Thornburg Strategic Income Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. This effect is also typically more pronounced for mortgage- and other asset-backed securities, the value of which may fluctuate more significantly in response to interest rate changes. When interest rates decrease, the Fund’s dividends may decline.
Retirement | Thornburg Strategic Income Fund | Prepayment and Extension Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Prepayment and Extension Risk – When market interest rates decline, certain debt obligations held by the Fund may be repaid more quickly than anticipated, requiring the Fund to reinvest the proceeds of those repayments in obligations which bear a lower interest rate. Conversely, when market interest rates increase, certain debt obligations held by the Fund may be repaid more slowly than anticipated, causing assets of the Fund to remain invested in relatively lower yielding obligations. These risks may be more pronounced for the Fund’s investments in mortgage-backed and asset-backed securities.
Retirement | Thornburg Strategic Income Fund | U.S. Government Obligations Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

U.S. Government Obligations Risk – U.S. government obligations are subject to the same risks affecting other debt obligations. Although securities backed by the full faith credit of the U.S. government are commonly regarded as having relatively less risk of default, it is possible that the U.S. government may be unwilling or unable to repay principal and interest when due and may require that the terms for payment be renegotiated. Further obligations that are backed by the full faith and credit of the U.S. government remain subject to the other general risks applicable to debt obligations, such as market risks, liquidity risks, and interest rate risks, and may be subject to ratings downgrades. U.S. government obligations also include obligations of U.S. government agencies, instrumentalities, and government-sponsored enterprises, commonly referred to as “agency obligations.” Some agency obligations are backed by the full faith and credit of the U.S. government, but other agency obligations have no specific backing or only limited support from the agency’s authority to borrow from the U.S. government or the discretionary authority of the Treasury to purchase obligations of the issuing agency.
Retirement | Thornburg Strategic Income Fund | Structured Products Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Structured Products Risk – Investments in securities that are backed by, or represent interests in, an underlying pool of securities or other assets, including investments in mortgage- and asset-backed securities and in collateralized mortgage obligations and collateralized debt obligations, involve the risks associated with the underlying assets (e.g., the risk of default by mortgagors whose mortgages are included in a mortgage-backed security or collateralized mortgage obligation), and may also involve different or greater risks, including the risk that distributions from the underlying assets will be inadequate to make interest or other payments to the Fund, the risk that the issuer of the securities will fail to administer the underlying assets properly or become insolvent, and the risk that the securities will be less liquid than other Fund investments.
Retirement | Thornburg Strategic Income Fund | Zero Coupon Bonds and Stripped Securities Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Zero Coupon Bonds and Stripped Securities Risk – Zero coupon bonds are corporate or government-issued debt obligations that do not provide for periodic or “coupon” payments of interest, and that are issued at a substantial discount to their face value. The buyer of a zero coupon bond realizes a stated rate of return determined by the gradual accretion in the value of the security. A “stripped” security is a debt obligation that has been transformed into a zero coupon bond by creating a separate, new security comprised of the separate income component of the debt obligation (commonly referred to as an “income only” or “I/O” security) or the separate principal component of the debt obligation (commonly referred to as a “principal only” or “P/O” security). Because zero coupon bonds do not provide for periodic payments of interest, their value is generally more volatile than the value of a comparable, interest-paying bond. The Fund may also have to recognize income on the bond and make distributions to shareholders before it has received any cash payments on the bond. To generate the cash necessary to satisfy such distributions, the Fund may have to sell portfolio securities that it otherwise might have continued to hold or use cash flows from other sources, including the proceeds from the sale of Fund shares.
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R3  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TSIRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 2.33%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 3.37%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (2.12%) [72]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.25%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 127
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 838
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,572
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 3,515
Annual Return 2015 rr_AnnualReturn2015 (2.43%)
Annual Return 2016 rr_AnnualReturn2016 7.71%
Annual Return 2017 rr_AnnualReturn2017 5.95%
Annual Return 2018 rr_AnnualReturn2018 0.13%
Annual Return 2019 rr_AnnualReturn2019 7.23%
Annual Return 2020 rr_AnnualReturn2020 7.55%
Annual Return 2021 rr_AnnualReturn2021 2.11%
Annual Return 2022 rr_AnnualReturn2022 (6.81%)
Annual Return 2023 rr_AnnualReturn2023 7.03%
Annual Return 2024 rr_AnnualReturn2024 4.06%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 7.85%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (5.71%)
1 Year rr_AverageAnnualReturnYear01 4.06%
5 Years rr_AverageAnnualReturnYear05 2.66%
10 Years rr_AverageAnnualReturnYear10 3.14%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R3 | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.20%
5 Years rr_AverageAnnualReturnYear05 1.15%
10 Years rr_AverageAnnualReturnYear10 1.68%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R3 | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.39%
5 Years rr_AverageAnnualReturnYear05 1.39%
10 Years rr_AverageAnnualReturnYear10 1.76%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R3 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R3 | Bloomberg U.S. Universal Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.04%
5 Years rr_AverageAnnualReturnYear05 0.06%
10 Years rr_AverageAnnualReturnYear10 1.73%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R3 | Blended Benchmark (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.57%
5 Years rr_AverageAnnualReturnYear05 2.07%
10 Years rr_AverageAnnualReturnYear10 3.17%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R4  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TSRIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.28%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.07%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.82%) [72]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.25%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 127
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 570
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,038
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,335
1 Year rr_AverageAnnualReturnYear01 4.06%
5 Years rr_AverageAnnualReturnYear05 2.67%
Since Inception rr_AverageAnnualReturnSinceInception 3.14%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 01, 2014
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R4 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
Since Inception rr_AverageAnnualReturnSinceInception 1.35%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R4 | Bloomberg U.S. Universal Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.04%
5 Years rr_AverageAnnualReturnYear05 0.06%
Since Inception rr_AverageAnnualReturnSinceInception 1.73%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R4 | Blended Benchmark (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.57%
5 Years rr_AverageAnnualReturnYear05 2.07%
Since Inception rr_AverageAnnualReturnSinceInception 3.17%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R5  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TSRRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.33%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.87%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.27%) [72]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.60%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 61
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 251
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 456
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,048
1 Year rr_AverageAnnualReturnYear01 4.74%
5 Years rr_AverageAnnualReturnYear05 3.32%
10 Years rr_AverageAnnualReturnYear10 3.71%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R5 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R5 | Bloomberg U.S. Universal Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.04%
5 Years rr_AverageAnnualReturnYear05 0.06%
10 Years rr_AverageAnnualReturnYear10 1.73%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R5 | Blended Benchmark (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.57%
5 Years rr_AverageAnnualReturnYear05 2.07%
10 Years rr_AverageAnnualReturnYear10 3.17%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R6  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol TSRSX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.15%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.69%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.16%) [72]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.53%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 54
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 205
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 368
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 843
1 Year rr_AverageAnnualReturnYear01 4.82%
5 Years rr_AverageAnnualReturnYear05 3.39%
Since Inception rr_AverageAnnualReturnSinceInception 3.91%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 10, 2017
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R6 | Bloomberg U.S. Aggregate Total Return Index Value USD (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
Since Inception rr_AverageAnnualReturnSinceInception 1.19%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R6 | Bloomberg U.S. Universal Total Return Index Value Unhedged (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 2.04%
5 Years rr_AverageAnnualReturnYear05 0.06%
Since Inception rr_AverageAnnualReturnSinceInception 1.51%
Retirement | Thornburg Strategic Income Fund | Thornburg Strategic Income Fund - Class R6 | Blended Benchmark (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.57%
5 Years rr_AverageAnnualReturnYear05 2.07%
Since Inception rr_AverageAnnualReturnSinceInception 3.31%
Managed Funds | Thornburg Emerging Markets Managed Account Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Emerging Markets Managed Account Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund’s primary investment goal is long-term capital appreciation.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. Fund shares are only available through certain retail or institutional separately managed accounts with which Thornburg Investment Management, Inc. (“Thornburg”) has an agreement to serve as investment adviser. The fees and expenses in the following tables do not reflect any charges that are imposed by those managed accounts.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 145.98% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 145.98%
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. The example does not reflect any charges imposed by the applicable retail or institutional separately managed accounts through which the Fund is sold, and if such charges were reflected, the amounts shown in the example would be higher. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements) your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund pursues its objective by investing at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of issuers which Thornburg views as having substantial economic ties to one or more emerging market countries. Emerging market countries are considered by Thornburg generally to be those countries which are not included in the MSCI World Index. The material factors that Thornburg considers when determining whether an issuer has substantial economic ties to an emerging market country include whether the issuer:

•is included in the MSCI Emerging Markets Index;

•is organized or headquartered in an emerging market country, or maintains most of its assets in one or more such countries;

•has equity securities that are traded principally on a stock exchange of an emerging market country; or

•derives, or is expected to derive, a majority of its profits, revenues, sales, or income from one or more non-U.S. countries.

The Fund may invest in issuers of any size of capitalization, including small companies, and expects that under normal conditions its assets will be invested in issuers domiciled in or tied economically to a variety of different emerging market countries. The Fund is non-diversified and may concentrate its investments in particular industries.

The Fund’s policy of investing at least 80% of its assets, plus the amount of any borrowings for investment purposes, in emerging markets issuers may be changed by the Fund’s Trustees without a shareholder vote upon 60 days’ notice to shareholders.

Among the specific factors considered in identifying securities for inclusion in the Fund are domestic and international economic developments, outlooks for securities markets, the supply and demand for equity securities, and analysis of specific issuers. Thornburg typically categorizes the Fund’s equity investments in one of the following three categories:

Basic Value: Companies generally operating in mature or cyclical industries and which generally exhibit more economic sensitivity and/or higher volatility in earnings and cash flow.

Consistent Earner: Companies which generally exhibit predictable growth, profitability, cash flow and/or dividends.

Emerging Franchise: Companies with the potential to grow at an above average rate because of a product or service that is establishing a new market and/or taking share from existing participants.

Inclusion of any investment in any of the three described categories represents Thornburg’s opinion concerning the characteristics and prospects of the investment. There is no assurance that any company selected for investment will, once categorized in one of the three described investment categories, continue to have the positive characteristics or fulfill the expectations that Thornburg had for the company when it was selected for investment, and any such company may not grow or may decline in earnings and size.

The Fund may sell an investment if Thornburg has identified a better investment opportunity, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, if Thornburg has a target price for the investment and that target price has been achieved, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Emerging Markets Managed Account Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class I shares have been different in each full year shown. The average annual total return figures compare Class I share performance to the MSCI Emerging Markets Net Total Return USD Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The index is not actively managed and is not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Emerging Markets Managed Account Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns - Class I Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 2.04%

3/31/2024

Lowest Quarterly Results

-3.89%

12/31/2024
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Managed Funds | Thornburg Emerging Markets Managed Account Fund | MSCI Emerging Markets Net Total Return USD Index (reflects no deduction for fees, expenses, or U.S. taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 7.50%
Since Inception rr_AverageAnnualReturnSinceInception 12.73%
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – The inability of an issuer to pay principal and interest on its debt obligations when due, or the downgrading of an issuer’s debt obligations by ratings agencies, may adversely affect the market’s perceptions of the issuer’s financial strength and may therefore result in declines in the issuer’s stock price.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Equity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Equity Risk – The value of the Fund’s equity investments may fluctuate significantly over time in response to factors affecting individual issuers, particular industries, or the market as a whole. Additionally, common stock ranks below preferred stock and debt securities in claims for dividends and for assets of a company in a liquidation or bankruptcy.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Foreign Currency Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Currency Risk – Fluctuations in currency exchange rates can adversely affect the value of the Fund’s foreign investments. Such fluctuations may occur for a number of reasons, including market and economic conditions, or a government’s decision to devalue its currency or impose currency controls.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Foreign Investment Risk – Investments in securities of foreign issuers may involve risks including adverse fluctuations in currency exchange rates, political instability, confiscations, taxes or restrictions on currency exchange, difficulty in selling foreign investments, and reduced legal protections.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell some or all of its investments promptly, or may only be able to sell investments at less than desired prices. This risk may be more pronounced for the Fund’s investments in emerging markets.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. The value of a security may change in response to developments affecting entire economies, markets or industries, including changes in interest rates, political and legal developments, and general market volatility. These risks may be more pronounced for the Fund’s investments in emerging markets.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – Fund shares may only be redeemed by Thornburg on behalf of separately managed accounts or by certain managed account program sponsors and not by individual investors. If a significant percentage of the Fund’s shares is owned or controlled by a single managed account shareholder, the Fund is subject to the risk that a redemption by that managed account shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining managed account shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity. See also “Purchase and Sale of Fund Shares” in the Fund Summary.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Risks Affecting Specific Countries or Regions [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Countries or Regions – If a significant portion of the Fund’s assets is invested in issuers that are economically exposed to one country or region, the Fund’s share value may be more susceptible to the conditions and developments in that country or region, and potentially more volatile than the share value of a more geographically diversified fund. A specific country or region could also be adversely affected by conditions or developments arising in other countries. For example, the U.S. government could take actions to prohibit or restrict individuals or companies within the U.S. from purchasing or holding the shares of issuers in another country, which may limit the Fund’s ability to invest in that country or cause the Fund to have to sell investments in that country at less than desired prices. The nature and degree of the risks affecting a given country or region, and the extent of the Fund’s exposure to any such country or region, is expected to vary over time.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Risks Affecting Specific Issuers [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Specific Issuers – The value of an equity security may decline in response to developments affecting the specific issuer of the security or obligation, even if the overall industry or economy is unaffected. These developments may include a variety of factors, including but not limited to management issues or other corporate disruption, a decline in revenues or profitability, an increase in costs, or an adverse effect on the issuer’s competitive position.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Small and Mid-Cap Company Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Small and Mid-Cap Company Risk – Investments in small-capitalization companies and mid-capitalization companies may involve additional risks, which may be relatively higher with smaller companies. These additional risks may result from limited product lines, more limited access to markets and financial resources, greater vulnerability to competition and changes in markets, lack of management depth, increased volatility in share price, and possible difficulties in valuing or selling these investments.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Risks Affecting Investments in China [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Risks Affecting Investments in China – A significant portion of the Fund’s assets may be invested in companies exposed to China. Risks affecting investments in China include a potential downturn in the Chinese economy, reduced liquidity or increased price volatility in the Chinese securities markets as a result of trading suspensions affecting Chinese issuers or other factors, the potential that the Chinese government may expand restrictions on foreign investments or the repatriation of capital, and the implementation of new tariffs or other trade barriers by China or its trading partners. A lack of transparency respecting Chinese companies may also reduce the Fund’s ability to conduct diligence respecting those companies’ accounting and governance standards, which may in turn reduce the Fund’s ability to detect fraudulent practices that may adversely affect the companies’ stock prices.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Emerging Markets Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Emerging Markets Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” below) may be more pronounced for investments in emerging markets because the economies of those markets are usually less diversified, communications, transportation and economic infrastructures are less developed, and emerging markets ordinarily have less established legal, political, business and social frameworks. At times the prices of equity securities of an emerging markets issuer may be extremely volatile. An issuer domiciled in an emerging market may be similarly affected by these emerging markets risks to the extent that the issuer conducts its business in emerging markets.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Risk Nondiversified Status [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Non-diversification Risk – The Fund is a non-diversified investment company, which means that it may invest a greater proportion of its assets in the securities of a single issuer. This may be riskier, because a default or other adverse condition affecting such an issuer could cause the Fund’s share price to decline to a greater degree.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Concentration Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Concentration Risk – Concentration in an industry may subject the Fund to greater market fluctuations than a fund that is more broadly invested across industries. The Fund may be susceptible to loss due to adverse events that affect the Fund’s investments more than the market as a whole, to the extent that the Fund’s investments are concentrated in the securities and/or other assets of a particular issuer or issuers, country, group of countries, region, market, industry group of industries, sector or asset class.
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Thornburg Emerging Markets Managed Account Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THMGX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets none [73]
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 13.87%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 13.87%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (13.87%) [74]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets none
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 none
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 none
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 none
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 none
Annual Return 2024 rr_AnnualReturn2024 (0.70%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2024
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 2.04%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2024
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.89%)
1 Year rr_AverageAnnualReturnYear01 (0.70%)
Since Inception rr_AverageAnnualReturnSinceInception 2.02%
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Thornburg Emerging Markets Managed Account Fund - Class I | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (2.21%)
Since Inception rr_AverageAnnualReturnSinceInception 0.60%
Managed Funds | Thornburg Emerging Markets Managed Account Fund | Thornburg Emerging Markets Managed Account Fund - Class I | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 (0.41%)
Since Inception rr_AverageAnnualReturnSinceInception 0.95%
Managed Funds | Thornburg Municipal Managed Account Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Municipal Managed Account Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The Fund seeks a high level of current income exempt from federal individual income tax.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. Fund shares are only available through certain retail or institutional separately managed accounts with which Thornburg Investment Management, Inc. (“Thornburg”) has an agreement to serve as investment adviser. The fees and expenses in the following tables do not reflect any charges that are imposed by the those managed accounts.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover.
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over”) its portfolio. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 21.60% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 21.60%
Expense Example [Heading] rr_ExpenseExampleHeading Example.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, dividends and distributions are reinvested, and that the Fund’s operating expenses remain the same. The example does not reflect any charges imposed by the applicable retail or institutional separately managed accounts through which the Fund is sold, and if such charges were reflected, the amounts shown in the example would be higher. Although your actual costs may be higher or lower, based on these assumptions (and giving effect to fee waivers and expense reimbursements) your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Thornburg Investment Management, Inc. (“Thornburg”) actively manages the Fund’s investments in pursuing the Fund’s investment goal. The Fund invests principally in a portfolio of municipal obligations issued by states and state agencies, local governments and their agencies, and by United States territories and possessions. Investment decisions are based upon outlooks for interest rates and securities markets, the supply of municipal debt obligations, the difference in yields between higher and lower-rated obligations, and analysis of specific obligations. The Fund invests in municipal obligations and participations in municipal obligations of any credit quality. The Fund may invest up to 80 percent of its portfolio in lower-quality municipal debt obligations rated by a nationally recognized statistical rating organization at the time of purchase as below investment grade (sometimes called “junk” bonds or “high yield” bonds) or, if unrated, issued by obligors which Thornburg determines have comparable below investment grade municipal obligations outstanding or which are deemed by Thornburg to be comparable to obligors with outstanding below investment grade obligations. The Fund may also invest in municipal obligations that are in default at the time of purchase. “Participations” are undivided interests in pools of securities where the underlying credit support passes through to the participants.

The Fund may invest in municipal obligations of any maturity or duration. Duration is a measure of estimated sensitivity to interest rate changes. A portfolio with a longer average effective duration will typically be more sensitive to interest rate changes than a portfolio with a shorter average effective duration. Duration is commonly expressed as a number, which is the expected percentage change in an obligation’s price upon a 1% change in interest rates. For example, an obligation with a duration of 10 would be expected to change in price by approximately 10% in response to a 1% change in interest rates. During temporary periods the Fund’s average effective duration and average portfolio maturity may be reduced for defensive purposes. There is no limitation on the duration or maturity of any specific security the Fund may purchase. The Fund may dispose of any security before it matures. The Fund attempts to meet its objective through credit analysis and security selection. The Fund is non-diversified.

The Fund ordinarily acquires and holds securities for investment rather than for realization of gains by short-term trading on market fluctuations. However, it may sell an investment prior to its scheduled maturity date to enhance income or reduce loss, to change the portfolio’s average duration or average maturity, to pursue other investment opportunities, in response to changes in the conditions or business of the investment’s issuer or changes in overall market conditions, or if, in Thornburg’s opinion, the investment no longer serves to achieve the Fund’s investment goals. The objective of preserving capital may prevent the Fund from obtaining the highest yields available.

The Fund normally invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in municipal obligations the income from which is exempt from the regular federal income tax, though the income on those investments may still be subject to the federal alternative minimum tax (“AMT”). Gains realized on investments held by the Fund and not offset by realized losses will be subject to federal income tax.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance of the Fund
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Municipal Managed Account Fund by showing how the Fund’s investment results vary from year to year. The bar chart shows how the annual total returns for Class I shares have been different in each full year shown. The average annual total return figures compare Class I share performance to the ICE BofA U.S. Municipal Securities Index, a broad-based securities market index that represents the overall applicable market in which the Fund invests. The index is not actively managed and is not available for direct investment. The bar charts and performance tables assume reinvestment of dividends and distributions. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. The performance information shown is as of the calendar year ended December 31, 2024. Updated performance information may be obtained on the Thornburg website at Thornburg.com or by calling 1-800-847-0200.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Municipal Managed Account Fund by showing how the Fund’s investment results vary from year to year.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-847-0200
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress Thornburg.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns - Class I Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

 

Total
Returns

Quarter
ended

Highest Quarterly Results

 6.46%

12/31/2023

Lowest Quarterly Results

-2.07%

9/30/2023
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (periods ended 12-31-24)
Managed Funds | Thornburg Municipal Managed Account Fund | ICE BofA U.S. Municipal Securities Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.62%
Since Inception rr_AverageAnnualReturnSinceInception 3.04%
Managed Funds | Thornburg Municipal Managed Account Fund | Risk Not Insured [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a deposit in any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.
Managed Funds | Thornburg Municipal Managed Account Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Accordingly, the loss of money is a risk of investing in the Fund.
Managed Funds | Thornburg Municipal Managed Account Fund | Credit Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Credit Risk – If obligations held by the Fund are downgraded by ratings agencies or go into default, or if legislation or other government action reduces the ability of issuers to pay principal and interest when due, the value of those obligations may decline and the Fund’s share value and the dividends paid by the Fund may be reduced. Because the ability of an issuer of a lower-rated or unrated obligation to pay principal and interest when due is typically less certain than for an issuer of a higher-rated obligation, lower-rated and unrated obligations are generally more vulnerable than higher-rated obligations to default, to ratings downgrades, and to liquidity risk. For example, municipal leases held by the Fund may be subject to non-appropriation provisions which permit governmental agencies or issuers to discontinue payments to the Fund under the municipal leases.
Managed Funds | Thornburg Municipal Managed Account Fund | Cybersecurity and Operational Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Cybersecurity and Operational Risk – Operational failures, cyber-attacks or other disruptions that affect the Fund’s service providers, the Fund’s counterparties, other market participants or the issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.
Managed Funds | Thornburg Municipal Managed Account Fund | Liquidity Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Liquidity Risk – Due to a lack of demand in the marketplace or other factors, the Fund may not be able to sell promptly some or all of the obligations that it holds, or may only be able to sell obligations at less than desired prices. The market for lower-rated and unrated obligations (including particularly “junk” or “high yield” bonds) may be less liquid than the market for other obligations, making it difficult for the Fund to value its investment in a lower-rated or unrated obligation or to sell the investment in a timely manner or at an acceptable price.
Managed Funds | Thornburg Municipal Managed Account Fund | Management Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Management Risk – The Fund is an actively managed portfolio, and the value of the Fund may be reduced if Thornburg pursues unsuccessful investments or fails to correctly identify risks affecting the broad economy or specific issuers in which the Fund invests.
Managed Funds | Thornburg Municipal Managed Account Fund | Market and Economic Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Market and Economic Risk – The value of the Fund’s investments may decline and its share value may be reduced due to changes in general economic and market conditions. This effect is typically more pronounced for the Fund’s investments in lower-rated and unrated municipal obligations (including particularly “junk” or “high yield” bonds), the value of which may fluctuate more significantly in response to poor economic growth or other changes in market conditions, political, economic and legal developments, and developments affecting specific issuers.
Managed Funds | Thornburg Municipal Managed Account Fund | Redemption Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Redemption Risk – Fund shares may only be redeemed by Thornburg on behalf of separately managed accounts or by certain managed account program sponsors and not by individual investors. If a significant percentage of the Fund’s shares is owned or controlled by a single managed account shareholder, the Fund is subject to the risk that a redemption by that

managed account shareholder of all or a large portion of its shares may require the Fund to sell securities at less than desired prices, and the Fund’s remaining managed account shareholders may also incur additional transaction costs or adverse tax consequences from such trading activity. See also “Purchase and Sale of Fund Shares” in the Fund Summary.
Managed Funds | Thornburg Municipal Managed Account Fund | High Yield Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

High Yield Risk – Debt obligations that are rated below investment grade and unrated obligations of similar credit quality (commonly referred to as “junk” or “high yield” bonds) may have a substantial risk of loss. These obligations are generally considered to be speculative with respect to the issuer’s ability to pay interest and principal when due. These obligations may be subject to greater price volatility than investment grade obligations, and their prices may decline significantly in periods of general economic difficulty or in response to adverse publicity, changes in investor perceptions or other factors. These obligations may also be subject to greater liquidity risk.
Managed Funds | Thornburg Municipal Managed Account Fund | Interest Rate Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Interest Rate Risk – When interest rates increase, the value of the Fund’s investments may decline and the Fund’s share value may be reduced. This effect is typically more pronounced for intermediate and longer-term obligations. When interest rates decrease, the Fund’s dividends may decline. Decreases in market interest rates may also result in prepayments of obligations the Fund acquires, requiring the Fund to reinvest at lower interest rates.
Managed Funds | Thornburg Municipal Managed Account Fund | Tax Risk [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Tax Risk – The income on the Fund’s municipal obligations could become subject to federal income or state income tax due to noncompliant conduct by issuers, unfavorable legislation or litigation or adverse interpretations by regulatory authorities. All or a portion of the Fund’s distributions that are exempt from regular federal income tax may nevertheless be taken into account for purposes of the federal AMT and state income tax.
Managed Funds | Thornburg Municipal Managed Account Fund | Risk Nondiversified Status [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock

Non-diversification Risk – The Fund is a non-diversified investment company, which means that it may invest a greater proportion of its assets in the securities of a single issuer. This may be riskier, because a default or other adverse condition affecting such an issuer could cause the Fund’s share price to decline to a greater degree.
Managed Funds | Thornburg Municipal Managed Account Fund | Thornburg Municipal Managed Account Fund - Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol THMMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets none [75]
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.87%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.87%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (1.87%) [76]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets none
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 none
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 none
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 none
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 none
Annual Return 2024 rr_AnnualReturn2024 4.99%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarterly Results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 6.46%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarterly Results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2023
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (2.07%)
1 Year rr_AverageAnnualReturnYear01 4.99%
Since Inception rr_AverageAnnualReturnSinceInception 5.92%
Managed Funds | Thornburg Municipal Managed Account Fund | Thornburg Municipal Managed Account Fund - Class I | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.99%
Since Inception rr_AverageAnnualReturnSinceInception 5.92%
Managed Funds | Thornburg Municipal Managed Account Fund | Thornburg Municipal Managed Account Fund - Class I | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 4.80%
Since Inception rr_AverageAnnualReturnSinceInception 5.57%
[1] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[2] Imposed only on redemptions of Class C shares within 12 months of purchase.
[3] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.99%. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[4] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[5] Imposed only on redemptions of Class C shares within 12 months of purchase.
[6] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.90%. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[7] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[8] Imposed only on redemptions of Class C shares within 12 months of purchase.
[9] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class C and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 2.19% and 0.90%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[10] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[11] Imposed only on redemptions of Class C shares within 12 months of purchase.
[12] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.99%. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if, after taking the recoupment into account, the Fund’s actual expenses fall below the expense cap during that same fiscal year.
[13] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[14] Imposed only on redemptions of Class C shares within 12 months of purchase.
[15] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class C and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 2.33% and 1.04%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[16] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[17] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class C and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 2.34% and 0.95%. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[18] Imposed only on redemptions of Class C shares within 12 months of purchase.
[19] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[20] Imposed only on redemptions of Class C shares within 12 months of purchase.
[21] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class C and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 2.34% and 0.95%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[22] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[23] The Total Annual Fund Operating Expenses do not match the Ratios to Average Net Assets shown in the Financial Highlights section of the Prospectus, which reflect the operating expenses of the Fund and do not include acquired fund fees and expenses (‘AFFE’). AFFE are expenses incurred indirectly by other investment companies in which the Fund holds shares, are not direct costs paid by Fund shareholders, and are not used to calculate the Fund’s net asset value.
[24] Imposed only on redemptions of Class C shares within 12 months of purchase.
[25] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[26] These expenses reflect the expenses the Fund will incur to sell securities short and interest expense on borrowed funds. These expenses are required to be treated as a Fund expense for accounting purposes and are not payable to the Fund’s investment advisor.
[27] The Total Annual Fund Operating Expenses and Total Annual Fund Operating Expenses After Fee Waiver/Expense Reimbursement do not match the Ratios to Average Net Assets shown in the Financial Highlights section of the Prospectus, which reflect the operating expenses of the Fund and do not include acquired fund fees and expenses (‘AFFE’). AFFE are expenses incurred indirectly by other investment companies in which the Fund holds shares, are not direct costs paid by Fund shareholders, and are not used to calculate the Fund’s net asset value.
[28] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class A and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.94% and 0.69%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if, after taking the recoupment into account, the Fund’s actual expenses fall below the expense cap during that same fiscal year.
[29] Up to a 0.50% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[30] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class A and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.50% and 0.30%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[31] Up to a 0.50% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[32] Imposed only on redemptions of Class C and Class C2 shares within 12 months of purchase.
[33] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class A, Class C and Class C2 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.99%, 1.24% and 1.24%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[34] Up to a 0.50% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[35] Imposed only on redemptions of Class C and Class C2 shares within 12 months of purchase.
[36] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class C2 and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 1.24% and 0.49%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[37] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[38] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class A, Class C, and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.75%, 1.50%, and 0.50%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[39] Imposed only on redemptions of Class C shares within 12 months of purchase.
[40] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[41] Imposed only on redemptions of Class C shares within 12 months of purchase.
[42] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.60%. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[43] Up to a 0.50% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[44] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class A and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.70% and 0.50%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[45] Up to a 0.50% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[46] Imposed only on redemptions of Class C and Class C2 shares within 12 months of purchase.
[47] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class C2 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 1.24%. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[48] Up to a 0.50% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[49] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class A, Class C, Class C2, and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.72%, 1.09%, 1.09%, and 0.48%. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[50] Imposed only on redemptions of Class C and Class C2 shares within 12 months of purchase.
[51] A 0.50% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[52] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class A, Class C, and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.81%, 1.28%, and 0.59%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[53] Imposed only on redemptions of Class C shares within 12 months of purchase.
[54] Up to a 0.50% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[55] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class A, Class C, Class C2, and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.74%, 1.02%, 1.02%, and 0.49%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[56] Imposed only on redemptions of Class C and Class C2 shares within 12 months of purchase.
[57] Up to a 0.50% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[58] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class A, Class D and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.99%, 1.24% and 0.67%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[59] Up to a 0.50% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[60] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class A and Class I expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.99% and 0.67%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[61] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class R3, Class R4, Class R5, and Class R6 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 1.50%, 1.40%, 0.99%, and 0.85%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[62] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class R3, Class R4, Class R5, and Class R6 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 1.36%, 1.16%, 0.90%, and 0.70%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[63] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class R3, Class R4, Class R5 and Class R6 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 1.50%, 1.40%, 0.99%, and 0.89%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2025, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[64] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class R5 and Class R6 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 1.04% and 0.94%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[65] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class R3, Class R4 and Class R5 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 1.31%, 1.21%, and 0.95%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[66] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class R3, Class R4 and Class R5 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 1.46%, 1.36%, and 0.95%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[67] The Total Annual Fund Operating Expenses and Total Annual Fund Operating Expenses After Fee Waiver/Expense Reimbursement do not match the Ratios to Average Net Assets shown in the Financial Highlights section of the Prospectus, which reflect the operating expenses of the Fund and do not include acquired fund fees and expenses (‘AFFE’). AFFE are expenses incurred indirectly by other investment companies in which the Fund holds shares, are not direct costs paid by Fund shareholders, and are not used to calculate the Fund’s net asset value.
[68] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class R3, Class R4, Class R5, and Class R6 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 1.50%, 1.40%, 0.99%, and 0.80% respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[69] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class R3, Class R4, and Class R5 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.99%, 0.99%, and 0.67%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[70] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class R3, Class R4, Class R5, and Class R6 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 0.99%, 0.99%, 0.49%, and 0.42%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[71] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class R3, Class R4, Class R5, and Class R6 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 1.00%, 0.75%, 0.50%, and 0.49%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[72] Thornburg Investment Management, Inc. (“Thornburg”) has contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class R3, Class R4, Class R5 and Class R6 expenses (excluding taxes, interest expenses, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs) do not exceed 1.25%, 1.25%, 0.60%, and 0.53%, respectively. The agreement to waive fees and reimburse expenses may be terminated by the Fund’s Trustees at any time, but may not be terminated by Thornburg before February 1, 2026, unless Thornburg ceases to be the investment advisor of the Fund prior to that date. Thornburg may recoup amounts waived or reimbursed during the Fund’s fiscal year if actual expenses fall below the expense cap during that same fiscal year.
[73] Thornburg does not charge a management fee for its investment management services. You will, however, incur a management fee through the managed account of which the Fund is a part.
[74] Thornburg has contractually agreed, irrevocably during the existence of the Fund, to waive, pay or reimburse all expenses of the Fund, except for taxes, interest expense, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs.
[75] Thornburg does not charge a management fee for its investment management services. You will, however, incur a management fee through the managed account of which the Fund is a part.
[76] Thornburg has contractually agreed, irrevocably during the existence of the Fund, to waive, pay or reimburse all expenses of the Fund, except for taxes, interest expense, acquired fund fees and expenses, brokerage commissions, borrowing costs, expenses relating to short sales, and unusual expenses such as contingency fees or litigation costs.