Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	THORNBURG INVESTMENT TRUST
Prospectus Date	rr_ProspectusDate	Feb. 01, 2015
Thornburg Strategic Income Fund | A C I
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	FUND SUMMARY 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 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 these and other discounts is available from your financial professional and in “Opening Your Account – Buying Fund Shares” on page 82 of this Prospectus.
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, 2016
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 51.20% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	51.20%
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. More information about these and other discounts is available from your financial professional and in “Opening Your Account – Buying Fund Shares” on page 82 of this Prospectus.
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, By Year, Caption [Text]	rr_ExpenseExampleNoRedemptionByYearCaption	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 and income-producing stocks. The Fund expects, under normal conditions, to invest a majority of its assets in the debt obligations described below, but the relative proportions of the Fund’s investments in debt obligations and in income producing stocks can be expected to vary over time. 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 convertible debt obligations obligations issued by foreign governments (including developing countries) collateralized mortgage obligations (“CMOs”), collateralized debt obligations (“CDOs”), collateralized bond obligations (“CBOs”), collateralized loan obligations (“CLOs”), and other structured finance arrangements 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 derivative instruments such as options, futures contracts, options on futures contracts, and swap agreements (including, but not limited to, credit default swap agreements) The Fund may invest in any stock or other equity security which the investment advisor believes may assist the Fund in pursuing its investment goals, including primarily income producing common and preferred stocks issued by domestic and foreign companies of any size (including smaller companies with market capitalizations of less than $500 million, and companies in developing countries), and also including publicly traded real estate investment trusts and other equity trusts and partnership interests. The Fund expects that its equity investments will be weighted in favor of companies that pay dividends or other current income. 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 investment 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.
Risk [Heading]	rr_RiskHeading	Principal Investment Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	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. Accordingly, the loss of money is a risk of investing in the Fund. The value of the Fund’s shares and its dividends may fluctuate from day to day and over time, and when you sell your shares they may be worth less than what you paid for them. The following is a summary of the principal risks of investing in the Fund. Please note that because the Fund’s objective is to provide high current income, the Fund invests with an emphasis on income, rather than stability of net asset value. 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. 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. Prepayment 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. 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. 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. 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. Risks Affecting Specific Issuers – The value of a debt obligation or equity security 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. 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. 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. 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. Foreign Investment Risk – Investments in the equity securities or 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. Structured Products Risk – The Fund’s investments in structured finance arrangements, including CMOs, CDOs, CBOs and CLOs, involve the risks associated with the underlying pool of securities or other assets, and also may involve risks different or greater than the risks affecting the underlying assets. In particular, these investments may be less liquid than other debt obligations, making it difficult for the Fund to value its investment or sell the investment in a timely manner or at an acceptable price. Derivatives Risk – The Fund’s investments in derivatives involve the risks associated with the securities or other assets underlying the 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. Real Estate Risk – The Fund’s investments in 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). Additional information about Fund investments, investment strategies and risks of investing in the Fund appears below beginning on page 74.
Risk Lose Money [Text]	rr_RiskLoseMoney	Accordingly, the loss of money is a risk of investing in the Fund.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	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.
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 how the annual total return for Class A shares has been different in each full year shown. The average annual total return figures compare Class A, Class C and Class I performance to the Barclays U.S. Universal Index, a broad measure of market performance, and to a Blended Benchmark, comprised of 80% Barclays U.S. Aggregate Bond Index, which represents a broad measure of bond market performance, and 20% MSCI World Index, which represents a broad measure of equity market performance in developed markets. 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, 2014. Updated performance information may be obtained on the Thornburg website at www.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 Additional Market Index [Text]	rr_PerformanceAdditionalMarketIndex	The average annual total return figures compare Class A, Class C and Class I performance to the Barclays U.S. Universal Index, a broad measure of market performance, and to a Blended Benchmark, comprised of 80% Barclays U.S. Aggregate Bond Index, which represents a broad measure of bond market performance, and 20% MSCI World Index, which represents a broad measure of equity market performance in developed markets.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-847-0200
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.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	Highest quarterly results for time period shown: 16.23% (quarter ended 6-30-09). Lowest quarterly results for time period shown: -10.38% (quarter ended 12-31-08). 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 12-31-14)
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 will vary for Class C and Class I shares because the returns of the classes are different.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	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 will vary for Class C and Class I shares because the returns of the classes are different.
Thornburg Strategic Income Fund | A C I | Class A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	4.50%
Maximum Deferred Sales Charge (Load) (as a percentage of redemption proceeds or original purchase price, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none	[1]
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.22%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.22%
Fee Waiver/Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets
Total Annual Fund Operating Expenses After Fee Waiver/Expense Reimbursement	rr_NetExpensesOverAssets	1.22%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	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.
1 Year	rr_ExpenseExampleYear01	569
3 Years	rr_ExpenseExampleYear03	820
5 Years	rr_ExpenseExampleYear05	1,090
10 Years	rr_ExpenseExampleYear10	1,861
2008	rr_AnnualReturn2008	(18.48%)
2009	rr_AnnualReturn2009	36.68%
2010	rr_AnnualReturn2010	13.10%
2011	rr_AnnualReturn2011	4.44%
2012	rr_AnnualReturn2012	12.55%
2013	rr_AnnualReturn2013	5.89%
2014	rr_AnnualReturn2014	3.19%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Highest quarterly results
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	16.23%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Lowest quarterly results
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(10.38%)
1 Year	rr_AverageAnnualReturnYear01	(1.42%)
5 Years	rr_AverageAnnualReturnYear05	6.77%
Since Inception	rr_AverageAnnualReturnSinceInception	6.70%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 19, 2007
Thornburg Strategic Income Fund | A C I | Class C
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of redemption proceeds or original purchase price, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	1.00%	[2]
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.23%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.98%
Fee Waiver/Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.18%)	[3]
Total Annual Fund Operating Expenses After Fee Waiver/Expense Reimbursement	rr_NetExpensesOverAssets	1.80%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	Imposed only on redemptions of Class C shares within 12 months of purchase.
1 Year	rr_ExpenseExampleYear01	283
3 Years	rr_ExpenseExampleYear03	604
5 Years	rr_ExpenseExampleYear05	1,051
10 Years	rr_ExpenseExampleYear10	2,292
1 Year	rr_ExpenseExampleNoRedemptionYear01	183
3 Years	rr_ExpenseExampleNoRedemptionYear03	604
5 Years	rr_ExpenseExampleNoRedemptionYear05	1,051
10 Years	rr_ExpenseExampleNoRedemptionYear10	2,292
1 Year	rr_AverageAnnualReturnYear01	1.69%
5 Years	rr_AverageAnnualReturnYear05	7.18%
Since Inception	rr_AverageAnnualReturnSinceInception	6.80%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 19, 2007
Thornburg Strategic Income Fund | A C I | Class I
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of redemption proceeds or original purchase price, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.15%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.90%
Fee Waiver/Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets
Total Annual Fund Operating Expenses After Fee Waiver/Expense Reimbursement	rr_NetExpensesOverAssets	0.90%
1 Year	rr_ExpenseExampleYear01	92
3 Years	rr_ExpenseExampleYear03	287
5 Years	rr_ExpenseExampleYear05	498
10 Years	rr_ExpenseExampleYear10	1,108
1 Year	rr_AverageAnnualReturnYear01	3.53%
5 Years	rr_AverageAnnualReturnYear05	8.11%
Since Inception	rr_AverageAnnualReturnSinceInception	7.73%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 19, 2007
Thornburg Strategic Income Fund | A C I | Return After Taxes on Distributions | Class A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(3.52%)
5 Years	rr_AverageAnnualReturnYear05	4.02%
Since Inception	rr_AverageAnnualReturnSinceInception	3.99%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 19, 2007
Thornburg Strategic Income Fund | A C I | Return After Taxes on Distributions and Sale of Fund Shares | Class A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(0.66%)
5 Years	rr_AverageAnnualReturnYear05	4.24%
Since Inception	rr_AverageAnnualReturnSinceInception	4.16%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 19, 2007
Thornburg Strategic Income Fund | A C I | Barclays U.S. Universal Index (reflects no deduction for fees, expenses, or taxes) | Class A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	5.56%
5 Years	rr_AverageAnnualReturnYear05	4.81%
Since Inception	rr_AverageAnnualReturnSinceInception	5.02%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 19, 2007
Thornburg Strategic Income Fund | A C I | Barclays U.S. Universal Index (reflects no deduction for fees, expenses, or taxes) | Class C
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	5.56%
5 Years	rr_AverageAnnualReturnYear05	4.81%
Since Inception	rr_AverageAnnualReturnSinceInception	5.02%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 19, 2007
Thornburg Strategic Income Fund | A C I | Barclays U.S. Universal Index (reflects no deduction for fees, expenses, or taxes) | Class I
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	5.56%
5 Years	rr_AverageAnnualReturnYear05	4.81%
Since Inception	rr_AverageAnnualReturnSinceInception	5.02%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 19, 2007
Thornburg Strategic Income Fund | A C I | Blended Benchmark (reflects no deduction for fees, expenses, or taxes) | Class A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	5.81%
5 Years	rr_AverageAnnualReturnYear05	5.77%
Since Inception	rr_AverageAnnualReturnSinceInception	4.84%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 19, 2007
Thornburg Strategic Income Fund | A C I | Blended Benchmark (reflects no deduction for fees, expenses, or taxes) | Class C
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	5.81%
5 Years	rr_AverageAnnualReturnYear05	5.77%
Since Inception	rr_AverageAnnualReturnSinceInception	4.84%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 19, 2007
Thornburg Strategic Income Fund | A C I | Blended Benchmark (reflects no deduction for fees, expenses, or taxes) | Class I
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	5.81%
5 Years	rr_AverageAnnualReturnYear05	5.77%
Since Inception	rr_AverageAnnualReturnSinceInception	4.84%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 19, 2007

[1] 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") and/or Thornburg Securities Corporation ("TSC") have contractually agreed to waive fees and reimburse expenses incurred by the Fund so that actual Class C expenses do not exceed 1.80%. The agreement to waive fees and reimburse expenses may be terminated by the Fund at any time, but may not be terminated by Thornburg or TSC before February 1, 2016, unless Thornburg or TSC ceases to be the investment advisor or distributor of the Fund prior to that date. Thornburg and TSC retain the ability to be repaid by the Fund for fee waivers and expense reimbursements during a fiscal year if Fund expenses fall below the relevant percentage threshold before the end of that fiscal year.