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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName THORNBURG INVESTMENT TRUST
Prospectus Date rr_ProspectusDate Feb. 01, 2015
Thornburg International Value Fund | R3 R4 R5 R6  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading FUND SUMMARY

International Value Fund
Objective [Heading] rr_ObjectiveHeading Investment Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock International Value 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.
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 37.25% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 37.25%rr_PortfolioTurnoverRate
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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 foreign securities or depository receipts of foreign securities. The Fund may invest in developing countries, but under normal conditions those investments are expected to comprise a smaller proportion of the Fund than investments in developed countries.

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 classified 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.

Thornburg primarily uses individual issuer and industry analysis to make investment decisions. Value, for purposes of the Fund’s selection criteria, may consider both current and projected measures. Among the specific factors considered by Thornburg in identifying securities for inclusion in the Fund are:
             
  profitability     undervalued assets
  price/earnings ratio     earnings growth potential
  price/book value ratio     industry growth characteristics
  price/cash flow ratio     industry leadership
  debt/capital ratio     franchise value
  dividend characteristics     potential for favorable developments
  security and consistency of revenues     EBIT (earnings before interest and taxes)/interest expense ratio
  EV (enterprise value)/ EBITDA (earnings before interest, taxes, depreciation and
amortization) ratio
       

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

Basic Value: Companies which, in Thornburg’s opinion, are financially sound with well established businesses selling at low valuations relative to the companies’ net assets or potential earning power.

Consistent Earner: Companies which normally exhibit steady earnings growth, cash flow characteristics and/or dividend growth. These companies may have above average profitability measures and normally sell at above average valuations.

Emerging Franchise: Companies which, in Thornburg’s opinion, are in the process of establishing a leading position in a product, service or market with the potential to grow at an above average rate. Under normal conditions, the proportion of the Fund invested in this category will be lower than the other categories.

Debt obligations may be considered for investment if Thornburg believes them to be more attractive than equity alternatives, or to manage risk. 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.
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 governmental agency. Accordingly, the loss of money is a risk of investing in the Fund. The value of the Fund’s shares varies 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.

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.

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.

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.

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.

Developing Country Risk – The risks which may affect investments in foreign issuers (see “Foreign Investment Risk,” above) 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.

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.

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 debt 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.

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. Decreases in market interest rates may result in prepayments of debt obligations the Fund acquires, requiring the Fund to reinvest at lower interest rates.

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.

Additional information about Fund investments, investment strategies, and risks of investing in the Fund appears below beginning on page 38.
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 governmental 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 International Value 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 Morgan Stanley Capital International (MSCI) Europe, Australasia and Far East (EAFE) Index and the MSCI All Country (AC) World ex-U.S. Index, each of which is a broad measure of market performance. 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 International Value 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 R3, Class R4, Class R5 and Class R6 share performance to the Morgan Stanley Capital International (MSCI) Europe, Australasia and Far East (EAFE) Index and the MSCI All Country (AC) World ex-U.S. Index, each of which is a broad measure of market performance.
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 R3 Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Highest quarterly results for time period shown: 22.73%
(quarter ended 6-30-09).

Lowest quarterly results for time period shown: -20.95%
(quarter ended 9-30-11).
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 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.
Thornburg International Value Fund | R3 R4 R5 R6 | Class R3  
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 0.68%rr_ManagementFeesOverAssets
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Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%rr_DistributionAndService12b1FeesOverAssets
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Other Expenses rr_OtherExpensesOverAssets 0.43%rr_OtherExpensesOverAssets
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Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.61%rr_ExpensesOverAssets
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Fee Waiver/Expense Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.16%)rr_FeeWaiverOrReimbursementOverAssets
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[1]
Total Annual Fund Operating Expenses After Fee Waiver/Expense Reimbursement rr_NetExpensesOverAssets 1.45%rr_NetExpensesOverAssets
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1 Year rr_ExpenseExampleYear01 148rr_ExpenseExampleYear01
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3 Years rr_ExpenseExampleYear03 492rr_ExpenseExampleYear03
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5 Years rr_ExpenseExampleYear05 861rr_ExpenseExampleYear05
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10 Years rr_ExpenseExampleYear10 1,898rr_ExpenseExampleYear10
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2005 rr_AnnualReturn2005 17.67%rr_AnnualReturn2005
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2006 rr_AnnualReturn2006 25.41%rr_AnnualReturn2006
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2007 rr_AnnualReturn2007 27.51%rr_AnnualReturn2007
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2008 rr_AnnualReturn2008 (41.95%)rr_AnnualReturn2008
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2009 rr_AnnualReturn2009 31.21%rr_AnnualReturn2009
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2010 rr_AnnualReturn2010 13.60%rr_AnnualReturn2010
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2011 rr_AnnualReturn2011 (13.46%)rr_AnnualReturn2011
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2012 rr_AnnualReturn2012 15.18%rr_AnnualReturn2012
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2013 rr_AnnualReturn2013 15.09%rr_AnnualReturn2013
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2014 rr_AnnualReturn2014 (6.06%)rr_AnnualReturn2014
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Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest quarterly results
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 22.73%rr_BarChartHighestQuarterlyReturn
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Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest quarterly results
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (20.95%)rr_BarChartLowestQuarterlyReturn
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1 Year rr_AverageAnnualReturnYear01 (6.06%)rr_AverageAnnualReturnYear01
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5 Years rr_AverageAnnualReturnYear05 4.13%rr_AverageAnnualReturnYear05
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10 Years rr_AverageAnnualReturnYear10 5.78%rr_AverageAnnualReturnYear10
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Thornburg International Value Fund | R3 R4 R5 R6 | Class R4  
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 0.68%rr_ManagementFeesOverAssets
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Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%rr_DistributionAndService12b1FeesOverAssets
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Other Expenses rr_OtherExpensesOverAssets 0.56%rr_OtherExpensesOverAssets
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Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.49%rr_ExpensesOverAssets
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Fee Waiver/Expense Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.24%)rr_FeeWaiverOrReimbursementOverAssets
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Total Annual Fund Operating Expenses After Fee Waiver/Expense Reimbursement rr_NetExpensesOverAssets 1.25%rr_NetExpensesOverAssets
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1 Year rr_ExpenseExampleYear01 127rr_ExpenseExampleYear01
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3 Years rr_ExpenseExampleYear03 447rr_ExpenseExampleYear03
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5 Years rr_ExpenseExampleYear05 790rr_ExpenseExampleYear05
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10 Years rr_ExpenseExampleYear10 1,759rr_ExpenseExampleYear10
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1 Year rr_AverageAnnualReturnYear01 (5.88%)rr_AverageAnnualReturnYear01
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5 Years rr_AverageAnnualReturnYear05 4.33%rr_AverageAnnualReturnYear05
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Since Inception rr_AverageAnnualReturnSinceInception 2.25%rr_AverageAnnualReturnSinceInception
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Inception Date rr_AverageAnnualReturnInceptionDate Feb. 01, 2007
Thornburg International Value Fund | R3 R4 R5 R6 | Class R5  
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 0.68%rr_ManagementFeesOverAssets
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Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.44%rr_OtherExpensesOverAssets
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Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.12%rr_ExpensesOverAssets
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Fee Waiver/Expense Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.13%)rr_FeeWaiverOrReimbursementOverAssets
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[1]
Total Annual Fund Operating Expenses After Fee Waiver/Expense Reimbursement rr_NetExpensesOverAssets 0.99%rr_NetExpensesOverAssets
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3 Years rr_ExpenseExampleYear03 343rr_ExpenseExampleYear03
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5 Years rr_ExpenseExampleYear05 604rr_ExpenseExampleYear05
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10 Years rr_ExpenseExampleYear10 1,352rr_ExpenseExampleYear10
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1 Year rr_AverageAnnualReturnYear01 (5.63%)rr_AverageAnnualReturnYear01
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5 Years rr_AverageAnnualReturnYear05 4.61%rr_AverageAnnualReturnYear05
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Since Inception rr_AverageAnnualReturnSinceInception 6.53%rr_AverageAnnualReturnSinceInception
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Inception Date rr_AverageAnnualReturnInceptionDate Feb. 01, 2005
Thornburg International Value Fund | R3 R4 R5 R6 | Class R6  
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 0.68%rr_ManagementFeesOverAssets
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Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.05%rr_OtherExpensesOverAssets
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Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.73%rr_ExpensesOverAssets
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Fee Waiver/Expense Reimbursement rr_FeeWaiverOrReimbursementOverAssets    [1]
Total Annual Fund Operating Expenses After Fee Waiver/Expense Reimbursement rr_NetExpensesOverAssets 0.73%rr_NetExpensesOverAssets
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1 Year rr_ExpenseExampleYear01 75rr_ExpenseExampleYear01
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3 Years rr_ExpenseExampleYear03 233rr_ExpenseExampleYear03
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5 Years rr_ExpenseExampleYear05 406rr_ExpenseExampleYear05
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10 Years rr_ExpenseExampleYear10 906rr_ExpenseExampleYear10
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1 Year rr_AverageAnnualReturnYear01 (5.37%)rr_AverageAnnualReturnYear01
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Since Inception rr_AverageAnnualReturnSinceInception 5.28%rr_AverageAnnualReturnSinceInception
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Inception Date rr_AverageAnnualReturnInceptionDate May 01, 2012
Thornburg International Value Fund | R3 R4 R5 R6 | Return After Taxes on Distributions | Class R3  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (8.20%)rr_AverageAnnualReturnYear01
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5 Years rr_AverageAnnualReturnYear05 3.42%rr_AverageAnnualReturnYear05
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10 Years rr_AverageAnnualReturnYear10 5.00%rr_AverageAnnualReturnYear10
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Thornburg International Value Fund | R3 R4 R5 R6 | Return After Taxes on Distributions and Sale of Fund Shares | Class R3  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (1.81%)rr_AverageAnnualReturnYear01
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5 Years rr_AverageAnnualReturnYear05 3.09%rr_AverageAnnualReturnYear05
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10 Years rr_AverageAnnualReturnYear10 4.54%rr_AverageAnnualReturnYear10
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/ rr_PerformanceMeasureAxis
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Thornburg International Value Fund | R3 R4 R5 R6 | EAFE Index (reflects no deduction for fees, expenses, or taxes) | Class R3  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (4.90%)rr_AverageAnnualReturnYear01
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5 Years rr_AverageAnnualReturnYear05 5.33%rr_AverageAnnualReturnYear05
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10 Years rr_AverageAnnualReturnYear10 4.43%rr_AverageAnnualReturnYear10
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/ rr_PerformanceMeasureAxis
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Thornburg International Value Fund | R3 R4 R5 R6 | EAFE Index (reflects no deduction for fees, expenses, or taxes) | Class R4  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (4.90%)rr_AverageAnnualReturnYear01
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5 Years rr_AverageAnnualReturnYear05 5.33%rr_AverageAnnualReturnYear05
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/ rr_PerformanceMeasureAxis
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Since Inception rr_AverageAnnualReturnSinceInception 0.84%rr_AverageAnnualReturnSinceInception
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Inception Date rr_AverageAnnualReturnInceptionDate Feb. 01, 2007
Thornburg International Value Fund | R3 R4 R5 R6 | EAFE Index (reflects no deduction for fees, expenses, or taxes) | Class R5  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (4.90%)rr_AverageAnnualReturnYear01
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5 Years rr_AverageAnnualReturnYear05 5.33%rr_AverageAnnualReturnYear05
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/ rr_PerformanceMeasureAxis
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Since Inception rr_AverageAnnualReturnSinceInception 4.67%rr_AverageAnnualReturnSinceInception
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/ rr_PerformanceMeasureAxis
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Inception Date rr_AverageAnnualReturnInceptionDate Feb. 01, 2005
Thornburg International Value Fund | R3 R4 R5 R6 | EAFE Index (reflects no deduction for fees, expenses, or taxes) | Class R6  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (4.90%)rr_AverageAnnualReturnYear01
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Since Inception rr_AverageAnnualReturnSinceInception 9.05%rr_AverageAnnualReturnSinceInception
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/ rr_PerformanceMeasureAxis
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/ rr_ProspectusShareClassAxis
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Inception Date rr_AverageAnnualReturnInceptionDate May 01, 2012
Thornburg International Value Fund | R3 R4 R5 R6 | MSCI AC World ex-U.S. Index (reflects no deduction for fees, expenses, or taxes) | Class R3  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (3.43%)rr_AverageAnnualReturnYear01
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/ rr_PerformanceMeasureAxis
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5 Years rr_AverageAnnualReturnYear05 4.89%rr_AverageAnnualReturnYear05
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/ rr_PerformanceMeasureAxis
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10 Years rr_AverageAnnualReturnYear10 5.59%rr_AverageAnnualReturnYear10
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/ rr_PerformanceMeasureAxis
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Thornburg International Value Fund | R3 R4 R5 R6 | MSCI AC World ex-U.S. Index (reflects no deduction for fees, expenses, or taxes) | Class R4  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (3.43%)rr_AverageAnnualReturnYear01
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5 Years rr_AverageAnnualReturnYear05 4.89%rr_AverageAnnualReturnYear05
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/ rr_PerformanceMeasureAxis
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Since Inception rr_AverageAnnualReturnSinceInception 1.82%rr_AverageAnnualReturnSinceInception
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/ rr_PerformanceMeasureAxis
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Inception Date rr_AverageAnnualReturnInceptionDate Feb. 01, 2007
Thornburg International Value Fund | R3 R4 R5 R6 | MSCI AC World ex-U.S. Index (reflects no deduction for fees, expenses, or taxes) | Class R5  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (3.43%)rr_AverageAnnualReturnYear01
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5 Years rr_AverageAnnualReturnYear05 4.89%rr_AverageAnnualReturnYear05
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/ rr_PerformanceMeasureAxis
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Since Inception rr_AverageAnnualReturnSinceInception 5.83%rr_AverageAnnualReturnSinceInception
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/ dei_LegalEntityAxis
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/ rr_PerformanceMeasureAxis
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Inception Date rr_AverageAnnualReturnInceptionDate Feb. 01, 2005
Thornburg International Value Fund | R3 R4 R5 R6 | MSCI AC World ex-U.S. Index (reflects no deduction for fees, expenses, or taxes) | Class R6  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (3.43%)rr_AverageAnnualReturnYear01
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Since Inception rr_AverageAnnualReturnSinceInception 6.95%rr_AverageAnnualReturnSinceInception
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Inception Date rr_AverageAnnualReturnInceptionDate May 01, 2012
[1] 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 R3, Class R4 and Class R5 expenses do not exceed 1.45%, 1.25% and 0.99%, respectively. 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.