Investment Risks - Retail [Member] |
Aug. 20, 2026 |
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| Thornburg Investment Income Builder Fund | Convertible Debt Obligation Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Credit Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Cybersecurity and Operational Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. The rapid development and increasingly widespread use of artificial intelligence, including machine learning technology and generative artificial intelligence such as ChatGPT, could exacerbate these risks. |
| Thornburg Investment Income Builder Fund | Developing Country Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Equity Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Foreign Currency Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Foreign Government Obligations Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Foreign Investment Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | High Yield Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Interest Rate Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Liquidity Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Management Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Market and Economic Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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, legal, and technological developments, and general market volatility. |
| Thornburg Investment Income Builder Fund | Prepayment and Extension Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Real Estate Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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). |
| Thornburg Investment Income Builder Fund | Redemption Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Risks Affecting Specific Countries or Regions [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Risks Affecting Specific Issuers [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Small and Mid-Cap Company Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | U.S. Government Obligations Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Investment Income Builder Fund | Risk Lose Money [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | Accordingly, the loss of money is a risk of investing in the Fund. |
| Thornburg Investment Income Builder Fund | Risk Not Insured [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Convertible Debt Obligation Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Credit Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Cybersecurity and Operational Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. The rapid development and increasingly widespread use of artificial intelligence, including machine learning technology and generative artificial intelligence such as ChatGPT, could exacerbate these risks. |
| Thornburg Summit Fund | Developing Country Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Equity Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Foreign Currency Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Foreign Government Obligations Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Foreign Investment Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | High Yield Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Interest Rate Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Liquidity Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Management Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Market and Economic Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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, legal, and technological 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. |
| Thornburg Summit Fund | Prepayment and Extension Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Real Estate Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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). |
| Thornburg Summit Fund | Redemption Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Risks Affecting Specific Issuers [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Small and Mid-Cap Company Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | U.S. Government Obligations Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Commodities-Related Investment Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Depositary Receipts Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Derivatives Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Inflation Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Structured Products Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |
| Thornburg Summit Fund | Zero Coupon Bonds and Stripped Securities Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. Additional information about Fund investments, investment strategies and risks of investing in the Fund appears below beginning on page 125 of the Prospectus. |
| Thornburg Summit Fund | Risk Lose Money [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | Accordingly, the loss of money is a risk of investing in the Fund. |
| Thornburg Summit Fund | Risk Not Insured [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | 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. |