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N-2 - USD ($) | 12 Months Ended |  |  |  |  |  |  |  |
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Oct. 31, 2023 | Oct. 31, 2014 | Oct. 31, 2022 | Oct. 31, 2021 | Oct. 31, 2020 | Oct. 31, 2019 | Oct. 31, 2018 | Oct. 31, 2017 | Oct. 31, 2016 | Oct. 31, 2015
Cover [Abstract] |  |  |  |  |  |  |  |  |  |  |
Entity Central Index Key |  | 0001195737 |  |  |  |  |  |  |  |  |
Amendment Flag |  | false |  |  |  |  |  |  |  |  |
Document Type |  | N-CSR |  |  |  |  |  |  |  |  |
Entity Registrant Name |  | Nuveen AMT-Free Quality Municipal Income Fund |  |  |  |  |  |  |  |  |
Financial Highlights [Abstract] |  |  |  |  |  |  |  |  |  |  |
Senior Securities [Table Text Block] |  | The following table sets forth information regarding the Fund’s outstanding senior securities as of the end of the Fund’s last ten fiscal years, as applicable. The Fund’s senior securities during this time period are comprised of borrowings that constitute “senior securities” as defined in the Investment Company Act of 1940, as amended (1940 Act). The information in this table has been audited by KPMG LLP, independent registered public accounting firm. The Fund’s audited financial statements, including the report of KPMG LLP thereon, and accompanying notes thereto, are included in this Annual Report.
|  | Adjustable Rate MuniFund Term Preferred (AMTP) Shares at the End of Period |  |  | MuniFund Preferred (MFP) Shares at the End of Period |  |  | MuniFund Term Preferred (MTP)Shares at the End of Period |  |  | Variable Rate MuniFund Term Preferred (VMTP) Shares at the End of Period |  |  | Variable Rate Demand Preferred (VRDP) Shares at the End of Period |  |  | AMTP, MFP, MTP, VMTP and/or VRDP Shares at the End of Period |
Year Ended 10/31: |  | Aggregate Amount |  |  | Asset Coverage Per $100,000 Share(2) |  |  | Aggregate Amount Outstanding (000)(1) |  |  | Asset Coverage Per $100,000 Share(2),(3) |  |  | Aggregate Amount Outstanding (000)(1) |  |  | Asset Coverage Per $10 Share(4) |  |  | Aggregate Amount Outstanding (000)(1) |  |  | Asset Coverage |  |  | Aggregate Amount Outstanding (000)(1) |  |  | Asset Coverage Per $100,000 Share(2) |  |  | Asset Coverage Per $1 Liquidation Preference |
2023 |  |  | $173,000 |  |  |  | $240,834 |  |  |  | $1,038,900 |  |  |  | $240,834 |  |  |  | $0 |  |  |  | $0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $1,159,400 |  |  |  | $240,834 |  |  |  | $2.41 |
2022 |  |  | $173,000 |  |  |  | $240,229 |  |  |  | $1,088,900 |  |  |  | $240,229 |  |  |  | $0 |  |  |  | $0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $1,159,400 |  |  |  | $240,229 |  |  |  | $2.40 |
2021 |  |  | $316,500 |  |  |  | $283,145 |  |  |  | $1,088,900 |  |  |  | $283,145 |  |  |  | $0 |  |  |  | $0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $1,159,400 |  |  |  | $283,145 |  |  |  | $2.83 |
2020 |  |  | $143,500 |  |  |  | $280,550 |  |  |  | $ 958,000 |  |  |  | $280,550 |  |  |  | $0 |  |  |  | $0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $1,290,300 |  |  |  | $280,550 |  |  |  | $2.81 |
2019 |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 958,000 |  |  |  | $282,066 |  |  |  | $0 |  |  |  | $0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $1,290,300 |  |  |  | $282,066 |  |  |  | $2.82 |
2018 |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 958,000 |  |  |  | $265,448 |  |  |  | $0 |  |  |  | $0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $1,290,300 |  |  |  | $265,448 |  |  |  | $2.65 |
2017 |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $0 |  |  |  | $0 |  |  |  | $773,000 |  |  |  | $291,919 |  |  |  | $1,290,300 |  |  |  | $291,919 |  |  |  | $2.92 |
2016 |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $0 |  |  |  | $0 |  |  |  | $773,000 |  |  |  | $295,667 |  |  |  | $1,290,300 |  |  |  | $295,667 |  |  |  | $2.96 |
2015 |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $0 |  |  |  | $0 |  |  |  | $151,000 |  |  |  | $333,349 |  |  |  | $ 349,900 |  |  |  | $333,349 |  |  |  | $3.33 |
2014 |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $0 |  |  |  | $0 |  |  |  | $151,000 |  |  |  | $338,193 |  |  |  | $ 349,900 |  |  |  | $338,193 |  |  |  | $3.38 |
(1) | Aggregate Amount Outstanding: Aggregate amount outstanding represents the liquidation preference as of the end of the relevant fiscal year and does not include any preferred shares noticed for redemption as noted on the Statement of Assets and Liabilities, where applicable.
(2) | Asset Coverage Per $100,000: Asset coverage per $100,000 is calculated by subtracting the Fund’s liabilities and indebtedness not represented by senior securities from the Fund’s total assets, dividing the result by the aggregate amount of the Fund’s senior securities representing indebtedness then outstanding (if applicable), plus the aggregate of the involuntary liquidation preference of the outstanding preferred shares, if applicable, and multiplying the result by 100,000.
(3) | The Fund’s Series D MFP Shares have a $1,000 liquidation preference per share, while all other MFP Shares have a $100,000 liquidation preference per share. The asset coverage per $1,000 share for the Fund’s Series D MFP Shares were as follows:
|  | Fiscal Year Ended October 31
Series D MFP Shares |  | 2023 |  | 2022 |  | 2021 |  | 2020 |  | 2019 |  | 2018
Asset Coverage Per $1,000 Share* |  | $2,408 |  | $2,402 |  | $2,831 |  | $2,805 |  | $2,800 |  | $0
* | Asset Coverage Per $1,000: Asset coverage per $1,000 is calculated by subtracting the Fund’s liabilities and indebtedness not represented by senior securities from the Fund’s total assets, dividing the result by the aggregate amount of the Fund’s senior securities representing indebtedness then outstanding, and multiplying the result by 1,000.
(4) | Asset Coverage Per $10: Asset coverage per $10 is calculated by subtracting the Fund’s liabilities and indebtedness not represented by senior securities from the Fund’s total assets, dividing the result by the aggregate amount of the Fund’s senior securities representing indebtedness then outstanding, and multiplying the result by 10. The Ending and Average Market Value Per Share for each Series of the Fund’s MTP Shares outstanding were as follows:
|  | Fiscal Year Ended October 31 |  |
Series 2015 (NEA PRCCL) |  | 2014
Ending Market Value per Share |  | $0
Average Market Value per Share |  | $10.05**
** | For the period November 1, 2013 through December 20, 2013.
Senior Securities, Note [Text Block] |  | SENIOR SECURITIES The following table sets forth information regarding the Fund’s outstanding senior securities as of the end of the Fund’s last ten fiscal years, as applicable. The Fund’s senior securities during this time period are comprised of borrowings that constitute “senior securities” as defined in the Investment Company Act of 1940, as amended (1940 Act). The information in this table has been audited by KPMG LLP, independent registered public accounting firm. The Fund’s audited financial statements, including the report of KPMG LLP thereon, and accompanying notes thereto, are included in this Annual Report.
|  | Adjustable Rate MuniFund Term Preferred (AMTP) Shares at the End of Period |  |  | MuniFund Preferred (MFP) Shares at the End of Period |  |  | MuniFund Term Preferred (MTP)Shares at the End of Period |  |  | Variable Rate MuniFund Term Preferred (VMTP) Shares at the End of Period |  |  | Variable Rate Demand Preferred (VRDP) Shares at the End of Period |  |  | AMTP, MFP, MTP, VMTP and/or VRDP Shares at the End of Period |
Year Ended 10/31: |  | Aggregate Amount |  |  | Asset Coverage Per $100,000 Share(2) |  |  | Aggregate Amount Outstanding (000)(1) |  |  | Asset Coverage Per $100,000 Share(2),(3) |  |  | Aggregate Amount Outstanding (000)(1) |  |  | Asset Coverage Per $10 Share(4) |  |  | Aggregate Amount Outstanding (000)(1) |  |  | Asset Coverage |  |  | Aggregate Amount Outstanding (000)(1) |  |  | Asset Coverage Per $100,000 Share(2) |  |  | Asset Coverage Per $1 Liquidation Preference |
2023 |  |  | $173,000 |  |  |  | $240,834 |  |  |  | $1,038,900 |  |  |  | $240,834 |  |  |  | $0 |  |  |  | $0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $1,159,400 |  |  |  | $240,834 |  |  |  | $2.41 |
2022 |  |  | $173,000 |  |  |  | $240,229 |  |  |  | $1,088,900 |  |  |  | $240,229 |  |  |  | $0 |  |  |  | $0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $1,159,400 |  |  |  | $240,229 |  |  |  | $2.40 |
2021 |  |  | $316,500 |  |  |  | $283,145 |  |  |  | $1,088,900 |  |  |  | $283,145 |  |  |  | $0 |  |  |  | $0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $1,159,400 |  |  |  | $283,145 |  |  |  | $2.83 |
2020 |  |  | $143,500 |  |  |  | $280,550 |  |  |  | $ 958,000 |  |  |  | $280,550 |  |  |  | $0 |  |  |  | $0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $1,290,300 |  |  |  | $280,550 |  |  |  | $2.81 |
2019 |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 958,000 |  |  |  | $282,066 |  |  |  | $0 |  |  |  | $0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $1,290,300 |  |  |  | $282,066 |  |  |  | $2.82 |
2018 |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 958,000 |  |  |  | $265,448 |  |  |  | $0 |  |  |  | $0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $1,290,300 |  |  |  | $265,448 |  |  |  | $2.65 |
2017 |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $0 |  |  |  | $0 |  |  |  | $773,000 |  |  |  | $291,919 |  |  |  | $1,290,300 |  |  |  | $291,919 |  |  |  | $2.92 |
2016 |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $0 |  |  |  | $0 |  |  |  | $773,000 |  |  |  | $295,667 |  |  |  | $1,290,300 |  |  |  | $295,667 |  |  |  | $2.96 |
2015 |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $0 |  |  |  | $0 |  |  |  | $151,000 |  |  |  | $333,349 |  |  |  | $ 349,900 |  |  |  | $333,349 |  |  |  | $3.33 |
2014 |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $ 0 |  |  |  | $0 |  |  |  | $0 |  |  |  | $151,000 |  |  |  | $338,193 |  |  |  | $ 349,900 |  |  |  | $338,193 |  |  |  | $3.38 |
(1) | Aggregate Amount Outstanding: Aggregate amount outstanding represents the liquidation preference as of the end of the relevant fiscal year and does not include any preferred shares noticed for redemption as noted on the Statement of Assets and Liabilities, where applicable.
(2) | Asset Coverage Per $100,000: Asset coverage per $100,000 is calculated by subtracting the Fund’s liabilities and indebtedness not represented by senior securities from the Fund’s total assets, dividing the result by the aggregate amount of the Fund’s senior securities representing indebtedness then outstanding (if applicable), plus the aggregate of the involuntary liquidation preference of the outstanding preferred shares, if applicable, and multiplying the result by 100,000.
(3) | The Fund’s Series D MFP Shares have a $1,000 liquidation preference per share, while all other MFP Shares have a $100,000 liquidation preference per share. The asset coverage per $1,000 share for the Fund’s Series D MFP Shares were as follows:
|  | Fiscal Year Ended October 31
Series D MFP Shares |  | 2023 |  | 2022 |  | 2021 |  | 2020 |  | 2019 |  | 2018
Asset Coverage Per $1,000 Share* |  | $2,408 |  | $2,402 |  | $2,831 |  | $2,805 |  | $2,800 |  | $0
* | Asset Coverage Per $1,000: Asset coverage per $1,000 is calculated by subtracting the Fund’s liabilities and indebtedness not represented by senior securities from the Fund’s total assets, dividing the result by the aggregate amount of the Fund’s senior securities representing indebtedness then outstanding, and multiplying the result by 1,000.
(4) | Asset Coverage Per $10: Asset coverage per $10 is calculated by subtracting the Fund’s liabilities and indebtedness not represented by senior securities from the Fund’s total assets, dividing the result by the aggregate amount of the Fund’s senior securities representing indebtedness then outstanding, and multiplying the result by 10. The Ending and Average Market Value Per Share for each Series of the Fund’s MTP Shares outstanding were as follows:
|  | Fiscal Year Ended October 31 |  |
Series 2015 (NEA PRCCL) |  | 2014
Ending Market Value per Share |  | $0
Average Market Value per Share |  | $10.05**
** | For the period November 1, 2013 through December 20, 2013.
Senior Securities Headings, Note [Text Block] |  | The following table sets forth information regarding the Fund’s outstanding senior securities as of the end of the Fund’s last ten fiscal years, as applicable. The Fund’s senior securities during this time period are comprised of borrowings that constitute “senior securities” as defined in the Investment Company Act of 1940, as amended (1940 Act). The information in this table has been audited by KPMG LLP, independent registered public accounting firm. The Fund’s audited financial statements, including the report of KPMG LLP thereon, and accompanying notes thereto, are included in this Annual Report. |  |  |  |  |  |  |  |  |
Senior Securities Highlights Audited, Note [Text Block] |  | The information in this table has been audited by KPMG LLP, independent registered public accounting firm. The Fund’s audited financial statements, including the report of KPMG LLP thereon, and accompanying notes thereto, are included in this Annual Report. |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Investment Objectives and Practices [Text Block] |  | Investment Objectives The Fund’s investment objectives are to provide current income exempt from regular federal income tax and federal alternative minimum tax applicable to individuals, and to enhance portfolio value relative to the municipal bond market by investing in tax-exempt municipal securities that the Fund’s investment adviser believes are underrated or undervalued or that represent municipal market sectors that are undervalued. Investment Policies As a fundamental investment policy, under normal circumstances, the Fund will invest at least 80% of its Assets (as defined below) in municipal securities and other related investments that pay interest exempt from regular federal income tax. Additionally, as a fundamental investment policy, under normal circumstances, the Fund will invest at least 80% of its Assets in a portfolio of securities, the income from which is exempt from the federal alternative minimum tax applicable to individuals. As a non-fundamental investment policy, under normal circumstances, the Fund will invest 100% of its Managed Assets (as defined below) in municipal securities and other related investments the income from which is exempt from the federal alternative minimum tax applicable to individuals at the time of purchase. “Assets” means net assets of the Fund plus the amount of any borrowings for investment purposes. “Managed Assets” means the total assets of the Fund, minus the sum of its accrued liabilities (other than Fund liabilities incurred for the express purpose of creating leverage). Total assets for this purpose shall include assets attributable to the Fund’s use of leverage (whether or not those assets are reflected in the Fund’s financial statements for purposes of generally accepted accounting principles), and derivatives will be valued at their market value. Additionally, as a non-fundamental policy, the Fund:
| ● |  | May invest up to 35% of its Managed Assets in securities rated, at the time of investment, below the three highest grades (Baa or BBB or lower) by at least one NRSRO which includes below-investment-grade securities, or unrated securities judged to be of comparable quality by the Fund’s sub-adviser.
| ● |  | May invest in distressed securities but may not invest in the securities of an issuer which, at the time of investment, is in default on its obligations to pay principal or interest thereon when due or that is involved in a bankruptcy proceeding (i.e., rated below C-, at the time of investment); provided, however, that the Fund’s sub-adviser may determine that it is in the best interest of shareholders in pursuing a workout arrangement with issuers of defaulted securities to make loans to the defaulted issuer or another party, or purchase a debt, equity or other interest from the defaulted issuer or another party, or take other related or similar steps involving the investment of additional monies, but only if that issuer’s securities are already held by the Fund.
| ● |  | May invest up to 15% of its Managed Assets in inverse floating rate securities.
| ● |  | The Fund may not enter into a futures contract or related options or forward contracts if more than 30% of the Fund’s Managed Assets would be represented by futures contracts or more than 5% of the Fund’s Managed Assets would be committed to initial margin deposits and premiums on futures contracts or related options.
| ● |  | The Fund will generally maintain an investment portfolio with an overall weighted average maturity of greater than 10 years.
The foregoing policies apply only at the time of any new investment. Approving Changes in Investment Policies The Board of Trustees of the Fund may change the policies described above without a shareholder vote. However, with respect to the Fund’s fundamental policy of investing at least 80% of its Assets in municipal securities and other related investments that pay interest exempt from both regular federal income tax and the federal alternative minimum tax applicable to individuals such policy may not be changed without 60 days’ prior written notice and the approval of the holders of a majority of the outstanding common shares and preferred shares voting together as a single class, and the approval of the holders of a majority of the outstanding preferred shares, voting separately as a single class. A “majority of the outstanding” shares means (i) 67% or more of the shares present at a meeting, if the holders of more than 50% of the shares are present or represented by proxy or (ii) more than 50% of the shares, whichever is less. Portfolio Contents The Fund generally invests its assets in a portfolio of municipal securities. Municipal securities include municipal bonds, notes, securities issued to finance and refinance public projects, certificates of participation, variable rate demand obligations, lease obligations, municipal notes, pre-refunded municipal bonds, private activity bonds, securities issued by TOB Trusts, including inverse floating rate securities, and other forms of municipal bonds and securities, and other related instruments that create exposure to municipal bonds, notes and securities that provide for the payment of interest income that is exempt from regular U.S. federal income tax. Municipal securities are debt obligations generally issued by states, cities and local authorities and certain possessions and territories of the United States (such as Puerto Rico and Guam) to finance or refinance public purpose projects such as roads, schools, and water supply systems. The Fund may invest in municipal securities that are additionally secured by insurance, bank credit agreements or escrow accounts. The Fund may invest in municipal securities that represent lease obligations and certificates of participation in such leases. A municipal lease is an obligation in the form of a lease or installment purchase that is issued by a state or local government to acquire equipment and facilities. Income from such obligations generally is exempt from state and local taxes in the state of issuance. A certificate of participation represents an undivided interest in an unmanaged pool of municipal leases, an installment purchase agreement or other instruments. The certificates typically are issued by a municipal agency, a trust or other entity that has received an assignment of the payments to be made by the state or political subdivision under such leases or installment purchase agreements. Such certificates provide the Fund with the right to a pro rata undivided interest in the underlying municipal securities. In addition, such participations generally provide the Fund with the right to demand payment, on not more than seven days’ notice, of all or any part of the Fund’s participation interest in the underlying municipal securities, plus accrued interest. The Fund may invest in municipal notes. Municipal securities in the form of notes generally are used to provide for short-term capital needs, in anticipation of an issuer’s receipt of other revenues or financing, and typically have maturities of up to three years. Such instruments may include tax anticipation notes, revenue anticipation notes, bond anticipation notes, tax and revenue anticipation notes and construction loan notes. Tax anticipation notes are issued to finance the working capital needs of governments. Generally, they are issued in anticipation of various tax revenues, such as income, sales, property, use and business taxes, and are payable from these specific future taxes. Revenue anticipation notes are issued in expectation of receipt of other kinds of revenue, such as federal revenues available under federal revenue sharing programs. Bond anticipation notes are issued to provide interim financing until long-term bond financing can be arranged. In most cases, the long-term bonds then provide the funds needed for repayment of the bond anticipation notes. Tax and revenue anticipation notes combine the funding sources of both tax anticipation notes and revenue anticipation notes. Construction loan notes are sold to provide construction financing. Mortgage notes insured by the Federal Housing Authority secure these notes; however, the proceeds from the insurance may be less than the economic equivalent of the payment of principal and interest on the mortgage note if there has been a default. The anticipated revenues from taxes, grants or bond financing generally secure the obligations of an issuer of municipal notes. The Fund may invest in “tobacco settlement bonds.” Tobacco settlement bonds are municipal securities that are secured or payable solely from the collateralization of the proceeds from class action or other litigation against the tobacco industry. The Fund may invest in pre-refunded municipal securities. The principal of and interest on pre-refunded municipal securities are no longer paid from the original revenue source for the securities. Instead, the source of such payments is typically an escrow fund consisting of U.S. government securities. The assets in the escrow fund are derived from the proceeds of refunding bonds issued by the same issuer as the pre-refunded municipal securities. Issuers of municipal securities use this advance refunding technique to obtain more favorable terms with respect to securities that are not yet subject to call or redemption by the issuer. For example, advance refunding enables an issuer to refinance debt at lower market interest rates, restructure debt to improve cash flow or eliminate restrictive covenants in the indenture or other governing instrument for the pre-refunded municipal securities. However, except for a change in the revenue source from which principal and interest payments are made, the pre-refunded municipal securities remain outstanding on their original terms until they mature or are redeemed by the issuer. The Fund may invest in private activity bonds. Private activity bonds are issued by or on behalf of public authorities to obtain funds to provide privately operated housing facilities, airport, mass transit or port facilities, sewage disposal, solid waste disposal or hazardous waste treatment or disposal facilities and certain local facilities for water supply, gas or electricity. Other types of private activity bonds, the proceeds of which are used for the construction, equipment, repair or improvement of privately operated industrial or commercial facilities, may constitute municipal securities, although the current federal tax laws place substantial limitations on the size of such issues. The Fund may invest in municipal securities issued by special taxing districts. Special taxing districts are organized to plan and finance infrastructure developments to induce residential, commercial and industrial growth and redevelopment. The bond financing methods such as tax increment finance, tax assessment, special services district and Mello-Roos bonds, are generally payable solely from taxes or other revenues attributable to the specific projects financed by the bonds without recourse to the credit or taxing power of related or overlapping municipalities. The Fund may invest in inverse floating rate securities issued by a TOB trust, the interest rate on which varies inversely with the Securities Industry Financial Markets Association short-term rate, which resets weekly, or a similar short-term rate, and is reduced by the expenses related to the TOB trust. Typically, inverse floating rate securities represent beneficial interests in a special purpose trust (sometimes called a TOB trust) formed by a third party sponsor for the purpose of holding municipal bonds. Inverse floating rate securities may increase or decrease in value at a greater rate than the underlying interest rate on the municipal bond held by the TOB trust, which effectively leverages the Fund’s investment. The Fund may invest in floating rate securities issued by special purpose trusts. Floating rate securities may take the form of short-term floating rate securities or the option period may be substantially longer. Generally, the interest rate earned will be based upon the market rates for municipal securities with maturities or remarketing provisions that are comparable in duration to the periodic interval of the tender option, which may vary from weekly, to monthly, to extended periods of one year or multiple years. Since the option feature has a shorter term than the final maturity or first call date of the underlying bond deposited in the trust, the Fund as the holder of the floating rate security relies upon the terms of the agreement with the financial institution furnishing the option as well as the credit strength of that institution. As further assurance of liquidity, the terms of the trust provide for a liquidation of the municipal security deposited in the trust and the application of the proceeds to pay off the floating rate security. The trusts that are organized to issue both short-term floating rate securities and inverse floaters generally include liquidation triggers to protect the investor in the floating rate security. The Fund may invest in zero coupon bonds. A zero coupon bond is a bond that typically does not pay interest for the entire life of the obligation or for an initial period after the issuance of the obligation. The Fund may buy and sell securities on a when-issued or delayed delivery basis, making payment or taking delivery at a later date, normally within 15 to 45 days of the trade date. The Fund may invest in illiquid securities (i.e., securities that are not readily marketable), including, but not limited to, restricted securities (securities the disposition of which is restricted under the federal securities laws), securities that may be resold only pursuant to Rule 144A under the 1933 Act, and repurchase agreements with maturities in excess of seven days. The Fund may enter into certain derivative instruments in pursuit of its investment objectives, including to seek to enhance return, to hedge certain risks of its investments in municipal securities or as a substitute for a position in the underlying asset. Such instruments include financial futures contracts, swap contracts (including interest rate swaps, credit default swaps and MMD Rate Locks), options on financial futures, options on swap contracts or other derivative instruments. The Fund may purchase and sell MMD Rate Locks. An MMD Rate Lock permits the Fund to lock in a specified municipal interest rate for a portion of its portfolio to preserve a return on a particular investment or a portion of its portfolio as a duration management technique or to protect against any increase in the price of securities to be purchased at a later date. By using an MMD Rate Lock, the Fund can create a synthetic long or short position, allowing the Fund to select what the manager believes is an attractive part of the yield curve. The Fund will ordinarily use these transactions as a hedge or for duration or risk management although it is permitted to enter into them to enhance income or gain or to increase the Fund’s yield, for example, during periods of steep interest rate yield curves (i.e., wide differences between short term and long term interest rates). The Fund may also invest in securities of other open-or closed-end investment companies (including ETFs) that invest primarily in municipal securities of the types in which the Fund may invest directly, to the extent permitted by the 1940 Act, the rules and regulations issued thereunder and applicable exemptive orders issued by the SEC. Use of Leverage The Fund uses leverage to pursue its investment objectives. The Fund may use leverage to the extent permitted by the 1940 Act. The Fund may source leverage through a number of methods including the issuance of Preferred Shares, investments in inverse floating rate securities, entering into reverse repurchase agreements (effectively a secured borrowing) and borrowings (subject to certain investment restrictions). In addition, the Fund may also use certain derivatives that have the economic effect of leverage by creating additional investment exposure. The amount and sources of leverage will vary depending on market conditions. Temporary Defensive Periods During temporary defensive periods or in order to help keep the Fund’s assets fully invested, including during the period within which the net proceeds of an offering of Securities are first being invested, the Fund may deviate from its investment policies and objectives. During such periods, the Fund may invest any percentage of its Managed As se ts in short-term investments, including high quality, short-term debt securities that may be either tax-exempt or taxable. The Fund may not achieve its investment objectives during such periods. |  |  |  |  |  |  |  |  |
Risk Factors [Table Text Block] |  | PRINCIPAL RISKS OF THE FUNDS The factors that are most likely to have a material effect on a particular Fund’s portfolio as a whole are called “principal risks.” Each Fund is subject to the principal risks indicated below, whether through direct investment or derivative positions. Each Fund may be subject to additional risks other than those identified and described below because the types of investments made by a Fund can change over time.
Risk |  | Nuveen Quality Municipal Income Fund (NAD) |  | Nuveen AMT-Free Quality Municipal Income Fund (NEA)
Portfolio Level Risks |  |  |  |  |  |  |  |  |  |
Alternative Minimum Tax Risk |  |  |  | X |  |  |  |  | - |
Below Investment Grade Risk |  |  |  | X |  |  |  |  | X |
Call Risk |  |  |  | X |  |  |  |  | X |
Credit Risk |  |  |  | X |  |  |  |  | X |
Credit Spread Risk |  |  |  | X |  |  |  |  | X |
Deflation Risk |  |  |  | X |  |  |  |  | X |
Derivatives Risk |  |  |  | X |  |  |  |  | X |
Distressed or Defaulted Securities Risk |  |  |  | X |  |  |  |  | X |
Duration Risk |  |  |  | X |  |  |  |  | X |
Economic Sector Risk |  |  |  | X |  |  |  |  | X |
Financial Futures and Options Risk |  |  |  | X |  |  |  |  | X |
Hedging Risk |  |  |  | X |  |  |  |  | X |
Illiquid Investments Risk |  |  |  | X |  |  |  |  | X |
Income Risk |  |  |  | X |  |  |  |  | X |
Inflation Risk |  |  |  | X |  |  |  |  | X |
Insurance Risk |  |  |  | X |  |  |  |  | X |
Interest Rate Risk |  |  |  | X |  |  |  |  | X |
Inverse Floating Rate Securities Risk |  |  |  | X |  |  |  |  | X |
Municipal Securities Market Liquidity Risk |  |  |  | X |  |  |  |  | X |
Municipal Securities Market Risk |  |  |  | X |  |  |  |  | X |
Other Investment Companies Risk |  |  |  | X |  |  |  |  | X |
Puerto Rico Municipal Securities Market Risk |  |  |  | X |  |  |  |  | X |
Reinvestment Risk |  |  |  | X |  |  |  |  | X |
Special Risks Related to Certain Municipal Obligations |  |  |  | X |  |  |  |  | X |
Swap Transactions Risk |  |  |  | X |  |  |  |  | X |
Tax Risk |  |  |  | X |  |  |  |  | X |
Taxability Risk |  |  |  | X |  |  |  |  | X |
Tobacco Settlement Bond Risk |  |  |  | X |  |  |  |  | X |
Unrated Securities Risk |  |  |  | X |  |  |  |  | X |
Valuation Risk |  |  |  | X |  |  |  |  | X |
Zero Coupon Bonds Risk |  |  |  | X |  |  |  |  | X |
Risk |  | Nuveen Quality Municipal Income Fund (NAD) |  | Nuveen AMT-Free Quality Municipal Income Fund (NEA)
Fund Level and Other Risks |  |  |  |  |  |  |  |  |  |
Anti-Takeover Provisions |  |  |  | X |  |  |  |  | X |
Counterparty Risk |  |  |  | X |  |  |  |  | X |
Cybersecurity Risk |  |  |  | X |  |  |  |  | X |
Economic and Political Events Risk |  |  |  | X |  |  |  |  | X |
Fund Tax Risk |  |  |  | X |  |  |  |  | X |
Global Economic Risk |  |  |  | X |  |  |  |  | X |
Investment and Market Risk |  |  |  | X |  |  |  |  | X |
Legislation and Regulatory Risk |  |  |  | X |  |  |  |  | X |
Leverage Risk |  |  |  | X |  |  |  |  | X |
Market Discount from Net Asset Value |  |  |  | X |  |  |  |  | X |
Recent Market Conditions |  |  |  | X |  |  |  |  | X |
Reverse Repurchase Agreement Risk |  |  |  | X |  |  |  |  | X |
Portfolio Level Risks: Alternative Minimum Tax Risk. The Fund may invest in AMT Bonds. Therefore, a portion of the Fund’s otherwise exempt-interest dividends may be taxable to those shareholders subject to the federal alternative minimum tax. Below Investment Grade Risk. Investments of below investment grade quality are regarded as having speculative characteristics with respect to the issuer’s capacity to pay dividends or interest and repay principal, and may be subject to higher price volatility and default risk than investment grade investments of comparable terms and duration. Issuers of lower grade investments may be highly leveraged and may not have available to them more traditional methods of financing. The prices of these lower grade investments are typically more sensitive to negative developments, such as a decline in the issuer’s revenues or a general economic downturn. The secondary market for lower rated investments may not be as liquid as the secondary market for more highly rated investments, a factor which may have an adverse effect on the Fund’s ability to dispose of a particular investment. If a below investment grade security goes into default, or its issuer enters bankruptcy, it might be difficult to sell that security in a timely manner at a reasonable price. Call Risk. The Fund may invest in municipal securities that are subject to call risk. Such municipal securities may be redeemed at the option of the issuer, or “called,” before their stated maturity or redemption date. In general, an issuer will call its instruments if they can be refinanced by issuing new instruments that bear a lower interest rate. The Fund is subject to the possibility that during periods of falling interest rates, an issuer will call its high yielding municipal securities. The Fund would then be forced to invest the unanticipated proceeds at lower interest rates, resulting in a decline in the Fund’s income. Credit Risk. Issuers of municipal securities in which the Fund may invest may default on their obligations to pay principal or interest when due. This non-payment would result in a reduction of income to the Fund, a reduction in the value of a municipal security experiencing non-payment and potentially a decrease in the net asset value (“NAV”) of the Fund. To the extent that the credit rating assigned to a municipal security in the Fund’s portfolio is downgraded, the market price and liquidity of such security may be adversely affected. Credit Spread Risk. Credit spread risk is the risk that credit spreads (i.e., the difference in yield between securities that is due to differences in their credit quality) may increase when the market believes that municipal securities generally have a greater risk of default. Increasing credit spreads may reduce the market values of the Fund’s securities. Credit spreads often increase more for lower rated and unrated securities than for investment grade securities. In addition, when credit spreads increase, reductions in market value will generally be greater for longer-maturity securities. Deflation Risk. Deflation risk is the risk that prices throughout the economy decline over time. Deflation may have an adverse effect on the creditworthiness of issuers and may make issuer default more likely, which may result in a decline in the value of the Fund’s portfolio. Derivatives Risk. The use of derivatives involves additional risks and transaction costs which could leave the Fund in a worse position than if it had not used these instruments. Derivative instruments can be used to acquire or to transfer the risk and returns of a municipal security or other asset without buying or selling the municipal security or asset. These instruments may entail investment exposures that are greater than their cost would suggest. As a result, a small investment in derivatives can result in losses that greatly exceed the original investment. Derivatives can be highly volatile, illiquid and difficult to value. An over-the-counter derivative transaction between the Fund and a counterparty that is not cleared through a central counterparty also involves the risk that a loss may be sustained as a result of the failure of the counterparty to the contract to make required payments. The payment obligation for a cleared derivative transaction is guaranteed by a central counterparty, which exposes the Fund to the creditworthiness of the central counterparty. The use of certain derivatives involves leverage, which can cause the Fund’s portfolio to be more volatile than if the portfolio had not been leveraged. Leverage can significantly magnify the effect of price movements of the reference asset, disproportionately increasing the Fund’s losses and reducing the Fund’s opportunities for gains when the reference asset changes in unexpected ways. In some instances, such leverage could result in losses that exceed the original amount invested. It is possible that regulatory or other developments in the derivatives market, including changes in government regulation, could adversely impact the Fund’s ability successfully use derivative instruments. Distressed or Defaulted Securities Risk. Investments in “distressed” securities, meaning those whose issuers are experiencing financial difficulties or distress at the time of acquisition, present a substantial risk of future default. In the event distressed securities become defaulted securities or the Fund otherwise holds defaulted securities, the Fund may incur losses, including additional expenses, to the extent it is required to seek recovery upon a default in the payment of principal or interest on those securities. In any reorganization or liquidation proceeding relating to a portfolio security, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Defaulted or distressed securities may be subject to restrictions on resale. Duration Risk. Duration is the sensitivity, expressed in years, of the price of a fixed-income security to changes in the general level of interest rates (or yields). Securities with longer durations tend to be more sensitive to interest rate (or yield) changes, which typically corresponds to increased volatility and risk, than securities with shorter durations. For example, if a security or portfolio has a duration of three years and interest rates increase by 1%, then the security or portfolio would decline in value by approximately 3%. Duration differs from maturity in that it considers potential changes to interest rates, and a security’s coupon payments, yield, price and par value and call features, in addition to the amount of time until the security matures. The duration of a security will be expected to change over time with changes in market factors and time to maturity. Economic Sector Risk. The Fund may invest a significant amount of its total assets in municipal securities in the same economic sector. This may make the Fund more susceptible to adverse economic, political or regulatory occurrences affecting an economic sector making the Fund more vulnerable to unfavorable developments in that sector than funds that invest more broadly. As the percentage of the Fund’s Managed Assets invested in a particular sector increases, so does the potential for fluctuation in the value of the Fund’s assets. In addition, the Fund may invest a significant portion of its assets in certain sectors of the municipal securities market, such as health care facilities, private educational facilities, special taxing districts and start-up utility districts, and private activity bonds including industrial development bonds on behalf of transportation companies, whose credit quality and performance may be more susceptible to economic, business, political, regulatory and other developments than other sectors of municipal issuers. If the Fund invests a significant portion of its assets in one or more particular sectors, the Fund’s performance may be subject to additional risk and variability. Financial Futures and Options Transactions Risk. The Fund may use certain transactions for hedging the portfolio’s exposure to credit risk and the risk of increases in interest rates, which could result in poorer overall performance for the Fund. There may be an imperfect correlation between price movements of the futures and options and price movements of the portfolio securities being hedged. If the Fund engages in futures transactions or in the writing of options on futures, it will be required to maintain initial margin and maintenance margin and may be required to make daily variation margin payments in accordance with applicable rules of the exchanges and the Commodity Futures Trading Commission (“CFTC”). If the Fund purchases a financial futures contract or a call option or writes a put option in order to hedge the anticipated purchase of municipal securities, and if the Fund fails to complete the anticipated purchase transaction, the Fund may have a loss or a gain on the futures or options transaction that will not be offset by price movements in the municipal securities that were the subject of the anticipatory hedge. There can be no assurance that a liquid market will exist at a time when the Fund seeks to close out a derivatives or futures or a futures option position, and the Fund would remain obligated to meet margin requirements until the position is closed. Hedging Risk. The Fund’s use of derivatives or other transactions to reduce risk involves costs and will be subject to the investment adviser’s and/or the sub-adviser’s ability to predict correctly changes in the relationships of such hedge instruments to the Fund’s portfolio holdings or other factors. No assurance can be given that the investment adviser’s and/or the sub-adviser’s judgment in this respect will be correct, and no assurance can be given that the Fund will enter into hedging or other transactions at times or under circumstances in which it may be advisable to do so. Hedging activities may reduce the Fund’s opportunities for gain by offsetting the positive effects of favorable price movements and may result in net losses. Illiquid Investments Risk. Illiquid investments are investments that are not readily marketable. These investments may include restricted investments, including Rule 144A securities, which cannot be resold to the public without an effective registration statement under the 1933 Act, or, if they are unregistered may be sold only in a privately negotiated transaction or pursuant to an available exemption from registration. The Fund may not be able to readily dispose of such investments at prices that approximate those at which the Fund could sell such investments if they were more widely traded and, as a result of such illiquidity, the Fund may have to sell other investments or engage in borrowing transactions if necessary to raise cash to meet its obligations. Limited liquidity can also affect the market price of investments, thereby adversely affecting the Fund’s NAV and ability to make dividend distributions. The financial markets in general have in recent years experienced periods of extreme secondary market supply and demand imbalance, resulting in a loss of liquidity during which market prices were suddenly and substantially below traditional measures of intrinsic value. During such periods, some investments could be sold only at arbitrary prices and with substantial losses. Periods of such market dislocation may occur again at any time. Income Risk. The Fund’s income could decline due to falling market interest rates. This is because, in a falling interest rate environment, the Fund generally will have to invest the proceeds from maturing portfolio securities in lower-yielding securities. Inflation Risk. Inflation risk is the risk that the value of assets or income from investments will be worth less in the future as inflation decreases the value of money. As inflation increases, the real value of the common shares and distributions can decline. Currently, inflation rates are elevated relative to normal market conditions and could increase. Insurance Risk. The Fund may purchase municipal securities that are secured by insurance, bank credit agreements or escrow accounts. The credit quality of the companies that provide such credit enhancements will affect the value of those securities. Certain significant providers of insurance for municipal securities have incurred significant losses as a result of exposure to sub-prime mortgages and other lower credit quality investments. As a result, such losses reduced the insurers’ capital and called into question their continued ability to perform their obligations under such insurance if they are called upon to do so in the future. While an insured municipal security will typically be deemed to have the rating of its insurer, if the insurer of a municipal security suffers a downgrade in its credit rating or the market discounts the value of the insurance provided by the insurer, the value of the municipal security would more closely, if not entirely, reflect such rating. In such a case, the value of insurance associated with a municipal security may not add any value. The insurance feature of a municipal security does not guarantee the full payment of principal and interest through the life of an insured obligation, the market value of the insured obligation or the NAV of the common shares represented by such insured obligation. Interest Rate Risk. Interest rate risk is the risk that municipal securities in the Fund’s portfolio will decline in value because of changes in market interest rates. Generally, when market interest rates rise, the market value of such securities will fall, and vice versa. As interest rates decline, issuers of municipal securities may prepay principal earlier than scheduled, forcing the Fund to reinvest in lower-yielding securities and potentially reducing the Fund’s income. As interest rates increase, slower than expected principal payments may extend the average life of municipal securities, potentially locking in a below-market interest rate and reducing the Fund’s value. In typical market interest rate environments, the prices of longer-term municipal securities generally fluctuate more than prices of shorter-term municipal securities as interest rates change. Inverse Floating Rate Securities Risk. The Fund may invest in inverse floating rate securities. In general, income on inverse floating rate securities will decrease when short-term interest rates increase and increase when short-term interest rates decrease. Investments in inverse floating rate securities may subject the Fund to the risks of reduced or eliminated interest payments and losses of principal. In addition, inverse floating rate securities may increase or decrease in value at a greater rate than the underlying interest rate, which effectively leverages the Fund’s investment. As a result, the market value of such securities generally will be more volatile than that of fixed rate securities. The Fund may invest in inverse floating rate securities issued by special purpose tr us ts that have recourse to the Fund. In such instances, the Fund may be at risk of loss that exceeds its investment in the inverse floating rate securities. The Fund may be required to sell its inverse floating rate securities at less than favorable prices, or liquidate other Fund portfolio holdings in certain circumstances, including, but not limited to, the following:
| ● |  | If the Fund has a need for cash and the securities in a special purpose trust are not actively trading due to adverse market conditions;
| ● |  | If special purpose trust sponsors (as a collective group or individually) experience financial hardship and consequently seek to terminate their respective outstanding special purpose trusts; and
| ● |  | If the value of an underlying security declines significantly and if additional collateral has not been posted by the Fund.
Municipal Securities Market Liquidity Risk. Inventories of municipal securities held by brokers and dealers have decreased in recent years, lessening their ability to make a market in these securities. This reduction in market making capacity has the potential to decrease the Fund’s ability to buy or sell municipal securities at attractive prices, and increase municipal security price volatility and trading costs, particularly during periods of economic or market stress. In addition, recent federal banking regulations may cause certain dealers to reduce their inventories of municipal securities, which may further decrease the Fund’s ability to buy or sell municipal securities. As a result, the Fund may be forced to accept a lower price to sell a security, to sell other securities to raise cash, or to give up an investment opportunity, any of which could have a negative effect on performance. If the Fund needed to sell large blocks of municipal securities to raise cash to meet its obligations, those sales could further reduce the municipal securities’ prices and hurt performance. Municipal Securities Market Risk. The amount of public information available about the municipal securities in the Fund’s portfolio is generally less than that for corporate equities or bonds, and the investment performance of the Fund may therefore be more dependent on the analytical abilities of the sub-adviser than if the Fund were a stock fund or taxable bond fund. The secondary market for municipal securities, particularly below investment grade municipal securities, also tends to be less well-developed or liquid than many other securities markets, which may adversely affect the Fund’s ability to sell its municipal securities at attractive prices. Other Investment Companies Risk. The Fund may invest in the securities of other investment companies, including ETFs. Investing in an investment company exposes the Fund to all of the risks of that investment company’s investments. The Fund, as a holder of the securities of other investment companies, will bear its pro rata portion of the other investment companies’ expenses, including advisory fees. These expenses are in addition to the direct expenses of the Fund’s own operations. As a result, the cost of investing in investment company shares may exceed the costs of investing directly in its underlying investments. In addition, securities of other investment companies may be leveraged. As a result, the Fund may be indirectly exposed to leverage through an investment in such securities and therefore magnify the Fund’s leverage risk. With respect to ETF’s, an ETF that is based on a specific index may not be able to replicate and maintain exactly the composition and relative weighting of securities in the index. The value of an ETF based on a specific index is subject to change as the values of its respective component assets fluctuate according to market volatility. ETFs typically rely on a limited pool of authorized participants to create and redeem shares, and an active trading market for ETF shares may not develop or be maintained. The market value of shares of ETFs and closed-end funds may differ from their NAV. Puerto Rico Municipal Securities Market Risk. To the extent that the Fund invests a significant portion of its assets in the securities issued by the Commonwealth of Puerto Rico or its political subdivisions, agencies, instrumentalities, or public corporations (collectively referred to as “Puerto Rico” or the “Commonwealth”), it will be disproportionally affected by political, social and economic conditions and developments in the Commonwealth. In addition, economic, political or regulatory changes in that territory could adversely affect the value of the Fund’s investment portfolio. Puerto Rico currently is experiencing significant fiscal and economic challenges, including substantial debt service obligations, high levels of unemployment, underfunded public retirement systems, and persistent government budget deficits. These challenges may negatively affect the value of the Fund’s investments in Puerto Rican municipal securities. Several major ratings agencies have downgraded the general obligation debt of Puerto Rico to below investment grade and continue to maintain a negative outlook for this debt, which increases the likelihood that the rating will be lowered further. Puerto Rico recently defaulted on its debt by failing to make full payment due on its outstanding bonds, and there can be no assurance that Puerto Rico will be able to satisfy its future debt obligations. Further downgrades or defaults may place additional strain on the Puerto Rico economy and may negatively affect the value, liquidity, and volatility of the Fund’s investments in Puerto Rican municipal securities. Additionally, numerous issuers have entered Title III of the Puerto Rico Oversite, Management and Economic Stability Act (“PROMESA”), which is similar to bankruptcy protection, through which the Commonwealth of Puerto Rico can restructure its debt. However, Puerto Rico’s case is the first ever heard under PROMESA and there is no existing case precedent to guide the proceedings. Accordingly, Puerto Rico’s debt restructuring process could take significantly longer than traditional municipal bankruptcy proceedings. Further, it is not clear whether a debt restructuring process will ultimately be approved or, if so, the extent to which it will apply to Puerto Rico municipal securities sold by an issuer other than the territory. A debt restructuring could reduce the principal amount due, the interest rate, the maturity, and other terms of Puerto Rico municipal securities, which could adversely affect the value of Puerto Rican municipal securities. Legislation that would allow Puerto Rico to restructure its municipal debt obligations, thus increasing the risk that Puerto Rico may never pay off municipal indebtedness, or may pay only a small fraction of the amount owed, could also impact the value of the Fund’s investments in Puerto Rican municipal securities. These challenges and uncertainties have been exacerbated by multiple hurricanes and the resulting natural disasters that have stuck Puerto Rico since 2017. The full extent of the natural disasters’ impact on Puerto Rico’s economy and foreign investment in Puerto Rico is difficult to estimate. Reinvestment Risk. Reinvestment risk is the risk that income from the Fund’s portfolio will decline if and when the Fund invests the proceeds from matured, traded or called municipal securities at market interest rates that are below the portfolio’s current earnings rate. A decline in income could affect the common shares’ market price, NAV and/or a common shareholder’s overall returns. Special Risks Related to Certain Municipal Obligations. Municipal leases and certificates of participation involve special risks not normally associated with general obligations or revenue bonds. Leases and installment purchase or conditional sale contracts (which normally provide for title to the leased asset to pass eventually to the governmental issuer) have evolved as a means for governmental issuers to acquire property and equipment without meeting the constitutional and statutory requirements for the issuance of debt. The debt issuance limitations are deemed to be inapplicable because of the inclusion in many leases or contracts of “non-appropriation” clauses that relieve the governmental issuer of any obligation to make future payments under the lease or contract unless money is appropriated for such purpose by the appropriate legislative body. In addition, such leases or contracts may be subject to the temporary abatement of payments in the event that the governmental issuer is prevented from maintaining occupancy of the leased premises or utilizing the leased equipment. Although the obligations may be secured by the leased equipment or facilities, the disposition of the property in the event of non-appropriation or foreclosure might prove difficult, time consuming and costly, and may result in a delay in recovering or the failure to fully recover the Fund’s original investment. In the event of non-appropriation, the issuer would be in default and taking ownership of the assets may be a remedy available to the Fund, although the Fund does not anticipate that such a remedy would normally be pursued. Certificates of participation involve the same risks as the underlying municipal leases. In addition, the Fund may be dependent upon the municipal authority issuing the certificates of participation to exercise remedies with respect to the underlying securities. Certificates of participation also entail a risk of default or bankruptcy, both of the issuer of the municipal lease and also the municipal agency issuing the certificate of participation. Swap Transactions Risk. The Fund may enter into debt-related derivative instruments such as credit default swap contracts and interest rate swaps. Like most derivative instruments, the use of swaps is a highly specialized activity that involves investment techniques and risks different from those associated with ordinary portfolio securities transactions. In addition, the use of swaps requires an understanding by the adviser and/or the sub-adviser of not only the referenced asset, rate or index, but also of the swap itself. If the investment adviser and/or the sub-adviser is incorrect in its forecasts of default risks, market spreads or other applicable factors or events, the investment performance of the Fund would diminish compared with what it would have been if these techniques were not used. Tax Risk. The value of the Fund’s investments and its NAV may be adversely affected by changes in tax rates, rules and policies. Because interest income from municipal securities is normally not subject to regular federal income taxation, the attractiveness of municipal securities in relation to other investment alternatives is affected by changes in federal income tax rates or changes in the tax exempt status of interest income from municipal securities. Additionally, the Fund is not a suitable investment for individual retirement accounts, for other tax exempt or tax-deferred accounts, for investors who are not sensitive to the federal income tax consequences of their investments. Taxability Risk. The Fund will invest in municipal securities in reliance at the time of purchase on an opinion of bond counsel to the issuer that the interest paid on those securities will be excludable from gross income for regular federal income tax purposes, and the sub-adviser will not independently verify that opinion. Subsequent to the Fund’s acquisition of such a municipal security, however, the security may be determined to pay, or to have paid, taxable income. As a result, the treatment of dividends previously paid or to be paid by the Fund as “exempt-interest dividends” could be adversely affected, subjecting the Fund’s shareholders to increased federal income tax liabilities. Certain other investments made by the Fund, including derivatives transactions, may result in the receipt of taxable income or gains by the Fund. Tobacco Settlement Bond Risk. The Fund may invest in tobacco settlement bonds. Tobacco settlement bonds are municipal securities that are backed solely by expected revenues to be derived from lawsuits involving tobacco related deaths and illnesses which were settled between certain states and American tobacco companies. Tobacco settlement bonds are secured by an issuing state’s proportionate share in the Master Settlement Agreement, an agreement between 46 states and nearly all of the U.S. tobacco manufacturers (the “MSA”). Under the terms of the MSA, the actual amount of future settlement payments by tobacco-manufacturers is dependent on many factors, including, among other things, reduced cigarette consumption. Payments made by tobacco manufacturers could be negatively impacted if the decrease in tobacco consumption is significantly greater than the forecasted decline. Unrated Securities Risk. The Fund may purchase securities that are not rated by any rating organization. Unrated securities determined by the Fund’s investment adviser to be of comparable quality to rated investments which the Fund may purchase may pay a higher dividend or interest rate than such rated investments and be subject to a greater risk of illiquidity or price changes. Less public information is typically available about unrated investments or issuers than rated investments or issuers. Some unrated securities may not have an active trading market or may be difficult to value, which means the Fund might have difficulty selling them promptly at an acceptable price. To the extent that the Fund invests in unrated securities, the Fund’s ability to achieve its investment objectives will be more dependent on the investment adviser’s credit analysis than would be the case when the Fund invests in rated securities. Valuation Risk. The municipal securities in which the Fund invests typically are valued by a pricing service utilizing a range of market-based inputs and assumptions, including readily available market quotations obtained from broker-dealers making markets in such instruments, cash flows and transactions for comparable instruments. There is no assurance that the Fund will be able to sell a portfolio security at the price established by the pricing service, which could result in a loss to the Fund. Pricing services generally price municipal securities assuming orderly transactions of an institutional “round lot” size, but some trades may occur in smaller, “odd lot” sizes, often at lower prices than institutional round lot trades. Different pricing services may incorporate different assumptions and inputs into their valuation methodologies, potentially resulting in different values for the same securities. As a result, if the Fund were to change pricing services, or if the Fund’s pricing service were to change its valuation methodology, there could be a material impact, either positive or negative, on the Fund’s NAV. Zero Coupon Bonds Risk. Because interest on zero coupon bonds is not paid on a current basis, the values of zero coupon bonds will be more volatile in response to interest rate changes than the values of bonds that distribute income regularly. Although zero coupon bonds generate income for accounting purposes, they do not produce cash flow, and thus the Fund could be forced to liquidate securities at an inopportune time in order to generate cash to distribute to shareholders as required by tax laws. Fund Level and Other Risks: Anti-Takeover Provisions. The Fund’s organizational documents include provisions that could limit the ability of other entities or persons to acquire control of the Fund or convert the Fund to open-end status, which include those commonly known as “Control Share Acquisition” provisions. Although the application of the “Control Share Acquisition” provisions has currently been suspended, these provisions could have the effect of depriving the common shareholders of opportunities to sell their common shares at a premium over the then-current market price of the common shares. Counterparty Risk. Changes in the credit quality of the companies that serve as the Fund’s counterparties with respect to derivatives or other transactions supported by another party’s credit will affect the value of those instruments. Certain entities that have served as counterparties in the markets for these transactions have incurred or may incur in the future significant financial hardships including bankruptcy and losses as a result of exposure to sub-prime mortgages and other lower-quality credit investments. As a result, such hardships have reduced these entities’ capital and called into question their continued ability to perform their obligations under such transactions. By using such derivatives or other transactions, the Fund assumes the risk that its counterparties could experience similar financial hardships. In the event of the insolvency of a counterparty, the Fund may sustain losses or be unable to liquidate a derivatives position. Cybersecurity Risk. The Fund and its service providers are susceptible to operational and information security risk resulting from cyber incidents. Cyber incidents refer to both intentional attacks and unintentional events including: processing errors, human errors, technical errors including computer glitches and system malfunctions, inadequate or failed internal or external processes, market-wide technical-related disruptions, unauthorized access to digital systems (through “hacking” or malicious software coding), computer viruses, and cyber-attacks which shut down, disable, slow or otherwise disrupt operations, business processes or website access or functionality (including denial of service attacks). Cyber incidents could adversely impact the Fund and cause the Fund to incur financial loss and expense, as well as face exposure to regulatory penalties, reputational damage, and additional compliance costs associated with corrective measures. In addition, substantial costs may be incurred in order to prevent any cyber incidents in the future. Furthermore, the Fund cannot control the cybersecurity plans and systems put in place by its service providers or any other third parties whose operations may affect the Fund. Economic and Political Events Risk. The Fund may be more sensitive to adverse economic, business or political developments if it invests a substantial portion of its assets in the municipal securities of similar projects (such as those relating to the education, health care, housing, transportation, or utilities industries), industrial development bonds, or in particular types of municipal securities (such as general obligation bonds, private activity bonds or moral obligation bonds). Such developments may adversely affect a specific industry or local political and economic conditions, and thus may lead to declines in the creditworthiness and value of such municipal securities. Fund Tax Risk. The Fund has elected to be treated and intends to qualify each year as a Regulated Investment Company (“RIC”) under the Internal Revenue Code of 1986, as amended (the “Code”). As a RIC, the Fund is not expected to be subject to U.S. federal income tax to the extent that it distributes its investment company taxable income and net capital gains. To qualify for the special tax treatment available to a RIC, the Fund must comply with certain investment, distribution, and diversification requirements. Under certain circumstances, the Fund may be forced to sell certain assets when it is not advantageous in order to meet these requirements, which may reduce the Fund’s overall return. If the Fund fails to meet any of these requirements, subject to the opportunity to cure such failures under applicable provisions of the Code, the Fund’s income would be subject to a double level of U.S. federal income tax. The Fund’s income, including its net capital gain, would first be subject to U.S. federal income tax at regular corporate rates, even if such income were distributed to shareholders and, second, all distributions by the Fund from earnings and profits, including distributions of net capital gain (if any), would be taxable to shareholders as dividends. Global Economic Risk. National and regional economies and financial markets are becoming increasingly interconnected, which increases the possibilities that conditions in one country, region or market might adversely impact issuers in a different country, region or market. Changes in legal, political, regulatory, tax and economic conditions may cause fluctuations in markets and assets prices around the world, which could negatively impact the value of the Fund’s investments. Major economic or political disruptions, particularly in large economies like China’s, may have global negative economic and market repercussions. Additionally, instability in various countries, such as Afghanistan and Syria, war and natural and environmental disasters, and the spread of infectious illnesses or other public health emergencies, terrorist attacks in the United States and around the world, growing social and political discord in the United States, the European debt crisis, the response of the international community—through economic sanctions and otherwise—to international events, further downgrade of U.S. government securities, changes in the U.S. president or political shifts in Congress and other similar events may adversely affect the global economy and the markets and issuers in which the Fund invests. Recent examples of such events include Hamas’ attack on Israel in October 2023 and the ensuing conflict, the outbreak of a novel coronavirus known as COVID-19 that was first detected in China in December 2019 and heightened concerns regarding North Korea’s nuclear weapons and long-range ballistic missile programs. In addition, Russia’s invasion of Ukraine in February 2022 has resulted in sanctions imposed by several nations, such as the United States, United Kingdom, European Union and Canada. The current sanctions and potential further sanctions may negatively impact certain sectors of Russia’s economy, but also may negatively impact the value of the Fund’s investments that do not have direct exposure to Russia. These events could reduce consumer demand or economic output, result in market closure, travel restrictions or quarantines, and generally have a significant impact on the global economy. These events could also impair the information technology and other operational systems upon which the Fund’s service providers, including the Fund’s sub-adviser, rely, and could otherwise disrupt the ability of employees of the Fund’s service providers to perform essential tasks on behalf of the Fund. The Fund does not know and cannot predict how long the securities markets may be affected by these events, and the future impact of these and similar events on the global economy and securities markets is uncertain. The Fund may be adversely affected by abrogation of international agreements and national laws which have created the market instruments in which the Fund may invest, failure of the designated national and international authorities to enforce compliance with the same laws and agreements, failure of local, national and international organizations to carry out the duties prescribed to them under the relevant agreements, revisions of these laws and agreements which dilute their effectiveness or conflicting interpretation of provisions of the same laws and agreements. Governmental and quasi-governmental authorities and regulators throughout the world have in the past responded to major economic disruptions with a variety of significant fiscal and monetary policy changes, including but not limited to, direct capital infusions into companies, new monetary programs and dramatically lower interest rates. An unexpected or quick reversal of these policies, or the ineffectiveness of these policies, could increase volatility in securities markets, which could adversely affect the Fund’s investments. Investment and Market Risk. An investment in common shares is subject to investment risk, including the possible loss of the entire principal amount that you invest. Common shares frequently trade at a discount to their NAV. An investment in common shares represents an indirect investment in the securities owned by the Fund. Common shares at any point in time may be worth less than your original investment, even after taking into account the reinvestment of Fund dividends and distributions. Legislation and Regulatory Risk. At any time after the date of this report, legislation or additional regulations may be enacted that could negatively affect the assets of the Fund, securities held by the Fund or the issuers of such securities. Fund shareholders may incur increased costs resulting from such legislation or additional regulation. There can be no assurance that future legislation, regulation or deregulation will not have a material adverse effect on the Fund or will not impair the ability of the Fund to achieve its investment objectives. Leverage Risk. The use of leverage creates special risks for common shareholders, including potential interest rate risks and the likelihood of greater volatility of NAV and market price of, and distributions on, the common shares. The use of leverage in a declining market will likely cause a greater decline in the Fund’s NAV, which may result at a greater decline of the common share price, than if the Fund were not to have used leverage. The Fund will pay (and common shareholders will bear) any costs and expenses relating to the Fund’s use of leverage, which will result in a reduction in the Fund’s NAV. The investment adviser may, based on its assessment of market conditions, composition of the Fund’s holdings, increase or decrease the amount of leverage. Such changes may impact the Fund’s distributions and the price of the common shares in the secondary market. There is no assurance that the Fund’s use of leverage will be successful. The Fund may seek to refinance its leverage over time, in the ordinary course, as current forms of leverage mature or it is otherwise desirable to refinance; however, the form that such leverage will take cannot be predicted at this time. If the Fund is unable to replace existing leverage on comparable terms, its costs of leverage will increase. Accordingly, there is no assurance that the use of leverage may result in a higher yield or return to common shareholders. The amount of fees paid to the investment adviser and the sub-advisor for investment advisory services will be higher if the Fund uses leverage because the fees will be calculated based on the Fund’s Managed Assets - this may create an incentive for the investment adviser and the sub-advisor to leverage the Fund or increase the Fund’s leverage. Market Discount from Net Asset Value. Shares of closed-end investment companies like the Fund frequently trade at prices lower than their NAV. This characteristic is a risk separate and distinct from the risk that the Fund’s NAV could decrease as a result of investment activities. Whether investors will realize gains or losses upon the sale of the common shares will depend not upon the Fund’s NAV but entirely upon whether the market price of the common shares at the time of sale is above or below the investor’s purchase price for the common shares. Furthermore, management may have difficulty meeting the Fund’s investment objectives and managing its portfolio when the underlying securities are redeemed or sold during periods of market turmoil and as investors’ perceptions regarding closed-end funds or their underlying investments change. Because the market price of the common shares will be determined by factors such as relative supply of and demand for the common shares in the market, general market and economic circumstances, and other factors beyond the control of the Fund, the Fund cannot predict whether the common shares will trade at, below or above NAV. The common shares are designed primarily for long-term investors, and you should not view the Fund as a vehicle for short-term trading purposes. Recent Market Conditions. Periods of unusually high financial market volatility and restrictive credit conditions, at times limited to a particular sector or geographic area, have occurred in the past and may be expected to recur in the future. Some countries, including the United States, have adopted or have signaled protectionist trade measures, relaxation of the financial industry regulations that followed the financial crisis, and/ or reductions to corporate taxes. The scope of these policy changes is still developing, but the equity and debt markets may react strongly to expectations of change, which could increase volatility, particularly if a resulting policy runs counter to the market’s expectations. The outcome of such changes cannot be foreseen at the present time. In addition, geopolitical and other risks, including environmental and public health risks, may add to instability in the world economy and markets generally. As a result of increasingly interconnected global economies and financial markets, the value and liquidity of the Fund’s investments may be negatively affected by events impacting a country or region, regardless of whether the Fund invests in issuers located in or with significant exposure to such country or region. Ukraine has experienced ongoing military conflict, most recently in February 2022 when Russia invaded Ukraine; this conflict may expand and military attacks could occur elsewhere in Europe. Europe has also been struggling with mass migration from the Middle East and Africa. The ultimate effects of these events and other socio-political or geographical issues are not known but could profoundly affect global economies and markets. Additionally, in October 2023 armed conflict broke out between Israel and the militant group Hamas after Hamas infiltrated Israel’s southern border from the Gaza Strip. Israel has since declared war against Hamas and it’s possible that this conflict could escalate into a greater regional conflict. The ultimate effects of these events and other socio-political or geographical issues are not known but could profoundly affect global economies and markets. The ongoing trade war between China and the United States, including the im posi tion of tariffs by each country on the other country’s products, has created a tense political environment. These actions may trigger a significant reduction in international trade, the oversupply of certain manufactured goods, substantial price reductions of goods and possible failure of individual companies and/or large segments of China’s export industry, which could have a negative impact on the Fund’s performance. U.S. companies that source material and goods from China and those that make large amounts of sales in China would be particularly vulnerable to an escalation of trade tensions. Uncertainty regarding the outcome of the trade tensions and the potential for a trade war could cause the U.S. dollar to decline against safe haven currencies, such as the Japanese yen and the euro. Events such as these and their consequences are difficult to predict and it is unclear whether further tariffs may be imposed or other escalating actions may be taken in the future. Recently the U.S. Federal Reserve (the “Fed”) has sharply raised interest rates and has signaled an intention to continue to do so or maintain higher interest rates until current inflation levels re-align with the Fed’s long-term inflation target. Changing interest rate environments impact the various sectors of the economy in different ways. For example, in March 2023, the Federal Deposit Insurance Corporation (“ “FDIC” ”) was appointed receiver for each of Silicon Valley Bank and Signature Bank, the second-and third-largest bank failures in U.S. history, which failures may be attributable, in part, to rising interest rates. Bank failures may have a destabilizing impact on the broader banking industry or markets generally. Reverse Repurchase Agreement Risk. A reverse repurchase agreement, in economic essence, constitutes a securitized borrowing by the Fund from the security purchaser. The Fund may enter into reverse repurchase agreements for the purpose of creating a leveraged investment exposure and, as such, their usage involves essentially the same risks associated with a leveraging strategy generally since the proceeds from these agreements may be invested in additional portfolio securities. Reverse repurchase agreements tend to be short-term in tenor, and there can be no assurances that the purchaser (lender) will commit to extend or “roll” a given agreement upon its agreed-upon repurchase date or an alternative purchaser can be identified on similar terms. Reverse repurchase agreements also involve the risk that the purchaser fails to return the securities as agreed upon, files for bankruptcy or becomes insolvent. The Fund may be restricted from taking normal portfolio actions during such time, could be subject to loss to the extent that the proceeds of the agreement are less than the value of securities subject to the agreement and may experience adverse tax consequences. |  |  |  |  |  |  |  |  |
Effects of Leverage [Text Block] |  | EFFECTS OF LEVERAGE The following table is furnished in response to requirements of the SEC. It is designed to illustrate the effects of leverage through the use of senior securities, as that term is defined under Section 18 of the 1940 Act, as well as certain other forms of leverage, such as reverse repurchase agreements and investments in inverse floating rate securities, on common share total return, assuming investment portfolio total returns (consisting of income and changes in the value of investments held in a Fund’s portfolio) of -10%, -5%, 0%, 5% and 10%. The table below reflects each Fund’s (i) continued use of leverage as of October 31, 2023 as a percentage of Managed Assets (including assets attributable to such leverage), (ii) the estimated annual effective interest expense rate payable by the Funds on such instruments (based on actual leverage costs incurred during the fiscal year ended October 31, 2023) as set forth in the table, and (iii) the annual return that the Fund’s portfolio must experience (net of expenses) in order to cover such costs of leverage based on such estimated annual effective interest expense rate. The information below does not reflect any Fund’s use of certain derivative instruments. The numbers are merely estimates, used for illustration. The costs of leverage may vary frequently and may be significantly higher or lower than the estimated rate. The assumed investment portfolio returns in the table below are hypothetical figures and are not necessarily indicative of the investment portfolio returns experienced or expected to be experienced by the Funds. Your actual returns may be greater or less than those appearing below.
|  | Nuveen Quality Municipal Income Fund (NAD) |  | Nuveen AMT-Free Quality Municipal Income Fund (NEA)
Estimated Leverage as a Percentage of Managed Assets (Including Assets Attributable to Leverage) |  | 42.58% |  | 42.58%
Estimated Annual Effective Leverage Expense Rate Payable by Fund on Leverage |  | 3.92% |  | 3.58%
Annual Return Fund Portfolio Must Experience (net of expenses) to Cover Estimated Annual Effective Interest Expense Rate on Leverage |  | 1.67% |  | 1.52%
Common Share Total Return for (10.00)% Assumed Portfolio Total Return |  | (20.32)% |  | (20.07)%
Common Share Total Return for (5.00)% Assumed Portfolio Total Return |  | (11.61)% |  | (11.36)%
Common Share Total Return for 0.00% Assumed Portfolio Total Return |  | (2.91)% |  | (2.65)%
Common Share Total Return for 5.00% Assumed Portfolio Total Return |  | 5.80% |  | 6.05%
Common Share Total Return for 10.00% Assumed Portfolio Total Return |  | 14.51% |  | 14.76%
Common Share total return is composed of two elements — the distributions paid by the Fund to holders of common shares (the amount of which is largely determined by the net investment income of the Fund after paying dividend payments on any preferred shares issued by the Fund and expenses on any forms of leverage outstanding) and gains or losses on the value of the securities and other instruments the Fund owns. As required by SEC rules, the table assumes that the Funds are more likely to suffer capital losses than to enjoy capital appreciation. For example, to assume a total return of 0%, the Fund must assume that the income it receives on its investments is entirely offset by losses in the value of those investments. This table reflects hypothetical performance of the Fund’s portfolio and not the actual performance of the Fund’s common shares, the value of which is determined by market forces and other factors. Should the Fund elect to add additional leverage to its portfolio, any benefits of such additional leverage cannot be fully achieved until the proceeds resulting from the use of such leverage have been received by the Fund and invested in accordance with the Fund’s investment objectives and policies. As noted above, the Fund’s willingness to use additional leverage, and the extent to which leverage is used at any time, will depend on many factors. |  |  |  |  |  |  |  |  |
Annual Interest Rate [Percent] |  | 42.58% |  |  |  |  |  |  |  |  |
Annual Interest Rate, Current [Percent] |  | 3.58% |  |  |  |  |  |  |  |  |
Annual Coverage Return Rate [Percent] |  | 1.52% |  |  |  |  |  |  |  |  |
Effects of Leverage [Table Text Block] |  | The numbers are merely estimates, used for illustration. The costs of leverage may vary frequently and may be significantly higher or lower than the estimated rate. The assumed investment portfolio returns in the table below are hypothetical figures and are not necessarily indicative of the investment portfolio returns experienced or expected to be experienced by the Funds. Your actual returns may be greater or less than those appearing below.
|  | Nuveen Quality Municipal Income Fund (NAD) |  | Nuveen AMT-Free Quality Municipal Income Fund (NEA)
Estimated Leverage as a Percentage of Managed Assets (Including Assets Attributable to Leverage) |  | 42.58% |  | 42.58%
Estimated Annual Effective Leverage Expense Rate Payable by Fund on Leverage |  | 3.92% |  | 3.58%
Annual Return Fund Portfolio Must Experience (net of expenses) to Cover Estimated Annual Effective Interest Expense Rate on Leverage |  | 1.67% |  | 1.52%
Common Share Total Return for (10.00)% Assumed Portfolio Total Return |  | (20.32)% |  | (20.07)%
Common Share Total Return for (5.00)% Assumed Portfolio Total Return |  | (11.61)% |  | (11.36)%
Common Share Total Return for 0.00% Assumed Portfolio Total Return |  | (2.91)% |  | (2.65)%
Common Share Total Return for 5.00% Assumed Portfolio Total Return |  | 5.80% |  | 6.05%
Common Share Total Return for 10.00% Assumed Portfolio Total Return |  | 14.51% |  | 14.76%
Return at Minus Ten [Percent] |  | (20.07%) |  |  |  |  |  |  |  |  |
Return at Minus Five [Percent] |  | (11.36%) |  |  |  |  |  |  |  |  |
Return at Zero [Percent] |  | (2.65%) |  |  |  |  |  |  |  |  |
Return at Plus Five [Percent] |  | 6.05% |  |  |  |  |  |  |  |  |
Return at Plus Ten [Percent] |  | 14.76% |  |  |  |  |  |  |  |  |
Share Price [Table Text Block] |  | As of October 31, 2023, the Funds’ common share prices were trading at a premium/(discount) to their common share NAVs and trading at an average premium/(discount) to NAV during the current reporting period, as follows:
|  | NAD |  |  | NEA |
Common share NAV |  |  | $11.56 |  |  |  | $11.17 |
Common share price |  |  | $9.81 |  |  |  | $9.47 |
Premium/(Discount) to NAV |  |  | (15.14)% |  |  |  | (15.22)% |
Average premium/(discount) to NAV |  |  | (13.10)% |  |  |  | (13.31)% |
Below Investment Grade Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Below Investment Grade Risk. Investments of below investment grade quality are regarded as having speculative characteristics with respect to the issuer’s capacity to pay dividends or interest and repay principal, and may be subject to higher price volatility and default risk than investment grade investments of comparable terms and duration. Issuers of lower grade investments may be highly leveraged and may not have available to them more traditional methods of financing. The prices of these lower grade investments are typically more sensitive to negative developments, such as a decline in the issuer’s revenues or a general economic downturn. The secondary market for lower rated investments may not be as liquid as the secondary market for more highly rated investments, a factor which may have an adverse effect on the Fund’s ability to dispose of a particular investment. If a below investment grade security goes into default, or its issuer enters bankruptcy, it might be difficult to sell that security in a timely manner at a reasonable price. |  |  |  |  |  |  |  |  |
Call Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Call Risk. The Fund may invest in municipal securities that are subject to call risk. Such municipal securities may be redeemed at the option of the issuer, or “called,” before their stated maturity or redemption date. In general, an issuer will call its instruments if they can be refinanced by issuing new instruments that bear a lower interest rate. The Fund is subject to the possibility that during periods of falling interest rates, an issuer will call its high yielding municipal securities. The Fund would then be forced to invest the unanticipated proceeds at lower interest rates, resulting in a decline in the Fund’s income. |  |  |  |  |  |  |  |  |
Credits Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Credit Risk. Issuers of municipal securities in which the Fund may invest may default on their obligations to pay principal or interest when due. This non-payment would result in a reduction of income to the Fund, a reduction in the value of a municipal security experiencing non-payment and potentially a decrease in the net asset value (“NAV”) of the Fund. To the extent that the credit rating assigned to a municipal security in the Fund’s portfolio is downgraded, the market price and liquidity of such security may be adversely affected. |  |  |  |  |  |  |  |  |
Credit Spread Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Credit Spread Risk. Credit spread risk is the risk that credit spreads (i.e., the difference in yield between securities that is due to differences in their credit quality) may increase when the market believes that municipal securities generally have a greater risk of default. Increasing credit spreads may reduce the market values of the Fund’s securities. Credit spreads often increase more for lower rated and unrated securities than for investment grade securities. In addition, when credit spreads increase, reductions in market value will generally be greater for longer-maturity securities. |  |  |  |  |  |  |  |  |
Deflation Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Deflation Risk. Deflation risk is the risk that prices throughout the economy decline over time. Deflation may have an adverse effect on the creditworthiness of issuers and may make issuer default more likely, which may result in a decline in the value of the Fund’s portfolio. |  |  |  |  |  |  |  |  |
Derivatives Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Derivatives Risk. The use of derivatives involves additional risks and transaction costs which could leave the Fund in a worse position than if it had not used these instruments. Derivative instruments can be used to acquire or to transfer the risk and returns of a municipal security or other asset without buying or selling the municipal security or asset. These instruments may entail investment exposures that are greater than their cost would suggest. As a result, a small investment in derivatives can result in losses that greatly exceed the original investment. Derivatives can be highly volatile, illiquid and difficult to value. An over-the-counter derivative transaction between the Fund and a counterparty that is not cleared through a central counterparty also involves the risk that a loss may be sustained as a result of the failure of the counterparty to the contract to make required payments. The payment obligation for a cleared derivative transaction is guaranteed by a central counterparty, which exposes the Fund to the creditworthiness of the central counterparty. The use of certain derivatives involves leverage, which can cause the Fund’s portfolio to be more volatile than if the portfolio had not been leveraged. Leverage can significantly magnify the effect of price movements of the reference asset, disproportionately increasing the Fund’s losses and reducing the Fund’s opportunities for gains when the reference asset changes in unexpected ways. In some instances, such leverage could result in losses that exceed the original amount invested. It is possible that regulatory or other developments in the derivatives market, including changes in government regulation, could adversely impact the Fund’s ability successfully use derivative instruments. |  |  |  |  |  |  |  |  |
Distressed or Defaulted Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Distressed or Defaulted Securities Risk. Investments in “distressed” securities, meaning those whose issuers are experiencing financial difficulties or distress at the time of acquisition, present a substantial risk of future default. In the event distressed securities become defaulted securities or the Fund otherwise holds defaulted securities, the Fund may incur losses, including additional expenses, to the extent it is required to seek recovery upon a default in the payment of principal or interest on those securities. In any reorganization or liquidation proceeding relating to a portfolio security, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Defaulted or distressed securities may be subject to restrictions on resale. |  |  |  |  |  |  |  |  |
Duration Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Duration Risk. Duration is the sensitivity, expressed in years, of the price of a fixed-income security to changes in the general level of interest rates (or yields). Securities with longer durations tend to be more sensitive to interest rate (or yield) changes, which typically corresponds to increased volatility and risk, than securities with shorter durations. For example, if a security or portfolio has a duration of three years and interest rates increase by 1%, then the security or portfolio would decline in value by approximately 3%. Duration differs from maturity in that it considers potential changes to interest rates, and a security’s coupon payments, yield, price and par value and call features, in addition to the amount of time until the security matures. The duration of a security will be expected to change over time with changes in market factors and time to maturity. |  |  |  |  |  |  |  |  |
Economic Sector Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Economic Sector Risk. The Fund may invest a significant amount of its total assets in municipal securities in the same economic sector. This may make the Fund more susceptible to adverse economic, political or regulatory occurrences affecting an economic sector making the Fund more vulnerable to unfavorable developments in that sector than funds that invest more broadly. As the percentage of the Fund’s Managed Assets invested in a particular sector increases, so does the potential for fluctuation in the value of the Fund’s assets. In addition, the Fund may invest a significant portion of its assets in certain sectors of the municipal securities market, such as health care facilities, private educational facilities, special taxing districts and start-up utility districts, and private activity bonds including industrial development bonds on behalf of transportation companies, whose credit quality and performance may be more susceptible to economic, business, political, regulatory and other developments than other sectors of municipal issuers. If the Fund invests a significant portion of its assets in one or more particular sectors, the Fund’s performance may be subject to additional risk and variability. |  |  |  |  |  |  |  |  |
Financial Futures and Options Transactions Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Financial Futures and Options Transactions Risk. The Fund may use certain transactions for hedging the portfolio’s exposure to credit risk and the risk of increases in interest rates, which could result in poorer overall performance for the Fund. There may be an imperfect correlation between price movements of the futures and options and price movements of the portfolio securities being hedged. If the Fund engages in futures transactions or in the writing of options on futures, it will be required to maintain initial margin and maintenance margin and may be required to make daily variation margin payments in accordance with applicable rules of the exchanges and the Commodity Futures Trading Commission (“CFTC”). If the Fund purchases a financial futures contract or a call option or writes a put option in order to hedge the anticipated purchase of municipal securities, and if the Fund fails to complete the anticipated purchase transaction, the Fund may have a loss or a gain on the futures or options transaction that will not be offset by price movements in the municipal securities that were the subject of the anticipatory hedge. There can be no assurance that a liquid market will exist at a time when the Fund seeks to close out a derivatives or futures or a futures option position, and the Fund would remain obligated to meet margin requirements until the position is closed. |  |  |  |  |  |  |  |  |
Hedging Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Hedging Risk. The Fund’s use of derivatives or other transactions to reduce risk involves costs and will be subject to the investment adviser’s and/or the sub-adviser’s ability to predict correctly changes in the relationships of such hedge instruments to the Fund’s portfolio holdings or other factors. No assurance can be given that the investment adviser’s and/or the sub-adviser’s judgment in this respect will be correct, and no assurance can be given that the Fund will enter into hedging or other transactions at times or under circumstances in which it may be advisable to do so. Hedging activities may reduce the Fund’s opportunities for gain by offsetting the positive effects of favorable price movements and may result in net losses. |  |  |  |  |  |  |  |  |
Illiquid Investments Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Illiquid Investments Risk. Illiquid investments are investments that are not readily marketable. These investments may include restricted investments, including Rule 144A securities, which cannot be resold to the public without an effective registration statement under the 1933 Act, or, if they are unregistered may be sold only in a privately negotiated transaction or pursuant to an available exemption from registration. The Fund may not be able to readily dispose of such investments at prices that approximate those at which the Fund could sell such investments if they were more widely traded and, as a result of such illiquidity, the Fund may have to sell other investments or engage in borrowing transactions if necessary to raise cash to meet its obligations. Limited liquidity can also affect the market price of investments, thereby adversely affecting the Fund’s NAV and ability to make dividend distributions. The financial markets in general have in recent years experienced periods of extreme secondary market supply and demand imbalance, resulting in a loss of liquidity during which market prices were suddenly and substantially below traditional measures of intrinsic value. During such periods, some investments could be sold only at arbitrary prices and with substantial losses. Periods of such market dislocation may occur again at any time. |  |  |  |  |  |  |  |  |
Income Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Income Risk. The Fund’s income could decline due to falling market interest rates. This is because, in a falling interest rate environment, the Fund generally will have to invest the proceeds from maturing portfolio securities in lower-yielding securities. |  |  |  |  |  |  |  |  |
Inflation Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Inflation Risk. Inflation risk is the risk that the value of assets or income from investments will be worth less in the future as inflation decreases the value of money. As inflation increases, the real value of the common shares and distributions can decline. Currently, inflation rates are elevated relative to normal market conditions and could increase. |  |  |  |  |  |  |  |  |
Insurance Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Insurance Risk. The Fund may purchase municipal securities that are secured by insurance, bank credit agreements or escrow accounts. The credit quality of the companies that provide such credit enhancements will affect the value of those securities. Certain significant providers of insurance for municipal securities have incurred significant losses as a result of exposure to sub-prime mortgages and other lower credit quality investments. As a result, such losses reduced the insurers’ capital and called into question their continued ability to perform their obligations under such insurance if they are called upon to do so in the future. While an insured municipal security will typically be deemed to have the rating of its insurer, if the insurer of a municipal security suffers a downgrade in its credit rating or the market discounts the value of the insurance provided by the insurer, the value of the municipal security would more closely, if not entirely, reflect such rating. In such a case, the value of insurance associated with a municipal security may not add any value. The insurance feature of a municipal security does not guarantee the full payment of principal and interest through the life of an insured obligation, the market value of the insured obligation or the NAV of the common shares represented by such insured obligation. |  |  |  |  |  |  |  |  |
Inverse Floating Rate Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Inverse Floating Rate Securities Risk. The Fund may invest in inverse floating rate securities. In general, income on inverse floating rate securities will decrease when short-term interest rates increase and increase when short-term interest rates decrease. Investments in inverse floating rate securities may subject the Fund to the risks of reduced or eliminated interest payments and losses of principal. In addition, inverse floating rate securities may increase or decrease in value at a greater rate than the underlying interest rate, which effectively leverages the Fund’s investment. As a result, the market value of such securities generally will be more volatile than that of fixed rate securities. The Fund may invest in inverse floating rate securities issued by special purpose tr us ts that have recourse to the Fund. In such instances, the Fund may be at risk of loss that exceeds its investment in the inverse floating rate securities. The Fund may be required to sell its inverse floating rate securities at less than favorable prices, or liquidate other Fund portfolio holdings in certain circumstances, including, but not limited to, the following:
| ● |  | If the Fund has a need for cash and the securities in a special purpose trust are not actively trading due to adverse market conditions;
| ● |  | If special purpose trust sponsors (as a collective group or individually) experience financial hardship and consequently seek to terminate their respective outstanding special purpose trusts; and
| ● |  | If the value of an underlying security declines significantly and if additional collateral has not been posted by the Fund.
Municipal Securities Market Liquidity Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Municipal Securities Market Liquidity Risk. Inventories of municipal securities held by brokers and dealers have decreased in recent years, lessening their ability to make a market in these securities. This reduction in market making capacity has the potential to decrease the Fund’s ability to buy or sell municipal securities at attractive prices, and increase municipal security price volatility and trading costs, particularly during periods of economic or market stress. In addition, recent federal banking regulations may cause certain dealers to reduce their inventories of municipal securities, which may further decrease the Fund’s ability to buy or sell municipal securities. As a result, the Fund may be forced to accept a lower price to sell a security, to sell other securities to raise cash, or to give up an investment opportunity, any of which could have a negative effect on performance. If the Fund needed to sell large blocks of municipal securities to raise cash to meet its obligations, those sales could further reduce the municipal securities’ prices and hurt performance. |  |  |  |  |  |  |  |  |
Municipal Securities Market Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Municipal Securities Market Risk. The amount of public information available about the municipal securities in the Fund’s portfolio is generally less than that for corporate equities or bonds, and the investment performance of the Fund may therefore be more dependent on the analytical abilities of the sub-adviser than if the Fund were a stock fund or taxable bond fund. The secondary market for municipal securities, particularly below investment grade municipal securities, also tends to be less well-developed or liquid than many other securities markets, which may adversely affect the Fund’s ability to sell its municipal securities at attractive prices. |  |  |  |  |  |  |  |  |
Other Investment Companies Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Other Investment Companies Risk. The Fund may invest in the securities of other investment companies, including ETFs. Investing in an investment company exposes the Fund to all of the risks of that investment company’s investments. The Fund, as a holder of the securities of other investment companies, will bear its pro rata portion of the other investment companies’ expenses, including advisory fees. These expenses are in addition to the direct expenses of the Fund’s own operations. As a result, the cost of investing in investment company shares may exceed the costs of investing directly in its underlying investments. In addition, securities of other investment companies may be leveraged. As a result, the Fund may be indirectly exposed to leverage through an investment in such securities and therefore magnify the Fund’s leverage risk. With respect to ETF’s, an ETF that is based on a specific index may not be able to replicate and maintain exactly the composition and relative weighting of securities in the index. The value of an ETF based on a specific index is subject to change as the values of its respective component assets fluctuate according to market volatility. ETFs typically rely on a limited pool of authorized participants to create and redeem shares, and an active trading market for ETF shares may not develop or be maintained. The market value of shares of ETFs and closed-end funds may differ from their NAV. |  |  |  |  |  |  |  |  |
Puerto Rico Municipal Securities Market Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Puerto Rico Municipal Securities Market Risk. To the extent that the Fund invests a significant portion of its assets in the securities issued by the Commonwealth of Puerto Rico or its political subdivisions, agencies, instrumentalities, or public corporations (collectively referred to as “Puerto Rico” or the “Commonwealth”), it will be disproportionally affected by political, social and economic conditions and developments in the Commonwealth. In addition, economic, political or regulatory changes in that territory could adversely affect the value of the Fund’s investment portfolio. Puerto Rico currently is experiencing significant fiscal and economic challenges, including substantial debt service obligations, high levels of unemployment, underfunded public retirement systems, and persistent government budget deficits. These challenges may negatively affect the value of the Fund’s investments in Puerto Rican municipal securities. Several major ratings agencies have downgraded the general obligation debt of Puerto Rico to below investment grade and continue to maintain a negative outlook for this debt, which increases the likelihood that the rating will be lowered further. Puerto Rico recently defaulted on its debt by failing to make full payment due on its outstanding bonds, and there can be no assurance that Puerto Rico will be able to satisfy its future debt obligations. Further downgrades or defaults may place additional strain on the Puerto Rico economy and may negatively affect the value, liquidity, and volatility of the Fund’s investments in Puerto Rican municipal securities. Additionally, numerous issuers have entered Title III of the Puerto Rico Oversite, Management and Economic Stability Act (“PROMESA”), which is similar to bankruptcy protection, through which the Commonwealth of Puerto Rico can restructure its debt. However, Puerto Rico’s case is the first ever heard under PROMESA and there is no existing case precedent to guide the proceedings. Accordingly, Puerto Rico’s debt restructuring process could take significantly longer than traditional municipal bankruptcy proceedings. Further, it is not clear whether a debt restructuring process will ultimately be approved or, if so, the extent to which it will apply to Puerto Rico municipal securities sold by an issuer other than the territory. A debt restructuring could reduce the principal amount due, the interest rate, the maturity, and other terms of Puerto Rico municipal securities, which could adversely affect the value of Puerto Rican municipal securities. Legislation that would allow Puerto Rico to restructure its municipal debt obligations, thus increasing the risk that Puerto Rico may never pay off municipal indebtedness, or may pay only a small fraction of the amount owed, could also impact the value of the Fund’s investments in Puerto Rican municipal securities. These challenges and uncertainties have been exacerbated by multiple hurricanes and the resulting natural disasters that have stuck Puerto Rico since 2017. The full extent of the natural disasters’ impact on Puerto Rico’s economy and foreign investment in Puerto Rico is difficult to estimate. |  |  |  |  |  |  |  |  |
Reinvestment Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Reinvestment Risk. Reinvestment risk is the risk that income from the Fund’s portfolio will decline if and when the Fund invests the proceeds from matured, traded or called municipal securities at market interest rates that are below the portfolio’s current earnings rate. A decline in income could affect the common shares’ market price, NAV and/or a common shareholder’s overall returns. |  |  |  |  |  |  |  |  |
Special Risks Related to Certain Municipal Obligations [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Special Risks Related to Certain Municipal Obligations. Municipal leases and certificates of participation involve special risks not normally associated with general obligations or revenue bonds. Leases and installment purchase or conditional sale contracts (which normally provide for title to the leased asset to pass eventually to the governmental issuer) have evolved as a means for governmental issuers to acquire property and equipment without meeting the constitutional and statutory requirements for the issuance of debt. The debt issuance limitations are deemed to be inapplicable because of the inclusion in many leases or contracts of “non-appropriation” clauses that relieve the governmental issuer of any obligation to make future payments under the lease or contract unless money is appropriated for such purpose by the appropriate legislative body. In addition, such leases or contracts may be subject to the temporary abatement of payments in the event that the governmental issuer is prevented from maintaining occupancy of the leased premises or utilizing the leased equipment. Although the obligations may be secured by the leased equipment or facilities, the disposition of the property in the event of non-appropriation or foreclosure might prove difficult, time consuming and costly, and may result in a delay in recovering or the failure to fully recover the Fund’s original investment. In the event of non-appropriation, the issuer would be in default and taking ownership of the assets may be a remedy available to the Fund, although the Fund does not anticipate that such a remedy would normally be pursued. Certificates of participation involve the same risks as the underlying municipal leases. In addition, the Fund may be dependent upon the municipal authority issuing the certificates of participation to exercise remedies with respect to the underlying securities. Certificates of participation also entail a risk of default or bankruptcy, both of the issuer of the municipal lease and also the municipal agency issuing the certificate of participation. |  |  |  |  |  |  |  |  |
Swap Transactions Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Swap Transactions Risk. The Fund may enter into debt-related derivative instruments such as credit default swap contracts and interest rate swaps. Like most derivative instruments, the use of swaps is a highly specialized activity that involves investment techniques and risks different from those associated with ordinary portfolio securities transactions. In addition, the use of swaps requires an understanding by the adviser and/or the sub-adviser of not only the referenced asset, rate or index, but also of the swap itself. If the investment adviser and/or the sub-adviser is incorrect in its forecasts of default risks, market spreads or other applicable factors or events, the investment performance of the Fund would diminish compared with what it would have been if these techniques were not used. |  |  |  |  |  |  |  |  |
Tax Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Tax Risk. The value of the Fund’s investments and its NAV may be adversely affected by changes in tax rates, rules and policies. Because interest income from municipal securities is normally not subject to regular federal income taxation, the attractiveness of municipal securities in relation to other investment alternatives is affected by changes in federal income tax rates or changes in the tax exempt status of interest income from municipal securities. Additionally, the Fund is not a suitable investment for individual retirement accounts, for other tax exempt or tax-deferred accounts, for investors who are not sensitive to the federal income tax consequences of their investments. |  |  |  |  |  |  |  |  |
Taxability Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Taxability Risk. The Fund will invest in municipal securities in reliance at the time of purchase on an opinion of bond counsel to the issuer that the interest paid on those securities will be excludable from gross income for regular federal income tax purposes, and the sub-adviser will not independently verify that opinion. Subsequent to the Fund’s acquisition of such a municipal security, however, the security may be determined to pay, or to have paid, taxable income. As a result, the treatment of dividends previously paid or to be paid by the Fund as “exempt-interest dividends” could be adversely affected, subjecting the Fund’s shareholders to increased federal income tax liabilities. Certain other investments made by the Fund, including derivatives transactions, may result in the receipt of taxable income or gains by the Fund. |  |  |  |  |  |  |  |  |
Tobacco Settlement Bond Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Tobacco Settlement Bond Risk. The Fund may invest in tobacco settlement bonds. Tobacco settlement bonds are municipal securities that are backed solely by expected revenues to be derived from lawsuits involving tobacco related deaths and illnesses which were settled between certain states and American tobacco companies. Tobacco settlement bonds are secured by an issuing state’s proportionate share in the Master Settlement Agreement, an agreement between 46 states and nearly all of the U.S. tobacco manufacturers (the “MSA”). Under the terms of the MSA, the actual amount of future settlement payments by tobacco-manufacturers is dependent on many factors, including, among other things, reduced cigarette consumption. Payments made by tobacco manufacturers could be negatively impacted if the decrease in tobacco consumption is significantly greater than the forecasted decline. |  |  |  |  |  |  |  |  |
Unrated Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Unrated Securities Risk. The Fund may purchase securities that are not rated by any rating organization. Unrated securities determined by the Fund’s investment adviser to be of comparable quality to rated investments which the Fund may purchase may pay a higher dividend or interest rate than such rated investments and be subject to a greater risk of illiquidity or price changes. Less public information is typically available about unrated investments or issuers than rated investments or issuers. Some unrated securities may not have an active trading market or may be difficult to value, which means the Fund might have difficulty selling them promptly at an acceptable price. To the extent that the Fund invests in unrated securities, the Fund’s ability to achieve its investment objectives will be more dependent on the investment adviser’s credit analysis than would be the case when the Fund invests in rated securities. |  |  |  |  |  |  |  |  |
Valuation Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Valuation Risk. The municipal securities in which the Fund invests typically are valued by a pricing service utilizing a range of market-based inputs and assumptions, including readily available market quotations obtained from broker-dealers making markets in such instruments, cash flows and transactions for comparable instruments. There is no assurance that the Fund will be able to sell a portfolio security at the price established by the pricing service, which could result in a loss to the Fund. Pricing services generally price municipal securities assuming orderly transactions of an institutional “round lot” size, but some trades may occur in smaller, “odd lot” sizes, often at lower prices than institutional round lot trades. Different pricing services may incorporate different assumptions and inputs into their valuation methodologies, potentially resulting in different values for the same securities. As a result, if the Fund were to change pricing services, or if the Fund’s pricing service were to change its valuation methodology, there could be a material impact, either positive or negative, on the Fund’s NAV. |  |  |  |  |  |  |  |  |
Zero Coupon Bonds Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Zero Coupon Bonds Risk. Because interest on zero coupon bonds is not paid on a current basis, the values of zero coupon bonds will be more volatile in response to interest rate changes than the values of bonds that distribute income regularly. Although zero coupon bonds generate income for accounting purposes, they do not produce cash flow, and thus the Fund could be forced to liquidate securities at an inopportune time in order to generate cash to distribute to shareholders as required by tax laws. |  |  |  |  |  |  |  |  |
AntiTakeover Provisions [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Anti-Takeover Provisions. The Fund’s organizational documents include provisions that could limit the ability of other entities or persons to acquire control of the Fund or convert the Fund to open-end status, which include those commonly known as “Control Share Acquisition” provisions. Although the application of the “Control Share Acquisition” provisions has currently been suspended, these provisions could have the effect of depriving the common shareholders of opportunities to sell their common shares at a premium over the then-current market price of the common shares. |  |  |  |  |  |  |  |  |
Counterparty Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Counterparty Risk. Changes in the credit quality of the companies that serve as the Fund’s counterparties with respect to derivatives or other transactions supported by another party’s credit will affect the value of those instruments. Certain entities that have served as counterparties in the markets for these transactions have incurred or may incur in the future significant financial hardships including bankruptcy and losses as a result of exposure to sub-prime mortgages and other lower-quality credit investments. As a result, such hardships have reduced these entities’ capital and called into question their continued ability to perform their obligations under such transactions. By using such derivatives or other transactions, the Fund assumes the risk that its counterparties could experience similar financial hardships. In the event of the insolvency of a counterparty, the Fund may sustain losses or be unable to liquidate a derivatives position. |  |  |  |  |  |  |  |  |
Cybersecurity Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Cybersecurity Risk. The Fund and its service providers are susceptible to operational and information security risk resulting from cyber incidents. Cyber incidents refer to both intentional attacks and unintentional events including: processing errors, human errors, technical errors including computer glitches and system malfunctions, inadequate or failed internal or external processes, market-wide technical-related disruptions, unauthorized access to digital systems (through “hacking” or malicious software coding), computer viruses, and cyber-attacks which shut down, disable, slow or otherwise disrupt operations, business processes or website access or functionality (including denial of service attacks). Cyber incidents could adversely impact the Fund and cause the Fund to incur financial loss and expense, as well as face exposure to regulatory penalties, reputational damage, and additional compliance costs associated with corrective measures. In addition, substantial costs may be incurred in order to prevent any cyber incidents in the future. Furthermore, the Fund cannot control the cybersecurity plans and systems put in place by its service providers or any other third parties whose operations may affect the Fund. |  |  |  |  |  |  |  |  |
Economic and Political Events Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Economic and Political Events Risk. The Fund may be more sensitive to adverse economic, business or political developments if it invests a substantial portion of its assets in the municipal securities of similar projects (such as those relating to the education, health care, housing, transportation, or utilities industries), industrial development bonds, or in particular types of municipal securities (such as general obligation bonds, private activity bonds or moral obligation bonds). Such developments may adversely affect a specific industry or local political and economic conditions, and thus may lead to declines in the creditworthiness and value of such municipal securities. |  |  |  |  |  |  |  |  |
Fund Tax Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Fund Tax Risk. The Fund has elected to be treated and intends to qualify each year as a Regulated Investment Company (“RIC”) under the Internal Revenue Code of 1986, as amended (the “Code”). As a RIC, the Fund is not expected to be subject to U.S. federal income tax to the extent that it distributes its investment company taxable income and net capital gains. To qualify for the special tax treatment available to a RIC, the Fund must comply with certain investment, distribution, and diversification requirements. Under certain circumstances, the Fund may be forced to sell certain assets when it is not advantageous in order to meet these requirements, which may reduce the Fund’s overall return. If the Fund fails to meet any of these requirements, subject to the opportunity to cure such failures under applicable provisions of the Code, the Fund’s income would be subject to a double level of U.S. federal income tax. The Fund’s income, including its net capital gain, would first be subject to U.S. federal income tax at regular corporate rates, even if such income were distributed to shareholders and, second, all distributions by the Fund from earnings and profits, including distributions of net capital gain (if any), would be taxable to shareholders as dividends. |  |  |  |  |  |  |  |  |
Global Economic Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Global Economic Risk. National and regional economies and financial markets are becoming increasingly interconnected, which increases the possibilities that conditions in one country, region or market might adversely impact issuers in a different country, region or market. Changes in legal, political, regulatory, tax and economic conditions may cause fluctuations in markets and assets prices around the world, which could negatively impact the value of the Fund’s investments. Major economic or political disruptions, particularly in large economies like China’s, may have global negative economic and market repercussions. Additionally, instability in various countries, such as Afghanistan and Syria, war and natural and environmental disasters, and the spread of infectious illnesses or other public health emergencies, terrorist attacks in the United States and around the world, growing social and political discord in the United States, the European debt crisis, the response of the international community—through economic sanctions and otherwise—to international events, further downgrade of U.S. government securities, changes in the U.S. president or political shifts in Congress and other similar events may adversely affect the global economy and the markets and issuers in which the Fund invests. Recent examples of such events include Hamas’ attack on Israel in October 2023 and the ensuing conflict, the outbreak of a novel coronavirus known as COVID-19 that was first detected in China in December 2019 and heightened concerns regarding North Korea’s nuclear weapons and long-range ballistic missile programs. In addition, Russia’s invasion of Ukraine in February 2022 has resulted in sanctions imposed by several nations, such as the United States, United Kingdom, European Union and Canada. The current sanctions and potential further sanctions may negatively impact certain sectors of Russia’s economy, but also may negatively impact the value of the Fund’s investments that do not have direct exposure to Russia. These events could reduce consumer demand or economic output, result in market closure, travel restrictions or quarantines, and generally have a significant impact on the global economy. These events could also impair the information technology and other operational systems upon which the Fund’s service providers, including the Fund’s sub-adviser, rely, and could otherwise disrupt the ability of employees of the Fund’s service providers to perform essential tasks on behalf of the Fund. The Fund does not know and cannot predict how long the securities markets may be affected by these events, and the future impact of these and similar events on the global economy and securities markets is uncertain. The Fund may be adversely affected by abrogation of international agreements and national laws which have created the market instruments in which the Fund may invest, failure of the designated national and international authorities to enforce compliance with the same laws and agreements, failure of local, national and international organizations to carry out the duties prescribed to them under the relevant agreements, revisions of these laws and agreements which dilute their effectiveness or conflicting interpretation of provisions of the same laws and agreements. Governmental and quasi-governmental authorities and regulators throughout the world have in the past responded to major economic disruptions with a variety of significant fiscal and monetary policy changes, including but not limited to, direct capital infusions into companies, new monetary programs and dramatically lower interest rates. An unexpected or quick reversal of these policies, or the ineffectiveness of these policies, could increase volatility in securities markets, which could adversely affect the Fund’s investments. |  |  |  |  |  |  |  |  |
Investment and Market Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Investment and Market Risk. An investment in common shares is subject to investment risk, including the possible loss of the entire principal amount that you invest. Common shares frequently trade at a discount to their NAV. An investment in common shares represents an indirect investment in the securities owned by the Fund. Common shares at any point in time may be worth less than your original investment, even after taking into account the reinvestment of Fund dividends and distributions. |  |  |  |  |  |  |  |  |
Legislation and Regulatory Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Legislation and Regulatory Risk. At any time after the date of this report, legislation or additional regulations may be enacted that could negatively affect the assets of the Fund, securities held by the Fund or the issuers of such securities. Fund shareholders may incur increased costs resulting from such legislation or additional regulation. There can be no assurance that future legislation, regulation or deregulation will not have a material adverse effect on the Fund or will not impair the ability of the Fund to achieve its investment objectives. |  |  |  |  |  |  |  |  |
Leverage Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Leverage Risk. The use of leverage creates special risks for common shareholders, including potential interest rate risks and the likelihood of greater volatility of NAV and market price of, and distributions on, the common shares. The use of leverage in a declining market will likely cause a greater decline in the Fund’s NAV, which may result at a greater decline of the common share price, than if the Fund were not to have used leverage. The Fund will pay (and common shareholders will bear) any costs and expenses relating to the Fund’s use of leverage, which will result in a reduction in the Fund’s NAV. The investment adviser may, based on its assessment of market conditions, composition of the Fund’s holdings, increase or decrease the amount of leverage. Such changes may impact the Fund’s distributions and the price of the common shares in the secondary market. There is no assurance that the Fund’s use of leverage will be successful. The Fund may seek to refinance its leverage over time, in the ordinary course, as current forms of leverage mature or it is otherwise desirable to refinance; however, the form that such leverage will take cannot be predicted at this time. If the Fund is unable to replace existing leverage on comparable terms, its costs of leverage will increase. Accordingly, there is no assurance that the use of leverage may result in a higher yield or return to common shareholders. The amount of fees paid to the investment adviser and the sub-advisor for investment advisory services will be higher if the Fund uses leverage because the fees will be calculated based on the Fund’s Managed Assets - this may create an incentive for the investment adviser and the sub-advisor to leverage the Fund or increase the Fund’s leverage. |  |  |  |  |  |  |  |  |
Market Discount from Net Asset Value [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Market Discount from Net Asset Value. Shares of closed-end investment companies like the Fund frequently trade at prices lower than their NAV. This characteristic is a risk separate and distinct from the risk that the Fund’s NAV could decrease as a result of investment activities. Whether investors will realize gains or losses upon the sale of the common shares will depend not upon the Fund’s NAV but entirely upon whether the market price of the common shares at the time of sale is above or below the investor’s purchase price for the common shares. Furthermore, management may have difficulty meeting the Fund’s investment objectives and managing its portfolio when the underlying securities are redeemed or sold during periods of market turmoil and as investors’ perceptions regarding closed-end funds or their underlying investments change. Because the market price of the common shares will be determined by factors such as relative supply of and demand for the common shares in the market, general market and economic circumstances, and other factors beyond the control of the Fund, the Fund cannot predict whether the common shares will trade at, below or above NAV. The common shares are designed primarily for long-term investors, and you should not view the Fund as a vehicle for short-term trading purposes. |  |  |  |  |  |  |  |  |
Recent Market Conditions [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Recent Market Conditions. Periods of unusually high financial market volatility and restrictive credit conditions, at times limited to a particular sector or geographic area, have occurred in the past and may be expected to recur in the future. Some countries, including the United States, have adopted or have signaled protectionist trade measures, relaxation of the financial industry regulations that followed the financial crisis, and/ or reductions to corporate taxes. The scope of these policy changes is still developing, but the equity and debt markets may react strongly to expectations of change, which could increase volatility, particularly if a resulting policy runs counter to the market’s expectations. The outcome of such changes cannot be foreseen at the present time. In addition, geopolitical and other risks, including environmental and public health risks, may add to instability in the world economy and markets generally. As a result of increasingly interconnected global economies and financial markets, the value and liquidity of the Fund’s investments may be negatively affected by events impacting a country or region, regardless of whether the Fund invests in issuers located in or with significant exposure to such country or region. Ukraine has experienced ongoing military conflict, most recently in February 2022 when Russia invaded Ukraine; this conflict may expand and military attacks could occur elsewhere in Europe. Europe has also been struggling with mass migration from the Middle East and Africa. The ultimate effects of these events and other socio-political or geographical issues are not known but could profoundly affect global economies and markets. Additionally, in October 2023 armed conflict broke out between Israel and the militant group Hamas after Hamas infiltrated Israel’s southern border from the Gaza Strip. Israel has since declared war against Hamas and it’s possible that this conflict could escalate into a greater regional conflict. The ultimate effects of these events and other socio-political or geographical issues are not known but could profoundly affect global economies and markets. The ongoing trade war between China and the United States, including the im posi tion of tariffs by each country on the other country’s products, has created a tense political environment. These actions may trigger a significant reduction in international trade, the oversupply of certain manufactured goods, substantial price reductions of goods and possible failure of individual companies and/or large segments of China’s export industry, which could have a negative impact on the Fund’s performance. U.S. companies that source material and goods from China and those that make large amounts of sales in China would be particularly vulnerable to an escalation of trade tensions. Uncertainty regarding the outcome of the trade tensions and the potential for a trade war could cause the U.S. dollar to decline against safe haven currencies, such as the Japanese yen and the euro. Events such as these and their consequences are difficult to predict and it is unclear whether further tariffs may be imposed or other escalating actions may be taken in the future. Recently the U.S. Federal Reserve (the “Fed”) has sharply raised interest rates and has signaled an intention to continue to do so or maintain higher interest rates until current inflation levels re-align with the Fed’s long-term inflation target. Changing interest rate environments impact the various sectors of the economy in different ways. For example, in March 2023, the Federal Deposit Insurance Corporation (“ “FDIC” ”) was appointed receiver for each of Silicon Valley Bank and Signature Bank, the second-and third-largest bank failures in U.S. history, which failures may be attributable, in part, to rising interest rates. Bank failures may have a destabilizing impact on the broader banking industry or markets generally. |  |  |  |  |  |  |  |  |
Reverse Repurchase Agreement Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Reverse Repurchase Agreement Risk. A reverse repurchase agreement, in economic essence, constitutes a securitized borrowing by the Fund from the security purchaser. The Fund may enter into reverse repurchase agreements for the purpose of creating a leveraged investment exposure and, as such, their usage involves essentially the same risks associated with a leveraging strategy generally since the proceeds from these agreements may be invested in additional portfolio securities. Reverse repurchase agreements tend to be short-term in tenor, and there can be no assurances that the purchaser (lender) will commit to extend or “roll” a given agreement upon its agreed-upon repurchase date or an alternative purchaser can be identified on similar terms. Reverse repurchase agreements also involve the risk that the purchaser fails to return the securities as agreed upon, files for bankruptcy or becomes insolvent. The Fund may be restricted from taking normal portfolio actions during such time, could be subject to loss to the extent that the proceeds of the agreement are less than the value of securities subject to the agreement and may experience adverse tax consequences. |  |  |  |  |  |  |  |  |
Interest Rate Risk [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Interest Rate Risk. Interest rate risk is the risk that municipal securities in the Fund’s portfolio will decline in value because of changes in market interest rates. Generally, when market interest rates rise, the market value of such securities will fall, and vice versa. As interest rates decline, issuers of municipal securities may prepay principal earlier than scheduled, forcing the Fund to reinvest in lower-yielding securities and potentially reducing the Fund’s income. As interest rates increase, slower than expected principal payments may extend the average life of municipal securities, potentially locking in a below-market interest rate and reducing the Fund’s value. In typical market interest rate environments, the prices of longer-term municipal securities generally fluctuate more than prices of shorter-term municipal securities as interest rates change. |  |  |  |  |  |  |  |  |
Common shares [Member] |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |
Share Price |  | $ 9.47 |  |  |  |  |  |  |  |  |
NAV Per Share |  | $ 11.17 |  |  |  |  |  |  |  |  |
Latest Premium (Discount) to NAV [Percent] |  | (15.22%) |  |  |  |  |  |  |  |  |
Capital Stock, Long-Term Debt, and Other Securities [Abstract] |  |  |  |  |  |  |  |  |  |  |
Outstanding Security, Held [Shares] |  | 298,992,392 |  |  |  |  |  |  |  |  |
Adjustable Rate MuniFund Term Preferred (AMTP) Shares [Member] |  |  |  |  |  |  |  |  |  |  |
Financial Highlights [Abstract] |  |  |  |  |  |  |  |  |  |  |
Senior Securities Amount |  | $ 173,000 | $ 0 | $ 173,000 | $ 316,500 | $ 143,500 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0
Senior Securities Coverage per Unit | [1] | $ 240,834 | $ 0 | $ 240,229 | $ 283,145 | $ 280,550 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0
MuniFund Preferred (MFP) Shares [Member] |  |  |  |  |  |  |  |  |  |  |
Financial Highlights [Abstract] |  |  |  |  |  |  |  |  |  |  |
Senior Securities Amount | [2] | $ 1,038,900,000 | $ 0 | $ 1,088,900,000 | $ 1,088,900,000 | $ 958,000,000 | $ 958,000,000 | $ 958,000,000 | $ 0 | $ 0 | $ 0
Senior Securities Coverage per Unit | [1],[3] | $ 240,834 | $ 0 | $ 240,229 | $ 283,145 | $ 280,550 | $ 282,066 | $ 265,448 | $ 0 | $ 0 | $ 0
MuniFund Term Preferred (MTP)Shares [Member] |  |  |  |  |  |  |  |  |  |  |
Financial Highlights [Abstract] |  |  |  |  |  |  |  |  |  |  |
Senior Securities Amount | [2] | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0
Senior Securities Coverage per Unit | [4] | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0
Variable Rate MuniFund Term Preferred (VMTP) Shares [Member] |  |  |  |  |  |  |  |  |  |  |
Financial Highlights [Abstract] |  |  |  |  |  |  |  |  |  |  |
Senior Securities Amount | [2] | $ 0 | $ 151,000,000 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 773,000,000 | $ 773,000,000 | $ 151,000,000
Senior Securities Coverage per Unit |  | $ 0 | $ 338,193 | $ 0 | $ 0 | $ 0 | $ 0 | $ 0 | $ 291,919 | $ 295,667 | $ 333,349
Variable Rate Demand Preferred (VRDP) Shares [Member] |  |  |  |  |  |  |  |  |  |  |
Financial Highlights [Abstract] |  |  |  |  |  |  |  |  |  |  |
Senior Securities Amount | [2] | $ 1,159,400,000 | $ 349,900,000 | $ 1,159,400,000 | $ 1,159,400,000 | $ 1,290,300,000 | $ 1,290,300,000 | $ 1,290,300,000 | $ 1,290,300,000 | $ 1,290,300,000 | $ 349,900,000
Senior Securities Coverage per Unit | [1] | $ 240,834 | $ 338,193 | $ 240,229 | $ 283,145 | $ 280,550 | $ 282,066 | $ 265,448 | $ 291,919 | $ 295,667 | $ 333,349
AMTP, MFP, MTP, VMTP andor VRDP Shares [Member] |  |  |  |  |  |  |  |  |  |  |
Financial Highlights [Abstract] |  |  |  |  |  |  |  |  |  |  |
Preferred Stock Liquidating Preference |  | 2.41 | 3.38 | 2.4 | 2.83 | 2.81 | 2.82 | 2.65 | $ 2.92 | $ 2.96 | $ 3.33
Series D MFP Shares [Member] |  |  |  |  |  |  |  |  |  |  |
Financial Highlights [Abstract] |  |  |  |  |  |  |  |  |  |  |
Senior Securities Coverage per Unit | [5] | $ 2,408 |  | $ 2,402 | $ 2,831 | $ 2,805 | $ 2,800 | $ 0 |  |  |
Series 2015 (NEA PRCCL) |  |  |  |  |  |  |  |  |  |  |
Financial Highlights [Abstract] |  |  |  |  |  |  |  |  |  |  |
Senior Securities Coverage per Unit | [6] |  | 0 |  |  |  |  |  |  |  |
Senior Securities Average Market Value per Unit | [6] |  | $ 10.05 |  |  |  |  |  |  |  |
[1] | Asset Coverage Per $100,000: Asset coverage per $100,000 is calculated by subtracting the Fund’s liabilities and indebtedness not represented by senior securities from the Fund’s total assets, dividing the result by the aggregate amount of the Fund’s senior securities representing indebtedness then outstanding (if applicable), plus the aggregate of the involuntary liquidation preference of the outstanding preferred shares, if applicable, and multiplying the result by 100,000.
[2] | Aggregate Amount Outstanding: Aggregate amount outstanding represents the liquidation preference as of the end of the relevant fiscal year and does not include any preferred shares noticed for redemption as noted on the Statement of Assets and Liabilities, where applicable.
[3] | The Fund’s Series D MFP Shares have a $1,000 liquidation preference per share, while all other MFP Shares have a $100,000 liquidation preference per share. The asset coverage per $1,000 share for the Fund’s Series D MFP Shares were as follows:
[4] | Asset Coverage Per $10: Asset coverage per $10 is calculated by subtracting the Fund’s liabilities and indebtedness not represented by senior securities from the Fund’s total assets, dividing the result by the aggregate amount of the Fund’s senior securities representing indebtedness then outstanding, and multiplying the result by 10. The Ending and Average Market Value Per Share for each Series of the Fund’s MTP Shares outstanding were as follows:
[5] | Asset Coverage Per $1,000: Asset coverage per $1,000 is calculated by subtracting the Fund’s liabilities and indebtedness not represented by senior securities from the Fund’s total assets, dividing the result by the aggregate amount of the Fund’s senior securities representing indebtedness then outstanding, and multiplying the result by 1,000.
[6] | For the period November 1, 2013 through December 20, 2013.

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