| N-2 | 12 Months Ended |
| Jun. 30, 2023 | |
| Cover [Abstract] | |
| Entity Central Index Key | 0001817159 |
| Amendment Flag | false |
| Entity Inv Company Type | N-2 |
| Document Type | N-CSR |
| Entity Registrant Name | RiverNorth Flexible Municipal Income Fund II, Inc. |
| General Description of Registrant [Abstract] | |
| Investment Objectives and Practices [Text Block] | Investment Objectives There have been no changes in the Fund’s investment objectives since the prior disclosure date that have not been approved by shareholders. The Fund’s primary investment objective is current income exempt from regular U.S. federal income taxes (but which may be includable in taxable income for purposes of the Federal alternative minimum tax). The Fund’s secondary investment objective is total return. Principal Investment Strategies and Policies There have been no changes in the Fund’s Principal Investment Strategies and Policies since the prior disclosure date. Under normal market conditions, the Fund seeks to achieve its investment objectives by investing, directly or indirectly, at least 80% of its Managed Assets in municipal bonds, the interest on which is, in the opinion of bond counsel to the issuers, generally excludable from gross income for regular U.S. federal income tax purposes, except that the interest may be includable in taxable income for purposes of the Federal alternative minimum tax (“Municipal Bonds”). In order to qualify to pay exempt-interest dividends, which are items of interest excludable from gross income for federal income tax purposes, the Fund seeks to invest at least 50% of its Managed Assets either directly (and indirectly through tender option bond transactions) in such Municipal Bonds or in other funds that are taxed as regulated investment companies. Municipal Bonds are debt obligations, which may have a variety of issuers, including governmental entities or other qualifying issuers. Issuers may be states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities. Such territories of the United States include Puerto Rico. Municipal Bonds include, among other instruments, general obligation bonds, revenue bonds, municipal leases, certificates of participation, private activity bonds, moral obligation bonds, and tobacco settlement bonds, as well as short-term, tax-exempt obligations such as municipal notes and variable rate demand obligations. The Fund seeks to allocate its assets between the two principal strategies described below. The Adviser determines the portion of the Fund’s Managed Assets to allocate to each strategy and may, from time to time, adjust the allocations. Under normal market conditions, the Fund may allocate between 25% and 65% of its Managed Assets to the Tactical Municipal Closed-End Fund (“CEF”) Strategy (as described below) and 35% to 75% of its Managed Assets to the Municipal Bond Income Strategy (as described below). Tactical Municipal CEF Strategy (25%-65% of Managed Assets). Under normal market conditions, the Fund limits its investments in CEFs that have been in operation for less than one year to no more than 10% of the Fund’s Managed Assets allocated to the Tactical Municipal CEF Strategy. The Fund will not invest in inverse ETFs or leveraged ETFs. Under normal market conditions, the Fund may not invest more than 35% of its Managed Assets in the Tactical Municipal CEF Strategy in single state municipal CEFs. The Fund’s shareholders will indirectly bear the expenses, including the management fees, of the Underlying Funds. Under Section 12(d)(1)(A) of the 1940 Act, the Fund may hold securities of an Underlying Fund in amounts which (i) do not exceed 3% of the total outstanding voting stock of the Underlying Fund, (ii) do not exceed 5% of the value of the Fund’s total assets and (iii) when added to all other Underlying Fund securities held by the Fund, do not exceed 10% of the value of the Fund’s total assets. These limits may be exceeded when permitted under Rule 12d1-4. The Fund intends to rely on either Section 12(d)(1)(F) of the 1940 Act, which provides that the provisions of Section 12(d)(1)(A) shall not apply to securities purchased or otherwise acquired by the Fund if (i) immediately after such purchase or acquisition not more than 3% of the total outstanding stock of such Underlying Fund is owned by the Fund and all affiliated persons of the Fund, and (ii) certain requirements are met with respect to sales charges, or Rule 12d1-4. The Fund may invest in Underlying Funds that invest in securities that are rated below investment grade, including those receiving the lowest ratings from S&P Global Ratings (“S&P”), Fitch Ratings, a part of the Fitch Group (“Fitch”), or Moody’s Investor Services, Inc. (“Moody’s”), or comparably rated by another nationally recognized statistical rating organization (“NRSRO”) or, if unrated, determined by the Adviser or the Subadviser to be of comparable credit quality, which indicates that the security is in default or has little prospect for full recovery of principal or interest. Below investment grade securities (such as securities rated below BBB- by S&P or Fitch or below Baa3 by Moody’s) are commonly referred to as “junk” and “high yield” securities. Below investment grade securities are considered speculative with respect to the issuer’s capacity to pay interest and repay principal. The Underlying Funds in which the Fund invests may invest in securities receiving the lowest ratings from the NRSROs, including securities rated C by Moody’s or D-by S&P. Lower rated below investment grade securities are considered more vulnerable to nonpayment than other below investment grade securities and their issuers are more dependent on favorable business, financial and economic conditions to meet their financial commitments. The lowest rated below investment grade securities are typically already in default. The Underlying Funds in which the Fund invests will not include those that are advised or subadvised by the Adviser, the Subadviser or their affiliates. Municipal Bond Income Strategy (35%-75% of Managed Assets). Under normal market conditions, the Fund invests at least 60% of the Fund’s Managed Assets allocated to the Municipal Bond Income Strategy directly in investment grade Municipal Bonds. The Subadviser invests no more than 20% of the Managed Assets allocated to the Municipal Bond Income Strategy in Municipal Bonds rated at or below Caa1 by Moody’s or CCC+ by S&P or Fitch, or comparably rated by another NRSRO, including unrated bonds judged to be of equivalent quality as determined by the Adviser or Subadviser, as applicable. Investment grade securities are those rated Baa or higher by Moody’s (although Moody’s considers securities rated Baa to have speculative characteristics) or BBB or higher by S&P or rated similarly by another NRSRO or, if unrated, judged to be of equivalent quality as determined by the Adviser or Subadviser, as applicable. If the independent ratings agencies assign different ratings to the same security, the Fund will use the higher rating for purposes of determining the security’s credit quality. Subject to the foregoing limitations, the Fund may invest in securities receiving the lowest ratings from the NRSROs, including securities rated C by Moody’s or D-by S&P, which indicates that the security is in default or has little prospect for full recovery of principal or interest. Under normal market conditions, the Fund, or the Underlying Funds in which the Fund invests, invests at least 50% of its Managed Assets, directly or indirectly in investment grade Municipal Bonds. “Managed Assets” means the total assets of the Fund, including assets attributable to leverage, minus liabilities (other than debt representing leverage and any preferred stock that may be outstanding). Such assets attributable to leverage include the portion of assets in tender option bond trusts of which the Fund owns TOB Residuals (as defined below) that has been effectively financed by the trust’s issuance of TOB Floaters (as defined below). Other Investments. The Fund may at times establish hedging positions, which may include short sales and derivatives, such as options, futures and swaps (“Hedging Positions”). Such Hedging Positions may be used to attempt to protect against possible changes in the value of securities held in or to be purchased for the Fund’s portfolio and to manage the effective maturity or duration of the Fund’s portfolio. The Fund’s Hedging Positions may, however, result in income or gain to the Fund that is not exempt from regular U.S. federal income taxes. A short sale is a transaction in which the Fund sells a security that it does not own in anticipation of a decline in the market price of the security. The Fund may benefit from a short position when the shorted security decreases in value by more than the cost of the transaction but will suffer a loss on a short sale if the security’s value does not decline or increase. The Fund will not engage in any short sales of securities issued by CEFs. The Fund also may attempt to enhance the return on the cash portion of its portfolio by investing in total return swap agreements. A total return swap agreement provides the Fund with a return based on the performance of an underlying asset, in exchange for fee payments to a counterparty based on a specific rate. The difference in the value of these income streams is recorded daily by the Fund, and is typically settled in cash at least monthly. If the underlying asset declines in value over the term of the swap, the Fund would be required to pay the dollar value of that decline plus any applicable fees to the counterparty. The Fund may use its own NAV or any other reference asset that the Adviser or Subadviser chooses as the underlying asset in a total return swap. The Fund limits the notional amount of all total return swaps in the aggregate to 15% of the Fund’s Managed Assets. In addition to the foregoing principal investment strategies of the Fund, the Adviser also may allocate the Fund’s Managed Assets among cash and short-term investments. There are no limits on the Fund’s portfolio turnover, and the Fund may buy and sell securities to take advantage of potential short-term trading opportunities without regard to length of time and when the Adviser or Subadviser believes investment considerations warrant such action. High portfolio turnover may result in the realization of net short-term capital gains by the Fund which, when distributed to common shareholders, will be taxable as ordinary income. In addition, a higher portfolio turnover rate results in correspondingly greater brokerage commissions and other transactional expenses that are borne by the Fund. All percentage limitations are measured at the time of investment and may be exceeded on a going-forward basis as a result of credit rating downgrades or market value fluctuations of the Fund’s portfolio securities. Unless otherwise specified herein, the Fund may count its holdings in Underlying Funds towards various guideline tests, including the 80% policy so long as the earnings on the underlying holdings of such Underlying Funds are exempt from regular U.S. federal income taxes (but which may be includable in taxable income for purposes of the Federal alternative minimum tax). Unless otherwise specified, the investment policies and limitations of the Fund are not considered to be fundamental by the Fund and can be changed without a vote of the common shareholders. The Fund’s primary investment objective, 80% policy and certain investment restrictions specifically identified as such in the Fund’s Statement of Additional Information are considered fundamental and may not be changed without the approval of the holders of a majority of the outstanding voting securities of the Fund, as defined in the 1940 Act, which includes common shares and Preferred Shares, if any, voting together as a single class, and the holders of the outstanding Preferred Shares, if any, voting as a single class. Portfolio Composition Set forth below is a description of the various types of Municipal Bonds in which the Fund may invest. Obligations are included within the term “Municipal Bonds” if the interest paid thereon is excluded from gross income for U.S. federal income tax purposes in the opinion of bond counsel to the issuer. Municipal Bonds are either general obligation or revenue bonds and typically are issued to finance public projects, such as roads or public buildings, to pay general operating expenses or to refinance outstanding debt. Municipal Bonds may also be issued for private activities, such as housing, medical and educational facility construction or for privately owned industrial development and pollution control projects. General obligation bonds are backed by the full faith and credit and taxing authority of the issuer and may be repaid from any revenue source. Revenue bonds may be repaid only from the revenues of a specific facility or source. The Fund also may purchase Municipal Bonds that represent lease obligations. These carry special risks because the issuer of the bonds may not be obligated to appropriate money annually to make payments under the lease. The Municipal Bonds in which the Fund primarily invests pay interest or income that, in the opinion of bond counsel to the issuer, is exempt from regular U.S. federal income tax. The Adviser and the Subadviser will not conduct their own analysis of the tax status of the interest paid by Municipal Bonds held by the Fund, but will rely on the opinion of counsel to the issuer of each such instrument. The Fund may also invest in Municipal Bonds issued by United States Territories (such as Puerto Rico or Guam) that are exempt from regular U.S. federal income tax. In addition, the Fund may invest in other securities that pay interest or income that is, or make other distributions that are, exempt from regular U.S. federal income tax and/or state and local taxes, regardless of the technical structure of the issuer of the instrument. The Fund treats all of such tax-exempt securities as Municipal Bonds. The yields on Municipal Bonds are dependent on a variety of factors, including prevailing interest rates and the condition of the general money market and the municipal bond market, the size of a particular offering, the maturity of the obligation and the rating of the issuer. The market value of Municipal Bonds will vary with changes in interest rate levels and as a result of changing evaluations of the ability of bond issuers to meet interest and principal payments. General Obligation Bonds. Revenue Bonds. Private Activity Bonds. Private activity bonds are secured primarily by revenues derived from loan repayments or lease payments due from the entity, which may or may not be guaranteed by a parent company or otherwise secured. Private activity bonds generally are not secured by a pledge of the taxing power of the issuer of such bonds. Therefore, an investor should be aware that repayment of such bonds generally depends on the revenues of a private entity and be aware of the risks that such an investment may entail. Continued ability of an entity to generate sufficient revenues for the payment of principal and interest on such bonds will be affected by many factors including the size of the entity, capital structure, demand for its products or services, competition, general economic conditions, government regulation and the entity’s dependence on revenues for the operation of the particular facility being financed. The Fund expects that, due to investments in private activity bonds, a portion of the distributions it makes on the common shares will be includable in the federal alternative minimum taxable income. Moral Obligation Bonds. Municipal Lease Obligations and Certificates of Participation. The certificates are typically 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. 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 leases, plus accrued interest. Tobacco Settlement Bonds. Zero Coupon Bonds. |
| Risk Factors [Table Text Block] | Risk Factors Investing in the Fund involves certain risks relating to its structure and investment objective. You should carefully consider these risk factors, together with all of the other information included in this report, before deciding whether to make an investment in the Fund. An investment in the Fund may not be appropriate for all investors, and an investment in the common shares of the Fund should not be considered a complete investment program. The risks set forth below are not the only risks of the Fund, and the Fund may face other risks that have not yet been identified, which are not currently deemed material or which are not yet predictable. If any of the following risks occur, the Fund’s financial condition and results of operations could be materially adversely affected. In such case, the Fund’s NAV and the trading price of its securities could decline, and you may lose all or part of your investment. Certain risk factors included below have been updated since the prior disclosure date to reflect certain non-material updates. Investment-Related Risks: With the exception of Underlying Fund risk (and except as otherwise noted below), the following risks apply to the direct investments the Fund may make, and generally apply to the Fund’s investments in Underlying Funds. That said, each risk described below may not apply to each Underlying Fund. Investment and Market Risks. Management Risks. Securities Risks. Municipal Bond Risks. Certain types of Municipal Bonds may be subject to specific risks. General obligation bonds are obligations involving the credit of an issuer possessing taxing power and are payable from such issuer’s general revenues and not from any particular source, and are subject to risks related to the issuer’s ability to raise tax revenues and ability to maintain an adequate tax base. Revenue bonds are subject to the risk that the underlying facilities may not generate sufficient income to pay expenses and interest costs, lack recourse to ensure payment, or might be subordinate to other debtors. Municipal lease obligations and certificates of participation are subject to the added risk that the governmental lessee will fail to appropriate funds to enable it to meet its payment obligations under the lease. Moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality. Municipalities and other public authorities issue private activity bonds to finance development of facilities for use by a private enterprise, which is solely responsible for paying the principal and interest on the bond. Failure of Municipal Bonds to meet regulatory requirements may cause the interest received by the Fund and distributed to shareholders to be taxable, which may apply retroactively to the date of the issuance of the bond. Municipal bonds are also subject to interest rate, credit, and liquidity risk, which are discussed generally under this Risks Factors section. The COVID-19 pandemic significantly stressed the financial resources of many municipalities and other issuers of municipal securities, which may impair their ability to meet their financial obligations and may harm the value or liquidity of the Fund’s investments in municipal securities. In particular, responses by municipalities to the COVID-19 pandemic caused disruptions in business activities. These and other effects of the COVID-19 pandemic, such as increased unemployment levels, impacted tax and other revenues of municipalities and other issuers of municipal securities and the financial conditions of such issuers. As a result, there is increased budgetary and financial pressure on municipalities and heightened risk of default or other adverse credit or similar events for issuers of municipal securities, which would adversely impact the Fund’s investments. State Specific and Industry Risk. Puerto Rico Municipal Bond Risks. Tobacco Settlement Bond Risks. Credit and Below Investment Grade Securities Risks. Interest Rate Risk. Interest rates in the United States and many other countries have risen in recent periods and may continue to rise in the future. Additionally, as a result of increasing interest rates, reserves held by banks and other financial institutions in bonds and other debt securities could face a significant decline in value relative to deposits and liabilities, which coupled with general economic headwinds resulting from a changing interest rate environment, creates liquidity pressures at such institutions, as evidenced by the bank run on the Silicon Valley Bank Financial Group (“SVB”) causing it to be placed into receivership. As a result, certain sectors of the credit markets could experience significant declines in liquidity, and it is possible that the Fund (or an Investment Fund) will not be able to manage this risk effectively. It is yet to be determined how the bank run on SVB will fully impact the overall performance of the Fund or one or more of its portfolio investments and how similar events may affect the ability of the Fund to execute its investment strategy. LIBOR Risk. SOFR Risk. Because SOFR is a financing rate based on overnight secured funding transactions, it differs fundamentally from LIBOR. LIBOR was intended to be an unsecured rate that represents interbank funding costs for different short-term maturities or tenors. It was a forward-looking rate reflecting expectations regarding interest rates for the applicable tenor. Thus, LIBOR was intended to be sensitive, in certain respects, to bank credit risk and to term interest rate risk. In contrast, SOFR is a secured overnight rate reflecting the credit of U.S. Treasury securities as collateral. Thus, it is largely insensitive to credit-risk considerations and to short-term interest rate risks. SOFR is a transaction-based rate, and it has been more volatile than other benchmark or market rates, such as three-month LIBOR, during certain periods. For these reasons, among others, there is no assurance that SOFR, or rates derived from SOFR, will perform in the same or similar way as LIBOR would have performed at any time, and there is no assurance that SOFR-based rates will be a suitable substitute for LIBOR. SOFR has a limited history, having been first published in April 2018. The future performance of SOFR, and SOFR-based reference rates, cannot be predicted based on SOFR’s history or otherwise. Levels of SOFR in the future, including following the discontinuation of LIBOR, may bear little or no relation to historical levels of SOFR, LIBOR or other rates. The inclusion of SOFR Risk is a change since the prior disclosure date. Inflation/Deflation Risk. Tactical Municipal CEF Strategy Risk. In fact, it is possible that this market discount may increase and the Fund may suffer realized or unrealized capital losses due to further decline in the market price of the securities of such CEFs, thereby adversely affecting the NAV of the Fund’s common shares. Similarly, there can be no assurance that any shares of a CEF purchased by the Fund at a premium will continue to trade at a premium or that the premium will not decrease subsequent to a purchase of such shares by the Fund. Underlying Fund Risks. The Fund’s NAV will fluctuate in response to changes in the NAVs of the Underlying Funds in which it invests and will be particularly sensitive to the risks associated with each of the Underlying Funds. Shareholders will bear additional layers of fees and expenses with respect to the Fund’s investments in Underlying Funds because each of the Fund and the Underlying Fund will charge fees and incur separate expenses, which may be magnified if the Underlying Funds use leverage. The Fund’s investments in Underlying Funds may be restricted by certain provisions of the 1940 Act. Under Section 12(d)(1)(A) of the 1940 Act, the Fund may hold securities of an Underlying Fund in amounts which (i) do not exceed 3% of the total outstanding voting stock of the Underlying Fund, (ii) do not exceed 5% of the value of the Fund’s total assets and (iii) when added to all other Underlying Fund securities held by the Fund, do not exceed 10% of the value of the Fund’s total assets. Under Section 12(d)(1)(C) of the 1940 Act, the Fund, together with any other investment companies for which the Adviser acts as an investment adviser, may not, in the aggregate, own more than 10% of the total outstanding voting stock of a registered closed-end investment company. Section 12(d)(1)(F) of the 1940 Act provides that the limitations of Section 12(d)(1) described above shall not apply to securities purchased or otherwise acquired by the Fund if (i) immediately after such purchase or acquisition not more than 3% of the total outstanding stock of such Underlying Fund is owned by the Fund and all affiliated persons of the Fund, and (ii) certain requirements are met with respect to sales charges. In addition, Rule 12d1-4 under the 1940 Act (“Rule 12d1-4”), effective as of January 19, 2022, permits the Fund to invest in Underlying Funds beyond the limitations of Section 12(d)(1) described above, subject to various conditions, including that the Fund enter into an investment agreement with the Underlying Fund (which agreements may impose additional conditions on the Fund). In matters upon which the Fund is solicited to vote as a shareholder of an Underlying Fund, the Adviser may be required to vote Underlying Fund shares in the same proportion as shares held by other shareholders of the Underlying Fund. Defaulted and Distressed Securities Risks. Illiquid Securities Risks. Valuation Risk. Tender Option Bonds Risks. The Fund’s use of proceeds received from tender option bond transactions will create economic leverage, creating an opportunity for increased income and returns, but will also create the possibility that long-term returns will be diminished if the cost of the TOB Floaters exceeds the return on the securities deposited in the TOB Issuer. If the income and gains earned on Municipal Bonds deposited in a TOB Issuer that issues TOB Residuals to the Fund are greater than the payments due on the TOB Floaters, the Fund’s returns will be greater than if it had not invested in the TOB Residuals. Insurance Risks. Tax Risks. Derivatives Risks. Derivatives may entail investment exposures that are greater than their cost would suggest, meaning that a small investment in a derivative could have a large potential impact on the performance of the Fund or an Underlying Fund. The Fund or an Underlying Fund could experience a loss if derivatives do not perform as anticipated, if they are not correlated with the performance of other investments which they are used to hedge or if the fund is unable to liquidate a position because of an illiquid secondary market. Except with respect to the Fund’s investments in total return swaps, the Fund expects its use of derivative instruments will be for hedging purposes. When used for speculative purposes, derivatives will produce enhanced investment exposure, which will magnify gains and losses. The Fund and the Underlying Funds also will be subject to credit risk with respect to the counterparties to the derivatives contracts purchased by such fund. If a counterparty becomes bankrupt or otherwise fails to perform its obligations under a derivative contract, the Fund or an Underlying Fund may obtain only a limited recovery or may obtain no recovery in such circumstances. Options and Futures Risks. Market Disruption, Geopolitical and Climate Change Risks. In February 2022, Russia commenced a military attack on Ukraine. The outbreak of hostilities between the two countries and the threat of wider-spread hostilities could have a severe adverse effect on the region and global economies, including significant negative impacts on the markets for certain securities and commodities, such as oil and natural gas. In addition, sanctions imposed on Russia by the United States and other countries, and any sanctions imposed in the future, could have a significant adverse impact on the Russian economy and related markets. The price and liquidity of investments may fluctuate widely as a result of the conflict and related events. How long the armed conflict and related events will last cannot be predicted. These tensions and any related events could have a significant impact on Fund performance and the value of Fund investments. Climate change poses long-term threats to physical and biological systems. Potential hazards and risks related to climate change for a State or municipality include, among other things, wildfires, rising sea levels, more severe coastal flooding and erosion hazards, and more intense storms. Storms in recent years have demonstrated vulnerabilities in a State's or municipality's infrastructure to extreme weather events. Climate change risks, if they materialize, can adversely impact a State's or municipality's financial plan in current or future years. In addition, economists and others have expressed increasing concern about the potential effects of global climate change on property and security values. A rise in sea levels, an increase in powerful windstorms and/or a climate-driven increase in sea levels or flooding could cause coastal properties to lose value or become unmarketable altogether. Economists warn that, unlike previous declines in the real estate market, properties in affected coastal zones may not ever recover their value. Large wildfires driven by high winds and prolonged drought may devastate businesses and entire communities and may be very costly to any business found to be responsible for the fire. Regulatory changes and divestment movements tied to concerns about climate change could adversely affect the value of certain land and the viability of industries whose activities or products are seen as accelerating climate change. These losses could adversely affect the bonds of municipalities that depend on tax or other revenues and tourist dollars generated by affected properties, and insurers of the property and/or of municipal securities. Since property and security values are driven largely by buyers' perceptions, it is difficult to know the time period over which these market effects might unfold. Since the prior disclosure date, the Fund has added the risk disclosures related to climate change. Pandemic Risk. Swap Risks. Short Sale Risks. Rating Agency Risk. United States Credit Rating Downgrade Risk. Legislation and Regulatory Risks. Defensive Measures. Structural Risks: Market Discount. Limited Term and Eligible Tender Offer Risk. The Board may, but is not required to, cause the Fund to conduct a tender offer to all common shareholders at a price equal to the NAV (an “Eligible Tender Offer”). If the Fund conducts an Eligible Tender Offer, there can be no assurance that the Fund’s net assets would not fall below $100 million (the “Termination Threshold”), in which case the Eligible Tender Offer will be terminated, and the Fund will terminate on or before the Termination Date (subject to possible extensions). If the Fund’s net assets are equal or greater than the Termination Threshold, the Fund will have a perpetual existence upon the affirmative vote of a majority of the Board, without shareholder approval. An Eligible Tender Offer or liquidation may require the Fund to sell securities when it otherwise would not, or at reduced prices, leading to losses for the Fund and increased transaction expenses. Thereafter, remaining shareholders may only be able to sell their shares at a discount to NAV. The Adviser may have a conflict of interest in recommending that the Fund have a perpetual existence. The potential required sale of portfolio securities, purchase of tendered shares in an Eligible Tender Offer, and/or potential liquidation of the Fund may also have adverse tax consequences for the Fund and shareholders. In addition, the completion of an Eligible Tender Offer may cause disruptions and changes in the Fund’s investment portfolio, increase the proportional burden of the Fund’s expenses on the remaining shareholders, and adversely impact the secondary market trading of such shares. Investment Style Risk. Multi-Manager Risk. Asset Allocation Risk. Leverage Risks. Portfolio Turnover Risk. Potential Conflicts of Interest Risk. Stockholder Activism. Cybersecurity Risk. A Anti-Takeover Provisions. Risks Associated with Additional Offerings. In the event any additional series of fixed rate preferred shares are issued and such shares are intended to be listed on an exchange, prior application will have been made to list such shares. During an initial period, which is not expected to exceed 30 days after the date of its initial issuance, such shares may not be listed on any securities exchange. During such period, the underwriters may make a market in such shares, although they will have no obligation to do so. Consequently, an investment in such shares may be illiquid during such period. Fixed rate preferred shares may trade at a premium to or discount from liquidation value. There are risks associated with an offering of Rights (in addition to the risks discussed herein related to the offering of shares and preferred shares). Shareholders who do not exercise their rights may, at the completion of such an offering, own a smaller proportional interest in the Fund than if they exercised their rights. As a result of such an offering, a shareholder may experience dilution in NAV per share if the subscription price per share is below the NAV per share on the expiration date. In addition to the economic dilution described above, if a shareholder does not exercise all of their Rights, the shareholder will incur voting dilution as a result of the Rights offering. This voting dilution will occur because the shareholder will own a smaller proportionate interest in the Fund after the rights offering than prior to the Rights offering. There is a risk that changes in market conditions may result in the underlying common shares or preferred shares purchasable upon exercise of Rights being less attractive to investors at the conclusion of the subscription period. This may reduce or eliminate the value of the Rights. If investors exercise only a portion of the rights, the number of shares issued may be reduced, and the shares may trade at less favorable prices than larger offerings for similar securities. Rights issued by the Fund may be transferable or non-transferable rights. Secondary Market for the Common Shares. |
| Effects of Leverage [Text Block] | Effects of Leverage. Assuming that the Fund’s leverage costs remain as described above (at an assumed annual cost of 3.16% of the principal amount outstanding) the annual return that the Fund’s portfolio must experience (net of expenses) in order to cover its leverage costs would be 1.24%. The following table is furnished in response to requirements of the SEC. It is designed to illustrate the effect of leverage on total return on common shares, assuming investment portfolio total returns (comprised of income, net expenses and changes in the value of investments held in the Fund’s portfolio) of -10%, -5%, 0%, 5% and 10%. These assumed investment portfolio returns are hypothetical figures and are not necessarily indicative of what the Fund’s investment portfolio returns will be. In other words, the Fund’s actual returns may be greater or less than those appearing in the table below. The table further reflects the use of leverage representing approximately 39.32% of the Fund’s Managed Assets and the Fund’s assumed annual leverage costs rate of 3.16% of the principal amounts outstanding. Assumed Portfolio Return -10.00% -5.00% 0.00% 5.00% 10.00% Common Share Total Return -18.53% -10.29% -2.05% 6.19% 14.43% Total return is composed of two elements—the dividends on common shares paid by the Fund (the amount of which is largely determined by the Fund’s net investment income after paying the cost of leverage) and realized and unrealized gains or losses on the value of the securities the Fund owns. As the table shows, leverage generally increases the return to common shareholders when portfolio return is positive or greater than the costs of leverage and decreases return when the portfolio return is negative or less than the costs of leverage. During the time in which the Fund is using leverage, the amount of the fees paid to the Adviser (and from the Adviser to the Subadviser) for investment management services (and subadvisory services) is higher than if the Fund did not use leverage because the fees paid are calculated based on the Fund’s Managed Assets. This may create a conflict of interest between the Adviser and the Subadviser, on the one hand, and the common shareholders, on the other. Also, because the leverage costs will be borne by the Fund at a specified interest rate, only the Fund’s common shareholders will bear the cost of the Fund’s management fees and other expenses. There can be no assurance that a leveraging strategy will be successful during any period in which it is employed. |
| Effects of Leverage [Table Text Block] | Assumed Portfolio Return -10.00% -5.00% 0.00% 5.00% 10.00% Common Share Total Return -18.53% -10.29% -2.05% 6.19% 14.43% |
| Return at Minus Ten [Percent] | (18.53%) |
| Return at Minus Five [Percent] | (10.29%) |
| Return at Zero [Percent] | (2.05%) |
| Return at Plus Five [Percent] | 6.19% |
| Return at Plus Ten [Percent] | 14.43% |
| Effects of Leverage, Purpose [Text Block] | The following table is furnished in response to requirements of the SEC. It is designed to illustrate the effect of leverage on total return on common shares, assuming investment portfolio total returns (comprised of income, net expenses and changes in the value of investments held in the Fund’s portfolio) of -10%, -5%, 0%, 5% and 10%. These assumed investment portfolio returns are hypothetical figures and are not necessarily indicative of what the Fund’s investment portfolio returns will be. In other words, the Fund’s actual returns may be greater or less than those appearing in the table below. The table further reflects the use of leverage representing approximately 39.32% of the Fund’s Managed Assets and the Fund’s assumed annual leverage costs rate of 3.16% of the principal amounts outstanding. |
| Investment And Market Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Investment and Market Risks. |
| Management Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Management Risks. |
| Securities Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Securities Risks. |
| Municipal Bond Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Municipal Bond Risks. Certain types of Municipal Bonds may be subject to specific risks. General obligation bonds are obligations involving the credit of an issuer possessing taxing power and are payable from such issuer’s general revenues and not from any particular source, and are subject to risks related to the issuer’s ability to raise tax revenues and ability to maintain an adequate tax base. Revenue bonds are subject to the risk that the underlying facilities may not generate sufficient income to pay expenses and interest costs, lack recourse to ensure payment, or might be subordinate to other debtors. Municipal lease obligations and certificates of participation are subject to the added risk that the governmental lessee will fail to appropriate funds to enable it to meet its payment obligations under the lease. Moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality. Municipalities and other public authorities issue private activity bonds to finance development of facilities for use by a private enterprise, which is solely responsible for paying the principal and interest on the bond. Failure of Municipal Bonds to meet regulatory requirements may cause the interest received by the Fund and distributed to shareholders to be taxable, which may apply retroactively to the date of the issuance of the bond. Municipal bonds are also subject to interest rate, credit, and liquidity risk, which are discussed generally under this Risks Factors section. The COVID-19 pandemic significantly stressed the financial resources of many municipalities and other issuers of municipal securities, which may impair their ability to meet their financial obligations and may harm the value or liquidity of the Fund’s investments in municipal securities. In particular, responses by municipalities to the COVID-19 pandemic caused disruptions in business activities. These and other effects of the COVID-19 pandemic, such as increased unemployment levels, impacted tax and other revenues of municipalities and other issuers of municipal securities and the financial conditions of such issuers. As a result, there is increased budgetary and financial pressure on municipalities and heightened risk of default or other adverse credit or similar events for issuers of municipal securities, which would adversely impact the Fund’s investments. |
| State Specific And Industry Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | State Specific and Industry Risk. |
| Puerto Rico Municipal Bond Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Puerto Rico Municipal Bond Risks. |
| Tobacco Settlement Bond Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Tobacco Settlement Bond Risks. |
| Credit And Below Investment Grade Securities Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Credit and Below Investment Grade Securities Risks. |
| Interest Rate Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Interest Rate Risk. Interest rates in the United States and many other countries have risen in recent periods and may continue to rise in the future. Additionally, as a result of increasing interest rates, reserves held by banks and other financial institutions in bonds and other debt securities could face a significant decline in value relative to deposits and liabilities, which coupled with general economic headwinds resulting from a changing interest rate environment, creates liquidity pressures at such institutions, as evidenced by the bank run on the Silicon Valley Bank Financial Group (“SVB”) causing it to be placed into receivership. As a result, certain sectors of the credit markets could experience significant declines in liquidity, and it is possible that the Fund (or an Investment Fund) will not be able to manage this risk effectively. It is yet to be determined how the bank run on SVB will fully impact the overall performance of the Fund or one or more of its portfolio investments and how similar events may affect the ability of the Fund to execute its investment strategy. |
| Libor Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | LIBOR Risk. |
| Sofr Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | SOFR Risk. Because SOFR is a financing rate based on overnight secured funding transactions, it differs fundamentally from LIBOR. LIBOR was intended to be an unsecured rate that represents interbank funding costs for different short-term maturities or tenors. It was a forward-looking rate reflecting expectations regarding interest rates for the applicable tenor. Thus, LIBOR was intended to be sensitive, in certain respects, to bank credit risk and to term interest rate risk. In contrast, SOFR is a secured overnight rate reflecting the credit of U.S. Treasury securities as collateral. Thus, it is largely insensitive to credit-risk considerations and to short-term interest rate risks. SOFR is a transaction-based rate, and it has been more volatile than other benchmark or market rates, such as three-month LIBOR, during certain periods. For these reasons, among others, there is no assurance that SOFR, or rates derived from SOFR, will perform in the same or similar way as LIBOR would have performed at any time, and there is no assurance that SOFR-based rates will be a suitable substitute for LIBOR. SOFR has a limited history, having been first published in April 2018. The future performance of SOFR, and SOFR-based reference rates, cannot be predicted based on SOFR’s history or otherwise. Levels of SOFR in the future, including following the discontinuation of LIBOR, may bear little or no relation to historical levels of SOFR, LIBOR or other rates. The inclusion of SOFR Risk is a change since the prior disclosure date. |
| Inflation Deflation Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Inflation/Deflation Risk. |
| Tactical Municipal Cef Strategy Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Tactical Municipal CEF Strategy Risk. In fact, it is possible that this market discount may increase and the Fund may suffer realized or unrealized capital losses due to further decline in the market price of the securities of such CEFs, thereby adversely affecting the NAV of the Fund’s common shares. Similarly, there can be no assurance that any shares of a CEF purchased by the Fund at a premium will continue to trade at a premium or that the premium will not decrease subsequent to a purchase of such shares by the Fund. |
| Underlying Fund Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Underlying Fund Risks. The Fund’s NAV will fluctuate in response to changes in the NAVs of the Underlying Funds in which it invests and will be particularly sensitive to the risks associated with each of the Underlying Funds. Shareholders will bear additional layers of fees and expenses with respect to the Fund’s investments in Underlying Funds because each of the Fund and the Underlying Fund will charge fees and incur separate expenses, which may be magnified if the Underlying Funds use leverage. The Fund’s investments in Underlying Funds may be restricted by certain provisions of the 1940 Act. Under Section 12(d)(1)(A) of the 1940 Act, the Fund may hold securities of an Underlying Fund in amounts which (i) do not exceed 3% of the total outstanding voting stock of the Underlying Fund, (ii) do not exceed 5% of the value of the Fund’s total assets and (iii) when added to all other Underlying Fund securities held by the Fund, do not exceed 10% of the value of the Fund’s total assets. Under Section 12(d)(1)(C) of the 1940 Act, the Fund, together with any other investment companies for which the Adviser acts as an investment adviser, may not, in the aggregate, own more than 10% of the total outstanding voting stock of a registered closed-end investment company. Section 12(d)(1)(F) of the 1940 Act provides that the limitations of Section 12(d)(1) described above shall not apply to securities purchased or otherwise acquired by the Fund if (i) immediately after such purchase or acquisition not more than 3% of the total outstanding stock of such Underlying Fund is owned by the Fund and all affiliated persons of the Fund, and (ii) certain requirements are met with respect to sales charges. In addition, Rule 12d1-4 under the 1940 Act (“Rule 12d1-4”), effective as of January 19, 2022, permits the Fund to invest in Underlying Funds beyond the limitations of Section 12(d)(1) described above, subject to various conditions, including that the Fund enter into an investment agreement with the Underlying Fund (which agreements may impose additional conditions on the Fund). In matters upon which the Fund is solicited to vote as a shareholder of an Underlying Fund, the Adviser may be required to vote Underlying Fund shares in the same proportion as shares held by other shareholders of the Underlying Fund. |
| Defaulted And Distressed Securities Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Defaulted and Distressed Securities Risks. |
| Illiquid Securities Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Illiquid Securities Risks. |
| Valuation Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Valuation Risk. |
| Tender Option Bonds Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Tender Option Bonds Risks. The Fund’s use of proceeds received from tender option bond transactions will create economic leverage, creating an opportunity for increased income and returns, but will also create the possibility that long-term returns will be diminished if the cost of the TOB Floaters exceeds the return on the securities deposited in the TOB Issuer. If the income and gains earned on Municipal Bonds deposited in a TOB Issuer that issues TOB Residuals to the Fund are greater than the payments due on the TOB Floaters, the Fund’s returns will be greater than if it had not invested in the TOB Residuals. |
| Insurance Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Insurance Risks. |
| Tax Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Tax Risks. |
| Derivatives Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Derivatives Risks. Derivatives may entail investment exposures that are greater than their cost would suggest, meaning that a small investment in a derivative could have a large potential impact on the performance of the Fund or an Underlying Fund. The Fund or an Underlying Fund could experience a loss if derivatives do not perform as anticipated, if they are not correlated with the performance of other investments which they are used to hedge or if the fund is unable to liquidate a position because of an illiquid secondary market. Except with respect to the Fund’s investments in total return swaps, the Fund expects its use of derivative instruments will be for hedging purposes. When used for speculative purposes, derivatives will produce enhanced investment exposure, which will magnify gains and losses. The Fund and the Underlying Funds also will be subject to credit risk with respect to the counterparties to the derivatives contracts purchased by such fund. If a counterparty becomes bankrupt or otherwise fails to perform its obligations under a derivative contract, the Fund or an Underlying Fund may obtain only a limited recovery or may obtain no recovery in such circumstances. |
| Options And Futures Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Options and Futures Risks. |
| Market Disruption Geopolitical And Climate Change Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Market Disruption, Geopolitical and Climate Change Risks. In February 2022, Russia commenced a military attack on Ukraine. The outbreak of hostilities between the two countries and the threat of wider-spread hostilities could have a severe adverse effect on the region and global economies, including significant negative impacts on the markets for certain securities and commodities, such as oil and natural gas. In addition, sanctions imposed on Russia by the United States and other countries, and any sanctions imposed in the future, could have a significant adverse impact on the Russian economy and related markets. The price and liquidity of investments may fluctuate widely as a result of the conflict and related events. How long the armed conflict and related events will last cannot be predicted. These tensions and any related events could have a significant impact on Fund performance and the value of Fund investments. Climate change poses long-term threats to physical and biological systems. Potential hazards and risks related to climate change for a State or municipality include, among other things, wildfires, rising sea levels, more severe coastal flooding and erosion hazards, and more intense storms. Storms in recent years have demonstrated vulnerabilities in a State's or municipality's infrastructure to extreme weather events. Climate change risks, if they materialize, can adversely impact a State's or municipality's financial plan in current or future years. In addition, economists and others have expressed increasing concern about the potential effects of global climate change on property and security values. A rise in sea levels, an increase in powerful windstorms and/or a climate-driven increase in sea levels or flooding could cause coastal properties to lose value or become unmarketable altogether. Economists warn that, unlike previous declines in the real estate market, properties in affected coastal zones may not ever recover their value. Large wildfires driven by high winds and prolonged drought may devastate businesses and entire communities and may be very costly to any business found to be responsible for the fire. Regulatory changes and divestment movements tied to concerns about climate change could adversely affect the value of certain land and the viability of industries whose activities or products are seen as accelerating climate change. These losses could adversely affect the bonds of municipalities that depend on tax or other revenues and tourist dollars generated by affected properties, and insurers of the property and/or of municipal securities. Since property and security values are driven largely by buyers' perceptions, it is difficult to know the time period over which these market effects might unfold. Since the prior disclosure date, the Fund has added the risk disclosures related to climate change. |
| Pandemic Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Pandemic Risk. |
| Swap Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Swap Risks. |
| Short Sale Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Short Sale Risks. |
| Rating Agency Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Rating Agency Risk. |
| United States Credit Rating Downgrade Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | United States Credit Rating Downgrade Risk. |
| Legislation And Regulatory Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Legislation and Regulatory Risks. |
| Defensive Measures [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Defensive Measures. |
| Market Discount [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Market Discount. |
| Limited Term And Eligible Tender Offer Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Limited Term and Eligible Tender Offer Risk. The Board may, but is not required to, cause the Fund to conduct a tender offer to all common shareholders at a price equal to the NAV (an “Eligible Tender Offer”). If the Fund conducts an Eligible Tender Offer, there can be no assurance that the Fund’s net assets would not fall below $100 million (the “Termination Threshold”), in which case the Eligible Tender Offer will be terminated, and the Fund will terminate on or before the Termination Date (subject to possible extensions). If the Fund’s net assets are equal or greater than the Termination Threshold, the Fund will have a perpetual existence upon the affirmative vote of a majority of the Board, without shareholder approval. An Eligible Tender Offer or liquidation may require the Fund to sell securities when it otherwise would not, or at reduced prices, leading to losses for the Fund and increased transaction expenses. Thereafter, remaining shareholders may only be able to sell their shares at a discount to NAV. The Adviser may have a conflict of interest in recommending that the Fund have a perpetual existence. The potential required sale of portfolio securities, purchase of tendered shares in an Eligible Tender Offer, and/or potential liquidation of the Fund may also have adverse tax consequences for the Fund and shareholders. In addition, the completion of an Eligible Tender Offer may cause disruptions and changes in the Fund’s investment portfolio, increase the proportional burden of the Fund’s expenses on the remaining shareholders, and adversely impact the secondary market trading of such shares. |
| Investment Style Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Investment Style Risk. |
| Multi Manager Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Multi-Manager Risk. |
| Asset Allocation Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Asset Allocation Risk. |
| Leverage Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Leverage Risks. |
| Portfolio Turnover Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Portfolio Turnover Risk. |
| Potential Conflicts Of Interest Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Potential Conflicts of Interest Risk. |
| Stockholder Activism [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Stockholder Activism. |
| Cybersecurity Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Cybersecurity Risk. A |
| Anti Takeover Provisions [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Anti-Takeover Provisions. |
| Risks Associated With Additional Offerings [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Risks Associated with Additional Offerings. In the event any additional series of fixed rate preferred shares are issued and such shares are intended to be listed on an exchange, prior application will have been made to list such shares. During an initial period, which is not expected to exceed 30 days after the date of its initial issuance, such shares may not be listed on any securities exchange. During such period, the underwriters may make a market in such shares, although they will have no obligation to do so. Consequently, an investment in such shares may be illiquid during such period. Fixed rate preferred shares may trade at a premium to or discount from liquidation value. There are risks associated with an offering of Rights (in addition to the risks discussed herein related to the offering of shares and preferred shares). Shareholders who do not exercise their rights may, at the completion of such an offering, own a smaller proportional interest in the Fund than if they exercised their rights. As a result of such an offering, a shareholder may experience dilution in NAV per share if the subscription price per share is below the NAV per share on the expiration date. In addition to the economic dilution described above, if a shareholder does not exercise all of their Rights, the shareholder will incur voting dilution as a result of the Rights offering. This voting dilution will occur because the shareholder will own a smaller proportionate interest in the Fund after the rights offering than prior to the Rights offering. There is a risk that changes in market conditions may result in the underlying common shares or preferred shares purchasable upon exercise of Rights being less attractive to investors at the conclusion of the subscription period. This may reduce or eliminate the value of the Rights. If investors exercise only a portion of the rights, the number of shares issued may be reduced, and the shares may trade at less favorable prices than larger offerings for similar securities. Rights issued by the Fund may be transferable or non-transferable rights. |
| Secondary Market For The Common Shares [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Secondary Market for the Common Shares. |
