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N-2 - USD ($) | 3 Months Ended | 12 Months Ended
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Dec. 31, 2023 | Sep. 30, 2023 | Jun. 30, 2023 | Mar. 31, 2023 | Dec. 31, 2022 | Sep. 30, 2022 | Jun. 30, 2022 | Mar. 31, 2022 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Feb. 28, 2019 | Feb. 28, 2018 | Feb. 28, 2017 | Feb. 29, 2016 | Feb. 28, 2015
Cover [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Entity Central Index Key |  |  |  |  |  |  |  |  |  | 0001051003 |  |  |  |  |  |  |  |  |
Amendment Flag |  |  |  |  |  |  |  |  |  | false |  |  |  |  |  |  |  |  |
Document Type |  |  |  |  |  |  |  |  |  | N-CSR |  |  |  |  |  |  |  |  |
Entity Registrant Name |  |  |  |  |  |  |  |  |  | BlackRock Debt Strategies Fund, Inc. |  |  |  |  |  |  |  |  |
Fee Table [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shareholder Transaction Expenses [Table Text Block] |  |  |  |  |  |  |  |  |  |
|  | DSU |  |  |
Shareholder Transaction Expenses |  |  |  |  |  |
Maximum sales load ( as a percentage of offering price ) (a) |  |  | 1.00% |  |  |
Offering expenses borne by the Fund ( as a percentage of offering price ) (a) |  |  | 0.05% |  |  |
Dividend reinvestment plan fees |  |  | $0.02 per share for open market purchases of common shares (b) |  |  |
| (a) | If the common shares are sold to or through underwriters, the Prospectus Supplement will set forth any applicable sales load and the estimated offering expenses. Fund shareholders will pay all offering expenses involved with an offering. |
| (b) | Computershare Trust Company, N.A.’s (the “Reinvestment Plan Agent”) fees for the handling of the reinvestment of dividends will be paid by DSU. However, shareholders will pay a $0.02 per share fee incurred in connection with open-market purchases, which will be deducted from the value of the dividend. Shareholders will also be charged a $0.02 per share fee if a shareholder directs the Reinvestment Plan Agent to sell the common shares held in a dividend reinvestment account. Per share fees include any applicable brokerage commissions the Reinvestment Plan Agent is required to pay. |
Sales Load [Percent] | [1] |  |  |  |  |  |  |  |  | 1.00% |  |  |  |  |  |  |  |  |
Dividend Reinvestment and Cash Purchase Fees | [2] |  |  |  |  |  |  |  |  | $ 0.02 |  |  |  |  |  |  |  |  |
Other Transaction Expenses [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other Transaction Expenses [Percent] | [1] |  |  |  |  |  |  |  |  | 0.05% |  |  |  |  |  |  |  |  |
Annual Expenses [Table Text Block] |  |  |  |  |  |  |  |  |  |
Estimated Annual Expenses ( as a percentage of net assets attributable to common shares ) |  |  |  |  |  |
Investment advisory fees (c)(d) |  |  | 0.70% |  |  |
Other expenses |  |  | 1.77 |  |  |
Miscellaneous |  |  | 0.09 |  |  |
Interest expense (e) |  |  | 1.68 |  |  |
Total annual expenses |  |  | 2.47 |  |  |
Fee waivers (d) |  |  | — |  |  |
Total annual Fund operating expenses after fee waivers (d) |  |  | 2.47 |  |  |
| (c) | DSU currently pays the Manager a monthly fee at an annual contractual investment advisory fee rate of 0.55% of the average daily value of DSU’s net assets, plus the proceeds of any outstanding debt securities or borrowings used for leverage (together, “average daily Managed Assets”). |
| (d) | DSU and the Manager have entered into a fee waiver agreement (the “Fee Waiver Agreement”), pursuant to which the Manager has contractually agreed to waive the investment advisory fees with respect to any portion of DSU’s assets attributable to investments in any equity and fixed-income mutual funds and exchange-traded funds (the “ETFs”) managed by the Manager or its affiliates that have a contractual management fee, through June 30, 2025. In addition, pursuant to the Fee Waiver Agreement, the Manager has contractually agreed to waive its investment advisory fees by the amount of investment advisory fees DSU pays to the Manager indirectly through its investment in money market funds managed by the Manager or its affiliates, through June 30, 2025. The Fee Waiver Agreement may be terminated at any time, without the payment of any penalty, only by DSU (upon the vote of a majority of the Directors who are not “interested persons” (as defined in the Investment Company Act of 1940, as amended (the “Investment Company Act”), of DSU (the “Independent Directors”)) or a majority of the outstanding voting securities of DSU), upon 90 days’ written notice by DSU to the Manager. |
| (e) | DSU uses leverage in the form of a credit facility, in an amount equal to approximately 22.7% of DSU’s Managed Assets at an annual interest expense to DSU of 5.91% which is based on current market conditions. The actual amount of interest expense borne by DSU will vary over time in accordance with the level of DSU’s use of leverage and variations in market interest rates. Interest expense is required to be treated as expense of DSU for accounting purposes. |
Management Fees [Percent] | [3],[4] |  |  |  |  |  |  |  |  | 0.70% |  |  |  |  |  |  |  |  |
Other Annual Expenses [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other Annual Expense 1 [Percent] |  |  |  |  |  |  |  |  |  | 0.09% |  |  |  |  |  |  |  |  |
Other Annual Expense 2 [Percent] | [5] |  |  |  |  |  |  |  |  | 1.68% |  |  |  |  |  |  |  |  |
Other Annual Expenses [Percent] |  |  |  |  |  |  |  |  |  | 1.77% |  |  |  |  |  |  |  |  |
Total Annual Expenses [Percent] |  |  |  |  |  |  |  |  |  | 2.47% |  |  |  |  |  |  |  |  |
Waivers and Reimbursements of Fees [Percent] | [3] |  |  |  |  |  |  |  |  | 0.00% |  |  |  |  |  |  |  |  |
Net Expense over Assets [Percent] | [3] |  |  |  |  |  |  |  |  | 2.47% |  |  |  |  |  |  |  |  |
Expense Example [Table Text Block] |  |  |  |  |  |  |  |  |  | The following example illustrates DSU’s expenses (including the sales load of $10.00 and offering costs of $0.47) that shareholders would pay on a $1,000 investment in common shares, assuming (i) total net annual expenses of 2.47% of net assets attributable to common shares and (ii) a 5% annual return:
|  |  | 1 Year |  |  |  | 3 Years |  |  |  | 5 Years |  |  |  | 10 Years |  |  |  |  |
Total expenses incurred |  |  | $ 35 |  |  |  | $  87 |  |  |  | $ 141 |  |  |  | $   288 |  |  |  |  |
Expense Example, Year 01 |  |  |  |  |  |  |  |  |  | $ 35 |  |  |  |  |  |  |  |  |
Expense Example, Years 1 to 3 |  |  |  |  |  |  |  |  |  | 87 |  |  |  |  |  |  |  |  |
Expense Example, Years 1 to 5 |  |  |  |  |  |  |  |  |  | 141 |  |  |  |  |  |  |  |  |
Expense Example, Years 1 to 10 |  |  |  |  |  |  |  |  |  | $ 288 |  |  |  |  |  |  |  |  |
Purpose of Fee Table , Note [Text Block] |  |  |  |  |  |  |  |  |  | The following table and example are intended to assist shareholders in understanding the various costs and expenses directly or indirectly associated with investing in DSU’s common shares. |  |  |  |  |  |  |  |  |
Basis of Transaction Fees, Note [Text Block] |  |  |  |  |  |  |  |  |  | as a percentage of offering price |  |  |  |  |  |  |  |  |
Other Transaction Fees, Note [Text Block] |  |  |  |  |  |  |  |  |  | Computershare Trust Company, N.A.’s (the “Reinvestment Plan Agent”) fees for the handling of the reinvestment of dividends will be paid by DSU. However, shareholders will pay a $0.02 per share fee incurred in connection with open-market purchases, which will be deducted from the value of the dividend. Shareholders will also be charged a $0.02 per share fee if a shareholder directs the Reinvestment Plan Agent to sell the common shares held in a dividend reinvestment account. Per share fees include any applicable brokerage commissions the Reinvestment Plan Agent is required to pay. |  |  |  |  |  |  |  |  |
Other Expenses, Note [Text Block] |  |  |  |  |  |  |  |  |  | The example should not be considered a representation of future expenses. The example assumes that the estimated “Other expenses” set forth in the Estimated Annual Expenses table are accurate and that all dividends and distributions are reinvested at NAV. Actual expenses may be greater or less than those assumed. DSU’s actual rate of return may be greater or less than the hypothetical 5% return shown in the example. |  |  |  |  |  |  |  |  |
Management Fee not based on Net Assets, Note [Text Block] |  |  |  |  |  |  |  |  |  | DSU and the Manager have entered into a fee waiver agreement (the “Fee Waiver Agreement”), pursuant to which the Manager has contractually agreed to waive the investment advisory fees with respect to any portion of DSU’s assets attributable to investments in any equity and fixed-income mutual funds and exchange-traded funds (the “ETFs”) managed by the Manager or its affiliates that have a contractual management fee, through June 30, 2025. In addition, pursuant to the Fee Waiver Agreement, the Manager has contractually agreed to waive its investment advisory fees by the amount of investment advisory fees DSU pays to the Manager indirectly through its investment in money market funds managed by the Manager or its affiliates, through June 30, 2025. The Fee Waiver Agreement may be terminated at any time, without the payment of any penalty, only by DSU (upon the vote of a majority of the Directors who are not “interested persons” (as defined in the Investment Company Act of 1940, as amended (the “Investment Company Act”), of DSU (the “Independent Directors”)) or a majority of the outstanding voting securities of DSU), upon 90 days’ written notice by DSU to the Manager. |  |  |  |  |  |  |  |  |
Financial Highlights [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Securities [Table Text Block] |  |  |  |  |  |  |  |  |  | The following table sets forth information regarding DSU’s outstanding senior securities as of the end of each of DSU’s last ten fiscal years, as applicable. DSU’s audited financial statements, including Deloitte & Touche LLP’s Report of Independent Registered Public Accounting Firm, and accompanying notes to financial statements, are included in this annual report.
DSU — Fiscal Year Ended |  |  | Total Amount Outstanding (000) |  |  |  | Asset Coverage | (a) |  |  | Liquidation Preference |  |  |  | Average Market Value (000) | (b) |  |  | Type of Senior Security |
December 31, 2023 |  | $ | 149,000 |  |  | $ | 4,405 |  |  | $ | N/A |  |  | $ | 137,195 |  |  |  | Bank Borrowings |
December 31, 2022 |  |  | 164,000 |  |  |  | 3,967 |  |  |  | N/A |  |  |  | 215,814 |  |  |  | Bank Borrowings |
December 31, 2021 |  |  | 248,000 |  |  |  | 3,172 |  |  |  | N/A |  |  |  | 239,134 |  |  |  | Bank Borrowings |
December 31, 2020 |  |  | 229,000 |  |  |  | 3,349 |  |  |  | N/A |  |  |  | 220,721 |  |  |  | Bank Borrowings |
December 31, 2019 |  |  | 262,000 |  |  |  | 3,310 |  |  |  | N/A |  |  |  | 264,317 |  |  |  | Bank Borrowings |
February 28, 2019 |  |  | 278,000 |  |  |  | 3,308 |  |  |  | N/A |  |  |  | 293,419 |  |  |  | Bank Borrowings |
February 28, 2018 |  |  | 338,000 |  |  |  | 3,196 |  |  |  | N/A |  |  |  | 348,104 |  |  |  | Bank Borrowings |
February 28, 2017 |  |  | 318,000 |  |  |  | 3,455 |  |  |  | N/A |  |  |  | 234,238 |  |  |  | Bank Borrowings |
February 29, 2016 |  |  | 190,000 |  |  |  | 4,733 |  |  |  | N/A |  |  |  | 254,199 |  |  |  | Bank Borrowings |
February 28, 2015 |  |  | 295,000 |  |  |  | 3,719 |  |  |  | N/A |  |  |  | 303,926 |  |  |  | Bank Borrowings |
| (a) | Calculated by subtracting the Fund’s total liabilities (not including bank borrowings) from the Fund’s total assets and dividing this by the amount of bank borrowings, and by multiplying the results by 1,000. |
| (b) | Represents the average daily amount outstanding for loans under the revolving credit agreements. |
Senior Securities Amount |  | $ 149,000 |  |  |  | $ 164,000 |  |  |  | $ 149,000 | $ 164,000 | $ 248,000 | $ 229,000 | $ 262,000 | $ 278,000 | $ 338,000 | $ 318,000 | $ 190,000 | $ 295,000
Senior Securities Coverage per Unit | [6] | $ 4,405 |  |  |  | $ 3,967 |  |  |  | $ 4,405 | $ 3,967 | $ 3,172 | $ 3,349 | $ 3,310 | $ 3,308 | $ 3,196 | $ 3,455 | $ 4,733 | $ 3,719
Preferred Stock Liquidating Preference |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Securities Average Market Value per Unit | [7] |  |  |  |  |  |  |  |  | $ 137,195 | $ 215,814 | $ 239,134 | $ 220,721 | $ 264,317 | $ 293,419 | $ 348,104 | $ 234,238 | $ 254,199 | $ 303,926
Senior Securities, Note [Text Block] |  |  |  |  |  |  |  |  |  | Senior Securities The following table sets forth information regarding DSU’s outstanding senior securities as of the end of each of DSU’s last ten fiscal years, as applicable. DSU’s audited financial statements, including Deloitte & Touche LLP’s Report of Independent Registered Public Accounting Firm, and accompanying notes to financial statements, are included in this annual report.
DSU — Fiscal Year Ended |  |  | Total Amount Outstanding (000) |  |  |  | Asset Coverage | (a) |  |  | Liquidation Preference |  |  |  | Average Market Value (000) | (b) |  |  | Type of Senior Security |
December 31, 2023 |  | $ | 149,000 |  |  | $ | 4,405 |  |  | $ | N/A |  |  | $ | 137,195 |  |  |  | Bank Borrowings |
December 31, 2022 |  |  | 164,000 |  |  |  | 3,967 |  |  |  | N/A |  |  |  | 215,814 |  |  |  | Bank Borrowings |
December 31, 2021 |  |  | 248,000 |  |  |  | 3,172 |  |  |  | N/A |  |  |  | 239,134 |  |  |  | Bank Borrowings |
December 31, 2020 |  |  | 229,000 |  |  |  | 3,349 |  |  |  | N/A |  |  |  | 220,721 |  |  |  | Bank Borrowings |
December 31, 2019 |  |  | 262,000 |  |  |  | 3,310 |  |  |  | N/A |  |  |  | 264,317 |  |  |  | Bank Borrowings |
February 28, 2019 |  |  | 278,000 |  |  |  | 3,308 |  |  |  | N/A |  |  |  | 293,419 |  |  |  | Bank Borrowings |
February 28, 2018 |  |  | 338,000 |  |  |  | 3,196 |  |  |  | N/A |  |  |  | 348,104 |  |  |  | Bank Borrowings |
February 28, 2017 |  |  | 318,000 |  |  |  | 3,455 |  |  |  | N/A |  |  |  | 234,238 |  |  |  | Bank Borrowings |
February 29, 2016 |  |  | 190,000 |  |  |  | 4,733 |  |  |  | N/A |  |  |  | 254,199 |  |  |  | Bank Borrowings |
February 28, 2015 |  |  | 295,000 |  |  |  | 3,719 |  |  |  | N/A |  |  |  | 303,926 |  |  |  | Bank Borrowings |
| (a) | Calculated by subtracting the Fund’s total liabilities (not including bank borrowings) from the Fund’s total assets and dividing this by the amount of bank borrowings, and by multiplying the results by 1,000. |
| (b) | Represents the average daily amount outstanding for loans under the revolving credit agreements. |
Senior Securities Headings, Note [Text Block] |  |  |  |  |  |  |  |  |  | The following table sets forth information regarding DSU’s outstanding senior securities as of the end of each of DSU’s last ten fiscal years, as applicable. DSU’s audited financial statements, including Deloitte & Touche LLP’s Report of Independent Registered Public Accounting Firm, and accompanying notes to financial statements, are included in this annual report. |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk Factors [Table Text Block] |  |  |  |  |  |  |  |  |  |
10. | PRINCIPAL RISKS
In the normal course of business, the Funds invest in securities or other instruments and may enter into certain transactions, and such activities subject each Fund to various risks, including among others, fluctuations in the market (market risk) or failure of an issuer to meet all of its obligations. The value of securities or other instruments may also be affected by various factors, including, without limitation: (i) the general economy; (ii) the overall market as well as local, regional or global political and/or social instability; (iii) regulation, taxation or international tax treaties between various countries; or (iv) currency, interest rate and price fluctuations. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues, recessions, or other events could have a significant impact on the Funds and their investments. Illiquidity Risk: Each Fund may invest without limitation in illiquid or less liquid investments or investments in which no secondary market is readily available or which are otherwise illiquid, including private placement securities. A Fund may not be able to readily dispose of such investments at prices that approximate those at which a Fund could sell such investments if they were more widely traded and, as a result of such illiquidity, a Fund may have to sell other investments or engage in borrowing transactions if necessary to raise funds to meet its obligations. Limited liquidity can also affect the market price of investments, thereby adversely affecting a Fund’s NAV and ability to make dividend distributions. Privately issued debt securities are often of below investment grade quality, frequently are unrated and present many of the same risks as investing in below investment grade public debt securities. Market Risk: Each Fund may be exposed to prepayment risk, which is the risk that borrowers may exercise their option to prepay principal earlier than scheduled during periods of declining interest rates, which would force each Fund to reinvest in lower yielding securities. Each Fund may also be exposed to reinvestment risk, which is the risk that income from each Fund’s portfolio will decline if each Fund invests the proceeds from matured, traded or called fixed-income securities at market interest rates that are below each Fund portfolio’s current earnings rate. Valuation Risk: The market values of equities, such as common stocks and preferred securities or equity related investments, such as futures and options, may decline due to general market conditions which are not specifically related to a particular company. They may also decline due to factors which affect a particular industry or industries. A Fund may invest in illiquid investments. An illiquid investment is any investment that a Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. A Fund may experience difficulty in selling illiquid investments in a timely manner at the price that it believes the investments are worth. Prices may fluctuate widely over short or extended periods in response to company, market or economic news. Markets also tend to move in cycles, with periods of rising and falling prices. This volatility may cause each Fund’s NAV to experience significant increases or decreases over short periods of time. If there is a general decline in the securities and other markets, the NAV of a Fund may lose value, regardless of the individual results of the securities and other instruments in which a Fund invests. The price a Fund could receive upon the sale of any particular portfolio investment may differ from a Fund’s valuation of the investment, particularly for securities that trade in thin or volatile markets or that are valued using a fair valuation technique or a price provided by an independent pricing service. Changes to significant unobservable inputs and assumptions (i.e., publicly traded company multiples, growth rate, time to exit) due to the lack of observable inputs may significantly impact the resulting fair value and therefore a Fund’s results of operations. As a result, the price received upon the sale of an investment may be less than the value ascribed by a Fund, and a Fund could realize a greater than expected loss or lesser than expected gain upon the sale of the investment. A Fund’s ability to value its investments may also be impacted by technological issues and/or errors by pricing services or other third-party service providers. Counterparty Credit Risk: The Funds may be exposed to counterparty credit risk, or the risk that an entity may fail to or be unable to perform on its commitments related to unsettled or open transactions, including making timely interest and/or principal payments or otherwise honoring its obligations. The Funds manage counterparty credit risk by entering into transactions only with counterparties that the Manager believes have the financial resources to honor their obligations and by monitoring the financial stability of those counterparties. Financial assets, which potentially expose the Funds to market, issuer and counterparty credit risks, consist principally of financial instruments and receivables due from counterparties. The extent of the Funds’ exposure to market, issuer and counterparty credit risks with respect to these financial assets is approximately their value recorded in the Statements of Assets and Liabilities, less any collateral held by the Funds. A derivative contract may suffer a mark-to-market loss if the value of the contract decreases due to an unfavorable change in the market rates or values of the underlying instrument. Losses can also occur if the counterparty does not perform under the contract. For OTC options purchased, each Fund bears the risk of loss in the amount of the premiums paid plus the positive change in market values net of any collateral held by the Funds should the counterparty fail to perform under the contracts. Options written by the Funds do not typically give rise to counterparty credit risk, as options written generally obligate the Funds, and not the counterparty, to perform. The Funds may be exposed to counterparty credit risk with respect to options written to the extent each Fund deposits collateral with its counterparty to a written option. With exchange-traded options purchased, exchange-traded futures and centrally cleared swaps, there is less counterparty credit risk to the Funds since the exchange or clearinghouse, as counterparty to such instruments, guarantees against a possible default. The clearinghouse stands between the buyer and the seller of the contract; therefore, credit risk is limited to failure of the clearinghouse. While offset rights may exist under applicable law, a Fund does not have a contractual right of offset against a clearing broker or clearinghouse in the event of a default (including the bankruptcy or insolvency). Additionally, credit risk exists in exchange-traded futures and centrally cleared swaps with respect to initial and variation margin that is held in a clearing broker’s customer accounts. While clearing brokers are required to segregate customer margin from their own assets, in the event that a clearing broker becomes insolvent or goes into bankruptcy and at that time there is a shortfall in the aggregate amount of margin held by the clearing broker for all its clients, typically the shortfall would be allocated on a pro rata basis across all the clearing broker’s customers, potentially resulting in losses to the Funds. Geographic/Asset Class Risk: A diversified portfolio, where this is appropriate and consistent with a fund’s objectives, minimizes the risk that a price change of a particular investment will have a material impact on the NAV of a fund. The investment concentrations within each Fund’s portfolio are disclosed in its Schedule of Investments. Certain Funds invest a significant portion of their assets in high yield securities. High yield securities that are rated below investment-grade (commonly referred to as “junk bonds”) or are unrated may be deemed speculative, involve greater levels of risk than higher-rated securities of similar maturity and are more likely to default. High yield securities may be issued by less creditworthy issuers, and issuers of high yield securities may be unable to meet their interest or principal payment obligations. High yield securities are subject to extreme price fluctuations, may be less liquid than higher rated fixed-income securities, even under normal economic conditions, and frequently have redemption features. The Funds invest a significant portion of their assets in fixed-income securities and/or use derivatives tied to the fixed-income markets. Changes in market interest rates or economic conditions may affect the value and/or liquidity of such investments. Interest rate risk is the risk that prices of bonds and other fixed-income securities will decrease as interest rates rise and increase as interest rates fall. The Funds may be subject to a greater risk of rising interest rates due to the period of historically low interest rates that ended in March 2022. The Federal Reserve has recently been raising the federal funds rate as part of its efforts to address inflation. There is a risk that interest rates will continue to rise, which will likely drive down the prices of bonds and other fixed-income securities, and could negatively impact the Funds’ performance. The Funds invest a significant portion of their assets in securities of issuers located in the United States. A decrease in imports or exports, changes in trade regulations, inflation and/or an economic recession in the United States may have a material adverse effect on the U.S. economy and the securities listed on U.S. exchanges. Proposed and adopted policy and legislative changes in the United States may also have a significant effect on U.S. markets generally, as well as on the value of certain securities. Governmental agencies project that the United States will continue to maintain elevated public debt levels for the foreseeable future which may constrain future economic growth. Circumstances could arise that could prevent the timely payment of interest or principal on U.S. government debt, such as reaching the legislative “debt ceiling.” Such non-payment would result in substantial negative consequences for the U.S. economy and the global financial system. If U.S. relations with certain countries deteriorate, it could adversely affect issuers that rely on the United States for trade. The United States has also experienced increased internal unrest and discord. If these trends were to continue, they may have an adverse impact on the U.S. economy and the issuers in which the Funds invest. Certain Funds invest a significant portion of their assets in securities backed by commercial or residential mortgage loans or in issuers that hold mortgage and other asset-backed securities. When a fund concentrates its investments in this manner, it assumes a greater risk of prepayment or payment extension by securities issuers. Changes in economic conditions, including delinquencies and/or defaults on assets underlying these securities, can affect the value, income and/or liquidity of such positions. Investment percentages in these securities are presented in the Schedules of Investments. LIBOR Transition Risk : The Funds may be exposed to financial instruments that recently transitioned from, or continue to be tied to, the London Interbank Offered Rate (“LIBOR”) to determine payment obligations, financing terms, hedging strategies or investment value. The United Kingdom’s Financial Conduct Authority, which regulates LIBOR, has ceased publishing all LIBOR settings, but some USD LIBOR settings will continue to be published under a synthetic methodology until September 30, 2024 for certain legacy contracts. SOFR has been used increasingly on a voluntary basis in new instruments and transactions. Under U.S. regulations that implement a statutory fallback mechanism to replace LIBOR, benchmark rates based on SOFR have replaced LIBOR in certain financial contracts. The ultimate effect of the LIBOR transition process on the Funds is uncertain. Risk Factors This section contains a discussion of the general risks of investing in each Fund. The net asset value and market price of, and dividends paid on, the common shares will fluctuate with and be affected by, among other things, the risks more fully described below. As with any fund, there can be no guarantee that a Fund will meet its investment objective or that the Fund’s performance will be positive for any period of time. Each risk noted below is applicable to each Fund unless the specific Fund or Funds are noted in a parenthetical. The order of the below risk factors does not indicate the significance of any particular risk. Investment and Market Discount Risk: An investment in the Fund’s common shares is subject to investment risk, including the possible loss of the entire amount that you invest. As with any stock, the price of the Fund’s common shares will fluctuate with market conditions and other factors. If shares are sold, the price received may be more or less than the original investment. Common shares are designed for long-term investors and the Fund should not be treated as a trading vehicle. Shares of closed-end management investment companies frequently trade at a discount from their net asset value. This risk is separate and distinct from the risk that the Fund’s net asset value could decrease as a result of its investment activities. At any point in time an investment in the Fund’s common shares may be worth less than the original amount invested, even after taking into account distributions paid by the Fund. During periods in which the Fund may use leverage, the Fund’s investment, market discount and certain other risks will be magnified. Concentration Risk (BIT): The Fund’s strategy of concentrating in mortgage related securities means that its performance will be closely tied to the performance of a particular market segment. The Fund’s concentration in these securities may present more risks than if it were broadly diversified over numerous industries and sectors of the economy. A downturn in these securities would have a larger impact on the Fund than on a mutual fund that does not concentrate in such securities. At times, the performance of these securities will lag the performance of other industries or the broader market as a whole. Debt Securities Risk: Debt securities, such as bonds, involve interest rate risk, such as credit risk, interest rate risk, extension risk, and prepayment risk, each of which are described in further detail below:
| • |  | Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.
| • |  | Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise.
The Fund may be subject to a greater risk of rising interest rates due to the recent period of historically low interest rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. (Duration is a measure of the price sensitivity of a debt security or portfolio of debt securities to relative changes in interest rates.) The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management. To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities. These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change. A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
| • |  | Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
| • |  | Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.
U.S. Government Obligations Risk: Certain securities in which the Fund may invest, including securities issued by certain U.S. Government agencies and U.S. Government sponsored enterprises, are not guaranteed by the U.S. Government or supported by the full faith and credit of the United States. In addition, circumstances could arise that could prevent the timely payment of interest or principal on U.S. Government obligations, such as reaching the legislative “debt ceiling.” Such non-payment could result in losses to the Fund and substantial negative consequences for the U.S. economy and the global financial system. U.S. Government Mortgage-Related Securities Risk (FRA, BKT and BLW): There are a number of important differences among the agencies and instrumentalities of the U.S. Government that issue mortgage-related securities and among the securities that they issue. Mortgage-related securities guaranteed by the Government National Mortgage Association (“GNMA” or “Ginnie Mae”) are guaranteed as to the timely payment of principal and interest by GNMA and such guarantee is backed by the full faith and credit of the United States. GNMA securities also are supported by the right of GNMA to borrow funds from the U.S. Treasury to make payments under its guarantee. Mortgage-related securities issued by Fannie Mae or Freddie Mac are solely the obligations of Fannie Mae or Freddie Mac, as the case may be, and are not backed by or entitled to the full faith and credit of the United States but are supported by the right of the issuer to borrow from the Treasury. Mortgage- and Asset-Backed Securities Risks (FRA, BKT, BLW and BIT): Mortgage- and asset-backed securities represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. Mortgage- and asset-backed securities are subject to credit, interest rate, prepayment and extension risks. These securities also are subject to risk of default on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities. Senior Loans Risk (DSU, FRA, BLW and BIT): There is less readily available, reliable information about most senior loans than is the case for many other types of securities. An economic downturn generally leads to a higher non-payment rate, and a senior loan may lose significant value before a default occurs. Moreover, any specific collateral used to secure a senior loan may decline in value or become illiquid, which would adversely affect the senior loan’s value. No active trading market may exist for certain senior loans, which may impair the ability of the Fund to realize full value in the event of the need to sell a senior loan and which may make it difficult to value senior loans. Although senior loans in which the Fund will invest generally will be secured by specific collateral, there can be no assurance that liquidation of such collateral would satisfy the borrower’s obligation in the event of non-payment of scheduled interest or principal or that such collateral could be readily liquidated. To the extent that a senior loan is collateralized by stock in the borrower or its subsidiaries, such stock may lose all of its value in the event of the bankruptcy of the borrower. Uncollateralized senior loans involve a greater risk of loss. Second Lien Loans Risk (BIT): Second lien loans generally are subject to similar risks as those associated with investments in senior loans. Because second lien loans are subordinated or unsecured and thus lower in priority of payment to senior loans, they are subject to the additional risk that the cash flow of the borrower and property securing the loan or debt, if any, may be insufficient to meet scheduled payments after giving effect to the senior secured obligations of the borrower. CLO Risk (BIT and FRA): In addition to the general risks associated with fixed-income securities discussed herein, CLOs carry additional risks, including: (i) the possibility that distributions from collateral securities will not be adequate to make interest or other payments; (ii) the quality of the collateral may decline in value or default; (iii) the possibility that the CLO securities are subordinate to other classes; and (iv) the complex structure of the security may not be fully understood at the time of investment and may produce disputes with the issuer or unexpected investment results. The credit quality of CLOs depends primarily upon the quality of the underlying assets and the level of credit support and/or enhancement provided. The underlying assets (e.g., loans) of CLOs are subject to prepayments, which shorten the weighted average maturity and may lower the return of the securities issued by the CLOs. The value of CLO securities also may change because of changes in the market’s perception of the creditworthiness of the servicing agent for the pool, the originator of the pool, or the financial institution or fund providing the credit support or enhancement. Furthermore, the leveraged nature of each subordinated class may magnify the adverse impact on such class of changes in the value of the assets, changes in the distributions on the assets, defaults and recoveries on the assets, capital gains and losses on the assets, prepayment on assets and availability, price and interest rates of assets. CLOs are typically privately offered and sold, and thus are not registered under the securities laws. Additionally, when the Fund purchases a newly issued CLO security in the primary market (rather than from the secondary market), there often may be a delayed settlement period. As a result, investments in CLOs may be characterized by the Fund as illiquid securities; however, an active dealer market may exist which would allow such securities to be considered liquid in some circumstances. Finally, CLOs are limited recourse and may not be paid in full and may be subject to up to 100% loss. Risks of Loan Assignments and Participations (BLW): As the purchaser of an assignment, the Fund typically succeeds to all the rights and obligations of the assigning institution and becomes a lender under the credit agreement with respect to the debt obligation; however, the Fund may not be able unilaterally to enforce all rights and remedies under the loan and with regard to any associated collateral. Because assignments may be arranged through private negotiations between potential assignees and potential assignors, the rights and obligations acquired by the Fund as the purchaser of an assignment may differ from, and be more limited than, those held by the assigning lender. In addition, if the loan is foreclosed, the Fund could become part owner of any collateral and could bear the costs and liabilities of owning and disposing of the collateral. The Fund may be required to pass along to a purchaser that buys a loan from the Fund by way of assignment a portion of any fees to which the Fund is entitled under the loan. In connection with purchasing participations, the Fund generally will have no right to enforce compliance by the borrower with the terms of the loan agreement relating to the loan, nor any rights of set-off against the borrower, and the Fund may not directly benefit from any collateral supporting the loan in which it has purchased the participation. As a result, the Fund will be subject to the credit risk of both the borrower and the lender that is selling the participation. In the event of the insolvency of the lender selling a participation, the Fund may be treated as a general creditor of the lender and may not benefit from any set-off between the lender and the borrower. Corporate Loans Risk (DSU): Commercial banks and other financial institutions or institutional investors make corporate loans to companies that need capital to grow or restructure. Borrowers generally pay interest on corporate loans at rates that change in response to changes in market interest rates such as the Secured Overnight Financing Rate (“SOFR”), the London Interbank Offered Rate (“LIBOR”) or the prime rates of U.S. banks. As a result, the value of corporate loan investments is generally less exposed to the adverse effects of shifts in market interest rates than investments that pay a fixed rate of interest. The market for corporate loans may be subject to irregular trading activity and wide bid/ask spreads. In addition, transactions in corporate loans may settle on a delayed basis. As a result, the proceeds from the sale of corporate loans may not be readily available to make additional investments or to meet the Fund’s redemption obligations. To the extent the extended settlement process gives rise to short-term liquidity needs, the Fund may hold additional cash, sell investments or temporarily borrow from banks and other lenders. The corporate loans in which the Fund invests are usually rated below investment grade. Variable and Floating Rate Instrument Risk (DSU, FRA and BLW): Variable and floating rate securities provide for periodic adjustment in the interest rate paid on the securities. These securities may be subject to greater illiquidity risk than other fixed income securities, meaning the absence of an active market for these securities could make it difficult for the Fund to dispose of them at any given time. Unrated Securities Risk (BIT): Because the Fund may purchase securities that are not rated by any rating organization, the Managers may, after assessing their credit quality, internally assign ratings to certain of those securities in categories similar to those of rating organizations. 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 Managers’ credit analysis than would be the case when the Fund invests in rated securities. High Yield Bonds Risk (DSU, FRA, BLW and BIT): Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that are considered speculative and may cause income and principal losses for the Fund. Distressed Securities Risk (DSU and FRA): Distressed securities are speculative and involve substantial risks in addition to the risks of investing in junk bonds. The Fund will generally not receive interest payments on the distressed securities and may incur costs to protect its investment. In addition, distressed securities involve the substantial risk that principal will not be repaid. These securities may present a substantial risk of default or may be in default at the time of investment. The Fund may incur additional expenses to the extent it is required to seek recovery upon a default in the payment of principal of or interest on its portfolio holdings. In any reorganization or liquidation proceeding relating to a portfolio company, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Distressed securities and any securities received in an exchange for such securities may be subject to restrictions on resale. Collateralized Bond Obligations Risk (BLW): The pool of high yield securities underlying collateralized bond obligations is typically separated into groupings called tranches representing different degrees of credit quality. The higher quality tranches have greater degrees of protection and pay lower interest rates. The lower tranches, with greater risk, pay higher interest rates. Collateralized Debt Obligations Risk (FRA): In addition to the typical risks associated with fixed-income securities and asset-backed securities, collateralized debt obligations (“CDOs”), including collateralized loan obligations, carry additional risks including, but not limited to: (i) the possibility that distributions from collateral securities will not be adequate to make interest or other payments; (ii) the risk that the collateral may default or decline in value or be downgraded, if rated by a nationally recognized statistical rating organization; (iii) the Fund may invest in tranches of CDOs that are subordinate to other tranches; (iv) the structure and complexity of the transaction and the legal documents could lead to disputes among investors regarding the characterization of proceeds; (v) the investment return achieved by the Fund could be significantly different than those predicted by financial models; (vi) the lack of a readily available secondary market for CDOs; (vii) the risk of forced “fire sale” liquidation due to technical defaults such as coverage test failures; and (viii) the CDO’s manager may perform poorly. Sovereign Debt Risk (FRA, BLW and BIT): Sovereign debt instruments are subject to the risk that a governmental entity may delay or refuse to pay interest or repay principal on its sovereign debt, due, for example, to cash flow problems, insufficient foreign currency reserves, political considerations, the relative size of the governmental entity’s debt position in relation to the economy or the failure to put in place economic reforms required by the International Monetary Fund or other multilateral agencies. Municipal Securities Risks (BIT): Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. Budgetary constraints of local, state, and federal governments upon which the issuers may be relying for funding may also impact municipal securities. These risks include:
| • |  | General Obligation Bonds Risks — Timely payments depend on the issuer’s credit quality, ability to raise tax revenues and ability to maintain an adequate tax base.
| • |  | Revenue Bonds Risks — These payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source.
| • |  | Private Activity Bonds Risks — Municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise. The private enterprise pays the principal and interest on the bond, and the issuer does not pledge its full faith, credit and taxing power for repayment. The Fund’s investments may consist of private activity bonds that may subject certain shareholders to an alternative minimum tax.
| • |  | Moral Obligation Bonds Risks — 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.
| • |  | Municipal Notes Risks — Municipal notes are shorter term municipal debt obligations. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money.
| • |  | Municipal Lease Obligations Risks — In a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property.
| • |  | Tax-Exempt Status Risk — The Fund and its investment manager will rely on the opinion of issuers’ bond counsel and, in the case of derivative securities, sponsors’ counsel, on the tax-exempt status of interest on municipal bonds and payments under derivative securities. Neither the Fund nor its investment manager will independently review the bases for those tax opinions, which may ultimately be determined to be incorrect and subject the Fund and its shareholders to substantial tax liabilities.
Brady Bonds Ris k (BLW): Brady Bonds involve various risk factors described above associated with investing in non-U.S. securities, including the history of defaults with respect to commercial bank loans by public and private entities of countries issuing Brady Bonds. Supranational Entities Risk (BLW): The Fund may invest in obligations issued or guaranteed by the World Bank. The government members, or “stockholders,” usually make initial capital contributions to the World Bank and in many cases are committed to make additional capital contributions if the World Bank is unable to repay its borrowings. There is no guarantee that one or more stockholders of the World Bank will continue to make any necessary additional capital contributions. If such contributions are not made, the entity may be unable to pay interest or repay principal on its debt securities, and the Fund may lose money on such investments. Yield and Ratings Risk (BKT) : The yields on debt obligations are dependent on a variety of factors, including general market conditions, conditions in the particular market for the obligation, the financial condition of the issuer, the size of the offering, the maturity of the obligation and the ratings of the issue. The ratings of Moody’s, S&P and Fitch, represent their respective opinions as to the quality of the obligations they undertake to rate. Ratings, however, are general and are not absolute standards of quality. Consequently, obligations with the same rating, maturity and interest rate may have different market prices. Subsequent to its purchase by the Fund, a rated security may cease to be rated. The Manager will consider such an event in determining whether the Fund should continue to hold the security. Repurchase Agreements and Purchase and Sale Contracts Risk (BKT and BIT) : If the other party to a repurchase agreement or purchase and sale contract defaults on its obligation under the agreement, the Fund may suffer delays and incur costs or lose money in exercising its rights under the agreement. If the seller fails to repurchase the security in either situation and the market value of the security declines, the Fund may lose money. Foreign Securities Risk (DSU, FRA, BLW and BIT): Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include:
| • |  | The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight.
| • |  | Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio.
| • |  | The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position.
| • |  | The governments of certain countries, or the U.S. Government with respect to certain countries, may prohibit or impose substantial restrictions through capital controls and/or sanctions on foreign investments in the capital markets or certain industries in those countries, which may prohibit or restrict the ability to own or transfer currency, securities, derivatives or other assets.
| • |  | Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws.
| • |  | Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments.
| • |  | The Fund’s claims to recover foreign withholding taxes may not be successful, and if the likelihood of recovery of foreign withholding taxes materially decreases, due to, for example, a change in tax regulation or approach in the foreign country, accruals in the Fund’s net asset value for such refunds may be written down partially or in full, which will adversely affect the Fund’s net asset value.
Emerging Markets Risk (FRA, BLW and BIT): Emerging markets are riskier than more developed markets because they tend to develop unevenly and may never fully develop. Investments in emerging markets may be considered speculative. Emerging markets are more likely to experience hyperinflation and currency devaluations, which adversely affect returns to U.S. investors. In addition, many emerging securities markets have far lower trading volumes and less liquidity than developed markets. Equity Securities Risk (DSU, FRA, BLW and BIT): Stock markets are volatile. The price of equity securities fluctuates based on changes in a company’s financial condition and overall market and economic conditions. Small and Mid-Capitalization Company Risk (BIT): Companies with small or mid-size market capitalizations will normally have more limited product lines, markets and financial resources and will be dependent upon a more limited management group than larger capitalized companies. In addition, it is more difficult to get information on smaller companies, which tend to be less well known, have shorter operating histories, do not have significant ownership by large investors and are followed by relatively few securities analysts. Preferred Securities Risk (DSU, FRA, BLW and BIT): Preferred securities may pay fixed or adjustable rates of return. Preferred securities are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred securities generally pay dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred securities will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. Preferred securities of smaller companies may be more vulnerable to adverse developments than preferred securities of larger companies. Convertible Securities Risk (DSU, FRA and BIT): The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest, principal or dividends when due, and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock, including the potential for increased volatility in the price of the convertible security. Warrants Risk (DSU and FRA): If the price of the underlying stock does not rise above the exercise price before the warrant expires, the warrant generally expires without any value and the Fund will lose any amount it paid for the warrant. Thus, investments in warrants may involve substantially more risk than investments in common stock. Warrants may trade in the same markets as their underlying stock; however, the price of the warrant does not necessarily move with the price of the underlying stock. Real Estate-Related Securities Risk (BLW): The main risk of real estate-related securities is that the value of the underlying real estate may go down. Many factors may affect real estate values. These factors include both the general and local economies, vacancy rates, changes in rent schedules, tenant bankruptcies, the ability to re-lease space under expiring leases on attractive terms, the amount of new construction in a particular area, the laws and regulations (including zoning, environmental and tax laws) affecting real estate and the costs of owning, maintaining and improving real estate. The availability of mortgage financing and changes in interest rates may also affect real estate values. If the Fund’s real estate-related investments are concentrated in one geographic area or in one property type, the Fund will be particularly subject to the risks associated with that area or property type. Many issuers of real estate-related securities are highly leveraged, which increases the risk to holders of such securities. The value of the securities the Fund buys will not necessarily track the value of the underlying investments of the issuers of such securities. In addition, certain issuers of real estate-related securities may have developed or commenced development on properties and may develop additional properties in the future. Real estate development involves significant risks in addition to those involved in the ownership and operation of established properties. Real estate securities may have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers or tenants. REIT Investment Risk (BLW and BIT): Investments in REITs involve unique risks. REITs may have limited financial resources, may trade less frequently and in limited volume, may engage in dilutive offerings of securities and may be more volatile than other securities. REIT issuers may also fail to maintain their exemptions from investment company registration or fail to qualify for the “dividends paid deduction” under the Internal Revenue Code of 1986, as amended, which allows REITs to reduce their corporate taxable income for dividends paid to their shareholders. Structured Securities Risk (BIT): Because structured securities of the type in which the Fund may invest typically involve no credit enhancement, their credit risk generally will be equivalent to that of the underlying instruments, index or reference obligation and will also be subject to counterparty risk. The Fund may have the right to receive payments only from the structured security, and generally does not have direct rights against the issuer or the entity that sold the assets to be securitized. In addition to the general risks associated with debt securities discussed herein, structured securities carry additional risks, including, but not limited to: the possibility that distributions from collateral securities will not be adequate to make interest or other payments; the quality of the collateral may decline in value or default; and the possibility that the structured securities are subordinate to other classes. The Fund is permitted to invest in a class of structured securities that is either subordinated or unsubordinated to the right of payment of another class. Subordinated structured securities typically have higher yields and present greater risks than unsubordinated structured securities. Structured securities are typically sold in private placement transactions, and there currently is no active trading market for structured securities. Structured securities are based upon the movement of one or more factors, including currency exchange rates, interest rates, reference bonds and stock indices, and changes in interest rates and impact of these factors may cause significant price fluctuations. Additionally, changes in the reference instrument or security may cause the interest rate on the structured security to be reduced to zero. Certain issuers of such structured securities may be deemed to be “investment companies” as defined in the Investment Company Act. As a result, the Fund’s investment in such securities may be limited by certain investment restrictions contained in the Investment Company Act. Derivatives Risk: The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:
| • |  | Leverage Risk — The Fund’s use of derivatives can magnify the Fund’s gains and losses. Relatively small market movements may result in large changes in the value of a derivatives position and can result in losses that greatly exceed the amount originally invested.
| • |  | Market Risk — Some derivatives are more sensitive to interest rate changes and market price fluctuations than other securities. The Fund could also suffer losses related to its derivatives positions as a result of unanticipated market movements, which losses are potentially unlimited. Finally, the Manager may not be able to predict correctly the direction of securities prices, interest rates and other economic factors, which could cause the Fund’s derivatives positions to lose value.
| • |  | Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will be unable or unwilling to fulfill its contractual obligation, and the related risks of having concentrated exposure to such a counterparty.
| • |  | Illiquidity Risk — The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately.
| • |  | Operational Risk — The use of derivatives includes the risk of potential operational issues, including documentation issues, settlement issues, systems failures, inadequate controls and human error.
| • |  | Legal Risk — The risk of insufficient documentation, insufficient capacity or authority of counterparty, or legality or enforceability of a contract.
| • |  | Volatility and Correlation Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.
| • |  | Valuation Risk — Valuation for derivatives may not be readily available in the market. Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them.
| • |  | Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences.
| • |  | Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments.
Structured Notes Risk (FRA): Structured notes and other related instruments purchased by the Fund are generally privately negotiated debt obligations where the principal and/or interest is determined by reference to the performance of a specific asset, benchmark asset, market or interest rate (“reference measure”). The purchase of structured notes exposes the Fund to the credit risk of the issuer of the structured product. Structured notes may be leveraged, increasing the volatility of each structured note’s value relative to the change in the reference measure. Structured notes may also be less liquid and more difficult to price accurately than less complex securities and instruments or more traditional debt securities. Leverage Risk: The Fund’s use of leverage may increase or decrease from time to time in its discretion and the Fund may, in the future, determine not to use leverage. The use of leverage creates an opportunity for increased common share net investment income dividends, but also creates risks for the holders of common shares. The Fund cannot assure you that the use of leverage will result in a higher yield on the common shares. Any leveraging strategy the Fund employs may not be successful. Leverage involves risks and special considerations for common shareholders, including:
| • |  | the likelihood of greater volatility of net asset value, market price and dividend rate of the common shares than a comparable portfolio without leverage;
| • |  | the risk that fluctuations in interest rates or dividend rates on any leverage that the Fund must pay will reduce the return to the common shareholders;
| • |  | the effect of leverage in a declining market, which is likely to cause a greater decline in the net asset value of the common shares than if the Fund were not leveraged, which may result in a greater decline in the market price of the common shares;
| • |  | leverage may increase operating costs, which may reduce total return.
| • |  | Any decline in the net asset value of the Fund’s investments will be borne entirely by the holders of common shares. Therefore, if the market value of the Fund’s portfolio declines, leverage will result in a greater decrease in net asset value to the holders of common shares than if the Fund were not leveraged. This greater net asset value decrease will also tend to cause a greater decline in the market price for the common shares.
Reverse Repurchase Agreements Risk: Reverse repurchase agreements involve the sale of securities held by the Fund with an agreement to repurchase the securities at an agreed-upon price, date and interest payment. Reverse repurchase agreements involve the risk that the other party may fail to return the securities in a timely manner or at all. The Fund could lose money if it is unable to recover the securities and the value of the collateral held by the Fund, including the value of the investments made with cash collateral, is less than the value of the securities. These events could also trigger adverse tax consequences for the Fund. In addition, reverse repurchase agreements involve the risk that the interest income earned in the investment of the proceeds will be less than the interest expense. Dollar Rolls Risk (BLW and BIT): Dollar rolls involve the risk that the market value of the securities that the Fund is committed to buy may decline below the price of the securities the Fund has sold. These transactions may involve leverage. Short Sales Risk (DSU and BIT): Because making short sales in securities that it does not own exposes the Fund to the risks associated with those securities, such short sales involve speculative exposure risk. The Fund will incur a loss as a result of a short sale if the price of the security increases between the date of the short sale and the date on which the Fund replaces the security sold short. Illiquid Investments Risk: The Fund may invest without limitation in illiquid or less liquid investments or investments in which no secondary market is readily available or which are otherwise illiquid, including private placement securities. 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 net asset value and ability to make dividend distributions. The financial markets in general, and certain segments of the mortgage-related securities markets in particular, 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. Privately issued debt securities are often of below investment grade quality, frequently are unrated and present many of the same risks as investing in below investment grade public debt securities. Inverse Floater and Related Securities Risk (BIT): Investments in inverse floaters, residual interest tender option bonds and similar instruments expose the Fund to the same risks as investments in fixed-income securities and derivatives, as well as other risks, including those associated with leverage and increased volatility. An investment in these securities typically will involve greater risk than an investment in a fixed rate security. Distributions on inverse floaters, residual interest tender option bonds and similar instruments will typically bear an inverse relationship to short term interest rates and typically will be reduced or, potentially, eliminated as interest rates rise. Inverse floaters, residual interest tender option bonds and similar instruments will underperform the market for fixed rate securities in a rising interest rate environment. Inverse floaters may be considered to be leveraged to the extent that their interest rates vary by a magnitude that exceeds the magnitude of the change in a reference rate of interest (typically a short term interest rate). The leverage inherent in inverse floaters is associated with greater volatility in their market values. Investments in inverse floaters, residual interest tender option bonds and similar instruments that have fixed-income securities underlying them will expose the Fund to the risks associated with those fixed-income securities and the values of those investments may be especially sensitive to changes in prepayment rates on the underlying fixed-income securities. Investment Companies and ETFs Risk (DSU, BLW and BIT): Subject to the limitations set forth in the Investment Company Act and the rules thereunder, the Fund may acquire shares in other investment companies and in ETFs, some of which may be affiliated investment companies. The market value of the shares of other investment companies and ETFs may differ from their net asset value. As an investor in investment companies and ETFs, the Fund would bear its ratable share of that entity’s expenses, including its investment advisory and administration fees, while continuing to pay its own advisory and administration fees and other expenses (to the extent not offset by the Manager through waivers). As a result, shareholders will be absorbing duplicate levels of fees with respect to investments in other investment companies and ETFs (to the extent not offset by the Manager through waivers). The securities of other investment companies and ETFs in which the Fund may invest may be leveraged. As a result, the Fund may be indirectly exposed to leverage through an investment in such securities. An investment in securities of other investment companies and ETFs that use leverage may expose the Fund to higher volatility in the market value of such securities and the possibility that the Fund’s long-term returns on such securities (and, indirectly, the long-term returns of shares of the Fund) will be diminished. As with other investments, investments in other investment companies, including ETFs, are subject to market and selection risk. To the extent the Fund is held by an affiliated fund, the ability of the Fund itself to hold other investment companies may be limited. Risk of Investing in the United States: Certain changes in the U.S. economy, such as when the U.S. economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Fund has exposure. Market Risk and Selection Risk: Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. The value of a security or other asset may decline due to changes in general market conditions, economic trends or events that are not specifically related to the issuer of the security or other asset, or factors that affect a particular issuer or issuers, exchange, country, group of countries, region, market, industry, group of industries, sector or asset class. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues like pandemics or epidemics, recessions, or other events could have a significant impact on the Fund and its investments. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money. An outbreak of an infectious coronavirus (COVID-19) that was first developed into a global pandemic that has resulted in numerous disruptions in the market and has had significant economic impact leaving general concern and uncertainty. Although vaccines have been developed and approved for use by various governments, the duration of the pandemic and its effects cannot be predicted with certainty. The impact of this coronavirus, and other epidemics and pandemics that may arise in the future, could affect the economies of many nations, individual companies and the market in general ways that cannot necessarily be foreseen at the present time. Shareholder Activism Risk: Shareholder activism involving closed-end funds has recently been increasing. Shareholder activism can take many forms, including engaging in public campaigns to demand that the Fund consider significant transactions such as a tender offer, merger or liquidation or to attempt to influence the Fund’s corporate governance and/or management, commencing proxy contests to attempt to elect the activists’ representatives or others to the Fund’s Board of Directors, or to seek other actions such as a termination of the Fund’s investment advisory contract with its current investment manager or commencing litigation. If the Fund becomes the subject of shareholder activism, then management and the Board may be required to divert significant resources and attention to respond to the activist and the Fund may incur substantial costs defending against such activism if management and the Board determine that the activist’s demands are not in the best interest of the Fund. Further, the Fund’s share price could be subject to significant fluctuation or otherwise be adversely affected by the events, risks and uncertainties of any shareholder activism. |  |  |  |  |  |  |  |  |
Share Price [Table Text Block] |  |  |  |  |  |  |  |  |  | The following tables summarize each Fund’s highest and lowest daily closing market prices on the NYSE per common share, the NAV per common share, and the premium to or discount from NAV, on the date of each of the high and low market prices. The trading volume indicates the number of common shares traded on the NYSE during the respective quarters.
|  | NYSE Market Price Per Common Share |  |  | NAV per Common Share on Date of Market Price |  |  | Premium/ (Discount) on Date of Market Price |  |  |  |
DSU — During Quarter Ended |  | High |  |  | Low |  |  | High |  |  | Low |  |  | High |  |  | Low |  |  | Trading Volume |
December 31, 2023 |  | $ | 10.85 |  |  | $ | 9.78 |  |  | $ | 10.87 |  |  | $ | 10.61 |  |  |  | (0.18 | )% |  |  | (7.82 | )% |  |  | 9,476,571 |
September 30, 2023 |  |  | 10.36 |  |  |  | 9.81 |  |  |  | 10.84 |  |  |  | 10.76 |  |  |  | (4.43 | ) |  |  | (8.83 | ) |  |  | 8,558,668 |
June 30, 2023 |  |  | 9.79 |  |  |  | 9.25 |  |  |  | 10.72 |  |  |  | 10.51 |  |  |  | (8.68 | ) |  |  | (11.99 | ) |  |  | 8,742,409 |
March 31, 2023 |  |  | 9.96 |  |  |  | 9.25 |  |  |  | 10.79 |  |  |  | 10.48 |  |  |  | (7.69 | ) |  |  | (11.74 | ) |  |  | 8,395,438 |
December 31, 2022 |  |  | 9.77 |  |  |  | 8.80 |  |  |  | 10.48 |  |  |  | 10.24 |  |  |  | (6.77 | ) |  |  | (14.06 | ) |  |  | 9,860,686 |
September 30, 2022 |  |  | 10.15 |  |  |  | 8.83 |  |  |  | 10.84 |  |  |  | 10.27 |  |  |  | (6.37 | ) |  |  | (14.02 | ) |  |  | 6,897,776 |
June 30, 2022 |  |  | 10.52 |  |  |  | 8.59 |  |  |  | 11.34 |  |  |  | 10.40 |  |  |  | (7.23 | ) |  |  | (17.40 | ) |  |  | 11,465,492 |
March 31, 2022 |  |  | 11.75 |  |  |  | 10.06 |  |  |  | 11.57 |  |  |  | 11.20 |  |  |  | 1.56 |  |  |  | (10.18 | ) |  |  | 11,354,361 |
As of December 31, 2023, DSU’s market price, NAV per Common Share, and premium/(discount) to NAV per Common Share were $10.79 , $10.89, and (0.92)%, respectively. |  |  |  |  |  |  |  |  |
Capital Stock, Long-Term Debt, and Other Securities [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capital Stock [Table Text Block] |  |  |  |  |  |  |  |  |  |
11. | CAPITAL SHARE TRANSACTIONS
DSU is authorized to issue 400 million shares, all of which were initially classified as Common Shares. FRA and BKT are authorized to issue 200 million shares, all of which were initially classified as Common Shares. BLW and BIT is authorized to issue an unlimited number of shares, all of which were initially classified as Common Shares. The par value for DSU’s, FRA’s, BKT’s, BLW’s and BIT’s shares is $0.10, $0.10, $0.010, $0.001 and $0.001, respectively. The Board for DSU, FRA, BLW and BIT are each authorized, however, to reclassify any unissued Common Shares to Preferred Shares without the approval of Common Shareholders. Common Shares For the periods shown, shares issued and outstanding increased by the following amounts as a result of dividend reinvestment:
|  | Year Ended |
Fund Name |  | 12/31/23 |  |  | 12/31/22 |
DSU |  |  | — |  |  |  | 3,721 |
BKT |  |  | 3,394 |  |  |  | 3,887 | (a)
| (a) | Share transactions reflect 1-for-3 reverse stock split effective after the close of trading on October 17, 2022. |
|  | Period from 11/01/23 |  |  | Year Ended |
Fund Name |  | to 12/31/23 |  |  | 10/31/23 |  |  | 10/31/22 |
BIT |  |  | 31,420 |  |  |  | 103,666 |  |  |  | 74,296 |
For the year ended December 31, 2023, shares issued and outstanding remained constant for DSU. For the year ended December 31, 2023 and the year ended December 31, 2022, shares issued and outstanding remained constant for FRA and BLW. The Funds participate in an open market share repurchase program (the “Repurchase Program”). From December 1, 2022 through November 30, 2023, each Fund may repurchase up to 5% of its outstanding common shares under the Repurchase Program, based on common shares outstanding as of the close of business on November 30, 2022, subject to certain conditions. From December 1, 2023 through November 30, 2024, each Fund may repurchase up to 5% of its outstanding common shares under the Repurchase Program, based on common shares outstanding as of the close of business on November 30, 2023, subject to certain conditions. The Repurchase Program has an accretive effect as shares are purchased at a discount to the Fund’s NAV. There is no assurance that the Funds will purchase shares in any particular amounts. For the period ended December 31, 2023, the Funds did not repurchase any shares. DSU, BKT, BLW and BIT have each filed a prospectus with the SEC allowing them to issue an additional 16,000,000, 8,333,333, 10,000,000 and 15,000,000 Common Shares, respectively, through an equity Shelf Offering. Under the Shelf Offering, DSU, BKT, BLW and BIT, subject to market conditions, may raise additional equity capital from time to time in varying amounts and utilizing various offering methods at a net price at or above each Fund’s NAV per Common Share (calculated within 48 hours of pricing). As of period end, 16,000,000, 8,333,333, 10,000,000 and 15,000,000 Common Shares, respectively, remain available for issuance under the Shelf Offering. For the period ended December 31, 2023, Common Shares issued and outstanding under the Shelf Offering remained constant for DSU, BKT, BLW and BIT. See Additional Information - Shelf Offering Program for additional information. Initial costs incurred by DSU, BKT, BLW and BIT in connection with their Shelf Offering are recorded as “Deferred offering costs” in the Statements of Assets and Liabilities. As shares are sold, a portion of the costs attributable to the shares sold will be charged against paid-in-capital. Any remaining deferred charges at the end of the Shelf Offering period will be charged to expense. |  |  |  |  |  |  |  |  |
Investment and Market Discount Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Investment and Market Discount Risk: An investment in the Fund’s common shares is subject to investment risk, including the possible loss of the entire amount that you invest. As with any stock, the price of the Fund’s common shares will fluctuate with market conditions and other factors. If shares are sold, the price received may be more or less than the original investment. Common shares are designed for long-term investors and the Fund should not be treated as a trading vehicle. Shares of closed-end management investment companies frequently trade at a discount from their net asset value. This risk is separate and distinct from the risk that the Fund’s net asset value could decrease as a result of its investment activities. At any point in time an investment in the Fund’s common shares may be worth less than the original amount invested, even after taking into account distributions paid by the Fund. During periods in which the Fund may use leverage, the Fund’s investment, market discount and certain other risks will be magnified. |  |  |  |  |  |  |  |  |
Concentration Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Concentration Risk (BIT): The Fund’s strategy of concentrating in mortgage related securities means that its performance will be closely tied to the performance of a particular market segment. The Fund’s concentration in these securities may present more risks than if it were broadly diversified over numerous industries and sectors of the economy. A downturn in these securities would have a larger impact on the Fund than on a mutual fund that does not concentrate in such securities. At times, the performance of these securities will lag the performance of other industries or the broader market as a whole. |  |  |  |  |  |  |  |  |
Debt Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Debt Securities Risk: Debt securities, such as bonds, involve interest rate risk, such as credit risk, interest rate risk, extension risk, and prepayment risk, each of which are described in further detail below:
| • |  | Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.
| • |  | Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise.
The Fund may be subject to a greater risk of rising interest rates due to the recent period of historically low interest rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. (Duration is a measure of the price sensitivity of a debt security or portfolio of debt securities to relative changes in interest rates.) The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management. To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities. These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change. A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
| • |  | Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
| • |  | Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.
U S Government Obligations Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | U.S. Government Obligations Risk: Certain securities in which the Fund may invest, including securities issued by certain U.S. Government agencies and U.S. Government sponsored enterprises, are not guaranteed by the U.S. Government or supported by the full faith and credit of the United States. In addition, circumstances could arise that could prevent the timely payment of interest or principal on U.S. Government obligations, such as reaching the legislative “debt ceiling.” Such non-payment could result in losses to the Fund and substantial negative consequences for the U.S. economy and the global financial system. |  |  |  |  |  |  |  |  |
U S Government MortgageRelated Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | U.S. Government Mortgage-Related Securities Risk (FRA, BKT and BLW): There are a number of important differences among the agencies and instrumentalities of the U.S. Government that issue mortgage-related securities and among the securities that they issue. Mortgage-related securities guaranteed by the Government National Mortgage Association (“GNMA” or “Ginnie Mae”) are guaranteed as to the timely payment of principal and interest by GNMA and such guarantee is backed by the full faith and credit of the United States. GNMA securities also are supported by the right of GNMA to borrow funds from the U.S. Treasury to make payments under its guarantee. Mortgage-related securities issued by Fannie Mae or Freddie Mac are solely the obligations of Fannie Mae or Freddie Mac, as the case may be, and are not backed by or entitled to the full faith and credit of the United States but are supported by the right of the issuer to borrow from the Treasury. |  |  |  |  |  |  |  |  |
Mortgage and AssetBacked Securities Risks [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Mortgage- and Asset-Backed Securities Risks (FRA, BKT, BLW and BIT): Mortgage- and asset-backed securities represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. Mortgage- and asset-backed securities are subject to credit, interest rate, prepayment and extension risks. These securities also are subject to risk of default on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities. |  |  |  |  |  |  |  |  |
Senior Loans Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Senior Loans Risk (DSU, FRA, BLW and BIT): There is less readily available, reliable information about most senior loans than is the case for many other types of securities. An economic downturn generally leads to a higher non-payment rate, and a senior loan may lose significant value before a default occurs. Moreover, any specific collateral used to secure a senior loan may decline in value or become illiquid, which would adversely affect the senior loan’s value. No active trading market may exist for certain senior loans, which may impair the ability of the Fund to realize full value in the event of the need to sell a senior loan and which may make it difficult to value senior loans. Although senior loans in which the Fund will invest generally will be secured by specific collateral, there can be no assurance that liquidation of such collateral would satisfy the borrower’s obligation in the event of non-payment of scheduled interest or principal or that such collateral could be readily liquidated. To the extent that a senior loan is collateralized by stock in the borrower or its subsidiaries, such stock may lose all of its value in the event of the bankruptcy of the borrower. Uncollateralized senior loans involve a greater risk of loss. |  |  |  |  |  |  |  |  |
Second Lien Loans Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Second Lien Loans Risk (BIT): Second lien loans generally are subject to similar risks as those associated with investments in senior loans. Because second lien loans are subordinated or unsecured and thus lower in priority of payment to senior loans, they are subject to the additional risk that the cash flow of the borrower and property securing the loan or debt, if any, may be insufficient to meet scheduled payments after giving effect to the senior secured obligations of the borrower. |  |  |  |  |  |  |  |  |
CLO Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | CLO Risk (BIT and FRA): In addition to the general risks associated with fixed-income securities discussed herein, CLOs carry additional risks, including: (i) the possibility that distributions from collateral securities will not be adequate to make interest or other payments; (ii) the quality of the collateral may decline in value or default; (iii) the possibility that the CLO securities are subordinate to other classes; and (iv) the complex structure of the security may not be fully understood at the time of investment and may produce disputes with the issuer or unexpected investment results. The credit quality of CLOs depends primarily upon the quality of the underlying assets and the level of credit support and/or enhancement provided. The underlying assets (e.g., loans) of CLOs are subject to prepayments, which shorten the weighted average maturity and may lower the return of the securities issued by the CLOs. The value of CLO securities also may change because of changes in the market’s perception of the creditworthiness of the servicing agent for the pool, the originator of the pool, or the financial institution or fund providing the credit support or enhancement. Furthermore, the leveraged nature of each subordinated class may magnify the adverse impact on such class of changes in the value of the assets, changes in the distributions on the assets, defaults and recoveries on the assets, capital gains and losses on the assets, prepayment on assets and availability, price and interest rates of assets. CLOs are typically privately offered and sold, and thus are not registered under the securities laws. Additionally, when the Fund purchases a newly issued CLO security in the primary market (rather than from the secondary market), there often may be a delayed settlement period. As a result, investments in CLOs may be characterized by the Fund as illiquid securities; however, an active dealer market may exist which would allow such securities to be considered liquid in some circumstances. Finally, CLOs are limited recourse and may not be paid in full and may be subject to up to 100% loss. |  |  |  |  |  |  |  |  |
Risks of Loan Assignments and Participations [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Risks of Loan Assignments and Participations (BLW): As the purchaser of an assignment, the Fund typically succeeds to all the rights and obligations of the assigning institution and becomes a lender under the credit agreement with respect to the debt obligation; however, the Fund may not be able unilaterally to enforce all rights and remedies under the loan and with regard to any associated collateral. Because assignments may be arranged through private negotiations between potential assignees and potential assignors, the rights and obligations acquired by the Fund as the purchaser of an assignment may differ from, and be more limited than, those held by the assigning lender. In addition, if the loan is foreclosed, the Fund could become part owner of any collateral and could bear the costs and liabilities of owning and disposing of the collateral. The Fund may be required to pass along to a purchaser that buys a loan from the Fund by way of assignment a portion of any fees to which the Fund is entitled under the loan. In connection with purchasing participations, the Fund generally will have no right to enforce compliance by the borrower with the terms of the loan agreement relating to the loan, nor any rights of set-off against the borrower, and the Fund may not directly benefit from any collateral supporting the loan in which it has purchased the participation. As a result, the Fund will be subject to the credit risk of both the borrower and the lender that is selling the participation. In the event of the insolvency of the lender selling a participation, the Fund may be treated as a general creditor of the lender and may not benefit from any set-off between the lender and the borrower. |  |  |  |  |  |  |  |  |
Corporate Loans Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Corporate Loans Risk (DSU): Commercial banks and other financial institutions or institutional investors make corporate loans to companies that need capital to grow or restructure. Borrowers generally pay interest on corporate loans at rates that change in response to changes in market interest rates such as the Secured Overnight Financing Rate (“SOFR”), the London Interbank Offered Rate (“LIBOR”) or the prime rates of U.S. banks. As a result, the value of corporate loan investments is generally less exposed to the adverse effects of shifts in market interest rates than investments that pay a fixed rate of interest. The market for corporate loans may be subject to irregular trading activity and wide bid/ask spreads. In addition, transactions in corporate loans may settle on a delayed basis. As a result, the proceeds from the sale of corporate loans may not be readily available to make additional investments or to meet the Fund’s redemption obligations. To the extent the extended settlement process gives rise to short-term liquidity needs, the Fund may hold additional cash, sell investments or temporarily borrow from banks and other lenders. The corporate loans in which the Fund invests are usually rated below investment grade. |  |  |  |  |  |  |  |  |
Variable and Floating Rate Instrument Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Variable and Floating Rate Instrument Risk (DSU, FRA and BLW): Variable and floating rate securities provide for periodic adjustment in the interest rate paid on the securities. These securities may be subject to greater illiquidity risk than other fixed income securities, meaning the absence of an active market for these securities could make it difficult for the Fund to dispose of them at any given time. |  |  |  |  |  |  |  |  |
Unrated Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Unrated Securities Risk (BIT): Because the Fund may purchase securities that are not rated by any rating organization, the Managers may, after assessing their credit quality, internally assign ratings to certain of those securities in categories similar to those of rating organizations. 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 Managers’ credit analysis than would be the case when the Fund invests in rated securities. |  |  |  |  |  |  |  |  |
High Yield Bonds Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | High Yield Bonds Risk (DSU, FRA, BLW and BIT): Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that are considered speculative and may cause income and principal losses for the Fund. |  |  |  |  |  |  |  |  |
Distressed Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Distressed Securities Risk (DSU and FRA): Distressed securities are speculative and involve substantial risks in addition to the risks of investing in junk bonds. The Fund will generally not receive interest payments on the distressed securities and may incur costs to protect its investment. In addition, distressed securities involve the substantial risk that principal will not be repaid. These securities may present a substantial risk of default or may be in default at the time of investment. The Fund may incur additional expenses to the extent it is required to seek recovery upon a default in the payment of principal of or interest on its portfolio holdings. In any reorganization or liquidation proceeding relating to a portfolio company, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Distressed securities and any securities received in an exchange for such securities may be subject to restrictions on resale. |  |  |  |  |  |  |  |  |
Collateralized Bond Obligations Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Collateralized Bond Obligations Risk (BLW): The pool of high yield securities underlying collateralized bond obligations is typically separated into groupings called tranches representing different degrees of credit quality. The higher quality tranches have greater degrees of protection and pay lower interest rates. The lower tranches, with greater risk, pay higher interest rates. |  |  |  |  |  |  |  |  |
Collateralized Debt Obligations Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Collateralized Debt Obligations Risk (FRA): In addition to the typical risks associated with fixed-income securities and asset-backed securities, collateralized debt obligations (“CDOs”), including collateralized loan obligations, carry additional risks including, but not limited to: (i) the possibility that distributions from collateral securities will not be adequate to make interest or other payments; (ii) the risk that the collateral may default or decline in value or be downgraded, if rated by a nationally recognized statistical rating organization; (iii) the Fund may invest in tranches of CDOs that are subordinate to other tranches; (iv) the structure and complexity of the transaction and the legal documents could lead to disputes among investors regarding the characterization of proceeds; (v) the investment return achieved by the Fund could be significantly different than those predicted by financial models; (vi) the lack of a readily available secondary market for CDOs; (vii) the risk of forced “fire sale” liquidation due to technical defaults such as coverage test failures; and (viii) the CDO’s manager may perform poorly. |  |  |  |  |  |  |  |  |
Sovereign Debt Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Sovereign Debt Risk (FRA, BLW and BIT): Sovereign debt instruments are subject to the risk that a governmental entity may delay or refuse to pay interest or repay principal on its sovereign debt, due, for example, to cash flow problems, insufficient foreign currency reserves, political considerations, the relative size of the governmental entity’s debt position in relation to the economy or the failure to put in place economic reforms required by the International Monetary Fund or other multilateral agencies. |  |  |  |  |  |  |  |  |
Municipal Securities Risks [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Municipal Securities Risks (BIT): Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. Budgetary constraints of local, state, and federal governments upon which the issuers may be relying for funding may also impact municipal securities. These risks include:
| • |  | General Obligation Bonds Risks — Timely payments depend on the issuer’s credit quality, ability to raise tax revenues and ability to maintain an adequate tax base.
| • |  | Revenue Bonds Risks — These payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source.
| • |  | Private Activity Bonds Risks — Municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise. The private enterprise pays the principal and interest on the bond, and the issuer does not pledge its full faith, credit and taxing power for repayment. The Fund’s investments may consist of private activity bonds that may subject certain shareholders to an alternative minimum tax.
| • |  | Moral Obligation Bonds Risks — 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.
| • |  | Municipal Notes Risks — Municipal notes are shorter term municipal debt obligations. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money.
| • |  | Municipal Lease Obligations Risks — In a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property.
| • |  | Tax-Exempt Status Risk — The Fund and its investment manager will rely on the opinion of issuers’ bond counsel and, in the case of derivative securities, sponsors’ counsel, on the tax-exempt status of interest on municipal bonds and payments under derivative securities. Neither the Fund nor its investment manager will independently review the bases for those tax opinions, which may ultimately be determined to be incorrect and subject the Fund and its shareholders to substantial tax liabilities.
Brady Bonds Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Brady Bonds Ris k (BLW): Brady Bonds involve various risk factors described above associated with investing in non-U.S. securities, including the history of defaults with respect to commercial bank loans by public and private entities of countries issuing Brady Bonds. |  |  |  |  |  |  |  |  |
Supranational Entities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Supranational Entities Risk (BLW): The Fund may invest in obligations issued or guaranteed by the World Bank. The government members, or “stockholders,” usually make initial capital contributions to the World Bank and in many cases are committed to make additional capital contributions if the World Bank is unable to repay its borrowings. There is no guarantee that one or more stockholders of the World Bank will continue to make any necessary additional capital contributions. If such contributions are not made, the entity may be unable to pay interest or repay principal on its debt securities, and the Fund may lose money on such investments. |  |  |  |  |  |  |  |  |
Yield and Ratings Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Yield and Ratings Risk (BKT) : The yields on debt obligations are dependent on a variety of factors, including general market conditions, conditions in the particular market for the obligation, the financial condition of the issuer, the size of the offering, the maturity of the obligation and the ratings of the issue. The ratings of Moody’s, S&P and Fitch, represent their respective opinions as to the quality of the obligations they undertake to rate. Ratings, however, are general and are not absolute standards of quality. Consequently, obligations with the same rating, maturity and interest rate may have different market prices. Subsequent to its purchase by the Fund, a rated security may cease to be rated. The Manager will consider such an event in determining whether the Fund should continue to hold the security. |  |  |  |  |  |  |  |  |
Repurchase Agreements and Purchase and Sale Contracts Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Repurchase Agreements and Purchase and Sale Contracts Risk (BKT and BIT) : If the other party to a repurchase agreement or purchase and sale contract defaults on its obligation under the agreement, the Fund may suffer delays and incur costs or lose money in exercising its rights under the agreement. If the seller fails to repurchase the security in either situation and the market value of the security declines, the Fund may lose money. |  |  |  |  |  |  |  |  |
Foreign Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Foreign Securities Risk (DSU, FRA, BLW and BIT): Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include:
| • |  | The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight.
| • |  | Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio.
| • |  | The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position.
| • |  | The governments of certain countries, or the U.S. Government with respect to certain countries, may prohibit or impose substantial restrictions through capital controls and/or sanctions on foreign investments in the capital markets or certain industries in those countries, which may prohibit or restrict the ability to own or transfer currency, securities, derivatives or other assets.
| • |  | Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws.
| • |  | Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments.
| • |  | The Fund’s claims to recover foreign withholding taxes may not be successful, and if the likelihood of recovery of foreign withholding taxes materially decreases, due to, for example, a change in tax regulation or approach in the foreign country, accruals in the Fund’s net asset value for such refunds may be written down partially or in full, which will adversely affect the Fund’s net asset value.
Emerging Markets Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Emerging Markets Risk (FRA, BLW and BIT): Emerging markets are riskier than more developed markets because they tend to develop unevenly and may never fully develop. Investments in emerging markets may be considered speculative. Emerging markets are more likely to experience hyperinflation and currency devaluations, which adversely affect returns to U.S. investors. In addition, many emerging securities markets have far lower trading volumes and less liquidity than developed markets. |  |  |  |  |  |  |  |  |
Small and Mid Capitalization Company Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Small and Mid-Capitalization Company Risk (BIT): Companies with small or mid-size market capitalizations will normally have more limited product lines, markets and financial resources and will be dependent upon a more limited management group than larger capitalized companies. In addition, it is more difficult to get information on smaller companies, which tend to be less well known, have shorter operating histories, do not have significant ownership by large investors and are followed by relatively few securities analysts. |  |  |  |  |  |  |  |  |
Preferred Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Preferred Securities Risk (DSU, FRA, BLW and BIT): Preferred securities may pay fixed or adjustable rates of return. Preferred securities are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred securities generally pay dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred securities will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. Preferred securities of smaller companies may be more vulnerable to adverse developments than preferred securities of larger companies. |  |  |  |  |  |  |  |  |
Convertible Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Convertible Securities Risk (DSU, FRA and BIT): The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest, principal or dividends when due, and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock, including the potential for increased volatility in the price of the convertible security. |  |  |  |  |  |  |  |  |
Warrants Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Warrants Risk (DSU and FRA): If the price of the underlying stock does not rise above the exercise price before the warrant expires, the warrant generally expires without any value and the Fund will lose any amount it paid for the warrant. Thus, investments in warrants may involve substantially more risk than investments in common stock. Warrants may trade in the same markets as their underlying stock; however, the price of the warrant does not necessarily move with the price of the underlying stock. |  |  |  |  |  |  |  |  |
Real Estate Related Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Real Estate-Related Securities Risk (BLW): The main risk of real estate-related securities is that the value of the underlying real estate may go down. Many factors may affect real estate values. These factors include both the general and local economies, vacancy rates, changes in rent schedules, tenant bankruptcies, the ability to re-lease space under expiring leases on attractive terms, the amount of new construction in a particular area, the laws and regulations (including zoning, environmental and tax laws) affecting real estate and the costs of owning, maintaining and improving real estate. The availability of mortgage financing and changes in interest rates may also affect real estate values. If the Fund’s real estate-related investments are concentrated in one geographic area or in one property type, the Fund will be particularly subject to the risks associated with that area or property type. Many issuers of real estate-related securities are highly leveraged, which increases the risk to holders of such securities. The value of the securities the Fund buys will not necessarily track the value of the underlying investments of the issuers of such securities. In addition, certain issuers of real estate-related securities may have developed or commenced development on properties and may develop additional properties in the future. Real estate development involves significant risks in addition to those involved in the ownership and operation of established properties. Real estate securities may have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers or tenants. |  |  |  |  |  |  |  |  |
REIT Investment Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | REIT Investment Risk (BLW and BIT): Investments in REITs involve unique risks. REITs may have limited financial resources, may trade less frequently and in limited volume, may engage in dilutive offerings of securities and may be more volatile than other securities. REIT issuers may also fail to maintain their exemptions from investment company registration or fail to qualify for the “dividends paid deduction” under the Internal Revenue Code of 1986, as amended, which allows REITs to reduce their corporate taxable income for dividends paid to their shareholders. |  |  |  |  |  |  |  |  |
Structured Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Structured Securities Risk (BIT): Because structured securities of the type in which the Fund may invest typically involve no credit enhancement, their credit risk generally will be equivalent to that of the underlying instruments, index or reference obligation and will also be subject to counterparty risk. The Fund may have the right to receive payments only from the structured security, and generally does not have direct rights against the issuer or the entity that sold the assets to be securitized. In addition to the general risks associated with debt securities discussed herein, structured securities carry additional risks, including, but not limited to: the possibility that distributions from collateral securities will not be adequate to make interest or other payments; the quality of the collateral may decline in value or default; and the possibility that the structured securities are subordinate to other classes. The Fund is permitted to invest in a class of structured securities that is either subordinated or unsubordinated to the right of payment of another class. Subordinated structured securities typically have higher yields and present greater risks than unsubordinated structured securities. Structured securities are typically sold in private placement transactions, and there currently is no active trading market for structured securities. Structured securities are based upon the movement of one or more factors, including currency exchange rates, interest rates, reference bonds and stock indices, and changes in interest rates and impact of these factors may cause significant price fluctuations. Additionally, changes in the reference instrument or security may cause the interest rate on the structured security to be reduced to zero. Certain issuers of such structured securities may be deemed to be “investment companies” as defined in the Investment Company Act. As a result, the Fund’s investment in such securities may be limited by certain investment restrictions contained in the Investment Company Act. |  |  |  |  |  |  |  |  |
Derivatives Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Derivatives Risk: The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:
| • |  | Leverage Risk — The Fund’s use of derivatives can magnify the Fund’s gains and losses. Relatively small market movements may result in large changes in the value of a derivatives position and can result in losses that greatly exceed the amount originally invested.
| • |  | Market Risk — Some derivatives are more sensitive to interest rate changes and market price fluctuations than other securities. The Fund could also suffer losses related to its derivatives positions as a result of unanticipated market movements, which losses are potentially unlimited. Finally, the Manager may not be able to predict correctly the direction of securities prices, interest rates and other economic factors, which could cause the Fund’s derivatives positions to lose value.
| • |  | Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will be unable or unwilling to fulfill its contractual obligation, and the related risks of having concentrated exposure to such a counterparty.
| • |  | Illiquidity Risk — The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately.
| • |  | Operational Risk — The use of derivatives includes the risk of potential operational issues, including documentation issues, settlement issues, systems failures, inadequate controls and human error.
| • |  | Legal Risk — The risk of insufficient documentation, insufficient capacity or authority of counterparty, or legality or enforceability of a contract.
| • |  | Volatility and Correlation Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.
| • |  | Valuation Risk — Valuation for derivatives may not be readily available in the market. Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them.
| • |  | Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences.
| • |  | Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments.
Structured Notes Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Structured Notes Risk (FRA): Structured notes and other related instruments purchased by the Fund are generally privately negotiated debt obligations where the principal and/or interest is determined by reference to the performance of a specific asset, benchmark asset, market or interest rate (“reference measure”). The purchase of structured notes exposes the Fund to the credit risk of the issuer of the structured product. Structured notes may be leveraged, increasing the volatility of each structured note’s value relative to the change in the reference measure. Structured notes may also be less liquid and more difficult to price accurately than less complex securities and instruments or more traditional debt securities. |  |  |  |  |  |  |  |  |
Leverage Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Leverage Risk: The Fund’s use of leverage may increase or decrease from time to time in its discretion and the Fund may, in the future, determine not to use leverage. The use of leverage creates an opportunity for increased common share net investment income dividends, but also creates risks for the holders of common shares. The Fund cannot assure you that the use of leverage will result in a higher yield on the common shares. Any leveraging strategy the Fund employs may not be successful. Leverage involves risks and special considerations for common shareholders, including:
| • |  | the likelihood of greater volatility of net asset value, market price and dividend rate of the common shares than a comparable portfolio without leverage;
| • |  | the risk that fluctuations in interest rates or dividend rates on any leverage that the Fund must pay will reduce the return to the common shareholders;
| • |  | the effect of leverage in a declining market, which is likely to cause a greater decline in the net asset value of the common shares than if the Fund were not leveraged, which may result in a greater decline in the market price of the common shares;
| • |  | leverage may increase operating costs, which may reduce total return.
| • |  | Any decline in the net asset value of the Fund’s investments will be borne entirely by the holders of common shares. Therefore, if the market value of the Fund’s portfolio declines, leverage will result in a greater decrease in net asset value to the holders of common shares than if the Fund were not leveraged. This greater net asset value decrease will also tend to cause a greater decline in the market price for the common shares.
Reverse Repurchase Agreements Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Reverse Repurchase Agreements Risk: Reverse repurchase agreements involve the sale of securities held by the Fund with an agreement to repurchase the securities at an agreed-upon price, date and interest payment. Reverse repurchase agreements involve the risk that the other party may fail to return the securities in a timely manner or at all. The Fund could lose money if it is unable to recover the securities and the value of the collateral held by the Fund, including the value of the investments made with cash collateral, is less than the value of the securities. These events could also trigger adverse tax consequences for the Fund. In addition, reverse repurchase agreements involve the risk that the interest income earned in the investment of the proceeds will be less than the interest expense. |  |  |  |  |  |  |  |  |
Dollar Rolls Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Dollar Rolls Risk (BLW and BIT): Dollar rolls involve the risk that the market value of the securities that the Fund is committed to buy may decline below the price of the securities the Fund has sold. These transactions may involve leverage. |  |  |  |  |  |  |  |  |
Short Sales Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Short Sales Risk (DSU and BIT): Because making short sales in securities that it does not own exposes the Fund to the risks associated with those securities, such short sales involve speculative exposure risk. The Fund will incur a loss as a result of a short sale if the price of the security increases between the date of the short sale and the date on which the Fund replaces the security sold short. |  |  |  |  |  |  |  |  |
Illiquid Investments Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Illiquid Investments Risk: The Fund may invest without limitation in illiquid or less liquid investments or investments in which no secondary market is readily available or which are otherwise illiquid, including private placement securities. 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 net asset value and ability to make dividend distributions. The financial markets in general, and certain segments of the mortgage-related securities markets in particular, 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. Privately issued debt securities are often of below investment grade quality, frequently are unrated and present many of the same risks as investing in below investment grade public debt securities. |  |  |  |  |  |  |  |  |
Inverse Floater and Related Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Inverse Floater and Related Securities Risk (BIT): Investments in inverse floaters, residual interest tender option bonds and similar instruments expose the Fund to the same risks as investments in fixed-income securities and derivatives, as well as other risks, including those associated with leverage and increased volatility. An investment in these securities typically will involve greater risk than an investment in a fixed rate security. Distributions on inverse floaters, residual interest tender option bonds and similar instruments will typically bear an inverse relationship to short term interest rates and typically will be reduced or, potentially, eliminated as interest rates rise. Inverse floaters, residual interest tender option bonds and similar instruments will underperform the market for fixed rate securities in a rising interest rate environment. Inverse floaters may be considered to be leveraged to the extent that their interest rates vary by a magnitude that exceeds the magnitude of the change in a reference rate of interest (typically a short term interest rate). The leverage inherent in inverse floaters is associated with greater volatility in their market values. Investments in inverse floaters, residual interest tender option bonds and similar instruments that have fixed-income securities underlying them will expose the Fund to the risks associated with those fixed-income securities and the values of those investments may be especially sensitive to changes in prepayment rates on the underlying fixed-income securities. |  |  |  |  |  |  |  |  |
Investment Companies and ETFs Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Investment Companies and ETFs Risk (DSU, BLW and BIT): Subject to the limitations set forth in the Investment Company Act and the rules thereunder, the Fund may acquire shares in other investment companies and in ETFs, some of which may be affiliated investment companies. The market value of the shares of other investment companies and ETFs may differ from their net asset value. As an investor in investment companies and ETFs, the Fund would bear its ratable share of that entity’s expenses, including its investment advisory and administration fees, while continuing to pay its own advisory and administration fees and other expenses (to the extent not offset by the Manager through waivers). As a result, shareholders will be absorbing duplicate levels of fees with respect to investments in other investment companies and ETFs (to the extent not offset by the Manager through waivers). The securities of other investment companies and ETFs in which the Fund may invest may be leveraged. As a result, the Fund may be indirectly exposed to leverage through an investment in such securities. An investment in securities of other investment companies and ETFs that use leverage may expose the Fund to higher volatility in the market value of such securities and the possibility that the Fund’s long-term returns on such securities (and, indirectly, the long-term returns of shares of the Fund) will be diminished. As with other investments, investments in other investment companies, including ETFs, are subject to market and selection risk. To the extent the Fund is held by an affiliated fund, the ability of the Fund itself to hold other investment companies may be limited. |  |  |  |  |  |  |  |  |
Risk of Investing in the United States [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Risk of Investing in the United States: Certain changes in the U.S. economy, such as when the U.S. economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Fund has exposure. |  |  |  |  |  |  |  |  |
Market Risk and Selection Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Market Risk and Selection Risk: Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. The value of a security or other asset may decline due to changes in general market conditions, economic trends or events that are not specifically related to the issuer of the security or other asset, or factors that affect a particular issuer or issuers, exchange, country, group of countries, region, market, industry, group of industries, sector or asset class. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues like pandemics or epidemics, recessions, or other events could have a significant impact on the Fund and its investments. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money. An outbreak of an infectious coronavirus (COVID-19) that was first developed into a global pandemic that has resulted in numerous disruptions in the market and has had significant economic impact leaving general concern and uncertainty. Although vaccines have been developed and approved for use by various governments, the duration of the pandemic and its effects cannot be predicted with certainty. The impact of this coronavirus, and other epidemics and pandemics that may arise in the future, could affect the economies of many nations, individual companies and the market in general ways that cannot necessarily be foreseen at the present time. |  |  |  |  |  |  |  |  |
Shareholder Activism Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Shareholder Activism Risk: Shareholder activism involving closed-end funds has recently been increasing. Shareholder activism can take many forms, including engaging in public campaigns to demand that the Fund consider significant transactions such as a tender offer, merger or liquidation or to attempt to influence the Fund’s corporate governance and/or management, commencing proxy contests to attempt to elect the activists’ representatives or others to the Fund’s Board of Directors, or to seek other actions such as a termination of the Fund’s investment advisory contract with its current investment manager or commencing litigation. If the Fund becomes the subject of shareholder activism, then management and the Board may be required to divert significant resources and attention to respond to the activist and the Fund may incur substantial costs defending against such activism if management and the Board determine that the activist’s demands are not in the best interest of the Fund. Further, the Fund’s share price could be subject to significant fluctuation or otherwise be adversely affected by the events, risks and uncertainties of any shareholder activism. |  |  |  |  |  |  |  |  |
Illiquidity Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Illiquidity Risk: Each Fund may invest without limitation in illiquid or less liquid investments or investments in which no secondary market is readily available or which are otherwise illiquid, including private placement securities. A Fund may not be able to readily dispose of such investments at prices that approximate those at which a Fund could sell such investments if they were more widely traded and, as a result of such illiquidity, a Fund may have to sell other investments or engage in borrowing transactions if necessary to raise funds to meet its obligations. Limited liquidity can also affect the market price of investments, thereby adversely affecting a Fund’s NAV and ability to make dividend distributions. Privately issued debt securities are often of below investment grade quality, frequently are unrated and present many of the same risks as investing in below investment grade public debt securities. |  |  |  |  |  |  |  |  |
Market Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Market Risk: Each Fund may be exposed to prepayment risk, which is the risk that borrowers may exercise their option to prepay principal earlier than scheduled during periods of declining interest rates, which would force each Fund to reinvest in lower yielding securities. Each Fund may also be exposed to reinvestment risk, which is the risk that income from each Fund’s portfolio will decline if each Fund invests the proceeds from matured, traded or called fixed-income securities at market interest rates that are below each Fund portfolio’s current earnings rate. |  |  |  |  |  |  |  |  |
Valuation Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Valuation Risk: The market values of equities, such as common stocks and preferred securities or equity related investments, such as futures and options, may decline due to general market conditions which are not specifically related to a particular company. They may also decline due to factors which affect a particular industry or industries. A Fund may invest in illiquid investments. An illiquid investment is any investment that a Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. A Fund may experience difficulty in selling illiquid investments in a timely manner at the price that it believes the investments are worth. Prices may fluctuate widely over short or extended periods in response to company, market or economic news. Markets also tend to move in cycles, with periods of rising and falling prices. This volatility may cause each Fund’s NAV to experience significant increases or decreases over short periods of time. If there is a general decline in the securities and other markets, the NAV of a Fund may lose value, regardless of the individual results of the securities and other instruments in which a Fund invests. The price a Fund could receive upon the sale of any particular portfolio investment may differ from a Fund’s valuation of the investment, particularly for securities that trade in thin or volatile markets or that are valued using a fair valuation technique or a price provided by an independent pricing service. Changes to significant unobservable inputs and assumptions (i.e., publicly traded company multiples, growth rate, time to exit) due to the lack of observable inputs may significantly impact the resulting fair value and therefore a Fund’s results of operations. As a result, the price received upon the sale of an investment may be less than the value ascribed by a Fund, and a Fund could realize a greater than expected loss or lesser than expected gain upon the sale of the investment. A Fund’s ability to value its investments may also be impacted by technological issues and/or errors by pricing services or other third-party service providers. |  |  |  |  |  |  |  |  |
Counterparty Credit Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Counterparty Credit Risk: The Funds may be exposed to counterparty credit risk, or the risk that an entity may fail to or be unable to perform on its commitments related to unsettled or open transactions, including making timely interest and/or principal payments or otherwise honoring its obligations. The Funds manage counterparty credit risk by entering into transactions only with counterparties that the Manager believes have the financial resources to honor their obligations and by monitoring the financial stability of those counterparties. Financial assets, which potentially expose the Funds to market, issuer and counterparty credit risks, consist principally of financial instruments and receivables due from counterparties. The extent of the Funds’ exposure to market, issuer and counterparty credit risks with respect to these financial assets is approximately their value recorded in the Statements of Assets and Liabilities, less any collateral held by the Funds. A derivative contract may suffer a mark-to-market loss if the value of the contract decreases due to an unfavorable change in the market rates or values of the underlying instrument. Losses can also occur if the counterparty does not perform under the contract. For OTC options purchased, each Fund bears the risk of loss in the amount of the premiums paid plus the positive change in market values net of any collateral held by the Funds should the counterparty fail to perform under the contracts. Options written by the Funds do not typically give rise to counterparty credit risk, as options written generally obligate the Funds, and not the counterparty, to perform. The Funds may be exposed to counterparty credit risk with respect to options written to the extent each Fund deposits collateral with its counterparty to a written option. With exchange-traded options purchased, exchange-traded futures and centrally cleared swaps, there is less counterparty credit risk to the Funds since the exchange or clearinghouse, as counterparty to such instruments, guarantees against a possible default. The clearinghouse stands between the buyer and the seller of the contract; therefore, credit risk is limited to failure of the clearinghouse. While offset rights may exist under applicable law, a Fund does not have a contractual right of offset against a clearing broker or clearinghouse in the event of a default (including the bankruptcy or insolvency). Additionally, credit risk exists in exchange-traded futures and centrally cleared swaps with respect to initial and variation margin that is held in a clearing broker’s customer accounts. While clearing brokers are required to segregate customer margin from their own assets, in the event that a clearing broker becomes insolvent or goes into bankruptcy and at that time there is a shortfall in the aggregate amount of margin held by the clearing broker for all its clients, typically the shortfall would be allocated on a pro rata basis across all the clearing broker’s customers, potentially resulting in losses to the Funds. |  |  |  |  |  |  |  |  |
Geographic Asset Class Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Geographic/Asset Class Risk: A diversified portfolio, where this is appropriate and consistent with a fund’s objectives, minimizes the risk that a price change of a particular investment will have a material impact on the NAV of a fund. The investment concentrations within each Fund’s portfolio are disclosed in its Schedule of Investments. Certain Funds invest a significant portion of their assets in high yield securities. High yield securities that are rated below investment-grade (commonly referred to as “junk bonds”) or are unrated may be deemed speculative, involve greater levels of risk than higher-rated securities of similar maturity and are more likely to default. High yield securities may be issued by less creditworthy issuers, and issuers of high yield securities may be unable to meet their interest or principal payment obligations. High yield securities are subject to extreme price fluctuations, may be less liquid than higher rated fixed-income securities, even under normal economic conditions, and frequently have redemption features. The Funds invest a significant portion of their assets in fixed-income securities and/or use derivatives tied to the fixed-income markets. Changes in market interest rates or economic conditions may affect the value and/or liquidity of such investments. Interest rate risk is the risk that prices of bonds and other fixed-income securities will decrease as interest rates rise and increase as interest rates fall. The Funds may be subject to a greater risk of rising interest rates due to the period of historically low interest rates that ended in March 2022. The Federal Reserve has recently been raising the federal funds rate as part of its efforts to address inflation. There is a risk that interest rates will continue to rise, which will likely drive down the prices of bonds and other fixed-income securities, and could negatively impact the Funds’ performance. The Funds invest a significant portion of their assets in securities of issuers located in the United States. A decrease in imports or exports, changes in trade regulations, inflation and/or an economic recession in the United States may have a material adverse effect on the U.S. economy and the securities listed on U.S. exchanges. Proposed and adopted policy and legislative changes in the United States may also have a significant effect on U.S. markets generally, as well as on the value of certain securities. Governmental agencies project that the United States will continue to maintain elevated public debt levels for the foreseeable future which may constrain future economic growth. Circumstances could arise that could prevent the timely payment of interest or principal on U.S. government debt, such as reaching the legislative “debt ceiling.” Such non-payment would result in substantial negative consequences for the U.S. economy and the global financial system. If U.S. relations with certain countries deteriorate, it could adversely affect issuers that rely on the United States for trade. The United States has also experienced increased internal unrest and discord. If these trends were to continue, they may have an adverse impact on the U.S. economy and the issuers in which the Funds invest. Certain Funds invest a significant portion of their assets in securities backed by commercial or residential mortgage loans or in issuers that hold mortgage and other asset-backed securities. When a fund concentrates its investments in this manner, it assumes a greater risk of prepayment or payment extension by securities issuers. Changes in economic conditions, including delinquencies and/or defaults on assets underlying these securities, can affect the value, income and/or liquidity of such positions. Investment percentages in these securities are presented in the Schedules of Investments. |  |  |  |  |  |  |  |  |
LIBOR Transition Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | LIBOR Transition Risk : The Funds may be exposed to financial instruments that recently transitioned from, or continue to be tied to, the London Interbank Offered Rate (“LIBOR”) to determine payment obligations, financing terms, hedging strategies or investment value. The United Kingdom’s Financial Conduct Authority, which regulates LIBOR, has ceased publishing all LIBOR settings, but some USD LIBOR settings will continue to be published under a synthetic methodology until September 30, 2024 for certain legacy contracts. SOFR has been used increasingly on a voluntary basis in new instruments and transactions. Under U.S. regulations that implement a statutory fallback mechanism to replace LIBOR, benchmark rates based on SOFR have replaced LIBOR in certain financial contracts. The ultimate effect of the LIBOR transition process on the Funds is uncertain. |  |  |  |  |  |  |  |  |
Equity Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Equity Securities Risk (DSU, FRA, BLW and BIT): Stock markets are volatile. The price of equity securities fluctuates based on changes in a company’s financial condition and overall market and economic conditions. |  |  |  |  |  |  |  |  |
Investment Objective [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment Objectives and Practices [Text Block] |  |  |  |  |  |  |  |  |  | Investment Objective BlackRock Debt Strategies Fund, Inc.’s (DSU) (the “Fund”) primary investment objective is to seek to provide current income by investing primarily in a diversified portfolio of U.S. companies’ debt instruments, including senior and subordinated corporate loans, both secured and unsecured, which are rated in the lower rating categories of the established rating services (BBB or lower by S&P Global Ratings (“S&P”) or Baa or lower by Moody’s Investors Service, Inc. (“Moody’s”)) or unrated debt instruments, which are in the judgment of the investment adviser of equivalent quality. The Fund may invest directly in debt instruments or synthetically through the use of derivatives. The Fund’s secondary investment objective is to seek to provide capital appreciation. No assurance can be given that the Fund’s investment objective will be ach ieved. |  |  |  |  |  |  |  |  |
Investment Objectives and Policies [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment Objectives and Practices [Text Block] |  |  |  |  |  |  |  |  |  | Investment Objectives and Policies BlackRock Debt Strategies Fund, Inc. (DSU) The Fund’s primary investment objective is to seek to provide current income by investing primarily in a diversified portfolio of U.S. companies’ debt instruments, including Corporate Loans (as defined below), which are rated in the lower rating categories of the established rating services (Baa or lower by Moody’s Investor’s Service (“Moody’s”) or BBB or lower by S&P Global Ratings (“S&P”)) or unrated debt instruments which are in the judgment of BlackRock Advisors, LLC (the “Manager”) of equivalent quality. Such investments generally involve greater volatility of price and risks to principal and income than securities in the higher rating categories. As a secondary objective, the Fund will seek to provide capital appreciation. The Fund’s investment objectives are fundamental policies and may not be changed without the approval of a majority of the outstanding voting securities of the Fund (as defined in the Investment Company Act of 1940, as amended (the “Investment Company Act”)). Under normal market conditions, at least 80% of the Fund’s total assets will be invested in debt instruments. The Fund may invest directly in debt instruments or synthetically through the use of derivatives. The Fund has no restrictions on portfolio maturity or duration of the debt securities in which it may invest. The Fund’s investment policies permit investment in the following asset classes which are described in greater detail below: (i) senior and subordinated corporate loans, both secured and unsecured (“Corporate Loans”), issued either directly by the borrower or in the form of participation interests in Corporate Loans made by banks and other financial institutions; (ii) publicly offered and privately placed high-yield debt securities, senior and subordinated, both secured and unsecured; and (iii) convertible debt instruments and preferred stock, each of which may be converted into common stock or other securities of the same or a different issuer, and nonconvertible preferred stock. The debt securities and Corporate Loans in which the Fund invests may pay interest at fixed rates or at rates that float at a margin above a generally recognized base lending rate such as the prime rate of a designated U.S. bank, or that adjust periodically at a margin above the CD rate or LIBOR. In connection with its investments in corporate debt securities, or restructuring of investments owned by the Fund, the Fund may receive warrants or other non-income producing debt or equity securities. The Fund may retain such securities until the Manager determines it is appropriate in light of current market conditions to effect a disposition of such securities. The Fund will not invest in Corporate Loans that would require the Fund to make any additional investments in connection with its obligation to make future advances to a borrower in connection with revolving credit facilities if such commitments would exceed 20% of the Fund’s total assets or would cause the Fund to fail to meet the diversification requirements described herein. The Fund may invest in high-yield corporate debt securities, including Corporate Loans, which are rated in the lower rating categories of the established rating services (Baa or lower by Moody’s and BBB or lower by S&P Global Ratings), or in unrated securities considered by the Manager to be of comparable quality. Securities rated below Baa or lower by Moody’s or BBB or lower by S&P and unrated securities of comparable quality, are commonly known as “junk bonds.” Securities which subsequently are downgraded may continue to be held by the Fund and will be sold only if, in the judgment of the Manager, it is advantageous to do so. Up to 20% of the Fund’s total assets may be invested in Distressed Securities (defined below), which includes publicly offered or privately placed debt securities and Corporate Loans which, at the time of investment, are the subject of bankruptcy proceedings or otherwise in default as to the repayment of principal and/or payment of interest or are rated in the lowest rating categories (Ca or lower by Moody’s and CC or lower by S&P) or which, if unrated, are in the judgment of the Manager of equivalent quality (“Distressed Securities”). Although the Fund will invest primarily in lower-rated securities, other than with respect to Distressed Securities (which are discussed below) it will not invest in securities in the lowest rating categories (Ca or below by Moody’s and CC or below by S&P) unless the Manager believes that the financial condition of the issuer or the protection afforded to the particular securities is stronger than would otherwise be indicated by such low ratings. Securities which subsequently are downgraded may continue to be held by the Fund and will be sold only if, in the judgment of the Manager, it is advantageous to do so. Up to 20% of the Fund’s total assets may be invested in financial instruments of issuers domiciled outside the United States or that are denominated in various foreign currencies and multinational foreign currency units, provided that the foreign issuers of any non-U.S. dollar denominated instruments purchased by the Fund are domiciled in a country that is a member of the Organisation for Economic Co-operation and Development (OECD). Up to 20% of the Fund’s total assets can be invested in convertible debt instruments and preferred stock, each of which may be converted into common stock or other securities of the same or a different issuer, and non-convertible preferred stock. The types of preferred securities in which the Fund may invest include trust preferred securities. As a result of conversions of convertible securities or upon an exchange offer or bankruptcy plan of reorganization, a significant portion of the Fund’s total assets may be invested in common stock at certain points in time. The Fund may engage in various portfolio strategies to seek to increase its return and to hedge its portfolio against movements in interest rates or foreign currencies through the use of interest rate or foreign currency swap transactions, the purchase of call and put options on securities, the sale of covered call and put options on its portfolio securities and transactions in financial futures and related options on such futures. There can be no assurance that the Fund will employ these strategies or that, if employed, they will be effective. The Fund may make short sales of securities, provided that the market value of all securities sold short does not exceed 10% of its total assets. The Fund may make short sales both as a form of hedging to offset potential declines in long positions in similar securities and in order to seek to enhance return. The Fund’s obligation to replace the borrowed security will be secured by collateral deposited with the broker dealer, usually cash, U.S. government securities or other liquid securities similar to those borrowed. The Fund also will be required to segregate similar collateral with its custodian or designate such collateral on its books and records to the extent, if any, necessary so that the value of both collateral amounts in the aggregate is at all times equal to at least 100% of the current market value of the security sold short. The Fund also may make short sales “against the box.” Short sales “against the box” are not subject to the foregoing 10% limitation. Subject to other investment restrictions applicable to the Fund, up to 10% of the Fund’s assets may be invested in debt instruments, including Corporate Loans, of investment companies (which may or may not be registered under the Investment Company Act) whose portfolio securities consist entirely of (i) corporate debt or equity securities acceptable to the Manager or (ii) money market instruments. The Fund has no limitation on the amount of its investments that are not readily marketable or are subject to restrictions on resale. Leverage: The Fund currently utilizes leverage for investment purposes in the form of a bank credit facility. The Fund generally will not utilize leverage if it anticipates that the Fund’s leveraged capital structure would result in a lower return to common stockholders than that obtainable if the common stock were unleveraged for any significant amount of time. At times, the Fund could utilize leverage through borrowings, including the issuance of short term debt securities, the issuance of shares of preferred stock or a combination thereof. The Fund also has the ability to utilize leverage through the issuance of shares of preferred stock. The Fund may also utilize leverage through the use of reverse repurchase agreements. The Fund may enter into derivative securities transactions that have leverage embedded in them. The Fund may also borrow money as a temporary measure for extraordinary or emergency purposes, including the payment of dividends and the settlement of securities transactions which may otherwise require untimely dispositions of Fund securities. The Fund at times may borrow from affiliates of the Manager, provided that the terms of such borrowings are no less favorable than those available from comparable sources of funds in the marketplace. There can be no assurance that the Fund will borrow in order to leverage its assets or, if it does, what percentage of the Fund’s assets such borrowings will represent. The Fund does not currently anticipate issuing any preferred stock. |  |  |  |  |  |  |  |  |
Common Shares [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other Annual Expenses [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Basis of Transaction Fees, Note [Text Block] |  |  |  |  |  |  |  |  |  | as a percentage of net assets attributable to common shares |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lowest Price or Bid |  | 9.78 | $ 9.81 | $ 9.25 | $ 9.25 | 8.8 | $ 8.83 | $ 8.59 | $ 10.06 |  |  |  |  |  |  |  |  |  |
Highest Price or Bid |  | 10.85 | 10.36 | 9.79 | 9.96 | 9.77 | 10.15 | 10.52 | 11.75 |  |  |  |  |  |  |  |  |  |
Lowest Price or Bid, NAV |  | 10.61 | 10.76 | 10.51 | 10.48 | 10.24 | 10.27 | 10.4 | 11.2 |  |  |  |  |  |  |  |  |  |
Highest Price or Bid, NAV |  | $ 10.87 | $ 10.84 | $ 10.72 | $ 10.79 | $ 10.48 | $ 10.84 | $ 11.34 | $ 11.57 |  |  |  |  |  |  |  |  |  |
Highest Price or Bid, Premium (Discount) to NAV [Percent] |  | (0.18%) | (4.43%) | (8.68%) | (7.69%) | (6.77%) | (6.37%) | (7.23%) | 1.56% |  |  |  |  |  |  |  |  |  |
Lowest Price or Bid, Premium (Discount) to NAV [Percent] |  | (7.82%) | (8.83%) | (11.99%) | (11.74%) | (14.06%) | (14.02%) | (17.40%) | (10.18%) |  |  |  |  |  |  |  |  |  |
Share Price |  | $ 10.79 |  |  |  |  |  |  |  | $ 10.79 |  |  |  |  |  |  |  |  |
NAV Per Share |  | $ 10.89 |  |  |  |  |  |  |  | $ 10.89 |  |  |  |  |  |  |  |  |
Latest Premium (Discount) to NAV [Percent] |  |  |  |  |  |  |  |  |  | (0.92%) |  |  |  |  |  |  |  |  |
Capital Stock, Long-Term Debt, and Other Securities [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding Securities [Table Text Block] |  |  |  |  |  |  |  |  |  | DSU is authorized to issue 400 million shares, all of which were initially classified as Common Shares. |  |  |  |  |  |  |  |  |
Outstanding Security, Authorized [Shares] |  |  |  |  |  |  |  |  |  | 400,000,000 |  |  |  |  |  |  |  |  |
Outstanding Security, Held [Shares] |  |  |  |  |  |  |  |  |  | 46,610,312 |  |  |  |  |  |  |  |  |
[1] | If the common shares are sold to or through underwriters, the Prospectus Supplement will set forth any applicable sales load and the estimated offering expenses. Fund shareholders will pay all offering expenses involved with an offering.
[2] | Computershare Trust Company, N.A.’s (the “Reinvestment Plan Agent”) fees for the handling of the reinvestment of dividends will be paid by DSU. However, shareholders will pay a $0.02 per share fee incurred in connection with open-market purchases, which will be deducted from the value of the dividend. Shareholders will also be charged a $0.02 per share fee if a shareholder directs the Reinvestment Plan Agent to sell the common shares held in a dividend reinvestment account. Per share fees include any applicable brokerage commissions the Reinvestment Plan Agent is required to pay.
[3] | DSU and the Manager have entered into a fee waiver agreement (the “Fee Waiver Agreement”), pursuant to which the Manager has contractually agreed to waive the investment advisory fees with respect to any portion of DSU’s assets attributable to investments in any equity and fixed-income mutual funds and exchange-traded funds (the “ETFs”) managed by the Manager or its affiliates that have a contractual management fee, through June 30, 2025. In addition, pursuant to the Fee Waiver Agreement, the Manager has contractually agreed to waive its investment advisory fees by the amount of investment advisory fees DSU pays to the Manager indirectly through its investment in money market funds managed by the Manager or its affiliates, through June 30, 2025. The Fee Waiver Agreement may be terminated at any time, without the payment of any penalty, only by DSU (upon the vote of a majority of the Directors who are not “interested persons” (as defined in the Investment Company Act of 1940, as amended (the “Investment Company Act”), of DSU (the “Independent Directors”)) or a majority of the outstanding voting securities of DSU), upon 90 days’ written notice by DSU to the Manager.
[4] | DSU currently pays the Manager a monthly fee at an annual contractual investment advisory fee rate of 0.55% of the average daily value of DSU’s net assets, plus the proceeds of any outstanding debt securities or borrowings used for leverage (together, “average daily Managed Assets”).
[5] | DSU uses leverage in the form of a credit facility, in an amount equal to approximately 22.7% of DSU’s Managed Assets at an annual interest expense to DSU of 5.91% which is based on current market conditions. The actual amount of interest expense borne by DSU will vary over time in accordance with the level of DSU’s use of leverage and variations in market interest rates. Interest expense is required to be treated as expense of DSU for accounting purposes.
[6] | Calculated by subtracting the Fund’s total liabilities (not including bank borrowings) from the Fund’s total assets and dividing this by the amount of bank borrowings, and by multiplying the results by 1,000.
[7] | Represents the average daily amount outstanding for loans under the revolving credit agreements.

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