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N-2 - USD ($) |  | 3 Months Ended | 12 Months Ended
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Dec. 31, 2022 | Dec. 31, 2022 | Sep. 30, 2022 | Jun. 30, 2022 | Mar. 31, 2022 | Dec. 31, 2021 | Sep. 30, 2021 | Jun. 30, 2021 | Mar. 31, 2021 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Oct. 31, 2019 | Oct. 31, 2018 | Oct. 31, 2017 | Oct. 31, 2016 | Oct. 31, 2015 | Oct. 31, 2014
Cover [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Entity Central Index Key |  | 0001287480 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amendment Flag |  | false |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Document Type |  | N-CSR |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Entity Registrant Name |  | BlackRock Floating Rate Income Trust |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fee Table [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shareholder Transaction Expenses [Table Text Block] |  |
|  | BGT |
Shareholder Transaction Expenses |  |  |  |
Maximum sales load (as a percentage of offering price) (a) |  |  | 1.00 | %
Offering expenses borne by the Trust (as a percentage of offering price) (a) |  |  | 0.04 | %
|  |  | $0.02 per share for open market purchases of |
Dividend reinvestment plan fees |  |  | common shares | (b)
Dividend reinvestment plan sale transaction fee (b) |  |  | $ 2.50 |
| (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. Trust shareholders will pay all offering expenses involved with an offering. |
| (b) | Computershare Trust Company, N.A. (the “Reinvestment Plan Agent”) fees for the handling of the reinvestment of dividends will be paid by the Trust. 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 $2.50 sales fee and pay a $0.15 per share fee if direct 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] | $ 2.5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other Transaction Expenses [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other Transaction Expenses [Percent] | [1] | 0.04% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual Expenses [Table Text Block] |  |
Estimated Annual Expenses (as a percentage of net assets attributable to common shares) |  |  |  |
Investment advisory fees (c),(d) |  |  | 1.07 | %
Other expenses |  |  | 1.13 |
Miscellaneous |  |  | 0.12 |
Interest expense (e) |  |  | 1.01 |
Total annual expenses |  |  | 2.20 |
Fee waiver (d) |  |  | — |
Total annual Trust operating expenses after fee waiver (d) |  |  | 2.20 |
| (c) | The Trust currently pays the Manager a monthly fee at an annual contractual investment advisory fee rate of 0.75% of the average weekly value of the Trust’s Managed Assets. “Managed Assets” means the total assets of the Trust (including any assets attributable to money borrowed for investment purposes) minus the sum of the Trust’s accrued liabilities (other than money borrowed for investment purposes). |
| (d) | The Trust 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 the Trust’s assets attributable to investments in any equity and fixed-income mutual funds and exchange-traded funds (“ETFs”) managed by the Manager or its affiliates that have a contractual management fee, through June 30, 2024. 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 the Trust pays to the Manager indirectly through its investment in money market funds managed by the Manager or its affiliates, through June 30, 2024. The Fee Waiver Agreement may be terminated at any time, without the payment of any penalty, only by the Trust (upon the vote of a majority of the Trustees who are not “interested persons” (as defined in the Investment Company Act) of the Trust (the “Independent Trustees”) or a majority of the outstanding voting securities of the Trust), upon 90 days’ written notice by the Trust to the Manager. |
| (e) | The Trust uses leverage in the form of a credit facility in an amount equal to approximately 24.7% of the Trust’s Managed Assets as of December 31, 2022. The interest expense borne by the Trust will vary over time in accordance with the level of the Trust’s use of leverage and variations in market interest rates. Interest expense is required to be treated as an expense of the Trust for accounting purposes. |
Management Fees [Percent] | [3],[4] | 1.07% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other Annual Expenses [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other Annual Expense 1 [Percent] |  | 0.12% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other Annual Expense 2 [Percent] | [5] | 1.01% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other Annual Expenses [Percent] |  | 1.13% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total Annual Expenses [Percent] |  | 2.20% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Waivers and Reimbursements of Fees [Percent] | [3] | 0.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net Expense over Assets [Percent] | [3] | 2.20% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expense Example [Table Text Block] |  | The following example illustrates the expenses (including the sales load of $10.00 and offering costs of $0.49) that shareholders would pay on a $1,000 investment in common shares, assuming (i) total net annual expenses of 2.20% of net assets attributable to common shares and (ii) a 5% annual return:
|  | 1 Year |  |  | 3 Years |  |  | 5 Years |  |  | 10 Years |
Total expenses incurred |  | $ | 33 |  |  | $ | 79 |  |  | $ | 127 |  |  | $ | 261 |
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. The Trust’s actual rate of return may be greater or less than the hypothetical 5% return shown in the example. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expense Example, Year 01 |  | $ 33 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expense Example, Years 1 to 3 |  | 79 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expense Example, Years 1 to 5 |  | 127 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expense Example, Years 1 to 10 |  | $ 261 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 BGT’s common shares. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Basis of Transaction Fees, Note [Text Block] | [1] | as a percentage of offering price |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other Transaction Fees, Note [Text Block] |  | Computershare Trust Company, N.A. (the “Reinvestment Plan Agent”) fees for the handling of the reinvestment of dividends will be paid by the Trust. 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 $2.50 sales fee and pay a $0.15 per share fee if direct 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. The Trust’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] |  | The Trust 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 the Trust’s assets attributable to investments in any equity and fixed-income mutual funds and exchange-traded funds (“ETFs”) managed by the Manager or its affiliates that have a contractual management fee, through June 30, 2024. 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 the Trust pays to the Manager indirectly through its investment in money market funds managed by the Manager or its affiliates, through June 30, 2024. The Fee Waiver Agreement may be terminated at any time, without the payment of any penalty, only by the Trust (upon the vote of a majority of the Trustees who are not “interested persons” (as defined in the Investment Company Act) of the Trust (the “Independent Trustees”) or a majority of the outstanding voting securities of the Trust), upon 90 days’ written notice by the Trust to the Manager. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Financial Highlights [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Securities [Table Text Block] |  | The following tables set forth information regarding each Trust’s outstanding senior securities as of the end of each of Trust’s last ten fiscal years, as applicable. Each of the Trust’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.
BGT — Fiscal Year Ended |  |  | Total Amount Outstanding (000) |  |  |  | Asset Coverage | (a) |  |  | Liquidating Preference |  |  |  | Average Market Value (000) | (b) |  |  | Type of Senior Security |
December 31, 2022 |  | $ | 91,000 |  |  | $ | 4,055 |  |  | $ | N/A |  |  | $ | 121,677 |  |  |  | Bank Borrowings |
December 31, 2021 |  |  | 143,000 |  |  |  | 3,103 |  |  |  | N/A |  |  |  | 134,068 |  |  |  | Bank Borrowings |
December 31, 2020 |  |  | 129,000 |  |  |  | 3,327 |  |  |  | N/A |  |  |  | 122,934 |  |  |  | Bank Borrowings |
December 31, 2019 |  |  | 130,000 |  |  |  | 3,490 |  |  |  | N/A |  |  |  | 122,426 |  |  |  | Bank Borrowings |
October 31, 2019 |  |  | 123,000 |  |  |  | 3,610 |  |  |  | N/A |  |  |  | 128,378 |  |  |  | Bank Borrowings |
October 31, 2018 |  |  | 142,000 |  |  |  | 3,389 |  |  |  | N/A |  |  |  | 144,490 |  |  |  | Bank Borrowings |
October 31, 2017 |  |  | 150,000 |  |  |  | 3,287 |  |  |  | N/A |  |  |  | 138,255 |  |  |  | Bank Borrowings |
October 31, 2016 |  |  | 148,000 |  |  |  | 3,304 |  |  |  | N/A |  |  |  | 117,885 |  |  |  | Bank Borrowings |
October 31, 2015 |  |  | 104,000 |  |  |  | 4,225 |  |  |  | N/A |  |  |  | 129,575 |  |  |  | Bank Borrowings |
October 31, 2014 |  |  | 145,000 |  |  |  | 3,377 |  |  |  | N/A |  |  |  | 131,570 |  |  |  | Bank Borrowings |
| (a) | Calculated by subtracting the Trust’s total liabilities (not including bank borrowings) from the Trust’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. |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment Objectives and Practices [Text Block] |  | BlackRock Floating Rate Income Trust’s (BGT) (the “Trust”) primary investment objective is to provide a high level of current income. The Trust’s secondary investment objective is to seek the preservation of capital to the extent consistent with its primary objective of high current income. The Trust seeks to achieve its investment objectives by investing primarily, under normal conditions, at least 80% of its assets in floating and variable rate instruments of U.S. and non-U.S. issuers, including a substantial portion of its assets in global floating and variable rate securities including senior secured floating rate loans made to corporate and other business entities. Under normal market conditions, the Trust expects that the average effective duration of its portfolio will be no more than 1.5 years. The Trust may invest directly in such securities or synthetically through the use of derivatives. The Trust’s investment objective is to provide a high level of current income. The Trust, as a secondary objective, also seeks the preservation of capital to the extent consistent with its primary objective of high current income. The Trust will pursue its objectives by investing in a global portfolio of floating rate securities, including investing a significant amount in U.S. and non-U.S. senior secured floating rate loans (“Senior Loans”). Senior Loans are made to corporations, partnerships and other business entities which operate in various industries and geographical regions. Senior Loans pay interest at rates which are redetermined periodically by reference to a base lending rate, primarily LIBOR, plus a premium. It is anticipated that the proceeds of the Senior Loans in which the Trust will acquire interests primarily will be used to finance leveraged buyouts, recapitalizations, mergers, acquisitions, stock repurchases, refinancing and internal growth and for other corporate purposes of borrowers. Under normal market conditions, the Trust will invest at least 80% of its Managed Assets in floating and variable rate instruments of U.S. and non-U.S. issuers, including a substantial portion of its assets in senior, secured loans made to corporate and other business entities. The Trust may invest directly in such securities or synthetically through the use of derivatives. The Trust will provide shareholders with notice at least 60 days prior to changing this non-fundamental policy of the Trust unless such change was previously approved by shareholders. The Trust may also invest up to 20% of its Managed Assets in fixed rate instruments of U.S. and non-U.S. issuers, including developed and emerging markets debt, investment grade and high yield corporate debt, sovereign debt, and mortgage-related and asset-backed securities. “Managed Assets” means the total assets of the Trust (including any assets attributable to money borrowed for investment purposes) minus the sum of the Trust’s accrued liabilities (other than money borrowed for investment purposes). Under normal market conditions, the Trust expects its portfolio to have a duration of no more than 1.5 years (including the effect of anticipated leverage). In comparison to maturity (which is the date on which the issuer of a debt instrument is obligated to repay the principal amount), duration is a measure of the price volatility of a debt instrument as a result in changes in market rates of interest, based on the weighted average timing of the instrument’s expected principal and interest payments. Duration differs from maturity in that it takes into account a security’s yield, coupon payments and its principal payments in addition to the amount of time until the security finally matures. As the value of a security changes over time, so will its duration. Prices of securities with longer durations tend to be more sensitive to interest rate changes than securities with shorter durations. In general, a portfolio of securities with a longer duration can be expected to be more sensitive to interest rate changes than a portfolio with a shorter duration. For example, a hypothetical portfolio with a duration of 1.5 years means that a 1% decrease in interest rates will increase the net asset value of the portfolio by approximately 1.5%; if interest rates increase by 1%, the net asset value will decrease by 1.5%. If this portfolio were leveraged, its net asset value, in the example, may fall more than 1.5% because changes in the net asset value of the Trust are borne entirely by the common shareholders. Under current market conditions, the Trust expects that substantially all of its portfolio will consist of below investment grade debt securities, commonly referred to as “junk bonds,” rated as such at the time of investment, meaning that such bonds are rated by national rating agencies below the four highest grades or are unrated but judged to be of comparable quality by BlackRock Advisors, LLC (the “Manager”) or BlackRock International Limited (“BIL” and together with the Manager, the “Advisors’), the Fund’s sub-advisor. S&P Global Ratings (“S&P”) and Fitch Ratings, Inc. ( “Fitch”) consider securities rated below BBB- to be below investment grade and Moody’s Investors Service, Inc. (“Moody’s”) considers securities rated below Baa3 to be below investment grade. Securities of below investment grade quality are regarded as having predominantly speculative characteristics with respect to issuers’ capacity to pay interest and repay principal. The remainder of the Trust’s assets will be invested in investment grade debt securities. The Trust may invest in individual securities of any credit quality. The Trust expects to invest 30% of its Managed Assets in securities of non-U.S. issuers. The Trust will generally invest in U.S. dollar-denominated securities or in non U.S. dollar-denominated securities for which currency exchange exposure versus the U.S. dollar has been hedged. However, the Trust may invest up to 10% of its Managed Assets in non-U.S. dollar-denominated securities whose currency exchange exposure versus the U.S. dollar remains unhedged. The Trust will not invest 25% or more of its Managed Assets in securities issued or guaranteed by any non-U.S. government, its agencies, instrumentalities or corporations. “Managed Assets” means the total assets of the Trust (including any assets attributable to money borrowed for investment purposes) minus the sum of the Trust’s accrued liabilities (other than money borrowed for investment purposes). The Trust may engage in foreign currency transactions, including foreign currency forward contracts, options, swaps and other strategic transactions in connection with its investments in non-U.S. securities. The Trust may invest in illiquid securities and securities for which prices are not readily available without limit. The Trust may implement various temporary “defensive” strategies at times when the Advisor determine that conditions in the markets make pursuing the Trust’s basic investment strategy inconsistent with the best interests of its shareholders. These strategies may include investing all or a portion of the Trust’s assets in U.S. Government obligations and high-quality, short-term debt securities. Leverage: The Trust currently utilizes leverage for investment purposes in the form of a bank credit facility. The Trust may borrow through reverse repurchase agreements, dollar rolls and other investment techniques. The Fund also has the ability to utilize leverage through the issuance of preferred shares . |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk Factors [Table Text Block] |  |
10. | PRINCIPAL RISKS
In the normal course of business, the Trusts invest in securities or other instruments and may enter into certain transactions, and such activities subject each Trust 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 Trusts and their investments. Each Trust 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 Trust may not be able to readily dispose of such investments at prices that approximate those at which a Trust could sell such investments if they were more widely traded and, as a result of such illiquidity, a Trust 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 Trust’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 Trust 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 Trust to reinvest in lower yielding securities. Each Trust may also be exposed to reinvestment risk, which is the risk that income from each Trust’s portfolio will decline if each Trust invests the proceeds from matured, traded or called fixed-income securities at market interest rates that are below each Trust portfolio’s current earnings rate. Municipal securities are subject to the risk that litigation, legislation or other political events, local business or economic conditions, credit rating downgrades, or the bankruptcy of the issuer could have a significant effect on an issuer’s ability to make payments of principal and/or interest or otherwise affect the value of such securities. Municipal securities can be significantly affected by political or economic changes, including changes made in the law after issuance of the securities, as well as uncertainties in the municipal market related to, taxation, legislative changes or the rights of municipal security holders, including in connection with an issuer insolvency. Municipal securities backed by current or anticipated revenues from a specific project or specific assets can be negatively affected by the discontinuance of the tax benefits supporting the project or assets or the inability to collect revenues for the project or from the assets. Municipal securities may be less liquid than taxable bonds, and there may be less publicly available information on the financial condition of municipal security issuers than for issuers of other securities. Infectious Illness Risk: An outbreak of an infectious illness, such as the COVID-19 pandemic, may adversely impact the economies of many nations and the global economy, and may impact individual issuers and capital markets in ways that cannot be foreseen. An infectious illness outbreak may result in, among other things, closed international borders, prolonged quarantines, supply chain disruptions, market volatility or disruptions and other significant economic, social and political impacts. 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 Trust may invest in illiquid investments. An illiquid investment is any investment that a Trust 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 Trust 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 Trust’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 Trust may lose value, regardless of the individual results of the securities and other instruments in which a Trust invests. The price a Trust could receive upon the sale of any particular portfolio investment may differ from a Trust’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 Trust’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 Trust, and a Trust could realize a greater than expected loss or lesser than expected gain upon the sale of the investment. A Trust’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 Trusts 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 Trusts 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 Trusts to market, issuer and counterparty credit risks, consist principally of financial instruments and receivables due from counterparties. The extent of the Trusts’ 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 Trusts. 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 Trust 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 Trusts should the counterparty fail to perform under the contracts. Options written by the Trusts do not typically give rise to counterparty credit risk, as options written generally obligate the Trusts, and not the counterparty, to perform. The Trusts may be exposed to counterparty credit risk with respect to options written to the extent each Trust deposits collateral with its counterparty to a written option. With exchange-traded options purchased and exchange-traded futures and centrally cleared swaps, there is less counterparty credit risk to the Trusts 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 Trust 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 options purchased and 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 Trusts. Concentration 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 Trust’s portfolio are disclosed in its Schedule of Investments. Certain Trusts 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. Certain Trusts 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 Trusts may be subject to a greater risk of rising interest rates due to the recent period of historically low interest rates. The Federal Reserve has recently begun to raise 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 Trusts’ performance. Certain Trusts 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 Trust 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 United Kingdom’s Financial Conduct Authority announced a phase out of the LIBOR. Although many LIBOR rates ceased to be published or no longer are representative of the underlying market they seek to measure after December 31, 2021, a selection of widely used USD LIBOR rates will continue to be published through June 2023 in order to assist with the transition. The Trusts may be exposed to financial instruments tied to LIBOR to determine payment obligations, financing terms, hedging strategies or investment value. The transition process away from LIBOR might lead to increased volatility and illiquidity in markets for, and reduce the effectiveness of new hedges placed against instruments whose terms currently include LIBOR. The ultimate effect of the LIBOR transition process on the Trusts is uncertain. Risk Factors This section contains a discussion of the general risks of investing in each Trust. 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 Trust will meet its investment objective or that the Trust’s performance will be positive for any period of time. Each risk noted below is applicable to each Trust unless the specific Trust or Trusts are noted in a parenthetical. The order of the below risk factors does not indicate the significance of any particular risk factor. Investment and Market Discount Risk: An investment in the Trust’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 Trust’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 Trust 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 Trust’s net asset value could decrease as a result of its investment activities. At any point in time an investment in the Trust’s common shares may be worth less than the original amount invested, even after taking into account distributions paid by the Trust. During periods in which the Trust may use leverage, the Trust’s investment, market discount and certain other risks will be magnified. Debt Securities Risk: Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.
| • |  | 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 Trust may be subject to a greater risk of rising interest rates due to the recent period of historically low 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 Trust’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 Trusts investments will not affect interest income derived from instruments already owned by the Trust, but will be reflected in the Trust’s net asset value. The Trust may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Trust management. To the extent the Trust 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 Trust) 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 Trust 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 Trust’s performance.
| • |  | 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 Trust’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.
| • |  | 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 Trust may have to invest the proceeds in securities with lower yields.
Mortgage- and Asset-Backed Securities Risks (BHK, BTZ and BGT): 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 o n 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. U.S. Government Obligations Risk (BHK, BTZ and BGT): Certain securities in which the Trust 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. Senior Loans Risk (BGT): 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 Trust 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 Trust 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. Variable and Floating Rate Instrument Risk (BGT): 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 Trust to dispose of them at any given time. Junk Bonds Risk: 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 Trust. Foreign Securities Risk: Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Trust will lose money. These risks include:
| • |  | The Trust 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 Trust’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 Trust’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 Trust’s net asset value for such refunds may be written down partially or in full, which will adversely affect the Trust’s net asset value.
| • |  | The European financial markets have recently experienced volatility and adverse trends due to concerns about economic downturns in, or rising government debt levels of, several European countries as well as acts of war in the region. These events may spread to other countries in Europe and may affect the value and liquidity of certain of the Trust’s investments.
Emerging Markets Risk (BTZ and BGT): 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. Sovereign Debt Risk (BGT): 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. Derivatives Risk: The Trust’s use of derivatives may increase its costs, reduce the Trust’s returns and/or increase volatility. Derivatives involve significant risks, including:
| • |  | Leverage Risk – The Trust’s use of derivatives can magnify the Trust’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 Trust 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 Trust’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 Trust to sell or otherwise close a derivatives position could expose the Trust to losses and could make derivatives more difficult for the Trust 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 Trust’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 Trust’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 Trust realizes from its investments.
Regulatory Risk: Derivative contracts are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, with respect to uncleared swaps, swap dealers are required to collect variation margin from the Trust and may be required by applicable regulations to collect initial margin from the Trust. Both initial and variation margin may be comprised of cash and/or securities, subject to applicable regulatory haircuts. Shares of investment companies (other than certain money market funds) may not be posted as collateral under applicable regulations. In addition, regulations adopted by global prudential regulators that are now in effect require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Trust, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Trust of trading in these instruments and, as a result, may affect returns to investors in the Trust Leverage Risk: The Trust’s use of leverage may increase or decrease from time to time in its discretion and the Trust 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 Trust cannot assure you that the use of leverage will result in a higher yield on the common shares. Any leveraging strategy the Trust 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 Trust 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 Trust 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 Trust’s investments will be borne entirely by the holders of common shares. Therefore, if the market value of the Trust’s portfolio declines, leverage will result in a greater decrease in net asset value to the holders of common shares than if the Trust 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 Trust 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 Trust could lose money if it is unable to recover the securities and the value of the collateral held by the Trust, 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 Trust. 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 (BHK, BTZ and BGT): Dollar rolls involve the risk that the market value of the securities that the Trust is committed to buy may decline below the price of the securities the Trust has sold. These transactions may involve leverage. Illiquid Investments Risk: The Trust 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 Trust may not be able to readily dispose of such investments at prices that approximate those at which the Trust could sell such investments if they were more widely traded and, as a result of such illiquidity, the Trust 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 Trust’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 g rade quality, frequently are unrated and present many of the same risks as investing in below investment grade public debt securities. Market Risk and Selection Risk: Market risk is the risk that one or more markets in which the Trust 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 Trust and its investments. Selection risk is the risk that the securities selected by Trust 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 detected in December 2019 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. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Price [Table Text Block] |  | Share Price Data The following tables summarize each Trust’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. As of December 31, 2022, HYT’s market price, NAV per Common Share, and premium/(discount) to NAV per Common Share were $8.74, $9.25, and (5.51)%, respectively.
|  | NYSE Market Price Per Common Share |  |  | NAV per Common Share on Date of Market Price |  |  | Premium/ (Discount) on Date of Market Price |  |  |  |
BGT — During Quarter Ended |  | High |  |  | Low |  |  | High |  |  | Low |  |  | High |  |  | Low |  |  | Trading Volume |
December 31, 2022 |  |  | $ 11.68 |  |  |  | $ 10.60 |  |  |  | $ 12.44 |  |  |  | $ 12.21 |  |  |  | (6.11 | )% |  |  | (13.19 | )% |  |  | 5,568,336 |
September 30, 2022 |  |  | 12.17 |  |  |  | 10.77 |  |  |  | 12.79 |  |  |  | 12.17 |  |  |  | (4.85 | ) |  |  | (11.50 | ) |  |  | 4,013,597 |
June 30, 2022 |  |  | 12.95 |  |  |  | 10.80 |  |  |  | 13.27 |  |  |  | 12.37 |  |  |  | (2.41 | ) |  |  | (12.69 | ) |  |  | 6,146,663 |
March 31, 2022 |  |  | 14.13 |  |  |  | 11.82 |  |  |  | 13.57 |  |  |  | 12.91 |  |  |  | 4.13 |  |  |  | (8.44 | ) |  |  | 5,978,514 |
December 31, 2021 |  |  | 12.62 |  |  |  | 13.21 |  |  |  | 13.49 |  |  |  | 13.58 |  |  |  | (6.45 | ) |  |  | (2.72 | ) |  |  | 6,270,147 |
September 30, 2021 |  |  | 12.91 |  |  |  | 12.69 |  |  |  | 13.57 |  |  |  | 13.53 |  |  |  | (4.86 | ) |  |  | (6.21 | ) |  |  | 5,430,380 |
June 30, 2021 |  |  | 13.37 |  |  |  | 12.45 |  |  |  | 13.59 |  |  |  | 13.54 |  |  |  | (1.62 | ) |  |  | (8.05 | ) |  |  | 6,202,740 |
March 31, 2021 |  |  | 14.51 |  |  |  | 11.73 |  |  |  | 13.53 |  |  |  | 13.42 |  |  |  | 7.24 |  |  |  | (12.59 | ) |  |  | 4,655,909 |
As of December 31, 2022, BGT’s market price, NAV per Common Share, and premium/(discount) to NAV per Common Share were $10.94, $12.43, and (11.99)%, respectively. Common shares of each Trust have historically traded at both a premium and discount to NAV. Shares of closed-end funds frequently trade at a discount to their NAV. Because of this possibility and the recognition that any such discount may not be in the interest of shareholders, the Board might consider from time to time engaging in open-market repurchases, managed distribution plans, or other programs intended to reduce the discount. We cannot guarantee or assure, however, that the Board will decide to engage in any of these actions. Nor is there any guarantee or assurance that such actions, if undertaken, would result in the shares trading at a price equal or close to the NAV. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capital Stock, Long-Term Debt, and Other Securities [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capital Stock [Table Text Block] |  |
11. | CAPITAL SHARE TRANSACTIONS
BHK, BTZ and BGT is authorized to issue an unlimited number of shares, par value $0.001, all of which were initially classified as Common Shares. HYT is authorized to issue 200 million shares, par value $0.10, all of which were initially classified as Common Shares. The Board is authorized, however, to reclassify any unissued Common Shares to Preferred Shares without the approval of Common Shareholders. As of the close of business on September 20, 2022, HYT issued transferrable rights to its Common Shareholders of record, entitling the holders of those rights to subscribe for shares of HYT’s common stock (the “Offer”). Shareholders received one right for each outstanding Common Share owned on the record date. The rights entitled their holders to purchase one new Common Share for every five rights held (1-for-5). The Offer expired on October 13, 2022. HYT received from the Offer gross proceeds of $167,749,786 for the issuance of 20,382,720 Common Shares. The rights offering resulted in $(0.13) or (1.42)% NAV dilution since the Common Shares were issued below HYT’s NAV. HYT received the entire proceeds from the shares issued under the Offer since the Manager agreed to pay for all expenses (including sales commissions) related to the Offer. BHK and HYT have filed a prospectus with the SEC allowing them to issue an additional 15,000,000 and 19,617,820 Common Shares, respectively, through an equity shelf program (a “Shelf Offering”). Under the Shelf Offering, BHK and HYT, 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 Trust’s NAV per Common Share (calculated within 48 hours of pricing). For the year ended December 31, 2022, BHK and HYT did not issue any Common Shares. As of year end, 15,000,000 and 19,617,820 Common Shares, respectively, remain available for issuance under the Shelf Offering. See Additional Information - Shelf Offering Program for additional information. BGT filed a registration statement with the SEC seeking the ability to issue additional Common Shares through an equity shelf program (a “Shelf Offering”), which was declared effective on December 28, 2022. BGT may not sell any Common Shares in the Shelf Offering until a definitive prospectus relating to the Shelf Offering has been filed with the SEC. Under the Shelf Offering, the Trust 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 the Trust’s NAV per Common Share (calculated within 48 hours of pricing). See Additional Information - Shelf Offering Program for additional information. Initial costs incurred by BHK, HYT and BGT in connection with their Shelf Offerings 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. For the periods shown, shares issued and outstanding increased by the following amounts as a result of dividend reinvestment:
|  | Year Ended |
Trust Name |  | 12/31/22 |  |  | 12/31/21 |
BHK |  |  | 17,666 |  |  |  | 57,910 |
HYT |  |  | 101,463 |  |  |  | 311,681 |
BTZ |  |  | — |  |  |  | 28,104 |
BGT |  |  | 2,386 |  |  |  | 7,902 |
The Trusts participate in an open market share repurchase program (the “Repurchase Program”). From December 1, 2021 through November 30, 2022, each Trust 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, 2021, subject to certain conditions. From December 1, 2022 through November 30, 2023, each Trust 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. The Repurchase Program has an accretive effect as shares are purchased at a discount to the Trust’s NAV. There is no assurance that the Trusts will purchase shares in any particular amounts. For the year ended December 31, 2022, the Trusts did not repurchase any shares. For the year ended December 31, 2022, shares issued and outstanding remained constant for BTZ. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Market Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Market Risk: Each Trust 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 Trust to reinvest in lower yielding securities. Each Trust may also be exposed to reinvestment risk, which is the risk that income from each Trust’s portfolio will decline if each Trust invests the proceeds from matured, traded or called fixed-income securities at market interest rates that are below each Trust portfolio’s current earnings rate. Municipal securities are subject to the risk that litigation, legislation or other political events, local business or economic conditions, credit rating downgrades, or the bankruptcy of the issuer could have a significant effect on an issuer’s ability to make payments of principal and/or interest or otherwise affect the value of such securities. Municipal securities can be significantly affected by political or economic changes, including changes made in the law after issuance of the securities, as well as uncertainties in the municipal market related to, taxation, legislative changes or the rights of municipal security holders, including in connection with an issuer insolvency. Municipal securities backed by current or anticipated revenues from a specific project or specific assets can be negatively affected by the discontinuance of the tax benefits supporting the project or assets or the inability to collect revenues for the project or from the assets. Municipal securities may be less liquid than taxable bonds, and there may be less publicly available information on the financial condition of municipal security issuers than for issuers of other securities. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Infectious Illness Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Infectious Illness Risk: An outbreak of an infectious illness, such as the COVID-19 pandemic, may adversely impact the economies of many nations and the global economy, and may impact individual issuers and capital markets in ways that cannot be foreseen. An infectious illness outbreak may result in, among other things, closed international borders, prolonged quarantines, supply chain disruptions, market volatility or disruptions and other significant economic, social and political impacts. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 Trust may invest in illiquid investments. An illiquid investment is any investment that a Trust 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 Trust 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 Trust’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 Trust may lose value, regardless of the individual results of the securities and other instruments in which a Trust invests. The price a Trust could receive upon the sale of any particular portfolio investment may differ from a Trust’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 Trust’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 Trust, and a Trust could realize a greater than expected loss or lesser than expected gain upon the sale of the investment. A Trust’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 Trusts 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 Trusts 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 Trusts to market, issuer and counterparty credit risks, consist principally of financial instruments and receivables due from counterparties. The extent of the Trusts’ 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 Trusts. 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 Trust 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 Trusts should the counterparty fail to perform under the contracts. Options written by the Trusts do not typically give rise to counterparty credit risk, as options written generally obligate the Trusts, and not the counterparty, to perform. The Trusts may be exposed to counterparty credit risk with respect to options written to the extent each Trust deposits collateral with its counterparty to a written option. With exchange-traded options purchased and exchange-traded futures and centrally cleared swaps, there is less counterparty credit risk to the Trusts 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 Trust 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 options purchased and 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 Trusts. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Concentration Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Concentration 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 Trust’s portfolio are disclosed in its Schedule of Investments. Certain Trusts 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. Certain Trusts 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 Trusts may be subject to a greater risk of rising interest rates due to the recent period of historically low interest rates. The Federal Reserve has recently begun to raise 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 Trusts’ performance. Certain Trusts 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 Trust 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 United Kingdom’s Financial Conduct Authority announced a phase out of the LIBOR. Although many LIBOR rates ceased to be published or no longer are representative of the underlying market they seek to measure after December 31, 2021, a selection of widely used USD LIBOR rates will continue to be published through June 2023 in order to assist with the transition. The Trusts may be exposed to financial instruments tied to LIBOR to determine payment obligations, financing terms, hedging strategies or investment value. The transition process away from LIBOR might lead to increased volatility and illiquidity in markets for, and reduce the effectiveness of new hedges placed against instruments whose terms currently include LIBOR. The ultimate effect of the LIBOR transition process on the Trusts is uncertain. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment and Market Discount Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Investment and Market Discount Risk: An investment in the Trust’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 Trust’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 Trust 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 Trust’s net asset value could decrease as a result of its investment activities. At any point in time an investment in the Trust’s common shares may be worth less than the original amount invested, even after taking into account distributions paid by the Trust. During periods in which the Trust may use leverage, the Trust’s investment, market discount and certain other risks will be magnified. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Debt Securities Risk: Debt securities, such as bonds, involve interest rate risk, credit risk, extension risk, and prepayment risk, among other things.
| • |  | 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 Trust may be subject to a greater risk of rising interest rates due to the recent period of historically low 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 Trust’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 Trusts investments will not affect interest income derived from instruments already owned by the Trust, but will be reflected in the Trust’s net asset value. The Trust may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Trust management. To the extent the Trust 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 Trust) 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 Trust 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 Trust’s performance.
| • |  | 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 Trust’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.
| • |  | 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 Trust may have to invest the proceeds in securities with lower yields.
Mortgage and AssetBacked Securities Risks [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Mortgage- and Asset-Backed Securities Risks (BHK, BTZ and BGT): 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 o n 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. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
U.S. Government Obligations Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | U.S. Government Obligations Risk (BHK, BTZ and BGT): Certain securities in which the Trust 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. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Loans Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Senior Loans Risk (BGT): 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 Trust 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 Trust 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. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable and Floating Rate Instrument Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Variable and Floating Rate Instrument Risk (BGT): 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 Trust to dispose of them at any given time. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Junk Bonds Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Junk Bonds Risk: 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 Trust. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Foreign Securities Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Foreign Securities Risk: Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Trust will lose money. These risks include:
| • |  | The Trust 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 Trust’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 Trust’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 Trust’s net asset value for such refunds may be written down partially or in full, which will adversely affect the Trust’s net asset value.
| • |  | The European financial markets have recently experienced volatility and adverse trends due to concerns about economic downturns in, or rising government debt levels of, several European countries as well as acts of war in the region. These events may spread to other countries in Europe and may affect the value and liquidity of certain of the Trust’s investments.
Emerging Markets Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Emerging Markets Risk (BTZ and BGT): 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. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sovereign Debt Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Sovereign Debt Risk (BGT): 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. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivatives Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Derivatives Risk: The Trust’s use of derivatives may increase its costs, reduce the Trust’s returns and/or increase volatility. Derivatives involve significant risks, including:
| • |  | Leverage Risk – The Trust’s use of derivatives can magnify the Trust’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 Trust 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 Trust’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 Trust to sell or otherwise close a derivatives position could expose the Trust to losses and could make derivatives more difficult for the Trust 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 Trust’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 Trust’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 Trust realizes from its investments.
Regulatory Risk: Derivative contracts are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, with respect to uncleared swaps, swap dealers are required to collect variation margin from the Trust and may be required by applicable regulations to collect initial margin from the Trust. Both initial and variation margin may be comprised of cash and/or securities, subject to applicable regulatory haircuts. Shares of investment companies (other than certain money market funds) may not be posted as collateral under applicable regulations. In addition, regulations adopted by global prudential regulators that are now in effect require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Trust, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Trust of trading in these instruments and, as a result, may affect returns to investors in the Trust |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Regulatory Risk: Derivative contracts are subject to regulation under the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”) in the United States and under comparable regimes in Europe, Asia and other non-U.S. jurisdictions. Under the Dodd-Frank Act, with respect to uncleared swaps, swap dealers are required to collect variation margin from the Trust and may be required by applicable regulations to collect initial margin from the Trust. Both initial and variation margin may be comprised of cash and/or securities, subject to applicable regulatory haircuts. Shares of investment companies (other than certain money market funds) may not be posted as collateral under applicable regulations. In addition, regulations adopted by global prudential regulators that are now in effect require certain bank-regulated counterparties and certain of their affiliates to include in certain financial contracts, including many derivatives contracts, terms that delay or restrict the rights of counterparties, such as the Trust, to terminate such contracts, foreclose upon collateral, exercise other default rights or restrict transfers of credit support in the event that the counterparty and/or its affiliates are subject to certain types of resolution or insolvency proceedings. The implementation of these requirements with respect to derivatives, as well as regulations under the Dodd-Frank Act regarding clearing, mandatory trading and margining of other derivatives, may increase the costs and risks to the Trust of trading in these instruments and, as a result, may affect returns to investors in the Trust |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Leverage Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Leverage Risk: The Trust’s use of leverage may increase or decrease from time to time in its discretion and the Trust 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 Trust cannot assure you that the use of leverage will result in a higher yield on the common shares. Any leveraging strategy the Trust 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 Trust 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 Trust 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 Trust’s investments will be borne entirely by the holders of common shares. Therefore, if the market value of the Trust’s portfolio declines, leverage will result in a greater decrease in net asset value to the holders of common shares than if the Trust 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 Trust 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 Trust could lose money if it is unable to recover the securities and the value of the collateral held by the Trust, 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 Trust. 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 (BHK, BTZ and BGT): Dollar rolls involve the risk that the market value of the securities that the Trust is committed to buy may decline below the price of the securities the Trust has sold. These transactions may involve leverage. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Illiquid Investments Risk [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  | Illiquid Investments Risk: The Trust 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 Trust may not be able to readily dispose of such investments at prices that approximate those at which the Trust could sell such investments if they were more widely traded and, as a result of such illiquidity, the Trust 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 Trust’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 g rade quality, frequently are unrated and present many of the same risks as investing in below investment grade public debt securities. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 Trust 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 Trust and its investments. Selection risk is the risk that the securities selected by Trust 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 detected in December 2019 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. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bank Borrowings [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Financial Highlights [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Securities Amount |  |  |  |  |  |  |  |  |  |  | $ 91,000 | $ 143,000 | $ 129,000 | $ 130,000 | $ 123,000 | $ 142,000 | $ 150,000 | $ 148,000 | $ 104,000 | $ 145,000
Senior Securities Coverage per Unit | [6] |  |  |  |  |  |  |  |  |  | $ 4,055 | $ 3,103 | $ 3,327 | $ 3,490 | $ 3,610 | $ 3,389 | $ 3,287 | $ 3,304 | $ 4,225 | $ 3,377
Senior Securities Involuntary Liquidating Preference per Unit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Senior Securities Average Market Value per Unit | [7] |  |  |  |  |  |  |  |  |  | $ 121,677 | $ 134,068 | $ 122,934 | $ 122,426 | $ 128,378 | $ 144,490 | $ 138,255 | $ 117,885 | $ 129,575 | $ 131,570
Senior Securities, Note [Text Block] |  | Senior Securities The following tables set forth information regarding each Trust’s outstanding senior securities as of the end of each of Trust’s last ten fiscal years, as applicable. Each of the Trust’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.
BGT — Fiscal Year Ended |  |  | Total Amount Outstanding (000) |  |  |  | Asset Coverage | (a) |  |  | Liquidating Preference |  |  |  | Average Market Value (000) | (b) |  |  | Type of Senior Security |
December 31, 2022 |  | $ | 91,000 |  |  | $ | 4,055 |  |  | $ | N/A |  |  | $ | 121,677 |  |  |  | Bank Borrowings |
December 31, 2021 |  |  | 143,000 |  |  |  | 3,103 |  |  |  | N/A |  |  |  | 134,068 |  |  |  | Bank Borrowings |
December 31, 2020 |  |  | 129,000 |  |  |  | 3,327 |  |  |  | N/A |  |  |  | 122,934 |  |  |  | Bank Borrowings |
December 31, 2019 |  |  | 130,000 |  |  |  | 3,490 |  |  |  | N/A |  |  |  | 122,426 |  |  |  | Bank Borrowings |
October 31, 2019 |  |  | 123,000 |  |  |  | 3,610 |  |  |  | N/A |  |  |  | 128,378 |  |  |  | Bank Borrowings |
October 31, 2018 |  |  | 142,000 |  |  |  | 3,389 |  |  |  | N/A |  |  |  | 144,490 |  |  |  | Bank Borrowings |
October 31, 2017 |  |  | 150,000 |  |  |  | 3,287 |  |  |  | N/A |  |  |  | 138,255 |  |  |  | Bank Borrowings |
October 31, 2016 |  |  | 148,000 |  |  |  | 3,304 |  |  |  | N/A |  |  |  | 117,885 |  |  |  | Bank Borrowings |
October 31, 2015 |  |  | 104,000 |  |  |  | 4,225 |  |  |  | N/A |  |  |  | 129,575 |  |  |  | Bank Borrowings |
October 31, 2014 |  |  | 145,000 |  |  |  | 3,377 |  |  |  | N/A |  |  |  | 131,570 |  |  |  | Bank Borrowings |
| (a) | Calculated by subtracting the Trust’s total liabilities (not including bank borrowings) from the Trust’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. |
Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lowest Price or Bid |  |  | $ 10.6 | $ 10.77 | $ 10.8 | $ 11.82 | $ 13.21 | $ 12.69 | $ 12.45 | $ 11.73 |  |  |  |  |  |  |  |  |  |
Highest Price or Bid |  |  | 11.68 | 12.17 | 12.95 | 14.13 | 12.62 | 12.91 | 13.37 | 14.51 |  |  |  |  |  |  |  |  |  |
Lowest Price or Bid, NAV |  |  | 12.21 | 12.17 | 12.37 | 12.91 | 13.58 | 13.53 | 13.54 | 13.42 |  |  |  |  |  |  |  |  |  |
Highest Price or Bid, NAV |  |  | $ 12.44 | $ 12.79 | $ 13.27 | $ 13.57 | $ 13.49 | $ 13.57 | $ 13.59 | $ 13.53 |  |  |  |  |  |  |  |  |  |
Highest Price or Bid, Premium (Discount) to NAV [Percent] |  |  | (6.11%) | (4.85%) | (2.41%) | 4.13% | (6.45%) | (4.86%) | (1.62%) | 7.24% |  |  |  |  |  |  |  |  |  |
Lowest Price or Bid, Premium (Discount) to NAV [Percent] |  |  | (13.19%) | (11.50%) | (12.69%) | (8.44%) | (2.72%) | (6.21%) | (8.05%) | (12.59%) |  |  |  |  |  |  |  |  |  |
Latest Share Price |  | $ 10.94 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Latest Premium (Discount) to NAV [Percent] |  | (11.99%) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Latest NAV |  | $ 12.43 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capital Stock, Long-Term Debt, and Other Securities [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding Securities [Table Text Block] |  | BHK, BTZ and BGT is authorized to issue an unlimited number of shares, par value $0.001, all of which were initially classified as Common Shares. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding Security, Held [Shares] |  | 22,370,659 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
[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. Trust shareholders will pay all offering expenses involved with an offering.
[2] | Computershare Trust Company, N.A. (the “Reinvestment Plan Agent”) fees for the handling of the reinvestment of dividends will be paid by the Trust. 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 $2.50 sales fee and pay a $0.15 per share fee if direct 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] | The Trust 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 the Trust’s assets attributable to investments in any equity and fixed-income mutual funds and exchange-traded funds (“ETFs”) managed by the Manager or its affiliates that have a contractual management fee, through June 30, 2024. 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 the Trust pays to the Manager indirectly through its investment in money market funds managed by the Manager or its affiliates, through June 30, 2024. The Fee Waiver Agreement may be terminated at any time, without the payment of any penalty, only by the Trust (upon the vote of a majority of the Trustees who are not “interested persons” (as defined in the Investment Company Act) of the Trust (the “Independent Trustees”) or a majority of the outstanding voting securities of the Trust), upon 90 days’ written notice by the Trust to the Manager.
[4] | The Trust currently pays the Manager a monthly fee at an annual contractual investment advisory fee rate of 0.75% of the average weekly value of the Trust’s Managed Assets. “Managed Assets” means the total assets of the Trust (including any assets attributable to money borrowed for investment purposes) minus the sum of the Trust’s accrued liabilities (other than money borrowed for investment purposes).
[5] | The Trust uses leverage in the form of a credit facility in an amount equal to approximately 24.7% of the Trust’s Managed Assets as of December 31, 2022. The interest expense borne by the Trust will vary over time in accordance with the level of the Trust’s use of leverage and variations in market interest rates. Interest expense is required to be treated as an expense of the Trust for accounting purposes.
[6] | Calculated by subtracting the Trust’s total liabilities (not including bank borrowings) from the Trust’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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