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N-2 - USD ($) | 3 Months Ended | 12 Months Ended
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Dec. 31, 2024 | Sep. 30, 2024 | Jun. 30, 2024 | Mar. 31, 2024 | Dec. 31, 2023 | Sep. 30, 2023 | Jun. 30, 2023 | Mar. 31, 2023 | Dec. 31, 2024
Cover [Abstract] |  |  |  |  |  |  |  |  |  |
Entity Central Index Key |  |  |  |  |  |  |  |  |  | 0001160864
Amendment Flag |  |  |  |  |  |  |  |  |  | false
Document Type |  |  |  |  |  |  |  |  |  | N-CSR
Entity Registrant Name |  |  |  |  |  |  |  |  |  | BlackRock Core Bond Trust
Fee Table [Abstract] |  |  |  |  |  |  |  |  |  |
Shareholder Transaction Expenses [Table Text Block] |  |  |  |  |  |  |  |  |  |
| BHK
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) | 0.00%
Dividend reinvestment plan fees | $0.02 per share for open market purchases of common shares (b)
Dividend reinvestment plan sale transaction fee | $2.50 (b)
(a) If the common shares are sold to or through underwriters, the Prospectus Supplement will set forth any applicable sales load and the estimated offering expenses. Trust shareholders will pay all offering expenses involved with an offering. (b) Computershare Trust Company, N.A.’s (the “Reinvestment Plan Agent”) fees for the handling of the reinvestment of dividends will be paid by BHK. 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 a shareholder directs the Reinvestment Plan Agent to sell the common shares held in a dividend reinvestment account. Per share fees include any applicable brokerage commissions the Reinvestment Plan Agent is required to pay.
Sales Load [Percent] | [1] |  |  |  |  |  |  |  |  | 1.00%
Dividend Reinvestment and Cash Purchase Fees | [2] |  |  |  |  |  |  |  |  | $ 2.5
Other Transaction Expenses [Abstract] |  |  |  |  |  |  |  |  |  |
Other Transaction Expenses [Percent] | [1] |  |  |  |  |  |  |  |  | 0.00%
Annual Expenses [Table Text Block] |  |  |  |  |  |  |  |  |  |
Estimated Annual Expenses (as a percentage of net assets attributable to common shares) |
Investment advisory fees (c)(d) | 0.77 %
Other expenses | 2.90
Miscellaneous | 0.11
Interest expense (e) | 2.79
Total annual expenses | 3.67
Fee waivers (d) | —
Total annual Trust operating expenses after fee waivers (d) | 3.67
(c) BHK currently pays the Manager a monthly fee at an annual contractual investment advisory fee rate of 0.50% of its average weekly managed assets. For purposes of calculating these fees, “managed assets” means the total assets of BHK (including any assets attributable to money borrowed) minus the sum of its accrued liabilities (other than money borrowed for investment purposes). (d) BHK 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 BHK’s assets attributable to investments in any equity and fixed-income mutual funds and exchange-traded funds managed by the Manager or its affiliates that have a contractual management fee, through June 30, 2026. 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 BHK pays to the Manager indirectly through its investment in money market funds managed by the Manager or its affiliates, through June 30, 2026. The Fee Waiver Agreement may be terminated at any time, without the payment of any penalty, only by BHK (upon the vote of a majority of the Trustees who are not “interested persons” (as defined in the Investment Company Act) of BHK or a majority of the outstanding voting securities of BHK), upon 90 days’ written notice by BHK to the Manager. (e) BHK uses leverage in the form of reverse repurchase agreements representing 39.5% of managed assets at an annual interest expense to BHK of 5.2%, which is based on current market conditions. The actual amount of interest expense borne by BHK will vary over time in accordance with the level of BHK’s use of reverse repurchase agreements and variations in market interest rates. Interest expense is required to be treated as an expense of BHK for accounting purposes.
Management Fees [Percent] | [3],[4] |  |  |  |  |  |  |  |  | 0.77%
Other Annual Expenses [Abstract] |  |  |  |  |  |  |  |  |  |
Other Annual Expense 1 [Percent] |  |  |  |  |  |  |  |  |  | 0.11%
Other Annual Expense 2 [Percent] | [5] |  |  |  |  |  |  |  |  | 2.79%
Other Annual Expenses [Percent] |  |  |  |  |  |  |  |  |  | 2.90%
Total Annual Expenses [Percent] |  |  |  |  |  |  |  |  |  | 3.67%
Waivers and Reimbursements of Fees [Percent] | [3] |  |  |  |  |  |  |  |  | 0.00%
Net Expense over Assets [Percent] | [3] |  |  |  |  |  |  |  |  | 3.67%
Expense Example [Table Text Block] |  |  |  |  |  |  |  |  |  | The following example illustrates BHK ’ s expenses (including the sales load of $10.00 and offering costs of $0.00) that shareholders would pay on a $1,000 investment in common shares, assuming (i) total net annual expenses of 3.67% of net assets attributable to common shares and (ii) a 5% annual return:
| 1 Year | 3 Years | 5 Years | 10 Years |  |
Total expenses incurred | $ 47 | $ 121 | $ 198 | $ 398 |  |
Expense Example, Year 01 |  |  |  |  |  |  |  |  |  | $ 47
Expense Example, Years 1 to 3 |  |  |  |  |  |  |  |  |  | 121
Expense Example, Years 1 to 5 |  |  |  |  |  |  |  |  |  | 198
Expense Example, Years 1 to 10 |  |  |  |  |  |  |  |  |  | $ 398
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 BHK ’ s common shares.
Basis of Transaction Fees, Note [Text Block] |  |  |  |  |  |  |  |  |  | as a percentage of offering price
Other Transaction Fees, Note [Text Block] |  |  |  |  |  |  |  |  |  | (b) Computershare Trust Company, N.A.’s (the “Reinvestment Plan Agent”) fees for the handling of the reinvestment of dividends will be paid by BHK. 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 a shareholder directs the Reinvestment Plan Agent to sell the common shares held in a dividend reinvestment account. Per share fees include any applicable brokerage commissions the Reinvestment Plan Agent is required to pay.
Other Expenses, Note [Text Block] |  |  |  |  |  |  |  |  |  | The example should not be considered a representation of future expenses. The example assumes that the estimated “Other expenses” set forth in the Estimated Annual Expenses table are accurate and that all dividends and distributions are reinvested at NAV. Actual expenses may be greater or less than those assumed. BHK’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] |  |  |  |  |  |  |  |  |  | (d) BHK 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 BHK’s assets attributable to investments in any equity and fixed-income mutual funds and exchange-traded funds managed by the Manager or its affiliates that have a contractual management fee, through June 30, 2026. 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 BHK pays to the Manager indirectly through its investment in money market funds managed by the Manager or its affiliates, through June 30, 2026. The Fee Waiver Agreement may be terminated at any time, without the payment of any penalty, only by BHK (upon the vote of a majority of the Trustees who are not “interested persons” (as defined in the Investment Company Act) of BHK or a majority of the outstanding voting securities of BHK), upon 90 days’ written notice by BHK to the Manager.
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Investment Objectives and Practices [Text Block] |  |  |  |  |  |  |  |  |  | Investment Objective BlackRock Core Bond Trust ’ s ( BHK ) (the “ Trust ”) investment objective is to provide current income and capital appreciation. The Trust seeks to achieve its investment objective by investing, under normal market conditions, at least 75% of its managed assets in bonds that are investment grade quality at the time of investment. Under normal market conditions, the Trust intends to invest its assets primarily in a diversified portfolio of investment grade bonds, which may include, but are not limited to, corporate bonds, U.S. government and agency securities and mortgage-related securities. The Trust may invest up to 25% of its total managed assets in bonds that, at the time of investment, are rated Ba/BB or below by Moody’s Investors Service, Inc. (“Moody’s”), S&P Global Ratings ("S&P"), Fitch Ratings (“Fitch”) or another nationally recognized rating agency or bonds that are unrated but judged to be of comparable quality by the investment adviser. The Trust may invest up to 10% of its total managed assets in bonds issued in foreign currencies. The Trust may invest directly in such securities or synthetically through the use of derivatives. No assurance can be given that the Trust’s investment objective will be achieved. Investment Objectives and Policies BlackRock Core Bond Trust (BHK) The Trust’s investment objective is to provide current income and capital appreciation. As a non-fundamental policy, under normal market conditions, the Trust invests at least 80% of its assets in bonds. For the purposes of this strategy, “bonds” include the following: obligations issued or guaranteed by the U.S. Government or a foreign government or their agencies, instrumentalities or political subdivisions; mortgage-backed securities, including agency mortgage pass-through securities and commercial mortgage-backed securities; mortgage to-be-announced (“TBA”) securities; debt obligations of U.S. or foreign issuers; municipal securities; and asset-backed securities. The Trust’s investments in derivatives will be counted toward the Trust’s 80% policy to the extent that they provide investment exposure to the securities included within that policy or to one or more market risk factors associated with such securities. The 80% policy is a non-fundamental policy of the Trust and may not be changed without 60 days’ prior notice to shareholders. Under current market conditions, the Trust intends to invest its assets primarily in a diversified portfolio of investment grade bonds, which may include, but are not limited to, corporate bonds, mortgage-related securities and U.S. government and agency debt securities. The Trust may invest up to 10% of its total managed assets in bonds issued in foreign currencies. The Trust may also purchase loan participations and assignments. The Trust may invest directly in securities or synthetically through the use of derivatives.The Trust will also invest in bonds that, in the opinion of BlackRock Advisors, LLC (the “Manager”) and BlackRock International Limited (“BIL”) and BlackRock (Singapore) Limited (“BSL” and collectively with the Manager and BIL, the “Advisors”), the Trust’s sub-advisors, are underrated or undervalued or have the potential for above-average current income and capital appreciation. Underrated bonds are those whose ratings do not, in Advisors’ opinion, reflect their true creditworthiness. Undervalued bonds are bonds that, in the opinion of the Advisors, are worth more than the value assigned to them in the marketplace. The Advisors may at times believe that bonds associated with a particular market sector (for example, mortgage-related securities), or issued by a particular issuer, are undervalued. The Advisors may purchase those bonds for the Trust’s portfolio because they represent a market sector or issuer that the Advisors consider undervalued, even if the value of those particular bonds appears to be consistent with the value of similar bonds. Bonds of particular issuers (for example, the Federal Home Loan Mortgage Association) may be undervalued because there is a temporary excess of supply in that market sector, or because of a general decline in the market price of bonds of the market sector for reasons that do not apply to the particular bonds that are considered undervalued. The Trust’s investment in underrated or undervalued bonds will be based on the Advisors’ belief that their yield is higher than that available on bonds bearing equivalent levels of interest rate risk, credit risk and other forms of risk, and that their prices will ultimately rise, relative to the market, to reflect their true value. The Trust may engage in active and frequent trading of portfolio securities to achieve its principal investment strategies. The Trust invests primarily in investment grade bonds. Under normal market conditions, the Trust invests at least 75% of its total managed assets in investment grade quality bonds. Investment grade quality means that such bonds are rated, at the time of investment, within the four highest grades (Baa or BBB or better by Moody’s Investors Service, Inc. (“Moody’s”), S&P Global Ratings (“S&P”), Fitch Ratings, Inc. (“Fitch”) or another nationally recognized rating agency) by one nationally recognized rating agency or are unrated but judged to be of comparable quality by the Advisors. Bonds that are rated by two or more nationally recognized rating agencies will be considered to have the higher credit rating. Changes in economic conditions or other circumstances are more likely to lead to a weakened capacity for bonds that are rated BBB or Baa (or that have equivalent ratings) to make principal and interest payments than is the case for higher rated bonds. The Trust may invest up to 25% of its total managed assets in bonds that are rated, at the time of investment, Ba/BB or below by Moody’s, S&P, Fitch or another nationally recognized rating agency or that are unrated but judged to be of comparable quality by the Advisors. Bonds of below investment grade quality are commonly referred to as “junk bonds.” Bonds of below investment grade quality are regarded as having predominantly speculative characteristics with respect to the issuer’s capacity to pay interest and repay principal. The lowest rated bonds in which the Trust may invest are securities rated in the category “C” or determined by the Advisors to be of comparable quality. Securities rated “C” are considered highly speculative and may be used to cover a situation where the issuer has filed a bankruptcy petition but debt service payments are continued. While such debt will likely have some quality and protective characteristics, those are outweighed by large uncertainties or major risk exposure to adverse conditions. These credit quality policies apply only at the time a security is purchased, and the Trust is not required to dispose of a security if a rating agency downgrades its assessment of the credit characteristics of a particular issue. In determining whether to retain or sell a security that a rating agency has downgraded, the Advisors may consider such factors as the Advisors’ assessment of the credit quality of the issuer of the security, the price at which the security could be sold and the rating, if any, assigned to the security by other rating agencies. The Trust may also invest in securities of other open- or closed-end investment companies that invest primarily in bonds of the types in which the Trust may invest directly. As part of the management of the Trust, the Advisors manage the effective duration of the Trust’s portfolio. The target duration of the Trust’s portfolio may change from time to time. The Advisors may, but are not required to, when consistent with the Trust’s investment objective, use various strategic investment transactions to earn income, facilitate portfolio management and mitigate risks, including currency risk. The Trust may purchase and sell derivative instruments such as exchange-listed and over-the-counter put and call options on securities, financial futures, equity, fixed-income and interest rate indices, and other financial instruments, purchase and sell financial futures contracts and options thereon, enter into various interest rate transactions such as swaps, caps, floors or collars and enter into various currency transactions such as currency forward contracts, currency futures contracts, currency swaps or options on currency or currency futures or credit transactions and credit default swaps. The Trust also may purchase derivative instruments that combine features of these instruments. Collectively, all of the above are referred to as “Strategic Transactions.” The Trust generally seeks to use Strategic Transactions as a portfolio management or hedging technique to seek to protect against possible adverse changes in the market value of securities held in or to be purchased for the Trust’s portfolio, protect the value of the Trust’s portfolio, facilitate the sale of certain securities for investment purposes, manage the effective interest rate exposure of the Trust, protect against changes in currency exchange rates, manage the effective maturity or duration of the Trust’s portfolio, or establish positions in the derivatives markets as a temporary substitute for purchasing or selling particular securities. The Trust may use Strategic Transactions to enhance potential gain, although no more than 5% of the Trust’s total managed assets will be committed to variation margin for Strategic Transactions for non-hedging purposes. During temporary defensive periods and in order to keep the Trust fully invested, the Trust may invest up to 100% of its total managed assets in short-term investments. The Trust may not achieve its investment objective under these circumstances.. Leverage: The Trust currently utilizes leverage for investment purposes in the form of reverse repurchase agreements. The Trust may borrow from banks or other financial institutions and may also borrow additional funds using such investment techniques and in such amounts as the Advisors may from time to time determine. Borrowings may be made by the Trust through dollar roll transactions. The Trust may enter into derivative securities transactions that have leverage embedded in them. Although the Trust is authorized to issue preferred shares, the Trust anticipates that under current market conditions it will not offer 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. Illiquidity Risk: 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. 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. 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. 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. 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 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. Geographic/Asset Class Risk: A diversified portfolio, where this is appropriate and consistent with a fund’s objectives, minimizes the risk that a price change of a particular investment will have a material impact on the NAV of a fund. The investment concentrations within each Trust’s portfolio are disclosed in its Schedule of Investments. The 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. The 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 during a period of historically low interest rates. Changing interest rates may have unpredictable effects on markets, may result in heightened market volatility, and could negatively impact the Trusts ’ performance. The Trusts invest a significant portion of their assets in securities of issuers located in the United States. A decrease in imports or exports, changes in trade regulations, inflation and/or an economic recession in the United States may have a material adverse effect on the U.S. economy and the securities listed on U.S. exchanges. Proposed and adopted policy and legislative changes in the United States may also have a significant effect on U.S. markets generally, as well as on the value of certain securities. Governmental agencies project that the United States will continue to maintain elevated public debt levels for the foreseeable future which may constrain future economic growth. Circumstances could arise that could prevent the timely payment of interest or principal on U.S. government debt, such as reaching the legislative “debt ceiling.” Such non-payment would result in substantial negative consequences for the U.S. economy and the global financial system. If U.S. relations with certain countries deteriorate, it could adversely affect issuers that rely on the United States for trade. The United States has also experienced increased internal unrest and discord. If these trends were to continue, they may have an adverse impact on the U.S. economy and the issuers in which the Trusts invest. 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 fund concentrates its investments in this manner, it assumes a greater risk of prepayment or payment extension by securities issuers. Changes in economic conditions, including delinquencies and/or defaults on assets underlying these securities, can affect the value, income and/or liquidity of such positions. Investment percentages in these securities are presented in the Schedules of Investments. 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 risks, such as credit risk, interest rate risk, extension risk, and prepayment risk, each of which are described in further detail below: • Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the 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. • 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 during a period of historically low interest rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the 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 Trust’s 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 Trust to sell assets at inopportune times or at a loss or depressed value and could hurt the Trust’s performance. • Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall. • Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the 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 on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities. 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. In addition, circumstances could arise that could prevent the timely payment of interest or principal on U.S. Government obligations, such as reaching the legislative “debt ceiling.” Such non-payment could result in losses to the Trust and substantial negative consequences for the U.S. economy and the global financial system. Risks of Loan Assignments and Participations (BHK): As the purchaser of an assignment, the Trust typically succeeds to all the rights and obligations of the assigning institution and becomes a lender under the credit agreement with respect to the debt obligation; however, the Trust may not be able unilaterally to enforce all rights and remedies under the loan and with regard to any associated collateral. Because assignments may be arranged through private negotiations between potential assignees and potential assignors, the rights and obligations acquired by the Trust as the purchaser of an assignment may differ from, and be more limited than, those held by the assigning lender. In addition, if the loan is foreclosed, the Trust could become part owner of any collateral and could bear the costs and liabilities of owning and disposing of the collateral. The Trust may be required to pass along to a purchaser that buys a loan from the Trust by way of assignment a portion of any fees to which the Trust is entitled under the loan. In connection with purchasing participations, the Trust generally will have no right to enforce compliance by the borrower with the terms of the loan agreement relating to the loan, nor any rights of set-off against the borrower, and the Trust may not directly benefit from any collateral supporting the loan in which it has purchased the participation. As a result, the Trust will be subject to the credit risk of both the borrower and the lender that is selling the participation. In the event of the insolvency of the lender selling a participation, the Trust may be treated as a general creditor of the lender and may not benefit from any set-off between the lender and the borrower. High Yield 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. Preferred Securities Risk (BHK, HYT and BTZ) : Preferred securities may pay fixed or adjustable rates of return. Preferred securities are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred securities generally pay dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred securities will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. Preferred securities of smaller companies may be more vulnerable to adverse developments than preferred securities of larger companies. Convertible Securities Risk (BHK, HYT and BTZ): The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest, principal or dividends when due, and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock, including the potential for increased volatility in the price of the convertible security. Warrants Risk (BHK and HYT): If the price of the underlying stock does not rise above the exercise price before the warrant expires, the warrant generally expires without any value and the Trust will lose any amount it paid for the warrant. Thus, investments in warrants may involve substantially more risk than investments in common stock. Warrants may trade in the same markets as their underlying stock; however, the price of the warrant does not necessarily move with the price of the underlying stock. 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. 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 grade quality, frequently are unrated and present many of the same risks as investing in below investment grade public debt securities. Investment Companies and ETFs Risk (BHK and HYT): Subject to the limitations set forth in the Investment Company Act and the rules thereunder, the Trust may acquire shares in other investment companies and in exchange-traded funds (“ETFs”), some of which may be affiliated investment companies. The market value of the shares of other investment companies and ETFs may differ from their net asset value. As an investor in investment companies and ETFs, the Trust would bear its ratable share of that entity’s expenses, including its investment advisory and administration fees, while continuing to pay its own advisory and administration fees and other expenses (to the extent not offset by the Manager through waivers). As a result, shareholders will be absorbing duplicate levels of fees with respect to investments in other investment companies and ETFs (to the extent not offset by the Manager through waivers). The securities of other investment companies and ETFs in which the Trust may invest may be leveraged. As a result, the Trust may be indirectly exposed to leverage through an investment in such securities. An investment in securities of other investment companies and ETFs that use leverage may expose the Trust to higher volatility in the market value of such securities and the possibility that the Trust’s long-term returns on such securities (and, indirectly, the long-term returns of shares of the Trust) will be diminished. As with other investments, investments in other investment companies, including ETFs, are subject to market and selection risk. To the extent the Trust is held by an affiliated fund, the ability of the Trust itself to hold other investment companies may be limited. Risk of Investing in the United States: Certain changes in the U.S. economy, such as when the U.S. economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Trust has exposure. 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. Shareholder Activism Risk: Shareholder activism involving closed-end funds has recently been increasing. Shareholder activism can take many forms, including engaging in public campaigns to demand that the Trust consider significant transactions such as a tender offer, merger or liquidation or to attempt to influence the Trust’s corporate governance and/or management, commencing proxy contests to attempt to elect the activists’ representatives or others to the Trust’s Board of Trustees, or to seek other actions such as a termination of the Trust’s investment advisory contract with its current investment manager or commencing litigation. If the Trust becomes the subject of shareholder activism, then management and the Board may be required to divert significant resources and attention to respond to the activist and the Trust may incur substantial costs defending against such activism if management and the Board determine that the activist’s demands are not in the best interest of the Trust. Further, the Trust’s share price could be subject to significant fluctuation or otherwise be adversely affected by the events, risks and uncertainties of any shareholder activism.
Share Price [Table Text Block] |  |  |  |  |  |  |  |  |  | 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.
| NYSE Market Price Per Common Share | NAV per Common Share on Date of Market Price | Premium/ (Discount) on Date of Market Price |
BHK — During Quarter Ended | High | Low | High | Low | High | Low | Trading Volume
December 31, 2024 | $ 12.03 | $ 10.39 | $ 11.08 | $ 10.31 | 8.57 % | 0.78 % | 9,289,850
September 30, 2024 | 12.06 | 10.55 | 11.15 | 10.46 | 8.16 | 0.86 | 10,186,620
June 30, 2024 | 10.86 | 10.23 | 10.71 | 10.24 | 1.40 | (0.10 ) | 8,354,790
March 31, 2024 | 11.00 | 10.37 | 11.02 | 10.61 | (0.18 ) | (2.26 ) | 11,686,607
December 31, 2023 | 10.97 | 9.14 | 11.10 | 9.70 | (1.17 ) | (5.77 ) | 13,106,334
September 30, 2023 | 10.90 | 9.85 | 10.89 | 10.12 | 0.09 | (2.67 ) | 8,953,910
June 30, 2023 | 11.06 | 10.21 | 11.19 | 10.75 | (1.16 ) | (5.02 ) | 10,756,216
March 31, 2023 | 11.68 | 10.51 | 11.77 | 11.01 | (0.76 ) | (4.54 ) | 11,042,755
As of December 31, 2024, BHK ’ s market price, NAV per Common Share, and premium/(discount) to NAV per Common Share were $10.46, $10.30, and 1.55%, respectively.
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. Common Shares BHK, HYT and BGT have filed a prospectus with the SEC allowing them to issue an additional 15,000,000, 40,000,000 and 11,000,000 Common Shares, respectively, through an equity shelf program (a “Shelf Offering”). Under the Shelf Offering, BHK, HYT and BGT, 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). As of period end December 31, 2024, 15,000,000, 30,202,277 and 7,859,595 Common Shares, respectively, remain available for issuance under the Shelf Offering. During the year ended December 31, 2024, BHK, HYT and BGT issued 0, 9,797,723 and 3,140,405 shares, respectively, under the Shelf Offering. 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 | 12/31/24 | 12/31/23
BHK | 109,695 | —
HYT | 1,085,559 | —
BGT | 65,437 | —
The Trusts participated in an open market share repurchase program (the “Repurchase Program”) through November 30, 2024. From December 1, 2023 through November 30, 2024, each Trust could repurchase up to 5% of its outstanding common shares under the Repurchase Program, based on common shares outstanding as of the close of business on November 30, 2023, subject to certain conditions. The Repurchase Program had an accretive effect as shares were purchased at a discount to the Trust’s NAV. The Repurchase Program expired on November 30, 2024 and was not renewed. For the year ended December 31, 2024, the Trusts did not repurchase any shares. For the year ended December 31, 2023, shares issued and outstanding decreased by 182,646 and 55,022 as a result of share repuchase for BTZ and BGT respectively. For the year ended December 31, 2023, shares issued and outstanding remained constant for BHK and HYT. For the year ended December 31, 2024, shares issued and outstanding remained constant for BTZ.
Illiquidity Risk [Member] |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Illiquidity Risk: 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 [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.
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. 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. 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.
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 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.
Geographic/Asset Class Risk [Member] |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Geographic/Asset Class Risk: A diversified portfolio, where this is appropriate and consistent with a fund’s objectives, minimizes the risk that a price change of a particular investment will have a material impact on the NAV of a fund. The investment concentrations within each Trust’s portfolio are disclosed in its Schedule of Investments. The 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. The 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 during a period of historically low interest rates. Changing interest rates may have unpredictable effects on markets, may result in heightened market volatility, and could negatively impact the Trusts ’ performance. The Trusts invest a significant portion of their assets in securities of issuers located in the United States. A decrease in imports or exports, changes in trade regulations, inflation and/or an economic recession in the United States may have a material adverse effect on the U.S. economy and the securities listed on U.S. exchanges. Proposed and adopted policy and legislative changes in the United States may also have a significant effect on U.S. markets generally, as well as on the value of certain securities. Governmental agencies project that the United States will continue to maintain elevated public debt levels for the foreseeable future which may constrain future economic growth. Circumstances could arise that could prevent the timely payment of interest or principal on U.S. government debt, such as reaching the legislative “debt ceiling.” Such non-payment would result in substantial negative consequences for the U.S. economy and the global financial system. If U.S. relations with certain countries deteriorate, it could adversely affect issuers that rely on the United States for trade. The United States has also experienced increased internal unrest and discord. If these trends were to continue, they may have an adverse impact on the U.S. economy and the issuers in which the Trusts invest. 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 fund concentrates its investments in this manner, it assumes a greater risk of prepayment or payment extension by securities issuers. Changes in economic conditions, including delinquencies and/or defaults on assets underlying these securities, can affect the value, income and/or liquidity of such positions. Investment percentages in these securities are presented in the Schedules of Investments.
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 risks, such as credit risk, interest rate risk, extension risk, and prepayment risk, each of which are described in further detail below: • Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the 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. • 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 during a period of historically low interest rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the 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 Trust’s 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 Trust to sell assets at inopportune times or at a loss or depressed value and could hurt the Trust’s performance. • Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall. • Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Trust may have to invest the proceeds in securities with lower yields.
Mortgage and Asset Backed 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 on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities.
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. In addition, circumstances could arise that could prevent the timely payment of interest or principal on U.S. Government obligations, such as reaching the legislative “debt ceiling.” Such non-payment could result in losses to the Trust and substantial negative consequences for the U.S. economy and the global financial system.
Risks of Loan Assignments and Participations [Member] |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Risks of Loan Assignments and Participations (BHK): As the purchaser of an assignment, the Trust typically succeeds to all the rights and obligations of the assigning institution and becomes a lender under the credit agreement with respect to the debt obligation; however, the Trust may not be able unilaterally to enforce all rights and remedies under the loan and with regard to any associated collateral. Because assignments may be arranged through private negotiations between potential assignees and potential assignors, the rights and obligations acquired by the Trust as the purchaser of an assignment may differ from, and be more limited than, those held by the assigning lender. In addition, if the loan is foreclosed, the Trust could become part owner of any collateral and could bear the costs and liabilities of owning and disposing of the collateral. The Trust may be required to pass along to a purchaser that buys a loan from the Trust by way of assignment a portion of any fees to which the Trust is entitled under the loan. In connection with purchasing participations, the Trust generally will have no right to enforce compliance by the borrower with the terms of the loan agreement relating to the loan, nor any rights of set-off against the borrower, and the Trust may not directly benefit from any collateral supporting the loan in which it has purchased the participation. As a result, the Trust will be subject to the credit risk of both the borrower and the lender that is selling the participation. In the event of the insolvency of the lender selling a participation, the Trust may be treated as a general creditor of the lender and may not benefit from any set-off between the lender and the borrower.
High Yield Bonds Risk [Member] |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | High Yield 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.
Preferred Securities Risk [Member] |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Preferred Securities Risk (BHK, HYT and BTZ) : Preferred securities may pay fixed or adjustable rates of return. Preferred securities are subject to issuer-specific and market risks applicable generally to equity securities. In addition, a company’s preferred securities generally pay dividends only after the company makes required payments to holders of its bonds and other debt. For this reason, the value of preferred securities will usually react more strongly than bonds and other debt to actual or perceived changes in the company’s financial condition or prospects. Preferred securities of smaller companies may be more vulnerable to adverse developments than preferred securities of larger companies.
Convertible Securities Risk [Member] |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Convertible Securities Risk (BHK, HYT and BTZ): The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest, principal or dividends when due, and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock, including the potential for increased volatility in the price of the convertible security.
Warrants Risk [Member] |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Warrants Risk (BHK and HYT): If the price of the underlying stock does not rise above the exercise price before the warrant expires, the warrant generally expires without any value and the Trust will lose any amount it paid for the warrant. Thus, investments in warrants may involve substantially more risk than investments in common stock. Warrants may trade in the same markets as their underlying stock; however, the price of the warrant does not necessarily move with the price of the underlying stock.
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.
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 grade quality, frequently are unrated and present many of the same risks as investing in below investment grade public debt securities.
Investment Companies And E T Fs Risk [Member] |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Investment Companies and ETFs Risk (BHK and HYT): Subject to the limitations set forth in the Investment Company Act and the rules thereunder, the Trust may acquire shares in other investment companies and in exchange-traded funds (“ETFs”), some of which may be affiliated investment companies. The market value of the shares of other investment companies and ETFs may differ from their net asset value. As an investor in investment companies and ETFs, the Trust would bear its ratable share of that entity’s expenses, including its investment advisory and administration fees, while continuing to pay its own advisory and administration fees and other expenses (to the extent not offset by the Manager through waivers). As a result, shareholders will be absorbing duplicate levels of fees with respect to investments in other investment companies and ETFs (to the extent not offset by the Manager through waivers). The securities of other investment companies and ETFs in which the Trust may invest may be leveraged. As a result, the Trust may be indirectly exposed to leverage through an investment in such securities. An investment in securities of other investment companies and ETFs that use leverage may expose the Trust to higher volatility in the market value of such securities and the possibility that the Trust’s long-term returns on such securities (and, indirectly, the long-term returns of shares of the Trust) will be diminished. As with other investments, investments in other investment companies, including ETFs, are subject to market and selection risk. To the extent the Trust is held by an affiliated fund, the ability of the Trust itself to hold other investment companies may be limited.
Risk of Investing in the United States [Member] |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Risk of Investing in the United States: Certain changes in the U.S. economy, such as when the U.S. economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Trust has exposure.
Market Risk and Selection Risk [Member] |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Market Risk and Selection Risk: Market risk is the risk that one or more markets in which the 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.
Shareholder Activism Risk [Member] |  |  |  |  |  |  |  |  |  |
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Risk [Text Block] |  |  |  |  |  |  |  |  |  | Shareholder Activism Risk: Shareholder activism involving closed-end funds has recently been increasing. Shareholder activism can take many forms, including engaging in public campaigns to demand that the Trust consider significant transactions such as a tender offer, merger or liquidation or to attempt to influence the Trust’s corporate governance and/or management, commencing proxy contests to attempt to elect the activists’ representatives or others to the Trust’s Board of Trustees, or to seek other actions such as a termination of the Trust’s investment advisory contract with its current investment manager or commencing litigation. If the Trust becomes the subject of shareholder activism, then management and the Board may be required to divert significant resources and attention to respond to the activist and the Trust may incur substantial costs defending against such activism if management and the Board determine that the activist’s demands are not in the best interest of the Trust. Further, the Trust’s share price could be subject to significant fluctuation or otherwise be adversely affected by the events, risks and uncertainties of any shareholder activism.
Common Shares [Member] |  |  |  |  |  |  |  |  |  |
Other Annual Expenses [Abstract] |  |  |  |  |  |  |  |  |  |
Basis of Transaction Fees, Note [Text Block] |  |  |  |  |  |  |  |  |  | as a percentage of net assets attributable to common shares
General Description of Registrant [Abstract] |  |  |  |  |  |  |  |  |  |
Lowest Price or Bid |  | $ 10.39 | $ 10.55 | $ 10.23 | $ 10.37 | $ 9.14 | $ 9.85 | $ 10.21 | $ 10.51 |
Highest Price or Bid |  | 12.03 | 12.06 | 10.86 | 11 | 10.97 | 10.9 | 11.06 | 11.68 |
Lowest Price or Bid, NAV |  | 10.31 | 10.46 | 10.24 | 10.61 | 9.7 | 10.12 | 10.75 | 11.01 |
Highest Price or Bid, NAV |  | $ 11.08 | $ 11.15 | $ 10.71 | $ 11.02 | $ 11.1 | $ 10.89 | $ 11.19 | $ 11.77 |
Highest Price or Bid, Premium (Discount) to NAV [Percent] |  | 8.57% | 8.16% | 1.40% | (0.18%) | (1.17%) | 0.09% | (1.16%) | (0.76%) |
Lowest Price or Bid, Premium (Discount) to NAV [Percent] |  | 0.78% | 0.86% | (0.10%) | (2.26%) | (5.77%) | (2.67%) | (5.02%) | (4.54%) |
Share Price |  | $ 10.46 |  |  |  |  |  |  |  | $ 10.46
NAV Per Share |  | $ 10.3 |  |  |  |  |  |  |  | $ 10.3
Latest Premium (Discount) to NAV [Percent] |  |  |  |  |  |  |  |  |  | 1.55%
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.
Shares Outstanding [Member] |  |  |  |  |  |  |  |  |  |
Capital Stock, Long-Term Debt, and Other Securities [Abstract] |  |  |  |  |  |  |  |  |  |
Outstanding Security, Held [Shares] |  |  |  |  |  |  |  |  |  | 54,120,397
[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.’s (the “Reinvestment Plan Agent”) fees for the handling of the reinvestment of dividends will be paid by BHK. 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 a shareholder directs the Reinvestment Plan Agent to sell the common shares held in a dividend reinvestment account. Per share fees include any applicable brokerage commissions the Reinvestment Plan Agent is required to pay.
[3] | BHK 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 BHK’s assets attributable to investments in any equity and fixed-income mutual funds and exchange-traded funds managed by the Manager or its affiliates that have a contractual management fee, through June 30, 2026. 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 BHK pays to the Manager indirectly through its investment in money market funds managed by the Manager or its affiliates, through June 30, 2026. The Fee Waiver Agreement may be terminated at any time, without the payment of any penalty, only by BHK (upon the vote of a majority of the Trustees who are not “interested persons” (as defined in the Investment Company Act) of BHK or a majority of the outstanding voting securities of BHK), upon 90 days’ written notice by BHK to the Manager.
[4] | BHK currently pays the Manager a monthly fee at an annual contractual investment advisory fee rate of 0.50% of its average weekly managed assets. For purposes of calculating these fees, “managed assets” means the total assets of BHK (including any assets attributable to money borrowed) minus the sum of its accrued liabilities (other than money borrowed for investment purposes).
[5] | BHK uses leverage in the form of reverse repurchase agreements representing 39.5% of managed assets at an annual interest expense to BHK of 5.2%, which is based on current market conditions. The actual amount of interest expense borne by BHK will vary over time in accordance with the level of BHK’s use of reverse repurchase agreements and variations in market interest rates. Interest expense is required to be treated as an expense of BHK for accounting purposes.

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