Objective, Primary [Text Block]

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Fund Overview Key Facts About BlackRock Diversified Fixed Income Fund

Objective [Heading]

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Investment Objective

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The investment objective of BlackRock Diversified Fixed Income Fund (the “Fund”), a series of BlackRock Funds III (the “Trust”), is to seek to provide a combination of income and capital growth.

Expense [Heading]

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Fees and Expenses of the Fund

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy, hold and sell Class K Shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to your financial professional or your selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock Fund Advisors (“BFA”) and its affiliates) (each, a “Financial Intermediary”), which are not reflected in the table and example below.

Operating Expenses Caption [Text]

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Annual Fund Operating Expenses(expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

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June 30, 2026

Portfolio Turnover [Heading]

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Portfolio Turnover:

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are

held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 506% of the average value of its portfolio.

Portfolio Turnover, Rate

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506.00%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

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The Total Annual Fund Operating Expenses do not correlate to the ratio of expenses to average net assets given in the Fund’s most recent annual financial statements, which do not include Acquired Fund Fees and Expenses.

Expense Example [Heading]

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Example:

Expense Example Narrative [Text Block]

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This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

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Principal Investment Strategies of the Fund

Strategy Narrative [Text Block]

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The Fund invests, under normal circumstances, at least 80% of the value of its net assets, plus the amount of any borrowings for investment purposes, in fixed income instruments. Investments in derivatives are counted toward the Fund’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 fixed income instruments in which the Fund may invest include, but are not limited to, the following: obligations issued or guaranteed by the U.S. Government, its agencies or instrumentalities; mortgage-backed securities issued or guaranteed by the U.S. Government or its agencies or instrumentalities, including U.S. agency mortgage pass-through securities; commercial mortgage-backed securities; mortgage to‑be‑announced (“TBA”) securities; debt obligations of U.S. issuers; municipal securities; asset-backed securities; money market securities; U.S.-registered dollar denominated debt obligations of foreign issuers, and derivatives with similar economic characteristics to such fixed-income securities.

The Fund seeks to invest a substantial portion (generally, at least 60% at notional value) of its assets in U.S. registered, dollar-denominated bonds or derivatives with similar economic characteristics. The Fund may invest in bonds issued by companies located in countries other than the United States, including companies in emerging markets. The fixed income instruments in which the Fund invests may have all types of interest rate payment and reset terms, including fixed rate, adjustable rate, floating rate, zero coupon, contingent, deferred, payment in kind and auction rate features.

The Fund may invest up to 20% of its assets in securities rated below investment grade or which are deemed to be of comparable quality by BFA (“high yield” or “junk” bonds) at the time of purchase. Investment grade bonds are bonds rated in the four highest categories by at least one of the major rating agencies or determined by Fund management to be of similar quality. The Fund may invest in bonds of any maturity or duration.

The Fund may invest a significant portion of its assets in U.S. agency mortgage pass-through securities, which are securities issued by entities such as the Government National Mortgage Association and the Federal National Mortgage Association that are backed by pools of mortgages. Most transactions in mortgage pass-through securities occur through standardized contracts for future delivery in which the exact mortgage-backed securities to be delivered are not specified until a few days prior to settlement. The Fund expects to enter into such contracts on a regular basis.

The Fund may invest up to 10% of its total assets in collateralized debt obligations (“CDOs”), including collateralized loan obligations (“CLOs”). CDOs are types of asset-backed securities. CLOs are ordinarily issued by a trust or other special purpose entity and are typically collateralized by a pool of loans, which may include, among others, domestic and non‑U.S. senior secured loans, senior unsecured loans, and subordinate corporate loans, including loans that may be rated below investment grade or equivalent unrated loans, held by such issuer.

The Fund may use derivatives, such as futures contracts, options (including, but not limited to, options on futures and swaps) and various other instruments (including, but not limited to, interest rate, total return, credit default and credit default index swaps (which can be used to transfer the credit risk of a security without actually transferring ownership of the security or to customize exposure to a particular credit risk) and indexed and inverse floating-rate securities). The Fund may also invest in credit-linked notes, credit-linked trust certificates, structured notes, or other instruments evidencing interests in special purpose vehicles, trusts, or other entities that hold or represent interests in fixed-income securities. The Fund may also invest in derivatives based on foreign currencies. In addition, the Fund may use derivatives and short sales to enhance returns as part of an overall investment strategy or to offset a potential decline in the value of other holdings (commonly referred to as a “hedge”), although the Fund is not required to hedge and may choose not to do so.

The Fund may engage in active and frequent trading of portfolio securities to achieve its primary investment strategies.

The Fund is classified as diversified under the Investment Company Act of 1940, as amended (the “Investment Company Act”).

Risk [Heading]

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Principal Risks of Investing in the Fund

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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The information shows you how the performance of the Fund has varied for the periods since inception and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the Bloomberg U.S. Aggregate Bond Index. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. The table includes all applicable fees. If BlackRock and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting www.blackrock.com or can be obtained by phone at (800) 882‑0052.

Performance Information Illustrates Variability of Returns [Text]

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The information shows you how the performance of the Fund has varied for the periods since inception and provides some indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

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(800) 882‑0052

Performance Availability Website Address [Text]

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www.blackrock.com

Performance Past Does Not Indicate Future [Text]

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As with all such investments, past performance (before and after taxes) is not an indication of future results.

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Class K Shares ANNUAL TOTAL RETURNS BlackRock Diversified Fixed Income Fund As of 12/31

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During the period shown in the bar chart, the highest return for a quarter was 5.28% (quarter ended September 30, 2024) and the lowest return for a quarter was (2.87)% (quarter ended December 31, 2024).

Performance Table Heading

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For the periods ended 12/31/24Average Annual Total Returns

Performance Table Uses Highest Federal Rate

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After‑tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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Actual after‑tax returns depend on the investor’s tax situation and may differ from those shown, and the after‑tax returns shown are not relevant to investors who hold their shares through tax‑deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Narrative

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After‑tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after‑tax returns depend on the investor’s tax situation and may differ from those shown, and the after‑tax returns shown are not relevant to investors who hold their shares through tax‑deferred arrangements, such as 401(k) plans or individual retirement accounts.

Class K [Member] | BlackRock Diversified Fixed Income Fund | Risk Lose Money [Member]

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Debt Securities Risk [Member]

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You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Mortgage and Asset Backed Securities Risks [Member]

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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 Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.

Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise.

The Fund may be subject to a greater risk of rising interest rates 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 Fund’s investments would be expected to decrease by 10%. (Duration is a measure of the price sensitivity of a debt security or portfolio of debt securities to relative changes in interest rates.) The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management.

Since rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities.

These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change.

A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.

Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.

Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | U S Government Mortgage Related Securities Risk [Member]

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Mortgage- and Asset-Backed Securities Risks — 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. TBA commitments are forward agreements for the purchase or sale of securities, including mortgage-backed securities for a fixed price, with payment and delivery on an agreed upon future settlement date. The specific securities to be delivered are not identified at the trade date. However, delivered securities must meet specified terms, including issuer, rate and mortgage terms.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Collateralized Debt Obligations Risk [Member]

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U.S. Government Mortgage-Related Securities Risk — There are a number of important differences among the agencies and instrumentalities of the U.S. Government that issue mortgage-related securities and among the securities that they issue. Mortgage-related securities guaranteed by the Government National Mortgage Association (“GNMA” or “Ginnie Mae”) are guaranteed as to the timely payment of principal and interest by GNMA and such guarantee is backed by the full faith and credit of the United States. GNMA securities also are supported by the right of GNMA to borrow funds from the U.S. Treasury to make payments under its guarantee. Mortgage-related securities issued by Fannie Mae or Freddie Mac are solely the obligations of Fannie Mae or Freddie Mac, as the case may be, and are not backed by or entitled to the full faith and credit of the United States but are supported by the right of the issuer to borrow from the Treasury.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Derivatives Risks [Member]

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Collateralized Debt Obligations Risk — In addition to the typical risks associated with fixed-income securities and asset-backed securities, CDOs, including CLOs, carry additional risks including, but not limited to: (i) the possibility that distributions from collateral securities will not be adequate to make interest or other payments; (ii) the risk that the collateral may default or decline in value or be downgraded, if rated by a nationally recognized statistical rating organization; (iii) the Fund may invest in tranches of CDOs that are subordinate to other tranches; (iv) the structure and complexity of the transaction and the legal documents could lead to disputes among investors regarding the characterization of proceeds; (v) the investment return achieved by the Fund could be significantly different than those predicted by financial models; (vi) the lack of a readily available secondary market for CDOs; (vii) the risk of forced “fire sale” liquidation due to technical defaults such as coverage test failures; and (viii) the CDO’s manager may perform poorly.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Emerging Markets Risk [Member]

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Derivatives Risk — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:

Leverage Risk — The Fund’s use of derivatives can magnify the Fund’s gains and losses. Relatively small market movements may result in large changes in the value of a derivatives position and can result in losses that greatly exceed the amount originally invested.

Market Risk — Some derivatives are more sensitive to interest rate changes and market price fluctuations than other securities. The Fund could also suffer losses related to its derivatives positions as a result of unanticipated market movements, which losses are potentially unlimited. Finally, BFA may not be able to predict correctly the direction of securities prices, interest rates and other economic factors, which could cause the Fund’s derivatives positions to lose value.

Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will be unable or unwilling to fulfill its contractual obligation, and the related risks of having concentrated exposure to such a counterparty.

Illiquidity Risk — The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately.

Operational Risk — The use of derivatives includes the risk of potential operational issues, including documentation issues, settlement issues, systems failures, inadequate controls and human error.

Legal Risk — The risk of insufficient documentation, insufficient capacity or authority of counterparty, or legality or enforceability of a contract.

Volatility and Correlation Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.

Valuation Risk — Valuation for derivatives may not be readily available in the market. Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them.

Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences.

Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Foreign Securities Risk [Member]

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Emerging Markets Risk — Emerging markets are riskier than more developed markets because they tend to develop unevenly and may never fully develop. Investments in emerging markets may be considered speculative. Emerging markets are more likely to experience hyperinflation and currency devaluations, which adversely affect returns to U.S. investors. In addition, many emerging securities markets have far lower trading volumes and less liquidity than developed markets.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | High Portfolio Turnover Risk [Member]

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Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include:

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The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight.

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Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio.

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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.

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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.

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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.

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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.

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The Fund’s claims to recover foreign withholding taxes may not be successful, and if the likelihood of recovery of foreign withholding taxes materially decreases, due to, for example, a change in tax regulation or approach in the foreign country, accruals in the Fund’s net asset value for such refunds may be written down partially or in full, which will adversely affect the Fund’s net asset value.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | High Yield Bonds Risk [Member]

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High Portfolio Turnover Risk — The Fund may engage in active and frequent trading of its portfolio securities. High portfolio turnover (more than 100%) may result in increased transaction costs to the Fund, including brokerage commissions, dealer mark‑ups and other transaction costs on the sale of the securities and on reinvestment in other securities. The sale of Fund portfolio securities may result in the realization and/or distribution to shareholders of higher capital gains or losses as compared to a fund with less active trading policies. These effects of higher than normal portfolio turnover may adversely affect Fund performance.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Illiquid Investments Risk [Member]

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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 Fund.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Indexed and Inverse Securities Risk [Member]

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Illiquid Investments Risk — The Fund may not acquire any illiquid investment if, immediately after the acquisition, the Fund would have invested more than 15% of its net assets in illiquid investments. An illiquid investment is any investment that the Fund reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. Liquid investments may become illiquid after purchase by the Fund, particularly during periods of market turmoil. There can be no assurance that a security or instrument that is deemed to be liquid when purchased will continue to be liquid for as long as it is held by the Fund, and any security or instrument held by the Fund may be deemed an illiquid investment pursuant to the Fund’s liquidity risk management program. The Fund’s illiquid investments may reduce the returns of the Fund because it may be difficult to sell the illiquid investments at an advantageous time or price. In addition, if the Fund is limited in its ability to sell illiquid investments during periods when shareholders are redeeming their shares, the Fund will need to sell liquid securities to meet redemption requests and illiquid securities will become a larger portion of the Fund’s holdings. An investment may be illiquid due to, among other things, the reduced number and capacity of traditional market participants to make a market in fixed-income securities or the lack of an active trading market. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to the risks associated with illiquid investments. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. This may be magnified in a rising interest rate environment or other circumstances where investor redemptions from fixed-income mutual funds may be higher than normal. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Leverage Risk [Member]

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Indexed and Inverse Securities Risk — Indexed and inverse securities provide a potential return based on a particular index of value or interest rates. The Fund’s return on these securities will be subject to risk with respect to the value of the particular index. These securities are subject to leverage risk and correlation risk. Certain indexed and inverse securities have greater sensitivity to changes in interest rates or index levels than other securities, and the Fund’s investment in such instruments may decline significantly in value if interest rates or index levels move in a way Fund management does not anticipate.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Market Risk and Selection Risk [Member]

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Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet the applicable requirements of the Investment Company Act and the rules thereunder. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Municipal Securities Risks [Member]

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Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. The value of a security or other asset may decline due to changes in general market conditions, economic trends or events that are not specifically related to the issuer of the security or other asset, or factors that affect a particular issuer or issuers, exchange, country, group of countries, region, market, industry, group of industries, sector or asset class. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues like pandemics or epidemics, recessions, or other events could have a significant impact on the Fund and its investments. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.

An outbreak of an infectious coronavirus (COVID‑19) that was first 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.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Pay in kind Bonds Risk [Member]

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Municipal Securities Risks — Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. Budgetary constraints of local, state, and federal governments upon which the issuers may be relying for funding may also impact municipal securities. These risks include:

General Obligation Bonds Risks — Timely payments depend on the issuer’s credit quality, ability to raise tax revenues and ability to maintain an adequate tax base.

Revenue Bonds Risks — These payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source.

Private Activity Bonds Risks — Municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise. The private enterprise pays the principal and interest on the bond, and the issuer does not pledge its full faith, credit and taxing power for repayment.

Moral Obligation Bonds Risks — Moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality.

Municipal Notes Risks — Municipal notes are shorter term municipal debt obligations. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money.

Municipal Lease Obligations Risks — In a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property.

Tax‑Exempt Status Risk — The Fund and its investment manager will rely on the opinion of issuers’ bond counsel and, in the case of derivative securities, sponsors’ counsel, on the tax‑exempt status of interest on municipal bonds and payments under derivative securities. Neither the Fund nor its investment manager will independently review the bases for those tax opinions, which may ultimately be determined to be incorrect and subject the Fund and its shareholders to substantial tax liabilities.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Risk of Investing in the United States [Member]

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Pay‑in‑kind Bonds Risk — Similar to zero coupon obligations, pay‑in‑kind bonds also carry additional risk as holders of these types of securities realize no cash until the cash payment date unless a portion of such securities is sold and, if the issuer defaults, the Fund may obtain no return at all on its investment. The market price of pay‑in‑kind bonds is affected by interest rate changes to a greater extent, and therefore tends to be more volatile, than that of securities which pay interest in cash.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Short Sales Risk [Member]

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Risk of Investing in the United States — Certain changes in the U.S. economy, such as when the U.S. economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Fund has exposure.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Structured Notes Risk [Member]

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Short Sales Risk — Because making short sales in securities that it does not own exposes the Fund to the risks associated with those securities, such short sales involve speculative exposure risk. The Fund will incur a loss as a result of a short sale if the price of the security increases between the date of the short sale and the date on which the Fund replaces the security sold short.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | U S Government Issuer Risk [Member]

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Structured Notes Risk — Structured notes and other related instruments purchased by the Fund are generally privately negotiated debt obligations where the principal and/or interest is determined by reference to the performance of a specific asset, benchmark asset, market or interest rate (“reference measure”). The purchase of structured notes exposes the Fund to the credit risk of the issuer of the structured product. Structured notes may be leveraged, increasing the volatility of each structured note’s value relative to the change in the reference measure. Structured notes may also be less liquid and more difficult to price accurately than less complex securities and instruments or more traditional debt securities.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Variable and Floating Rate Instrument Risk [Member]

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U.S. Government Issuer Risk — Treasury obligations may differ in their interest rates, maturities, times of issuance and other characteristics. Obligations of U.S. Government agencies and authorities are supported by varying degrees of credit but generally are not backed by the full faith and credit of the U.S. Government. No assurance can be given that the U.S. Government will provide financial support to its agencies and authorities if it is not obligated by law to do so.

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Class K [Member] | BlackRock Diversified Fixed Income Fund | Zero Coupon Securities Risk [Member]

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Variable and Floating Rate Instrument Risk — Variable and floating rate securities provide for periodic adjustment in the interest rate paid on the securities. Securities with floating or variable interest rates can be less sensitive to interest rate changes than securities with fixed interest rates, but may decline in value if their coupon rates do not reset as high, or as quickly, as comparable market interest rates, and generally carry lower yields than fixed securities of the same maturity. These securities will not generally increase in value if interest rates decline. A decline in interest rates may result in a reduction in income received from variable and floating rate securities held by the Fund and may adversely affect the value of the Fund’s shares. These securities may be subject to greater illiquidity risk than other fixed income securities, meaning the absence of an active market for these securities could make it difficult for the Fund to dispose of them at any given time. Floating rate securities generally are subject to legal or contractual restrictions on resale, may trade infrequently, and their value may be impaired when the Fund needs to liquidate such loans. Benchmark interest rates may not accurately track market interest rates. Although floating rate securities are less sensitive to interest rate risk than fixed-rate securities, they are subject to credit risk and default risk, which could impair their value.

rr_RiskReturnAbstract

Class K [Member] | BlackRock Diversified Fixed Income Fund | Class K Shares

rr_RiskTextBlock

∎

Zero Coupon Securities Risk — While interest payments are not made on such securities, holders of such securities are deemed to have received income (“phantom income”) annually, notwithstanding that cash may not be received currently. The effect of owning instruments that do not make current interest payments is that a fixed yield is earned not only on the original investment but also, in effect, on all discount accretion during the life of the obligations. This implicit reinvestment of earnings at a fixed rate eliminates the risk of being unable to invest distributions at a rate as high as the implicit yield on the zero coupon bond, but at the same time eliminates the holder’s ability to reinvest at higher rates in the future. For this reason, some of these securities may be subject to substantially greater price fluctuations during periods of changing market interest rates than are comparable securities that pay interest currently. Longer term zero coupon bonds are more exposed to interest rate risk than shorter term zero coupon bonds. These investments benefit the issuer by mitigating its need for cash to meet debt service, but also require a higher rate of return to attract investors who are willing to defer receipt of cash.

Distribution and/or Service (12b-1) Fees

rr_RiskReturnAbstract

Management Fee

rr_ManagementFeesOverAssets

0.25%

^[1],[2]

rr_DistributionAndService12b1FeesOverAssets

none

Administration Fees

rr_Component1OtherExpensesOverAssets

0.10%

^[2]

Independent Expenses

rr_Component2OtherExpensesOverAssets

0.01%

^[3]

Other Expenses

rr_OtherExpensesOverAssets

0.11%

^[2],[3]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[4]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.38%

^[4]

Fee Waivers and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.22%)

^[1],[2],[3]

Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements

rr_NetExpensesOverAssets

0.16%

^[1],[2],[3]

Highest Quarterly Return, Label

rr_ExpenseExampleYear01

$ 16

3 Years

rr_ExpenseExampleYear03

5 Years

rr_ExpenseExampleYear05

187

10 Years

rr_ExpenseExampleYear10

$ 447

2024

rr_AnnualReturn2024

1.82%

rr_HighestQuarterlyReturnLabel

highest return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2024

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

5.28%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

lowest return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2024

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(2.87%)

rr_AverageAnnualReturnYear01

1.82%

Class K [Member] | BlackRock Diversified Fixed Income Fund | Return After Taxes on Distributions | Class K Shares

rr_AverageAnnualReturnSinceInception

1.92%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 18, 2023

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

(0.76%)

Class K [Member] | BlackRock Diversified Fixed Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class K Shares

rr_AverageAnnualReturnSinceInception

(0.32%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 18, 2023

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

1.07%

Class K [Member] | BlackRock Diversified Fixed Income Fund | Bloomberg U.S. Aggregate Bond Index (Reflects no deduction for fees, expenses or taxes)

rr_AverageAnnualReturnSinceInception

0.52%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 18, 2023

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

1.25%