Investment Strategy - BlackRock Advantage CoreAlpha Bond Fund	Dec. 31, 2025
Investor A, C and Institutional
Prospectus [Line Items]
Strategy [Heading]	Principal Investment Strategies of the Fund
Strategy Narrative [Text Block]	The Fund invests, under normal circumstances, at least 80% of the value of the Fund’s net assets, plus the amount of any borrowing for investment purposes, 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 Fund’s investments in derivatives will be counted towards 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 Fund may invest in bonds issued by companies located in countries other than the United States, including companies in emerging markets. These securities 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 seeks to invest a substantial portion of its assets in U.S.-registered, dollar-denominated bonds. The Fund may invest up to 10% of its assets in securities rated below investment grade or which are deemed to be of comparable quality by BlackRock (“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 use derivatives, such as futures contracts, options and various other instruments. 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 is a “feeder” fund that invests all of its assets in the Master Portfolio, which has the same investment objective and strategies as the Fund. All investments are made at the Master Portfolio level. This structure is sometimes called a “master/feeder” structure. The Fund’s investment results will correspond directly to the investment results of the Master Portfolio. For simplicity, the prospectus uses the name of the Fund or the term “Fund” (as applicable) to include the Master Portfolio.
Class K
Prospectus [Line Items]
Strategy [Heading]	Principal Investment Strategies of the Fund
Strategy Narrative [Text Block]	The Fund invests, under normal circumstances, at least 80% of the value of the Fund’s net assets, plus the amount of any borrowing for investment purposes, 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 Fund’s investments in derivatives will be counted towards 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 Fund may invest in bonds issued by companies located in countries other than the United States, including companies in emerging markets. These securities 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 seeks to invest a substantial portion of its assets in U.S.-registered, dollar-denominated bonds. The Fund may invest up to 10% of its assets in securities rated below investment grade or which are deemed to be of comparable quality by BlackRock (“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 use derivatives, such as futures contracts, options and various other instruments. 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 is a “feeder” fund that invests all of its assets in the Master Portfolio, which has the same investment objective and strategies as the Fund. All investments are made at the Master Portfolio level. This structure is sometimes called a “master/feeder” structure. The Fund’s investment results will correspond directly to the investment results of the Master Portfolio. For simplicity, the prospectus uses the name of the Fund or the term “Fund” (as applicable) to include the Master Portfolio.

The Fund invests, under normal circumstances, at least 80% of the value of the Fund’s net assets, plus the amount of any borrowing for investment purposes, 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 Fund’s investments in derivatives will be counted towards 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 Fund may invest in bonds issued by companies located in countries other than the United States, including companies in emerging markets. These securities 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 seeks to invest a substantial portion of its assets in U.S.-registered, dollar-denominated bonds. The Fund may invest up to 10% of its assets in securities rated below investment grade or which are deemed to be of comparable quality by BlackRock (“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 use derivatives, such as futures contracts, options and various other instruments. 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 is a “feeder” fund that invests all of its assets in the Master Portfolio, which has the same investment objective and strategies as the Fund. All investments are made at the Master Portfolio level. This structure is sometimes called a “master/feeder” structure. The Fund’s investment results will correspond directly to the investment results of the Master Portfolio. For simplicity, the prospectus uses the name of the Fund or the term “Fund” (as applicable) to include the Master Portfolio.

Prospectus [Line Items]

Strategy Narrative [Text Block]

The Fund invests, under normal circumstances, at least 80% of the value of the Fund’s net assets, plus the amount of any borrowing for investment purposes, 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 Fund’s investments in derivatives will be counted towards 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 Fund may invest in bonds issued by companies located in countries other than the United States, including companies in emerging markets. These securities 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 seeks to invest a substantial portion of its assets in U.S.-registered, dollar-denominated bonds. The Fund may invest up to 10% of its assets in securities rated below investment grade or which are deemed to be of comparable quality by BlackRock (“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 use derivatives, such as futures contracts, options and various other instruments. 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 is a “feeder” fund that invests all of its assets in the Master Portfolio, which has the same investment objective and strategies as the Fund. All investments are made at the Master Portfolio level. This structure is sometimes called a “master/feeder” structure. The Fund’s investment results will correspond directly to the investment results of the Master Portfolio. For simplicity, the prospectus uses the name of the Fund or the term “Fund” (as applicable) to include the Master Portfolio.