The Fund invests primarily in non‑investment grade bonds with maturities of ten years or less. The Fund normally invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in high yield bonds. The Fund’s investments in derivatives will be 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 high yield securities (commonly called “junk bonds”) acquired by the Fund will generally be in the lower rating categories of the major rating agencies (BB or lower by S&P Global Ratings (“S&P”) or Fitch Ratings Inc. (“Fitch”), or Ba or lower by Moody’s Investors Service, Inc. (“Moody’s”)) or will be determined by the Fund management team to be of similar quality. Split rated bonds and other fixed-income securities (securities that receive different ratings from two or more rating agencies) are valued as follows: if three agencies rate a security, the security will be considered to have the median credit rating; if two of the three agencies rate a security, the security will be considered to have the lower credit rating. The Fund may invest up to 30% of its assets in non‑dollar denominated bonds of issuers located outside of the United States. The Fund’s investment in non‑dollar denominated bonds may be on a currency hedged or unhedged basis. The Fund may also invest in convertible and preferred securities. These securities will be counted toward the Fund’s 80% policy to the extent they have characteristics similar to the securities included within that policy.

To add additional diversification, the management team can invest in a wide range of securities including corporate bonds, mezzanine investments, collateralized bond obligations, bank loans and mortgage-backed and asset-backed securities. The Fund can also invest, to the extent consistent with its investment objective, in non‑U.S. and emerging market securities and currencies. The Fund may invest in securities of any rating, and may invest up to 10% of its assets (measured at the time of investment) in distressed securities that are in default or the issuers of which are in bankruptcy.

The Fund may buy or sell options or futures on a security or an index of securities, or enter into credit default swaps and interest rate or foreign currency transactions, including swaps (collectively, commonly known as derivatives). The Fund may use derivative instruments to hedge its investments or to seek to enhance returns. The Fund may seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as reverse repurchase agreements or dollar rolls).

Investment Strategy - BlackRock High Yield Portfolio	Dec. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	Principal Investment Strategies of the Fund
Strategy Narrative [Text Block]	The Fund invests primarily in non‑investment grade bonds with maturities of ten years or less. The Fund normally invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in high yield bonds. The Fund’s investments in derivatives will be 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 high yield securities (commonly called “junk bonds”) acquired by the Fund will generally be in the lower rating categories of the major rating agencies (BB or lower by S&P Global Ratings (“S&P”) or Fitch Ratings Inc. (“Fitch”), or Ba or lower by Moody’s Investors Service, Inc. (“Moody’s”)) or will be determined by the Fund management team to be of similar quality. Split rated bonds and other fixed-income securities (securities that receive different ratings from two or more rating agencies) are valued as follows: if three agencies rate a security, the security will be considered to have the median credit rating; if two of the three agencies rate a security, the security will be considered to have the lower credit rating. The Fund may invest up to 30% of its assets in non‑dollar denominated bonds of issuers located outside of the United States. The Fund’s investment in non‑dollar denominated bonds may be on a currency hedged or unhedged basis. The Fund may also invest in convertible and preferred securities. These securities will be counted toward the Fund’s 80% policy to the extent they have characteristics similar to the securities included within that policy. To add additional diversification, the management team can invest in a wide range of securities including corporate bonds, mezzanine investments, collateralized bond obligations, bank loans and mortgage-backed and asset-backed securities. The Fund can also invest, to the extent consistent with its investment objective, in non‑U.S. and emerging market securities and currencies. The Fund may invest in securities of any rating, and may invest up to 10% of its assets (measured at the time of investment) in distressed securities that are in default or the issuers of which are in bankruptcy. The Fund may buy or sell options or futures on a security or an index of securities, or enter into credit default swaps and interest rate or foreign currency transactions, including swaps (collectively, commonly known as derivatives). The Fund may use derivative instruments to hedge its investments or to seek to enhance returns. The Fund may seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as reverse repurchase agreements or dollar rolls). The Fund may engage in active and frequent trading of portfolio securities to achieve its principal investment strategies.