Class K [Member] Investment Strategy - Class K - BlackRock Advantage SMID Cap Fund, Inc.	Mar. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	Principal Investment Strategies of the Fund
Strategy Narrative [Text Block]	Under normal circumstances, the Fund seeks to invest at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of U.S. small and medium capitalization companies, and derivatives that have similar economic characteristics to such securities. 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 Fund primarily intends to invest in equity securities or other financial instruments that are components of, or have characteristics similar to, the securities included in the Russell 2500™ Index. The Russell 2500™ Index is an index that measures the performance of the small to mid-cap segment of the U.S. equity universe, commonly referred to as “smid” cap. The Russell 2500™ Index is a subset of the Russell 3000® Index. It includes approximately 2500 of the smallest securities based on a combination of their market cap and current index membership. The Fund may invest in issuers of any market capitalization. The equity securities in which the Fund invests primarily consist of common stock, but may also include preferred stock. From time to time, the Fund may invest in shares of companies through “new issues” or initial public offerings (“IPOs”). The Fund may also purchase convertible securities. The Fund may use derivatives, including options, futures, swaps (including, but not limited to, total return swaps that may be referred to as contracts for difference) and forward contracts, both to seek to increase the return of the Fund and to hedge (or protect) the value of its assets against adverse movements in interest rates and movements in the securities markets. In order to manage cash flows into or out of the Fund effectively, the Fund may buy and sell financial futures contracts or options on such contracts. Derivatives are financial instruments whose value is derived from another security, a currency or an index, including but not limited to the Russell 2500TM Index. The Fund seeks to pursue its investment objective by investing in securities in a disciplined manner, by using proprietary return forecast models that incorporate quantitative analysis. These forecast models are designed to identify aspects of mispricing across stocks which the Fund can seek to capture by over- and under-weighting particular equity securities while seeking to control incremental risk. BlackRock then constructs and rebalances the portfolio by integrating its investment insights with the model-based optimization process. The Fund may engage in active and frequent trading of portfolio securities to seek to achieve its primary investment strategies.

Under normal circumstances, the Fund seeks to invest at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of U.S. small and medium capitalization companies, and derivatives that have similar economic characteristics to such securities. 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 Fund primarily intends to invest in equity securities or other financial instruments that are components of, or have characteristics similar to, the securities included in the Russell 2500™ Index. The Russell 2500™ Index is an index that measures the performance of the small to mid-cap segment of the U.S. equity universe, commonly referred to as “smid” cap. The Russell 2500™ Index is a subset of the Russell 3000® Index. It includes approximately 2500 of the smallest securities based on a combination of their market cap and current index membership. The Fund may invest in issuers of any market capitalization. The equity securities in which the Fund invests primarily consist of common stock, but may also include preferred stock. From time to time, the Fund may invest in shares of companies through “new issues” or initial public offerings (“IPOs”). The Fund may also purchase convertible securities.

The Fund may use derivatives, including options, futures, swaps (including, but not limited to, total return swaps that may be referred to as contracts for difference) and forward contracts, both to seek to increase the return of the Fund and to hedge (or protect) the value of its assets against adverse movements in interest rates and movements in the securities markets. In order to manage cash flows into or out of the Fund effectively, the Fund may buy and sell financial futures contracts or options on such contracts. Derivatives are financial instruments whose value is derived from another security, a currency or an index, including but not limited to the Russell 2500TM Index.

The Fund seeks to pursue its investment objective by investing in securities in a disciplined manner, by using proprietary return forecast models that incorporate quantitative analysis. These forecast models are designed to identify aspects of mispricing across stocks which the Fund can seek to capture by over- and under-weighting particular equity securities while seeking to control incremental risk. BlackRock then constructs and rebalances the portfolio by integrating its investment insights with the model-based optimization process.