Strategy. The Portfolio invests primarily in common stocks of large capitalization U.S. growth companies. Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus borrowings for investment purposes, if any) in stocks of large capitalization companies (that is, those with market capitalizations at the time of investment that are within the range of market capitalizations of the companies in the Russell 1000 Growth Index for the previous 12 months). From time to time the Portfolio may also have substantial positions in securities of foreign companies. In addition, from time to time the Portfolio may also have substantial positions in a particular sector of the economy. The Portfolio is actively managed by BlackRock Investment Management, LLC (BlackRock) under … Show more… The Portfolio invests primarily in common stocks of large capitalization U.S. growth companies. Under normal circumstances, the Portfolio invests at least 80% of its net assets (plus borrowings for investment purposes, if any) in stocks of large capitalization companies (that is, those with market capitalizations at the time of investment that are within the range of market capitalizations of the companies in the Russell 1000 Growth Index for the previous 12 months). From time to time the Portfolio may also have substantial positions in securities of foreign companies. In addition, from time to time the Portfolio may also have substantial positions in a particular sector of the economy. The Portfolio is actively managed by BlackRock Investment Management, LLC (BlackRock) under a sub-advisory agreement with the Adviser. BlackRock began managing the Portfolio in February 2019. BlackRock seeks to pursue the Portfolios investment objective by investing in large cap 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 that the Portfolio can seek to capture by over- and under-weighting particular equities while seeking to control incremental risk. BlackRock then constructs and rebalances the Portfolio by integrating its investment insights with the model-based optimization process. BlackRock has no stated minimum holding period for investments and may buy or sell securities whenever it sees an appropriate opportunity. The Portfolio may engage in active and frequent trading of portfolio securities to achieve its primary investment strategies. The Portfolio may use derivatives to hedge its portfolio against market and currency risks or to gain exposure to equity markets. The Portfolio may also use derivatives to hedge its investment portfolio against interest rate risks or to seek to enhance its return. Derivatives are financial instruments whose value is derived from another security, a commodity, a currency or an index. The derivatives that the Portfolio intends to use are futures contracts, which may include financial and currency futures, and options on such futures. The portfolio managers consider a variety of factors in determining whether to sell a security, including changes in market conditions, changes in prospects for the security, alternative investment possibilities and other factors they believe to be relevant. Show less