Large Cap Core Stock Portfolio Investment Strategy - Large Cap Core Stock Portfolio	Dec. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">PRINCIPAL INVESTMENT STRATEGIES</span>
Strategy Narrative [Text Block]	Normally, the Portfolio invests at least 80% of net assets (plus any borrowings for investment purposes) in stocks of large-capitalization companies. For this purpose, large-capitalization stocks are those whose market capitalizations are above $5 billion at the time of purchase. In managing the Portfolio, the adviser allocates the Portfolio’s assets across a variety of industries, selecting companies in each industry based on the research of a team of global industry analysts. The Portfolio typically seeks to maintain representation in each major industry represented by broad-based, large cap U.S. equity indices. In analyzing a prospective investment for the Portfolio, the adviser utilizes a “bottom-up” approach, which is the use of fundamental analysis to identify specific securities for purchase or sale. Fundamental analysis of a company involves the assessment of a variety of factors, including the company’s business environment, management quality, balance sheet, income statement, anticipated earnings, revenues and dividends, and other related measures or indicators of valuation and growth potential. The Portfolio’s sector exposures generally conform with the sector weights present in the Portfolio’s benchmark index and as a result, in combination with the Portfolio’s reliance on fundamental company analysis, and based upon market or economic conditions, the Portfolio may at times have a relatively high percentage of its assets invested in a particular sector of the market, such as the information technology sector. Further, the Portfolio may hold and maintain large positions in a single or small number of securities as a result of the adviser’s investment strategy. The Portfolio invests primarily in U.S. common stocks. Up to 20% of the Portfolio’s net assets may be invested in foreign based companies listed on foreign exchanges, either directly or through American Depositary Receipts (ADRs). The Portfolio may also invest in real estate investment trusts (REITs). The Portfolio may sell a security for a variety of reasons, including a significant adverse change in the company’s business fundamentals, if the company has become significantly overvalued in terms of earnings, assets or growth prospects, or more attractive alternatives exist.

Large Cap Core Stock Portfolio Investment Strategy - Large Cap Core Stock Portfolio

Dec. 31, 2025

<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">PRINCIPAL INVESTMENT STRATEGIES</span>

Strategy Narrative [Text Block]

Normally, the Portfolio invests at least 80% of net assets (plus any borrowings for investment purposes) in stocks of large-capitalization companies. For this purpose, large-capitalization stocks are those whose market capitalizations are above $5 billion at the time of purchase. In managing the Portfolio, the adviser allocates the Portfolio’s assets across a variety of industries, selecting companies in each industry based on the research of a team of global industry analysts. The Portfolio typically seeks to maintain representation in each major industry represented by broad-based, large cap U.S. equity indices. In analyzing a prospective investment for the Portfolio, the adviser utilizes a “bottom-up” approach, which is the use of fundamental analysis to identify specific securities for purchase or sale. Fundamental analysis of a company involves the assessment of a variety of factors, including the company’s business environment, management quality, balance sheet, income statement, anticipated earnings, revenues and dividends, and other related measures or indicators of valuation and growth potential. The Portfolio’s sector exposures generally conform with the sector weights present in the Portfolio’s benchmark index and as a result, in combination with the Portfolio’s reliance on fundamental company analysis, and based upon market or economic conditions, the Portfolio may at times have a relatively high percentage of its assets invested in a particular sector of the market, such as the information technology sector. Further, the Portfolio may hold and maintain large positions in a single or small number of securities as a result of the adviser’s investment strategy. The Portfolio invests primarily in U.S. common stocks. Up to 20% of the Portfolio’s net assets may be invested in foreign based companies listed on foreign exchanges, either directly or through American Depositary Receipts (ADRs). The Portfolio may also invest in real estate investment trusts (REITs). The Portfolio may sell a security for a variety of reasons, including a significant adverse change in the company’s business fundamentals, if the company has become significantly overvalued in terms of earnings, assets or growth prospects, or more attractive alternatives exist.