High Yield Bond Portfolio Investment Strategy - High Yield Bond 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 non-investment grade debt securities. Non-investment grade securities are generally securities rated below investment grade by major credit rating agencies (BB+ or lower by S&P; Ba1 or lower by Moody’s; BB+ or lower by Fitch), or, if unrated, determined by the Portfolio’s adviser to be of comparable quality. There is no minimal acceptable rating for a security to be purchased or held by the Portfolio. The Portfolio may invest up to 30% of net assets in non-investment grade foreign securities, including those of issuers located in emerging markets, consistent with its investment objective. Foreign securities held by the Portfolio consist primarily of U.S. dollar denominated securities but may also include non-U.S. dollar denominated securities. The securities in which the Portfolio primarily invests are considered speculative and are sometimes known as “junk bonds.” These securities tend to offer higher yields than higher rated securities of comparable maturities primarily because of the market’s greater uncertainty about the issuer’s ability to make all required interest and principal payments, and therefore about the returns that will in fact be realized by the Portfolio. The adviser selects securities that it believes have attractive investment characteristics and seeks to minimize default risk and other risks through careful security selection and diversification. The adviser’s securities selection process consists of a credit-intensive, fundamental analysis of the issuer. The adviser’s analysis focuses on the issuer’s financial condition, business and product strength, competitive position and management expertise. Further, the adviser considers current economic, financial market and industry factors, which may affect the issuer. The adviser does not limit the Portfolio’s investments to securities of a particular maturity range and does not target an average effective maturity or duration.The adviser strives to adhere to a strong sell discipline and generally effects a sale if it believes a security’s future total return has become less attractive relative to other securities, the company begins to perform poorly, the industry outlook changes, or any other event occurs that changes the adviser’s conclusion.

High Yield Bond Portfolio Investment Strategy - High Yield Bond 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 non-investment grade debt securities. Non-investment grade securities are generally securities rated below investment grade by major credit rating agencies (BB+ or lower by S&P; Ba1 or lower by Moody’s; BB+ or lower by Fitch), or, if unrated, determined by the Portfolio’s adviser to be of comparable quality. There is no minimal acceptable rating for a security to be purchased or held by the Portfolio. The Portfolio may invest up to 30% of net assets in non-investment grade foreign securities, including those of issuers located in emerging markets, consistent with its investment objective. Foreign securities held by the Portfolio consist primarily of U.S. dollar denominated securities but may also include non-U.S. dollar denominated securities. The securities in which the Portfolio primarily invests are considered speculative and are sometimes known as “junk bonds.” These securities tend to offer higher yields than higher rated securities of comparable maturities primarily because of the market’s greater uncertainty about the issuer’s ability to make all required interest and principal payments, and therefore about the returns that will in fact be realized by the Portfolio. The adviser selects securities that it believes have attractive investment characteristics and seeks to minimize default risk and other risks through careful security selection and diversification. The adviser’s securities selection process consists of a credit-intensive, fundamental analysis of the issuer. The adviser’s analysis focuses on the issuer’s financial condition, business and product strength, competitive position and management expertise. Further, the adviser considers current economic, financial market and industry factors, which may affect the issuer. The adviser does not limit the Portfolio’s investments to securities of a particular maturity range and does not target an average effective maturity or duration.The adviser strives to adhere to a strong sell discipline and generally effects a sale if it believes a security’s future total return has become less attractive relative to other securities, the company begins to perform poorly, the industry outlook changes, or any other event occurs that changes the adviser’s conclusion.