Multi-Sector Bond Portfolio Investment Strategy - Multi-Sector 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 debt securities. The debt securities may be represented by forwards or derivatives such as options, futures contracts or swap agreements that have economic characteristics that are similar to the debt securities included in the 80% policy. The average portfolio duration of the Portfolio normally varies from three to eight years, based on the adviser’s forecast for interest rates. Duration is a measure of the sensitivity of the price of the Portfolio’s fixed income securities to changes in interest rates; the longer the duration, the more sensitive the price will be to changes in interest rates. The Portfolio may invest, without limitation, in high yield securities subject to a maximum of 10% of its total assets in securities rated below B by Moody’s or equivalently rated by S&P or Fitch or, if unrated, determined by the Portfolio’s adviser to be of comparable quality. High yield securities, commonly referred to as “junk” bonds, are non-investment grade securities. A security is considered to be non-investment grade when it is rated below investment grade by at least two of the three credit ratings 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. The Portfolio may invest, without limitation, in securities denominated in foreign currencies and U.S. dollar denominated securities of foreign issuers. In addition, the Portfolio may invest, without limitation, in fixed income securities of issuers that are economically tied to emerging securities markets. The Portfolio may invest in illiquid securities. The Portfolio may also invest up to 10% of its net assets in preferred stocks. The Portfolio may invest, without limitation, in derivative instruments, such as options, futures contracts or swap agreements including the purchase or sale of credit defaults swaps, and interest rate swaps (to take a position on interest rates moving either up or down), in municipal bonds, contingent convertible securities, or in mortgage- or asset-backed securities, subject to the Portfolio’s objective and policies. The Portfolio may utilize currency forwards and currency options to manage or hedge currency exposure. The Portfolio may invest in mortgage- or asset-backed securities which are non-investment grade. Mortgage-backed securities may include residential and commercial mortgage-backed securities issued by a Federal agency and private label residential and commercial mortgage-backed securities. The adviser may invest in derivatives at any time it deems appropriate, generally when relative value and liquidity conditions make these investments more attractive relative to cash bonds. The Portfolio may purchase or sell securities on a when-issued, delayed delivery or forward commitment basis and may engage in short sales. A short sale involves the sale of a security that is borrowed from a broker or other institution, and which must be purchased in the market at a later date and returned to the lender. The Portfolio may, without limitation, 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 buy backs or dollar rolls). The Portfolio may invest in repurchase agreements; however, it may not invest more than 10% of its total assets in repurchase agreements which have maturities of more than seven days, nor invest in any repurchase agreements with maturities over 30 days. The Portfolio may invest up to 10% of its net assets in fixed- and floating-rate loans, including senior loans, and such investments may be in the form of loan participations and assignments. Senior loans are considered speculative instruments. The “total return” sought by the Portfolio consists of income earned on the Portfolio’s investments, plus capital appreciation, if any, which generally arises from a decrease in interest rates or improving credit fundamentals for a particular sector or security. The Portfolio may engage in frequent and active trading of portfolio securities to achieve its investment objective, particularly during periods of volatile market movements. In selecting securities for a Portfolio, the adviser develops an outlook for interest rates, foreign currency exchange rates and the economy, analyzes credit and call risks, which involves both macro and fundamental analysis. The proportion of a Portfolio’s assets committed to investment in securities with particular characteristics (such as quality, sector, interest rate or maturity) varies based on the adviser’s outlook for the U.S. and foreign economies, the financial markets and other factors. The adviser attempts to identify areas of the bond market that are undervalued relative to the rest of the market. The adviser identifies these areas by grouping bonds into the following sectors: money markets, governments, corporates, mortgages, asset-backed and international. Sophisticated proprietary software then assists in evaluating sectors and pricing specific securities. Once investment opportunities are identified, the adviser will shift assets among sectors depending upon changes in relative valuations and credit spreads. The Portfolio may sell a position when, in the adviser’s opinion, it no longer represents a good value, when a superior risk/return opportunity exists in a substitute position, or when it no longer fits within the Portfolio’s macroeconomic or structural strategy.

Multi-Sector Bond Portfolio Investment Strategy - Multi-Sector 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 debt securities. The debt securities may be represented by forwards or derivatives such as options, futures contracts or swap agreements that have economic characteristics that are similar to the debt securities included in the 80% policy. The average portfolio duration of the Portfolio normally varies from three to eight years, based on the adviser’s forecast for interest rates. Duration is a measure of the sensitivity of the price of the Portfolio’s fixed income securities to changes in interest rates; the longer the duration, the more sensitive the price will be to changes in interest rates. The Portfolio may invest, without limitation, in high yield securities subject to a maximum of 10% of its total assets in securities rated below B by Moody’s or equivalently rated by S&P or Fitch or, if unrated, determined by the Portfolio’s adviser to be of comparable quality. High yield securities, commonly referred to as “junk” bonds, are non-investment grade securities. A security is considered to be non-investment grade when it is rated below investment grade by at least two of the three credit ratings 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. The Portfolio may invest, without limitation, in securities denominated in foreign currencies and U.S. dollar denominated securities of foreign issuers. In addition, the Portfolio may invest, without limitation, in fixed income securities of issuers that are economically tied to emerging securities markets. The Portfolio may invest in illiquid securities. The Portfolio may also invest up to 10% of its net assets in preferred stocks. The Portfolio may invest, without limitation, in derivative instruments, such as options, futures contracts or swap agreements including the purchase or sale of credit defaults swaps, and interest rate swaps (to take a position on interest rates moving either up or down), in municipal bonds, contingent convertible securities, or in mortgage- or asset-backed securities, subject to the Portfolio’s objective and policies. The Portfolio may utilize currency forwards and currency options to manage or hedge currency exposure. The Portfolio may invest in mortgage- or asset-backed securities which are non-investment grade. Mortgage-backed securities may include residential and commercial mortgage-backed securities issued by a Federal agency and private label residential and commercial mortgage-backed securities. The adviser may invest in derivatives at any time it deems appropriate, generally when relative value and liquidity conditions make these investments more attractive relative to cash bonds. The Portfolio may purchase or sell securities on a when-issued, delayed delivery or forward commitment basis and may engage in short sales. A short sale involves the sale of a security that is borrowed from a broker or other institution, and which must be purchased in the market at a later date and returned to the lender. The Portfolio may, without limitation, 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 buy backs or dollar rolls). The Portfolio may invest in repurchase agreements; however, it may not invest more than 10% of its total assets in repurchase agreements which have maturities of more than seven days, nor invest in any repurchase agreements with maturities over 30 days. The Portfolio may invest up to 10% of its net assets in fixed- and floating-rate loans, including senior loans, and such investments may be in the form of loan participations and assignments. Senior loans are considered speculative instruments. The “total return” sought by the Portfolio consists of income earned on the Portfolio’s investments, plus capital appreciation, if any, which generally arises from a decrease in interest rates or improving credit fundamentals for a particular sector or security. The Portfolio may engage in frequent and active trading of portfolio securities to achieve its investment objective, particularly during periods of volatile market movements. In selecting securities for a Portfolio, the adviser develops an outlook for interest rates, foreign currency exchange rates and the economy, analyzes credit and call risks, which involves both macro and fundamental analysis. The proportion of a Portfolio’s assets committed to investment in securities with particular characteristics (such as quality, sector, interest rate or maturity) varies based on the adviser’s outlook for the U.S. and foreign economies, the financial markets and other factors. The adviser attempts to identify areas of the bond market that are undervalued relative to the rest of the market. The adviser identifies these areas by grouping bonds into the following sectors: money markets, governments, corporates, mortgages, asset-backed and international. Sophisticated proprietary software then assists in evaluating sectors and pricing specific securities. Once investment opportunities are identified, the adviser will shift assets among sectors depending upon changes in relative valuations and credit spreads. The Portfolio may sell a position when, in the adviser’s opinion, it no longer represents a good value, when a superior risk/return opportunity exists in a substitute position, or when it no longer fits within the Portfolio’s macroeconomic or structural strategy.