Core Bond Fund Investment Strategy - Core Bond Fund	May 31, 2026
Prospectus [Line Items]
Strategy [Heading]	<span style="color:#000000;font-family:Arial;font-size:12pt;font-weight:bold;">Principal Investment Strategies of the Fund</span>
Strategy Narrative [Text Block]	The Fund invests, under normal circumstances, at least 80% of its net assets in fixed-income securities.The Fund primarily invests in medium- to high-quality fixed-income securities, including corporate debt securities of domestic and foreign companies, or in securities issued or guaranteed by the U.S. Government such as treasury obligations, including treasury coupon strips and treasury principal strips, and other U.S. Government securities, mortgage-related and mortgage-backed or non-mortgage asset-backed securities.The Fund may invest significantly in U.S. Government securities, which are securities issued or guaranteed by the U.S. Government, its agencies and instrumentalities. Some U.S. Government securities are issued or unconditionally guaranteed by the U.S. Treasury. While these securities are subject to variations in market value due to fluctuations in interest rates, they will be paid in full if held to maturity. Other U.S. Government securities are neither direct obligations of, nor guaranteed by, the U.S. Treasury. However, they involve federal sponsorship in one way or another. The Fund may invest a significant portion or all of its assets in mortgage-related and mortgage-backed securities at the subadviser’s discretion, including securities issued or guaranteed by the Federal National Mortgage Association (“FNMA”), the Federal Home Loan Mortgage Corporation (“FHLMC”) or the Government National Mortgage Association. Mortgage-related and mortgage-backed securities may be structured as collateralized mortgage obligations (agency and non-agency), stripped mortgage-backed securities, commercial mortgage-backed securities, mortgage pass-through securities and cash and cash equivalents. These securities may be structured such that payments consist of interest-only (IO), principal-only (PO) or principal and interest.Up to 40% of the Fund’s total assets may be invested in U.S. dollar-denominated fixed-income securities issued by foreign issuers, including fixed-income securities issued by issuers in emerging markets. Emerging market countries are countries that major international financial institutions and financial organizations, such as the World Bank and Bloomberg, generally consider to be less economically mature than developed nations, and include most countries in the world except Australia, Canada, Japan, New Zealand, the U.S., the United Kingdom and most western European countries and Hong Kong. These fixed-income securities are rated investment grade or higher at the time of investment (or the unrated equivalent). However, the subadvisers are not required to dispose of a security if its rating is downgraded. Although the Fund invests primarily in medium-to high-quality fixed-income securities, which are considered investment-grade, up to 20% of its net assets may be invested in lower-quality fixed-income securities (often referred to as “junk bonds”), including “sub-prime mortgages,” which are considered below investment-grade. A fixed-income security will be considered investment-grade if it is rated Baa3 or higher by Moody’s Investor Services, Inc. or BBB- or higher by S&P Global Ratings or determined to be of comparable quality by the subadviser. The Fund expects to invest no more than 10% of its assets in “sub-prime” mortgage-related securities at the time of purchase. Up to 20% of the Fund’s net assets may be invested in interest-bearing short-term investments, such as commercial paper, bankers’ acceptances, bank certificates of deposit, and other cash equivalents and cash. One subadviser’s investment strategy relies on many short-term factors, including current information about a company, investor interest, price movements of a company’s securities and general market and monetary conditions. The other subadviser buys and sells securities and investments for the Fund based on its view of individual securities and market sectors. Taking a long-term approach, the subadviser looks for individual fixed income investments that it believes will perform well over market cycles. The subadviser is value oriented and makes decisions to purchase and sell individual securities and instruments after performing a risk/reward analysis that includes an evaluation of interest rate risk, credit risk, duration, liquidity, legal provisions and the structure of the transaction. Consequently, the Fund may engage in active and frequent trading of portfolio securities in an effort to achieve its investment objective. In order to generate additional income, the Fund may lend portfolio securities to broker-dealers and other financial institutions provided that the value of the loaned securities does not exceed 30% of the Fund’s total assets. These loans earn income for the Fund and are collateralized by cash and securities issued or guaranteed by the U.S. Government or its agencies or instrumentalities.

Core Bond Fund Investment Strategy - Core Bond Fund

May 31, 2026

<span style="color:#000000;font-family:Arial;font-size:12pt;font-weight:bold;">Principal Investment Strategies of the Fund</span>

Strategy Narrative [Text Block]

The Fund invests, under normal circumstances, at least 80% of its net assets in fixed-income securities.The Fund primarily invests in medium- to high-quality fixed-income securities, including corporate debt securities of domestic and foreign companies, or in securities issued or guaranteed by the U.S. Government such as treasury obligations, including treasury coupon strips and treasury principal strips, and other U.S. Government securities, mortgage-related and mortgage-backed or non-mortgage asset-backed securities.The Fund may invest significantly in U.S. Government securities, which are securities issued or guaranteed by the U.S. Government, its agencies and instrumentalities. Some U.S. Government securities are issued or unconditionally guaranteed by the U.S. Treasury. While these securities are subject to variations in market value due to fluctuations in interest rates, they will be paid in full if held to maturity. Other U.S. Government securities are neither direct obligations of, nor guaranteed by, the U.S. Treasury. However, they involve federal sponsorship in one way or another. The Fund may invest a significant portion or all of its assets in mortgage-related and mortgage-backed securities at the subadviser’s discretion, including securities issued or guaranteed by the Federal National Mortgage Association (“FNMA”), the Federal Home Loan Mortgage Corporation (“FHLMC”) or the Government National Mortgage Association. Mortgage-related and mortgage-backed securities may be structured as collateralized mortgage obligations (agency and non-agency), stripped mortgage-backed securities, commercial mortgage-backed securities, mortgage pass-through securities and cash and cash equivalents. These securities may be structured such that payments consist of interest-only (IO), principal-only (PO) or principal and interest.Up to 40% of the Fund’s total assets may be invested in U.S. dollar-denominated fixed-income securities issued by foreign issuers, including fixed-income securities issued by issuers in emerging markets. Emerging market countries are countries that major international financial institutions and financial organizations, such as the World Bank and Bloomberg, generally consider to be less economically mature than developed nations, and include most countries in the world except Australia, Canada, Japan, New Zealand, the U.S., the United Kingdom and most western European countries and Hong Kong. These fixed-income securities are rated investment grade or higher at the time of investment (or the unrated equivalent). However, the subadvisers are not required to dispose of a security if its rating is downgraded. Although the Fund invests primarily in medium-to high-quality fixed-income securities, which are considered investment-grade, up to 20% of its net assets may be invested in lower-quality fixed-income securities (often referred to as “junk bonds”), including “sub-prime mortgages,” which are considered below investment-grade. A fixed-income security will be considered investment-grade if it is rated Baa3 or higher by Moody’s Investor Services, Inc. or BBB- or higher by S&P Global Ratings or determined to be of comparable quality by the subadviser. The Fund expects to invest no more than 10% of its assets in “sub-prime” mortgage-related securities at the time of purchase. Up to 20% of the Fund’s net assets may be invested in interest-bearing short-term investments, such as commercial paper, bankers’ acceptances, bank certificates of deposit, and other cash equivalents and cash. One subadviser’s investment strategy relies on many short-term factors, including current information about a company, investor interest, price movements of a company’s securities and general market and monetary conditions. The other subadviser buys and sells securities and investments for the Fund based on its view of individual securities and market sectors. Taking a long-term approach, the subadviser looks for individual fixed income investments that it believes will perform well over market cycles. The subadviser is value oriented and makes decisions to purchase and sell individual securities and instruments after performing a risk/reward analysis that includes an evaluation of interest rate risk, credit risk, duration, liquidity, legal provisions and the structure of the transaction. Consequently, the Fund may engage in active and frequent trading of portfolio securities in an effort to achieve its investment objective. In order to generate additional income, the Fund may lend portfolio securities to broker-dealers and other financial institutions provided that the value of the loaned securities does not exceed 30% of the Fund’s total assets. These loans earn income for the Fund and are collateralized by cash and securities issued or guaranteed by the U.S. Government or its agencies or instrumentalities.