Stock Index Fund Investment Strategy - Stock Index 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 is managed to seek to track the performance of the Index, which measures the stock performance of 500 large- and mid-cap companies and is often used to indicate the performance of the overall stock market.The Subadviser may endeavor to track the Index by purchasing every stock included in the Index, in the same proportions. Or, in the alternative, the Subadviser may invest in a sampling of Index stocks by utilizing a statistical technique known as “optimization.” The goal of optimization is to select stocks which ensure that various industry weightings, market capitalizations, and fundamental characteristics, (e.g., price-to-book, price-to-earnings, debt-to-asset ratios and dividend yields) closely approximate those of the Index.The Fund invests, under normal circumstances, at least 80% of net assets in stocks that are in the Index. Although the Fund seeks to track the performance of the Index, the performance of the Fund will not match that of the Index exactly because, among other reasons, the Fund incurs operating expenses and other investment overhead as part of its normal operations. The subadviser may use derivatives to seek to track the performance of the Index, including futures and total return swaps. The Fund is classified as diversified under the Investment Company Act of 1940, as amended. However, the Fund may become non-diversified (which means that it can invest a greater percentage of its assets in the securities of fewer issuers than can a diversified fund), solely as a result of a change in the relative market capitalization or index weighting of one or more of the Index constituents. In these circumstances, the Fund may hold larger positions in a smaller number of issuers than a diversified fund. Shareholder approval will not be sought if the Fund becomes non-diversified due solely to a change in the relative market capitalization or index weighting of one or more constituents of the Index. 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.

Stock Index Fund Investment Strategy - Stock Index 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 is managed to seek to track the performance of the Index, which measures the stock performance of 500 large- and mid-cap companies and is often used to indicate the performance of the overall stock market.The Subadviser may endeavor to track the Index by purchasing every stock included in the Index, in the same proportions. Or, in the alternative, the Subadviser may invest in a sampling of Index stocks by utilizing a statistical technique known as “optimization.” The goal of optimization is to select stocks which ensure that various industry weightings, market capitalizations, and fundamental characteristics, (e.g., price-to-book, price-to-earnings, debt-to-asset ratios and dividend yields) closely approximate those of the Index.The Fund invests, under normal circumstances, at least 80% of net assets in stocks that are in the Index. Although the Fund seeks to track the performance of the Index, the performance of the Fund will not match that of the Index exactly because, among other reasons, the Fund incurs operating expenses and other investment overhead as part of its normal operations. The subadviser may use derivatives to seek to track the performance of the Index, including futures and total return swaps. The Fund is classified as diversified under the Investment Company Act of 1940, as amended. However, the Fund may become non-diversified (which means that it can invest a greater percentage of its assets in the securities of fewer issuers than can a diversified fund), solely as a result of a change in the relative market capitalization or index weighting of one or more of the Index constituents. In these circumstances, the Fund may hold larger positions in a smaller number of issuers than a diversified fund. Shareholder approval will not be sought if the Fund becomes non-diversified due solely to a change in the relative market capitalization or index weighting of one or more constituents of the Index. 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.