| The investment seeks high current return and safety of principal. The fund primarily invests at least 80% of assets in debt securities issued by the U.S. government, its agencies and instrumentalities, repurchase agreements on those securities and hedging instruments approved by its board of trustees. It may invest up to 20% of assets in mortgage-backed securities that are not issued or guaranteed by the U.S. government, investment grade corporate debt obligations, its agencies or instrumentalities, asset-backed securities, investment grade corporate debt obligations and certain other high quality debt obligations. |