U.S. Government Securities Fund Class A Class 529-A Class C Class 529-C Class 529-E Class F-1 Class F-2 Class F-3 Class 529-F-2 Class 529-F-3 Class R-1 Class R-2 Class R-3 Class R-4 Class R-5 Class R-6 Class R-2E Class R-5E Market conditions [Member] Issuer risks [Member] Investing in debt instruments [Member] Investing in securities backed by the U.S. government [Member] Investing in mortgage-related and other asset-backed securities [Member] Investments in future delivery contracts [Member] Investing in inflation-linked bonds [Member] Investing in derivatives [Member] Management [Member] Bloomberg U.S. Aggregate Index (reflects no deductions for sales charges, account fees, expenses or U.S. federal income taxes) Bloomberg U.S. Government/Mortgage-Backed Securities Index (reflects no deductions for sales charges, account fees, expenses or U.S. federal income taxes) C000025134 Member index_ Bloomberg_ US_ Aggregate_ Index_reflects_no_deductions_for_sales_charges_account_fees_expenses_or_ US_federal_income_taxes Member C000068600 Member C000179952 Member C000164800 Member C000025144 Member Market Conditions Member Investments In Future Delivery Contracts Member C000025139 Member C000224557 Member C000025140 Member C000077855 Member C000025141 Member C000025136 Member C000148357 Member index_ Bloomberg_ US_ Government Mortgage Backed_ Securities_ Index_reflects_no_deductions_for_sales_charges_account_fees_expenses_or_ US_federal_income_taxes Member S000009235 Member Issuer Risks Member Investing In Derivatives Member C000025143 Member C000025133 Member C000224558 Member C000025135 Member Investing In Mortgagerelated And Other Assetbacked Securities Member Investing In Inflationlinked Bonds Member Investing In Securities Backed By The USGovernment Member ManagementMember Investing In Debt Instruments Member C000025132 Member C000025137 Member