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Label Element Value
Prospectus: rr_ProspectusTable  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Mar. 31, 2020
Entity Registrant Name dei_EntityRegistrantName American Century Government Income Trust
Central Index Key dei_EntityCentralIndexKey 0000773674
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Jul. 29, 2020
Document Effective Date dei_DocumentEffectiveDate Aug. 01, 2020
Prospectus Date rr_ProspectusDate Aug. 01, 2020
American Century Government Income Trust | CAPITAL PRESERVATION FUND  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading Capital Preservation Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund is a money market fund that seeks maximum safety and liquidity.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock
Its secondary objective is to seek to pay shareholders the highest rate of return consistent with safety and liquidity.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
The following table describes the fees and expenses you may pay if you buy, hold, and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
The example below is intended to help you compare the costs of investing in the fund with the costs of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods, that you earn a 5% return each year and that the fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, Capital Preservation invests exclusively in short-term money market securities issued by the U.S. Treasury that are guaranteed by the direct full faith and credit pledge of the U.S. government. The income from these securities is exempt from state income tax. Examples of U.S. Treasury securities in which the fund may invest include Treasury bills and notes, and Treasury floating-rate notes.
Because this fund is a government money market fund, both retail and institutional shareholders may invest in the fund. This fund does not have the ability to impose a liquidity fee on the sale of shares or temporarily suspend redemptions in response to decreases in liquidity.
The fund may purchase U.S. Treasury securities through buy/sell back transactions. The fund may commit up to 35% of its total assets to such transactions.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
Because short-term money market securities are among the safest securities available, the interest they pay is among the lowest for income-paying securities. Accordingly, the yield on this fund will likely be lower than the yield on funds that invest in longer-term or lower-quality securities.
Investments in U.S. Treasury securities are sensitive to interest rate changes. Generally, the value of debt securities and the funds that hold them decline as interest rates rise. The fund’s investments in short-term U.S. Treasury securities are designed to minimize this risk. However, a sharp and unexpected rise in interest rates could cause the fund’s share price to drop.
You could lose money by investing in the fund. Although the fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The fund’s sponsor has no legal obligation to provide financial support to the fund, and you should not expect that the sponsor will provide financial support to the fund at any time.
Risk Lose Money [Text] rr_RiskLoseMoney You could lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Fund Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. For current performance information, including yields, please visit americancentury.com.
Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress americancentury.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance is not necessarily an indication of how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Calendar Year Total Returns
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
(1Q 2019): 0.49%            Lowest Performance Quarter (2Q 2015): 0.00%

As of June 30, 2020, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 0.24%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2019
American Century Government Income Trust | CAPITAL PRESERVATION FUND | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol CPFXX
Maximum Account Fee rr_MaximumAccountFee $ 25
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.47%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.48%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 49
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 154
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 269
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 604
Annual Return 2010 rr_AnnualReturn2010 0.01%
Annual Return 2011 rr_AnnualReturn2011 0.01%
Annual Return 2012 rr_AnnualReturn2012 0.01%
Annual Return 2013 rr_AnnualReturn2013 0.01%
Annual Return 2014 rr_AnnualReturn2014 0.01%
Annual Return 2015 rr_AnnualReturn2015 0.01%
Annual Return 2016 rr_AnnualReturn2016 0.01%
Annual Return 2017 rr_AnnualReturn2017 0.41%
Annual Return 2018 rr_AnnualReturn2018 1.38%
Annual Return 2019 rr_AnnualReturn2019 1.75%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2020
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.24%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2019
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 0.49%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2015
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn none
Label rr_AverageAnnualReturnLabel Investor Class
1 Year rr_AverageAnnualReturnYear01 1.75%
5 Years rr_AverageAnnualReturnYear05 0.71%
10 Years rr_AverageAnnualReturnYear10 0.36%
American Century Government Income Trust | GINNIE MAE FUND  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading Ginnie Mae Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
Ginnie Mae seeks high current income while maintaining liquidity and safety of principal by investing primarily in GNMA certificates.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
The following table describes the fees and expenses you may pay if you buy, hold and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in Calculation of Sales Charges on page 30 of the fund’s prospectus, Appendix A of the fund’s prospectus and Sales Charges in Appendix B of the statement of additional information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 270% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 270.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in Calculation of Sales Charges on page 30 of the fund’s prospectus, Appendix A of the fund’s prospectus and Sales Charges in Appendix B of the statement of additional information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
The example below is intended to help you compare the costs of investing in the fund with the costs of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods, that you earn a 5% return each year and that the fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal market conditions, the fund invests at least 80% of its net assets in securities issued by the Government National Mortgage Association (GNMA). GNMA certificates represent interests in pools of mortgage loans and in the cash flows from these loans. Unlike many other mortgage-backed securities, the timely payment of principal and interest on these certificates is guaranteed by GNMA. GNMA’s payment guarantee is stronger than most other government agencies’ because it is backed by the full faith and credit pledge of the U.S. government.
In addition, the fund may buy other U.S. government debt securities, including U.S. Treasury securities and other securities issued or guaranteed by the U.S. government and its agencies and instrumentalities. Securities issued or guaranteed by other U.S. government agencies or instrumentalities, such as the Federal National Mortgage Association (Fannie Mae), the Federal Home Loan Mortgage Corporation (Freddie Mac), and the Federal Home Loan Bank are not guaranteed by the U.S. Treasury or supported by the full faith and credit of the U.S. government. However, these agencies or instrumentalities are authorized to borrow from the U.S. Treasury to meet their obligations.
To generate additional income, the fund may purchase securities, including mortgage dollar rolls, in advance through when-issued and forward commitment transactions. The fund may commit up to 35% of its total assets to such transactions.
The fund also may invest in derivative instruments such as options, futures contracts, options on futures contracts and swap agreements, or in mortgage- or asset-backed securities, provided that such investments are in keeping with the fund’s investment objective.
When determining whether to sell a security, the portfolio managers consider, among other things, current and anticipated changes in interest rates, current valuation relative to alternatives in the market, general market conditions and any other factors deemed relevant by the portfolio managers.
The fund may engage in active and frequent trading of portfolio securities to achieve its principal investment strategies. This may cause higher transaction costs and may affect performance. It may also result in the realization and distribution of capital gains.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Interest Rate Risk—Generally, when interest rates rise, the fund’s share value will decline. The opposite is true when interest rates decline. This risk is higher for the fund than for other funds that have shorter weighted average maturities, such as money market funds and short-term bond funds. A period of rising interest rates may negatively affect the fund’s performance.
•
Prepayment Risk—The fund may invest in debt securities backed by mortgages or other assets. If these underlying assets are prepaid, the fund may benefit less from declining interest rates than funds that have similar weighted average maturities.
•
Derivatives Risk—The use of derivative instruments involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other traditional instruments. Derivatives are subject to a number of risks including liquidity, interest rate, market, credit and correlation risk.
•
Market Risk—The value of the securities owned by the fund may go up and down, sometimes rapidly or unpredictably. Market risks, including political, regulatory, economic and social developments, can affect the value of the fund’s investments. Natural disasters, public health emergencies, terrorism and other unforeseeable events may lead to increased market volatility and may have adverse long-term effects on world economies and markets generally.
•
Redemption Risk—The fund may need to sell securities at times it would not otherwise do so in order to meet shareholder redemption requests. Selling securities to meet such redemptions may cause the fund to experience a loss, increase the fund’s transaction costs or have tax consequences. To the extent that a large shareholder (including a fund of funds or 529 college savings plan) invests in the fund, the fund may experience relatively large redemptions as such shareholder reallocates its assets.
•
Principal Loss—At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.
An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney Principal Loss—At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Fund Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, including yields, please visit americancentury.com.
Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress americancentury.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Calendar Year Total Returns
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
(2Q 2010): 3.21%        Lowest Performance Quarter (2Q 2013): -2.72%

As of June 30, 2020, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 3.47%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2019
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as 401(k) plans or IRAs.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as 401(k) plans or IRAs.
American Century Government Income Trust | GINNIE MAE FUND | Bloomberg Barclays U.S. GNMA Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays U.S. GNMA Index    (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 5.85%
5 Years rr_AverageAnnualReturnYear05 2.32%
10 Years rr_AverageAnnualReturnYear10 3.21%
American Century Government Income Trust | GINNIE MAE FUND | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol BGNMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee $ 25
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.55%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 56
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 177
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 308
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 690
Annual Return 2010 rr_AnnualReturn2010 6.33%
Annual Return 2011 rr_AnnualReturn2011 7.31%
Annual Return 2012 rr_AnnualReturn2012 2.37%
Annual Return 2013 rr_AnnualReturn2013 (2.32%)
Annual Return 2014 rr_AnnualReturn2014 4.87%
Annual Return 2015 rr_AnnualReturn2015 0.77%
Annual Return 2016 rr_AnnualReturn2016 1.05%
Annual Return 2017 rr_AnnualReturn2017 1.21%
Annual Return 2018 rr_AnnualReturn2018 0.42%
Annual Return 2019 rr_AnnualReturn2019 6.16%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2020
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 3.47%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 3.21%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2013
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (2.72%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.16%
5 Years rr_AverageAnnualReturnYear05 1.90%
10 Years rr_AverageAnnualReturnYear10 2.77%
American Century Government Income Trust | GINNIE MAE FUND | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel    Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 5.00%
5 Years rr_AverageAnnualReturnYear05 0.84%
10 Years rr_AverageAnnualReturnYear10 1.61%
American Century Government Income Trust | GINNIE MAE FUND | INVESTOR CLASS | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel    Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 3.63%
5 Years rr_AverageAnnualReturnYear05 0.97%
10 Years rr_AverageAnnualReturnYear10 1.65%
American Century Government Income Trust | GINNIE MAE FUND | I CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol AGMHX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.44%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.45%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 46
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 145
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 252
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 567
Label rr_AverageAnnualReturnLabel I Class1 Return Before Taxes [1]
1 Year rr_AverageAnnualReturnYear01 6.27% [1]
5 Years rr_AverageAnnualReturnYear05 2.01% [1]
10 Years rr_AverageAnnualReturnYear10 2.87% [1]
American Century Government Income Trust | GINNIE MAE FUND | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol BGNAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [2]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.80%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 528
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 694
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 875
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,396
Label rr_AverageAnnualReturnLabel A Class2 Return Before Taxes [3]
1 Year rr_AverageAnnualReturnYear01 1.14% [3]
5 Years rr_AverageAnnualReturnYear05 0.72% [3]
10 Years rr_AverageAnnualReturnYear10 2.05% [3]
American Century Government Income Trust | GINNIE MAE FUND | C CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol BGNCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.55%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 158
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 490
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 845
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,844
Label rr_AverageAnnualReturnLabel C Class3 Return Before Taxes [4]
1 Year rr_AverageAnnualReturnYear01 5.11% [4]
5 Years rr_AverageAnnualReturnYear05 0.89% [4]
10 Years rr_AverageAnnualReturnYear10 1.75% [4]
American Century Government Income Trust | GINNIE MAE FUND | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol AGMWX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.05%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 107
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 335
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 580
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,282
Label rr_AverageAnnualReturnLabel R Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.64%
5 Years rr_AverageAnnualReturnYear05 1.39%
10 Years rr_AverageAnnualReturnYear10 2.25%
American Century Government Income Trust | GINNIE MAE FUND | R5 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol AGMNX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.34%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.35%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 36
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 113
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 197
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 444
Label rr_AverageAnnualReturnLabel R5 Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.37%
5 Years rr_AverageAnnualReturnYear05 2.10%
10 Years rr_AverageAnnualReturnYear10 2.98%
American Century Government Income Trust | GOVERNMENT BOND FUND  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading Government Bond Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks high current income.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
The following table describes the fees and expenses you may pay if you buy, hold and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in Calculation of Sales Charges on page 30 of the fund’s prospectus, Appendix A of the fund’s prospectus and Sales Charges in Appendix B of the statement of additional information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 103% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 103.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in Calculation of Sales Charges on page 30 of the fund’s prospectus, Appendix A of the fund’s prospectus and Sales Charges in Appendix B of the statement of additional information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
The example below is intended to help you compare the costs of investing in the fund with the costs of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods, that you earn a 5% return each year and that the fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal market conditions, the fund invests at least 80% of its net assets in U.S. government debt securities, including U.S. Treasury securities and other securities issued or guaranteed by the U.S. government and its agencies and instrumentalities.
Securities issued or guaranteed by the U.S. Treasury and certain U.S. government agencies or instrumentalities, such as the Government National Mortgage Association (Ginnie Mae), are supported by the full faith and credit of the U.S. government. Securities issued or guaranteed by other U.S. government agencies or instrumentalities, such as the Federal National Mortgage Association (Fannie Mae), the Federal Home Loan Mortgage Corporation (Freddie Mac), and the Federal Home Loan Bank are not guaranteed by the U.S. Treasury or supported by the full faith and credit of the U.S. government. However, these agencies or instrumentalities are authorized to borrow from the U.S. Treasury to meet their obligations.
To generate additional income, the fund may purchase securities, including mortgage dollar rolls, in advance through when-issued and forward commitment transactions. The fund may commit up to 35% of its total assets to such transactions.
The fund also may invest in derivative instruments such as options, futures contracts, options on futures contracts and swap agreements, or in mortgage- or asset-backed securities, provided that such investments are in keeping with the fund’s investment objective.
When determining whether to sell a security, the portfolio managers consider, among other things, current and anticipated changes in interest rates, current valuation relative to alternatives in the market, general market conditions and any other factors deemed relevant by the portfolio managers.
The fund may engage in active and frequent trading of portfolio securities to achieve its principal investment strategies. This may cause higher transaction costs and may affect performance. It may also result in the realization and distribution of capital gains.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Interest Rate Risk—Generally, when interest rates rise, the fund’s share value will decline. The opposite is true when interest rates decline. This risk is higher for the fund than for other funds that have shorter weighted average maturities, such as money market funds or short-term bond funds. A period of rising interest rates may negatively affect the fund’s performance.
•
Prepayment Risk—The fund may invest in debt securities backed by mortgages or other assets. If these underlying assets are prepaid, the fund may benefit less from declining interest rates than funds that have similar weighted average maturities.
•
Derivatives Risk—The use of derivative instruments involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other traditional instruments. Derivatives are subject to a number of risks including liquidity, interest rate, market, credit and correlation risk.
•
Market Risk—The value of the securities owned by the fund may go up and down, sometimes rapidly or unpredictably. Market risks, including political, regulatory, economic and social developments, can affect the value of the fund’s investments. Natural disasters, public health emergencies, terrorism and other unforeseeable events may lead to increased market volatility and may have adverse long-term effects on world economies and markets generally.
•
Principal Loss—At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.
An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney Principal Loss—At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Fund Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, including yields, please visit americancentury.com.
Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress americancentury.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Calendar Year Total Returns
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
(3Q 2011): 4.45%        Lowest Performance Quarter (4Q 2016): -3.17%

As of June 30, 2020, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 6.47%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2019
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as 401(k) plans or IRAs.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as 401(k) plans or IRAs.
American Century Government Income Trust | GOVERNMENT BOND FUND | Bloomberg Barclays U.S. Government/MBS Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes  (reflects no deduction for fees, expenses or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays U.S. Government/MBS Index     (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 6.63%
5 Years rr_AverageAnnualReturnYear05 2.45%
10 Years rr_AverageAnnualReturnYear10 3.07%
American Century Government Income Trust | GOVERNMENT BOND FUND | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol CPTNX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee $ 25
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.46%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.47%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 48
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 151
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 264
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 592
Annual Return 2010 rr_AnnualReturn2010 5.35%
Annual Return 2011 rr_AnnualReturn2011 7.50%
Annual Return 2012 rr_AnnualReturn2012 2.18%
Annual Return 2013 rr_AnnualReturn2013 (2.88%)
Annual Return 2014 rr_AnnualReturn2014 4.60%
Annual Return 2015 rr_AnnualReturn2015 0.51%
Annual Return 2016 rr_AnnualReturn2016 0.85%
Annual Return 2017 rr_AnnualReturn2017 2.14%
Annual Return 2018 rr_AnnualReturn2018 0.56%
Annual Return 2019 rr_AnnualReturn2019 6.16%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2020
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 6.47%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2011
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.45%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.17%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.16%
5 Years rr_AverageAnnualReturnYear05 2.02%
10 Years rr_AverageAnnualReturnYear10 2.65%
Inception Date rr_AverageAnnualReturnInceptionDate May 16, 1980
American Century Government Income Trust | GOVERNMENT BOND FUND | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel    Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 5.08%
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 1.67%
Inception Date rr_AverageAnnualReturnInceptionDate May 16, 1980
American Century Government Income Trust | GOVERNMENT BOND FUND | INVESTOR CLASS | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel    Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 3.63%
5 Years rr_AverageAnnualReturnYear05 1.12%
10 Years rr_AverageAnnualReturnYear10 1.64%
Inception Date rr_AverageAnnualReturnInceptionDate May 16, 1980
American Century Government Income Trust | GOVERNMENT BOND FUND | I CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol ABHTX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.36%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.37%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 38
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 119
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 208
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 469
Label rr_AverageAnnualReturnLabel I Class1 Return Before Taxes [5]
1 Year rr_AverageAnnualReturnYear01 6.27% [5]
5 Years rr_AverageAnnualReturnYear05 2.11% [5]
Since Inception rr_AverageAnnualReturnSinceInception 2.63% [5]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 10, 2017 [5]
American Century Government Income Trust | GOVERNMENT BOND FUND | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol ABTAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [6]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.46%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.72%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 520
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 670
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 833
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,305
Label rr_AverageAnnualReturnLabel A Class2 Return Before Taxes [7]
1 Year rr_AverageAnnualReturnYear01 1.09% [7]
5 Years rr_AverageAnnualReturnYear05 0.85% [7]
10 Years rr_AverageAnnualReturnYear10 1.92% [7]
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 09, 1997 [7]
American Century Government Income Trust | GOVERNMENT BOND FUND | C CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol ABTCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.46%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.47%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 150
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 466
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 803
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,756
Label rr_AverageAnnualReturnLabel C Class3 Return Before Taxes [8]
1 Year rr_AverageAnnualReturnYear01 5.21% [8]
5 Years rr_AverageAnnualReturnYear05 1.03% [8]
10 Years rr_AverageAnnualReturnYear10 1.63% [8]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010 [8]
American Century Government Income Trust | GOVERNMENT BOND FUND | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol ABTRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.46%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.97%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 99
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 310
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 537
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,190
Label rr_AverageAnnualReturnLabel R Class3 Return Before Taxes [8]
1 Year rr_AverageAnnualReturnYear01 5.63% [8]
5 Years rr_AverageAnnualReturnYear05 1.53% [8]
10 Years rr_AverageAnnualReturnYear10 2.14% [8]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010 [8]
American Century Government Income Trust | GOVERNMENT BOND FUND | R5 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol ABTIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.26%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.27%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 28
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 87
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 152
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 344
Label rr_AverageAnnualReturnLabel R5 Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.37%
5 Years rr_AverageAnnualReturnYear05 2.24%
Since Inception rr_AverageAnnualReturnSinceInception 2.75%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010
American Century Government Income Trust | SHORT-TERM GOVERNMENT FUND  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading Short-Term Government Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks high current income while maintaining safety of principal.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
The following table describes the fees and expenses you may pay if you buy, hold and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in Calculation of Sales Charges on page 30 of the fund’s prospectus, Appendix A of the fund’s prospectus and Sales Charges in Appendix B of the statement of additional information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 206% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 206.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in Calculation of Sales Charges on page 30 of the fund’s prospectus, Appendix A of the fund’s prospectus and Sales Charges in Appendix B of the statement of additional information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
The example below is intended to help you compare the costs of investing in the fund with the costs of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods, that you earn a 5% return each year and that the fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal market conditions, the fund buys short-term debt securities and will invest at least 80% of its net assets in U.S. government securities, including U.S. Treasury securities and other securities issued or guaranteed by the U.S. government and its agencies and instrumentalities. In addition, the fund may invest a portion of its assets in investment-grade debt securities, including debt securities of U.S. companies, and non-U.S. government mortgage-backed, asset-backed and other fixed-income securities. Under normal market conditions, the portfolio managers maintain a weighted average maturity of three years or less.
Securities issued or guaranteed by the U.S. Treasury and certain U.S. government agencies or instrumentalities, such as the Government National Mortgage Association (Ginnie Mae), are supported by the full faith and credit of the U.S. government. Securities issued or guaranteed by other U.S. government agencies or instrumentalities, such as the Federal National Mortgage Association (Fannie Mae), the Federal Home Loan Mortgage Corporation (Freddie Mac), and the Federal Home Loan Bank are not guaranteed by the U.S. Treasury or supported by the full faith and credit of the U.S. government. However, these agencies or instrumentalities are authorized to borrow from the U.S. Treasury to meet their obligations. In general, securities issued by non-U.S. government entities such as corporations are backed only by the credit of the issuer.
To generate additional income, the fund may purchase securities, including mortgage dollar rolls, in advance through when-issued and forward commitment transactions. The fund may commit up to 35% of its total assets to such transactions.
The fund also may invest in derivative instruments such as options, futures contracts, options on futures contracts and swap agreements (including, but not limited to, credit default swap agreements), or in mortgage- or asset-backed securities, provided that such investments are in keeping with the fund’s investment objective.
When determining whether to sell a security, the portfolio managers consider, among other things, current and anticipated changes in interest rates, current valuation relative to alternatives in the market, general market conditions and any other factors deemed relevant by the portfolio managers.
The fund may engage in active and frequent trading of portfolio securities to achieve its principal investment strategies. This may cause higher transaction costs and may affect performance. It may also result in the realization and distribution of capital gains.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Interest Rate Risk—Generally, when interest rates rise, the fund’s share value will decline. The opposite is true when interest rates decline. This risk is higher for the fund than for other funds that have shorter weighted average maturities, such as money market funds. A period of rising interest rates may negatively affect the fund’s performance.
•
Prepayment Risk—The fund may invest in debt securities backed by mortgages or other assets. If these underlying assets are prepaid, the fund may benefit less from declining interest rates than funds that have similar weighted average maturities.
•
Derivatives Risk—The use of derivative instruments involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other traditional instruments. Derivatives are subject to a number of risks including liquidity, interest rate, market, credit and correlation risk.
•
Market Risk—The value of the securities owned by the fund may go up and down, sometimes rapidly or unpredictably. Market risks, including political, regulatory, economic and social developments, can affect the value of the fund’s investments. Natural disasters, public health emergencies, terrorism and other unforeseeable events may lead to increased market volatility and may have adverse long-term effects on world economies and markets generally.
•
Principal Loss—At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.
An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney Principal Loss—At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Fund Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, including yields, please visit americancentury.com.
Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress americancentury.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Calendar Year Total Return
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
(2Q 2010): 1.30%        Lowest Performance Quarter (2Q 2013): -0.53%

As of June 30, 2020, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 3.01%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2019
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as 401(k) plans or IRAs.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as 401(k) plans or IRAs.
American Century Government Income Trust | SHORT-TERM GOVERNMENT FUND | Bloomberg Barclays U.S. 1-3 Year Government Bond Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays U.S. 1-3 Year Government Bond Index    (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 3.59%
5 Years rr_AverageAnnualReturnYear05 1.40%
10 Years rr_AverageAnnualReturnYear10 1.25%
American Century Government Income Trust | SHORT-TERM GOVERNMENT FUND | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol TWUSX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee $ 25
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.55%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 56
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 177
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 308
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 690
Annual Return 2010 rr_AnnualReturn2010 2.27%
Annual Return 2011 rr_AnnualReturn2011 1.54%
Annual Return 2012 rr_AnnualReturn2012 0.30%
Annual Return 2013 rr_AnnualReturn2013 (0.41%)
Annual Return 2014 rr_AnnualReturn2014 0.33%
Annual Return 2015 rr_AnnualReturn2015 0.11%
Annual Return 2016 rr_AnnualReturn2016 0.41%
Annual Return 2017 rr_AnnualReturn2017 0.21%
Annual Return 2018 rr_AnnualReturn2018 1.11%
Annual Return 2019 rr_AnnualReturn2019 2.91%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2020
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 3.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 1.30%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2013
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (0.53%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.91%
5 Years rr_AverageAnnualReturnYear05 0.95%
10 Years rr_AverageAnnualReturnYear10 0.87%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 15, 1982
American Century Government Income Trust | SHORT-TERM GOVERNMENT FUND | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel    Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 2.15%
5 Years rr_AverageAnnualReturnYear05 0.46%
10 Years rr_AverageAnnualReturnYear10 0.48%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 15, 1982
American Century Government Income Trust | SHORT-TERM GOVERNMENT FUND | INVESTOR CLASS | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel    Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 1.72%
5 Years rr_AverageAnnualReturnYear05 0.51%
10 Years rr_AverageAnnualReturnYear10 0.52%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 15, 1982
American Century Government Income Trust | SHORT-TERM GOVERNMENT FUND | I CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol ASGHX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.44%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.45%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 46
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 145
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 252
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 567
Label rr_AverageAnnualReturnLabel I Class1 Return Before Taxes [9]
1 Year rr_AverageAnnualReturnYear01 3.01% [9]
5 Years rr_AverageAnnualReturnYear05 1.05% [9]
Since Inception rr_AverageAnnualReturnSinceInception 0.90% [9]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 10, 2017 [9]
American Century Government Income Trust | SHORT-TERM GOVERNMENT FUND | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol TWAVX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.25%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [10]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.80%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 305
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 475
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 660
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,193
Label rr_AverageAnnualReturnLabel A Class2 Return Before Taxes [11]
1 Year rr_AverageAnnualReturnYear01 0.32% [11]
5 Years rr_AverageAnnualReturnYear05 0.26% [11]
10 Years rr_AverageAnnualReturnYear10 0.40% [11]
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 08, 1998 [11]
American Century Government Income Trust | SHORT-TERM GOVERNMENT FUND | C CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol TWACX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.55%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 158
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 490
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 845
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,844
Label rr_AverageAnnualReturnLabel C Class3 Return Before Taxes [12]
1 Year rr_AverageAnnualReturnYear01 1.91% [12]
5 Years rr_AverageAnnualReturnYear05 (0.03%) [12]
10 Years rr_AverageAnnualReturnYear10 (0.12%) [12]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010 [12]
American Century Government Income Trust | SHORT-TERM GOVERNMENT FUND | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol TWARX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.54%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.05%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 107
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 335
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 580
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,282
Label rr_AverageAnnualReturnLabel R Class3 Return Before Taxes [12]
1 Year rr_AverageAnnualReturnYear01 2.40% [12]
5 Years rr_AverageAnnualReturnYear05 0.46% [12]
10 Years rr_AverageAnnualReturnYear10 0.38% [12]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010 [12]
American Century Government Income Trust | SHORT-TERM GOVERNMENT FUND | R5 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol TWUOX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.34%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.35%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 36
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 113
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 197
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 444
Label rr_AverageAnnualReturnLabel R5 Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 3.22%
5 Years rr_AverageAnnualReturnYear05 1.17%
Since Inception rr_AverageAnnualReturnSinceInception 1.01%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading Inflation-Adjusted Bond Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks to provide total return and inflation protection consistent with investment in inflation-indexed securities.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
The following table describes the fees and expenses you may pay if you buy, hold, and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in Calculation of Sales Charges on page 15 of the fund’s prospectus, Appendix A of the fund’s prospectus and Sales Charges in Appendix B of the statement of additional information
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 24% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 24.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in Calculation of Sales Charges on page 15 of the fund’s prospectus, Appendix A of the fund’s prospectus and Sales Charges in Appendix B of the statement of additional information
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
The example below is intended to help you compare the costs of investing in the fund with the costs of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods, and that you earn a 5% return each year. The example also assumes that the fund’s operating expenses remain the same, except that it reflects the rate and duration of any fee waivers noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal market conditions, the fund invests at least 80% of its net assets in inflation-adjusted bonds. The advisor considers inflation-adjusted bonds to include inflation-indexed bonds, notes, commercial paper, short-term instruments and other debt securities issued by the U.S. Treasury, by other U.S. government agencies and instrumentalities, and by other, non-U.S. government entities such as corporations and foreign governments. Inflation-indexed securities are designed to protect the future purchasing power of the money invested in them; their principal value may be indexed for changes in inflation. In addition, the fund may invest a portion of its assets in traditional U.S. Treasury, U.S. government agency or other non-U.S. government securities that are not inflation-indexed.
Securities issued or guaranteed by the U.S. Treasury and certain U.S. government agencies or instrumentalities, such as the Government National Mortgage Association (Ginnie Mae), are supported by the full faith and credit of the U.S. government. Securities issued or guaranteed by other U.S. government agencies or instrumentalities, such as the Federal National Mortgage Association (Fannie Mae), the Federal Home Loan Mortgage Corporation (Freddie Mac), and the Federal Home Loan Bank are not guaranteed by the U.S. Treasury or supported by the full faith and credit of the U.S. government. However, these agencies or instrumentalities are authorized to borrow from the U.S. Treasury to meet their obligations. In general, securities issued by non-U.S. government entities are backed only by the credit of the issuer.
The fund invests primarily in investment-grade securities, but may also invest a portion of its assets in high-yield securities, or junk bonds. A high-yield security is one that has been rated below the four highest categories by a nationally recognized rating organization.
There are no maturity or duration restrictions for the securities in which the fund may invest.
Although the fund invests primarily in U.S. dollar-denominated securities, the fund also may invest in securities denominated in foreign currencies.
To generate additional income, the fund may purchase securities, including mortgage dollar rolls, in advance through when-issued and forward commitment transactions. The fund may commit up to 35% of its total assets to such transactions.
The fund also may invest in derivative instruments such as futures contracts and swap agreements (including, but not limited to, inflation swap agreements and credit default swap agreements), bank loans, securities backed by mortgages or other assets and collateralized debt obligations (including collateralized loan obligations). The fund may invest in U.S. Treasury futures, inflation swap agreements and credit default swap agreements to manage duration, inflation and credit exposure.
When determining whether to sell a security, the portfolio managers consider, among other things, current and anticipated changes in interest rates, current valuation relative to alternatives in the market, general market conditions and any other factors deemed relevant by the portfolio managers.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Inflation-Indexed Bonds Risk—If the index measuring inflation falls, the principal value of inflation-indexed bonds will be adjusted downward, and consequently the interest payable on these securities will be reduced. In addition, interest payments on inflation-indexed bonds may be difficult to predict and may vary as the principal and/or interest is adjusted for inflation. In periods of deflation, the fund may have no income at all from such investments.
•
Interest Rate Risk—Investments in debt securities are sensitive to interest rate changes. Generally, the value of debt securities and the funds that hold them decline as interest rates rise. The fund’s interest rate risk is generally higher than for funds with shorter-weighted average maturities, such as money market and short-term bond funds. A period of rising interest rates may negatively affect the fund’s performance.
•
Credit Risk—The value of the fund’s debt securities will be affected adversely by the inability or perceived inability of the issuers of these securities to make interest and principal payments as they become due. As a result, the fund’s share price could also decrease. Changes in the credit rating of a debt security held by the fund could have a similar effect.
•
High-Yield Risk—Issuers of high-yield securities, or junk bonds, are more vulnerable to real or perceived economic changes (such as an economic downturn or a prolonged period of rising interest rates), political changes or adverse developments specific to an issuer. These factors may be more likely to cause an issuer of low quality bonds to default on its obligations. High-yield securities (junk bonds) are also inherently speculative.
•
Liquidity Risk—During periods of market turbulence or unusually low trading activity, in order to meet redemptions it may be necessary for the fund to sell securities at prices that could have an adverse effect on the fund’s share price. The market for lower-quality debt securities is generally less liquid than the market for higher-quality securities. Changing regulatory and market conditions, including increases in interest rates and credit spreads may adversely affect the liquidity of the fund’s investments.
•
Foreign Securities Risk—Foreign securities have certain unique risks, such as currency risk, social, political and economic risk, and foreign market and trading risk. Securities of foreign issuers may be less liquid, more volatile and harder to value than U.S. securities.
•
Bank Loan Risk — The market for bank loans may not be highly liquid and the fund may have difficulty selling them. In connection with purchasing loan participations, the fund generally will have no right to enforce compliance by borrowers with loan terms nor any set off rights, and the fund may not benefit directly from any posted collateral. As a result, the fund may be subject to the credit risk of both the borrower and the lender selling the participation. Bank loan transactions may take more than seven days to settle, meaning that proceeds would be unavailable to make additional investments or meet redemptions.
•
Collateralized Debt Obligations Risk — Collateralized debt obligations and collateralized loan obligations (CLOs) are subject to credit, interest rate, valuation, and prepayment and extension risks. These securities also are subject to risk of default on the underlying asset, particularly during periods of economic downturn. The market value of CLOs may be affected by, among other things, changes in the market value of the underlying assets held by the CLO, changes in the distributions on the underlying assets, defaults and recoveries on the underlying assets, capital gains and losses on the underlying assets, prepayments on underlying assets and the availability, prices and interest rate of underlying assets.
•
Derivatives Risk—The use of derivative instruments involves risks different from the risks associated with investing directly in securities and other traditional instruments. The fund’s use of derivatives, and in particular its use of inflation swap agreements and credit default swap agreements, are subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation. Derivatives are also subject to a number of additional risks including liquidity, interest rate, market, credit and correlation risk. In addition, gains or losses involving some futures and other derivatives may be substantial - in part because a relatively small price movement in these securities may result in an immediate and substantial gain or loss for the fund.
•
Market Risk—The value of the securities owned by the fund may go up and down, sometimes rapidly or unpredictably. Market risks, including political, regulatory, economic and social developments, can affect the value of the fund’s investments. Natural disasters, public health emergencies, terrorism and other unforeseeable events may lead to increased market volatility and may have adverse long-term effects on world economies and markets generally.
•
Redemption Risk—The fund may need to sell securities at times it would not otherwise do so in order to meet shareholder redemption requests. Selling securities to meet such redemptions may cause the fund to experience a loss, increase the fund’s transaction costs or have tax consequences. To the extent that a large shareholder (including a fund of funds or 529 college savings plan) invests in the fund, the fund may experience relatively large redemptions as such shareholder reallocates its assets.
•
When-Issued and Forward Commitment Risk—When-issued and forward commitments involve the risk that the security the fund buys will lose value prior to its delivery. There also is the risk that the security will not be issued or that the other party to the transaction will not meet its obligation. If this occurs, the fund may lose both the investment opportunity for the assets it set aside to pay for the security and any gain in the security’s price.
•
Mortgage- and Asset-Backed Securities Risks—Mortgage- and asset backed securities are subject to credit, interest rate, prepayment and extension risks. These securities also are subject to risk of default on the underlying mortgage or asset, particularly during periods of economic downturn.
•
Mortgage Dollar Rolls Risk—If the counterparty to whom the fund sells the security becomes insolvent, the fund’s right to repurchase the security may be restricted. Other risks involved in entering into mortgage dollar rolls include the risk that the value of the security may change adversely over the term of the mortgage dollar roll and that the security the fund is required to repurchase may be worth less than the security that the fund originally held.
•
Principal Loss—At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.
An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney Principal Loss—At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Fund Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, including yields, please visit americancentury.com.
Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress americancentury.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Calendar Year Total Returns
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
(3Q 2011): 4.66%        Lowest Performance Quarter (2Q 2013): -7.52%

As of June 30, 2020, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 5.09%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2019
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as 401(k) plans or IRAs.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
The after-tax returns are shown only for Investor Class shares. After-tax returns for other share classes will vary. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as 401(k) plans or IRAs.
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | Bloomberg Barclays U.S. Treasury Inflation Protected Securities (TIPS) Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays U.S. Treasury Inflation Protected Securities (TIPS) Index    (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 8.43%
5 Years rr_AverageAnnualReturnYear05 2.61%
10 Years rr_AverageAnnualReturnYear10 3.36%
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol ACITX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee $ 25
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.46%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.47%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.47%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 48
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 151
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 264
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 592
Annual Return 2010 rr_AnnualReturn2010 5.49%
Annual Return 2011 rr_AnnualReturn2011 13.00%
Annual Return 2012 rr_AnnualReturn2012 6.68%
Annual Return 2013 rr_AnnualReturn2013 (9.13%)
Annual Return 2014 rr_AnnualReturn2014 2.67%
Annual Return 2015 rr_AnnualReturn2015 (2.15%)
Annual Return 2016 rr_AnnualReturn2016 4.72%
Annual Return 2017 rr_AnnualReturn2017 3.08%
Annual Return 2018 rr_AnnualReturn2018 (2.51%)
Annual Return 2019 rr_AnnualReturn2019 7.85%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2020
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 5.09%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2011
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.66%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2013
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (7.52%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.85%
5 Years rr_AverageAnnualReturnYear05 2.12%
10 Years rr_AverageAnnualReturnYear10 2.80%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 10, 1997
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel    Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 6.79%
5 Years rr_AverageAnnualReturnYear05 1.22%
10 Years rr_AverageAnnualReturnYear10 1.81%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 10, 1997
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | INVESTOR CLASS | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel    Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 4.64%
5 Years rr_AverageAnnualReturnYear05 1.22%
10 Years rr_AverageAnnualReturnYear10 1.80%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 10, 1997
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | I CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol AIAHX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.36%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.37%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.37%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 38
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 119
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 208
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 469
Label rr_AverageAnnualReturnLabel I Class1 Return Before Taxes [13]
1 Year rr_AverageAnnualReturnYear01 7.87% [13]
5 Years rr_AverageAnnualReturnYear05 2.19% [13]
10 Years rr_AverageAnnualReturnYear10 2.89% [13]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 10, 2017 [13]
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | Y CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol AIAYX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.26%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.27%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.27%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 28
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 87
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 152
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 344
Label rr_AverageAnnualReturnLabel Y Class1 Return Before Taxes [13]
1 Year rr_AverageAnnualReturnYear01 7.98% [13]
5 Years rr_AverageAnnualReturnYear05 2.30% [13]
10 Years rr_AverageAnnualReturnYear10 2.99% [13]
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 10, 2017 [13]
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol AIAVX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [14]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.46%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.72%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.72%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 520
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 670
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 833
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,305
Label rr_AverageAnnualReturnLabel A Class2 Return Before Taxes [15]
1 Year rr_AverageAnnualReturnYear01 2.65% [15]
5 Years rr_AverageAnnualReturnYear05 0.93% [15]
10 Years rr_AverageAnnualReturnYear10 2.07% [15]
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 15, 1998 [15]
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | C CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol AINOX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.46%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.47%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.47%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 150
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 466
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 803
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,756
Label rr_AverageAnnualReturnLabel C Class3 Return Before Taxes [16]
1 Year rr_AverageAnnualReturnYear01 6.77% [16]
5 Years rr_AverageAnnualReturnYear05 1.10% [16]
10 Years rr_AverageAnnualReturnYear10 1.77% [16]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010 [16]
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol AIARX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.46%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.97%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.97%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 99
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 310
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 537
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,190
Label rr_AverageAnnualReturnLabel R Class3 Return Before Taxes [16]
1 Year rr_AverageAnnualReturnYear01 7.29% [16]
5 Years rr_AverageAnnualReturnYear05 1.61% [16]
10 Years rr_AverageAnnualReturnYear10 2.28% [16]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010 [16]
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | R5 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol AIANX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.26%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.27%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.27%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 28
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 87
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 152
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 344
Label rr_AverageAnnualReturnLabel R5 Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 8.07%
5 Years rr_AverageAnnualReturnYear05 2.33%
10 Years rr_AverageAnnualReturnYear10 3.00%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 01, 2002
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | R6 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol AIADX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.21%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.22%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.22%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 23
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 71
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 124
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 281
Label rr_AverageAnnualReturnLabel R6 Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 8.14%
Since Inception rr_AverageAnnualReturnSinceInception 3.01%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 28, 2017
American Century Government Income Trust | INFLATION-ADJUSTED BOND FUND | G CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol AINGX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.21%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.22%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.21%) [17]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.01%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 1
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 3
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 6
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 13
Label rr_AverageAnnualReturnLabel G Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 8.35%
Since Inception rr_AverageAnnualReturnSinceInception 3.25%
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 28, 2017
[1] Historical performance for the I Class prior to its inception (April 10, 2017) is based on the performance of R5 Class shares. I Class performance has been adjusted to reflect differences in expenses between classes, if applicable.
[2] Purchases of $1 million or more may be subject to a contingent deferred sales charge of 1.00% if the shares are redeemed within one year of the date of purchase.
[3] Prior to March 1, 2010, the A Class was referred to as the Advisor Class and did not have a front-end sales charge. Performance prior to that date has been restated to reflect this charge.
[4] Historical performance for the C Class prior to its inception (March 1, 2010) is based on the performance of Investor Class shares. C Class performance has been adjusted to reflect differences in sales charges, if applicable, and expenses between classes.
[5] Historical performance for the I Class prior to its inception is based on the performance of R5 Class shares. I Class performance has been adjusted to reflect differences in expenses between classes, if applicable. Since inception performance for the I Class is based on the R5 Class inception date.
[6] Purchases of $1 million or more may be subject to a contingent deferred sales charge of 1.00% if the shares are redeemed within one year of the date of purchase.
[7] Prior to March 1, 2010, the A Class was referred to as the Advisor Class and did not have a front-end sales charge. Performance prior to that date has been restated to reflect this charge.
[8] Historical performance for the C and R Classes prior to their inception is based on the performance of Investor Class shares. C and R Class performance has been adjusted to reflect differences in sales charges, if applicable, and expenses between classes.
[9] Historical performance for the I Class prior to its inception is based on the performance of R5 Class shares. I Class performance has been adjusted to reflect differences in expenses between classes, if applicable. Since inception performance for the I Class is based on the R5 Class inception date.
[10] Purchases of $500,000 or more may be subject to a contingent deferred sales charge of 1.00% if the shares are redeemed within one year of the date of purchase.
[11] Prior to March 1, 2010, the A Class was referred to as the Advisor Class and did not have a front-end sales charge. Performance prior to that date has been restated to reflect this charge.
[12] Historical performance for the C and R Classes prior to their inception is based on the performance of Investor Class shares. C and R Class performance has been adjusted to reflect differences in sales charges, if applicable, and expenses between classes.
[13] Historical performance for the I and Y Classes prior to their inception is based on the performance of R5 Class shares. I and Y Class performance has been adjusted to reflect differences in expenses between classes, if applicable.
[14] Purchases of $1 million or more may be subject to a contingent deferred sales charge of 1.00% if the shares are redeemed within one year of the date of purchase.
[15] Prior to March 1, 2010, the A Class was referred to as the Advisor Class and did not have a front-end sales charge. Performance prior to that date has been restated to reflect this charge.
[16] Historical performance for the C and R Classes prior to their inception is based on the performance of Investor Class shares. C and R Class performance has been adjusted to reflect differences in sales charges, if applicable, and expenses between classes.
[17] The advisor has agreed to waive the G Class’s management fee in its entirety. The advisor expects this waiver to remain in effect permanently and cannot terminate it without the approval of the Board of Trustees.