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American Century Target Maturities Trust | ZERO COUPON 2025 FUND  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Zero Coupon 2025 Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks the highest return consistent with investment in U.S. Treasury 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 example 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)
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 13% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 13.00%
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, the fund will invest at least 80% of the value of its net assets in zero-coupon securities. Typically, other than during the fund’s target maturity year, the fund intends to exceed this 80% requirement and be fully invested in zero-coupon securities.
The fund invests primarily in zero-coupon U.S. Treasury securities and their equivalents (including certain zero-coupon U.S. government agency securities), and may invest up to 20% of its assets in other zero-coupon U.S. government agency securities that are AAA-rated. Zero-coupon securities make no periodic interest or principal payments. Instead, they trade at a deep discount to their face value and all of the interest and principal is paid when the securities mature.
The fund is managed to mature in the year 2025 and will be liquidated near the end of its target maturity year. If shares of the fund are held until the fund is liquidated and all distributions are reinvested, the fund’s performance should be similar to an investment in a zero-coupon U.S. Treasury security with the same term to maturity as the fund. The advisor expects that shareholders who hold their shares until the fund is liquidated and reinvest all distributions will realize an investment return and maturity value that do not differ significantly from the anticipated growth rate (AGR) and anticipated value at maturity (AVM) calculated on the day the shares were purchased.
 
The fund’s anticipated growth rate is an estimate of the annualized rate of growth of the fund that an investor may expect from the purchase date to the fund’s weighted average maturity date.
 
 
 
The anticipated value at maturity is an estimate of the fund’s net asset value as of the fund’s weighted average maturity date. It is based on the maturity values of the zero-coupon securities held by the fund.
 
As of the fund’s most recent fiscal year end, September 30, 2021, the fund’s Investor Class AGR was 0.46% and its AVM was $116.11. The AGR and AVM for the Advisor Class will differ from that of the Investor Class, depending on the expenses of that class.
When determining whether to buy or sell a security, the portfolio managers consider, among other things, the fund’s average maturity, 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.
Securities issued or guaranteed by the U.S. Treasury and certain U.S. government agencies or instrumentalities are supported by the full faith and credit of the U.S. government. Zero-coupon U.S. government agency securities that are ultimately backed by securities or payment obligations of the U.S. Treasury and are considered by the market to be of comparable credit quality, such as Resolution Funding Corporation (REFCORP) bonds, are considered to be zero-coupon U.S. Treasury equivalents by the fund’s managers. 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.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•Interest Rate Risk – Investments in debt securities are sensitive to interest rate changes and zero coupon securities are more sensitive to interest rate changes than traditional coupon-bearing securities. Generally, when interest rates rise, the fund’s share value will decline. The opposite is true when interest rates decline. Funds with longer weighted average maturities are more sensitive to interest rate changes. A period of rising interest rates may negatively affect the fund’s performance. Additionally, in extreme low interest rate environments, the fund’s expenses may exceed the yields on the securities in which the fund invests, resulting in a negative anticipated growth rate (AGR). You may lose money as a result of holding fund shares with a negative AGR.
•Unanticipated Capital Gains or Losses – When shareholders redeem their shares before the target maturity date, the fund may need to liquidate holdings to meet these redemptions and unanticipated capital gains or losses may result. The fund will distribute these capital gains or losses to all shareholders.
•Zero-Coupon U.S. Treasury Correlation – Although the fund’s investment policies are designed to provide an investment that is similar to investing in a zero-coupon U.S. Treasury security that matures in the year 2025, a precise forecast of the fund’s final maturity value and yield to maturity is not possible.
•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 economics and markets generally.
•Public Health Emergency Risk - A pandemic, caused by the infectious respiratory illness COVID-19, is causing market disruption and other economic impacts. Markets have experienced volatility, reduced liquidity, and increased trading costs. These events may continue to impact the fund and its underlying investments.
•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 table also shows results for a U.S. Treasury zero-coupon security (STRIPS Issue) with a maturity date similar to the fund. 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 Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The table also shows results for a U.S. Treasury zero-coupon security (STRIPS Issue) with a maturity date similar to the fund.
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 Highest Performance Quarter (2Q 2012): 10.59%           Lowest Performance Quarter (4Q 2016): -6.90%
Performance Table Heading rr_PerformanceTableHeading Average Annual Total ReturnsFor the calendar year ended December 31, 2021
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 Target Maturities Trust | ZERO COUPON 2025 FUND | 11/15/2025 STRIPS Issue  
Prospectus [Line Items] rr_ProspectusLineItems  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses or taxes)
Label rr_AverageAnnualReturnLabel 11/15/2025 STRIPS Issue   (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 (2.15%)
5 Years rr_AverageAnnualReturnYear05 3.78%
10 Years rr_AverageAnnualReturnYear10 3.27%
American Century Target Maturities Trust | ZERO COUPON 2025 FUND | Bloomberg U.S. 1-5 Year Treasury  
Prospectus [Line Items] rr_ProspectusLineItems  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg U.S. 1-5 Year Treasury   (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 (1.19%)
5 Years rr_AverageAnnualReturnYear05 1.90%
10 Years rr_AverageAnnualReturnYear10 1.33%
American Century Target Maturities Trust | ZERO COUPON 2025 FUND | INVESTOR CLASS  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol BTTRX
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 none
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.54%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 55
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 173
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 302
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 678
Annual Return 2012 rr_AnnualReturn2012 5.71%
Annual Return 2013 rr_AnnualReturn2013 (10.82%)
Annual Return 2014 rr_AnnualReturn2014 16.50%
Annual Return 2015 rr_AnnualReturn2015 0.88%
Annual Return 2016 rr_AnnualReturn2016 1.32%
Annual Return 2017 rr_AnnualReturn2017 4.62%
Annual Return 2018 rr_AnnualReturn2018 0.14%
Annual Return 2019 rr_AnnualReturn2019 7.10%
Annual Return 2020 rr_AnnualReturn2020 8.85%
Annual Return 2021 rr_AnnualReturn2021 (2.65%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2012
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 10.59%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (6.90%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (2.65%)
5 Years rr_AverageAnnualReturnYear05 3.52%
10 Years rr_AverageAnnualReturnYear10 2.93%
American Century Target Maturities Trust | ZERO COUPON 2025 FUND | INVESTOR CLASS | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (3.89%)
5 Years rr_AverageAnnualReturnYear05 1.93%
10 Years rr_AverageAnnualReturnYear10 1.22%
American Century Target Maturities Trust | ZERO COUPON 2025 FUND | INVESTOR CLASS | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 (1.51%)
5 Years rr_AverageAnnualReturnYear05 2.10%
10 Years rr_AverageAnnualReturnYear10 1.63%
American Century Target Maturities Trust | ZERO COUPON 2025 FUND | ADVISOR CLASS  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol ACTVX
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 none
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.79%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 81
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 253
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 439
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 978
Label rr_AverageAnnualReturnLabel Advisor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (2.89%)
5 Years rr_AverageAnnualReturnYear05 3.26%
10 Years rr_AverageAnnualReturnYear10 2.67%