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Label Element Value
Prospectus: rr_ProspectusTable  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Jul. 31, 2017
Entity Registrant Name dei_EntityRegistrantName AMERICAN CENTURY ASSET ALLOCATION PORTFOLIOS, INC.
Central Index Key dei_EntityCentralIndexKey 0001293210
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Jul. 28, 2017
Document Effective Date dei_DocumentEffectiveDate Jul. 31, 2017
Prospectus Date rr_ProspectusDate Jul. 31, 2017
American Century Asset Allocation Portfolio | ONE CHOICE IN RETIREMENT PORTFOLIO  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading One Choice® In Retirement Portfolio
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks current income.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock
Capital appreciation is a secondary objective. 
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 and hold shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 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 64 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 Expenses3 (expenses that you pay each year as a percentage of the value of your investment) [1]
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination July 30, 2018
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Because the fund buys and sells shares of other American Century mutual funds (the underlying funds) directly from the issuers, the fund is not expected to incur transaction costs directly. However, as a shareholder in the underlying funds, the fund indirectly pays transaction costs, such as commissions, when the underlying funds buy and sell securities (or “turn over” their portfolios). 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 14% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 14.00%
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 $50,000 in American Century Investments funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
Acquired Fund Fees and Expenses, Based on Estimates [Text] rr_AcquiredFundFeesAndExpensesBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
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. You may be required to pay brokerage commissions on your purchases of Investor or I Class shares of the fund, which are not reflected in the example.  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
One Choice In Retirement Portfolio is a “fund of funds,” meaning that it seeks to achieve its objective by investing in other American Century mutual funds (the underlying funds) that represent a variety of asset classes and investment styles. The underlying stock funds draw on growth, value and quantitative investment techniques and diversify investments among small, medium and large U.S. and foreign companies. The underlying bond funds invest in fixed-income securities that vary by issuer type (corporate and government), credit quality (investment-grade and high-yield or “junk bonds”) and geographic exposure (domestic and international). The following table indicates the fund’s neutral mix; that is, how the fund’s investments generally will be allocated among the major asset classes. The table also shows the neutral weightings of each underlying fund currently being used within the various asset classes. This information is as of December 1, 2016, except the allocation to NT High Income Fund was changed from an equivalent allocation to High-Yield Fund on May 19, 2017.
.
Equity Securities (Stock Funds)
45.00
%
NT Core Equity Plus Fund
3.00
%
NT Disciplined Growth Fund
1.50
%
NT Equity Growth Fund
10.00
%
NT Global Real Estate Fund
1.00
%
NT Growth Fund
4.50
%
NT Heritage Fund
2.25
%
NT International Growth Fund
4.50
%
NT International Value Fund
2.25
%
NT Large Company Value Fund
9.50
%
NT Mid Cap Value Fund
4.50
%
NT Small Company Fund
2.00
%
 
Fixed-Income Securities (Bond Funds)
45.00
%
 
Global Bond Fund
7.00
%
 
NT High Income Fund
3.80
%
 
Inflation-Adjusted Bond Fund
1.50
%
 
International Bond Fund
5.00
%
 
NT Diversified Bond Fund
21.60
%
 
Short Duration Inflation Protection Bond Fund
6.10
%
 
 
 
 
Cash Equivalents (Money Market Fund)
10.00
%
 
U.S. Government Money Market Fund
10.00
%
 
 
 
 
 
 
The neutral mix of One Choice In Retirement Portfolio is expected to remain fixed over time. The fund is generally intended for investors near to, at, or in retirement and who likely are no longer making new investments in the fund. The fund is designed for investors who plan to gradually withdraw the value of their account after retirement. The fund assumes a retirement age of 65 and may not be appropriate for an investor retiring at an age well before or after age 65.
The portfolio managers regularly review the fund’s allocations to determine whether rebalancing is appropriate. In order to better balance risks in changing market environments, the portfolio managers may make modest deviations from the neutral mix in light of prevailing market conditions. We reserve the right to modify the neutral mix and underlying funds from time to time should circumstances warrant a change.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Allocation Risk – The fund’s performance and risks depend in part on the managers’ skill in determining the fund’s neutral mix, selecting and weighting the underlying funds, and implementing any deviations from the neutral mix. The managers’ evaluations and assumptions regarding asset classes or underlying funds may differ from actual market conditions.
•
Fund of Funds Risks – The fund’s performance and risks reflect the performance and risks of the underlying American Century Investments funds in which it invests. The fund’s investment in other American Century Investments funds may create a conflict of interest for the fund’s advisor.
•
“Growth” and “Value” Style Risks – The underlying funds represent a mix of investment styles, each of which has risks associated with it. Growth stocks can be volatile and may lack dividends that can cushion share prices during market declines. Value stocks may continue to be undervalued by the market for long periods of time.
•
Small- and Mid-Cap Stock Risks – Stocks of smaller companies may be more volatile than larger-company stocks. Smaller companies may have limited financial resources, product lines and markets, and their securities may trade less frequently and in more limited volumes than the securities of larger companies, which could lead to higher transaction costs. To the extent an underlying fund invests in these companies, it may take on more risk.
•
Interest Rate Risk – Generally, when interest rates rise, the value of an underlying fund’s fixed-income securities will decline. The opposite is true when interest rates decline. Underlying funds with longer weighted average maturities are more sensitive to interest rate changes. A period of rising interest rates may negatively affect the performance of underlying fixed-income funds.
•
Credit Risk – The value of an underlying fund’s fixed-income securities will be affected adversely by any erosion in the ability of the issuers of these securities to make interest and principal payments as they become due. Changes in the credit rating of a fixed-income security held by an underlying fund could have a similar effect.
•
Foreign Securities Risk – Some of the underlying funds invest in foreign securities, which are generally riskier than U.S. securities. Securities of foreign issuers may be less liquid, more volatile and harder to value than U.S. securities. Fluctuations in currency exchange rates also may affect an underlying fund’s share price.
•
High-Yield Securities Risk – Some of the underlying funds may invest in high-yield securities, which are considered to have speculative characteristics and are more likely to be negatively affected by changes in economic conditions.
•
Tobacco Exclusion – The underlying funds do not invest in securities issued by companies assigned the Global Industry Classification Standard (GICS) or the Bloomberg Industry Classification Standard (BICS) for the tobacco industry. This exclusion may cause an underlying fund to forego profitable investment opportunities.
•
Market Risk – The value of the fund’s shares will go up and down based on the performance of the underlying funds in which it invests. The value of the underlying funds’ shares will, in turn, fluctuate based on the performance of the securities they own and other factors generally affecting the securities market.
•
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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
Highest Performance Quarter (3Q 2009): 9.30% Lowest Performance Quarter (4Q 2008): -9.20%
As of June 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 5.15%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2016
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses or taxes)
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 Asset Allocation Portfolio | ONE CHOICE IN RETIREMENT PORTFOLIO | S&P Target Date Retirement Income Index  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel S&P Target Date Retirement Income Index (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 5.01%
5 Years rr_AverageAnnualReturnYear05 4.66%
10 Years rr_AverageAnnualReturnYear10 3.88%
American Century Asset Allocation Portfolio | ONE CHOICE IN RETIREMENT PORTFOLIO | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARTOX
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 0.76%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [2]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.79%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.02%) [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.77%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 79
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 251
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 437
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 976
Annual Return 2007 rr_AnnualReturn2007 7.18%
Annual Return 2008 rr_AnnualReturn2008 (16.57%)
Annual Return 2009 rr_AnnualReturn2009 16.42%
Annual Return 2010 rr_AnnualReturn2010 10.07%
Annual Return 2011 rr_AnnualReturn2011 3.58%
Annual Return 2012 rr_AnnualReturn2012 10.13%
Annual Return 2013 rr_AnnualReturn2013 11.11%
Annual Return 2014 rr_AnnualReturn2014 6.20%
Annual Return 2015 rr_AnnualReturn2015 (1.69%)
Annual Return 2016 rr_AnnualReturn2016 5.91%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 5.15%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 9.30%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (9.20%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.91%
5 Years rr_AverageAnnualReturnYear05 6.23%
10 Years rr_AverageAnnualReturnYear10 4.85%
American Century Asset Allocation Portfolio | ONE CHOICE IN RETIREMENT PORTFOLIO | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 5.04%
5 Years rr_AverageAnnualReturnYear05 5.16%
10 Years rr_AverageAnnualReturnYear10 3.85%
American Century Asset Allocation Portfolio | ONE CHOICE IN RETIREMENT PORTFOLIO | 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 3.82%
5 Years rr_AverageAnnualReturnYear05 4.64%
10 Years rr_AverageAnnualReturnYear10 3.54%
American Century Asset Allocation Portfolio | ONE CHOICE IN RETIREMENT PORTFOLIO | INSTITUTIONAL CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ATTIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [4]
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [4]
Maximum Account Fee rr_MaximumAccountFee none [4]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.58%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [2]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.61%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.57%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 58
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 192
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 337
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 759
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.12%
5 Years rr_AverageAnnualReturnYear05 6.46%
10 Years rr_AverageAnnualReturnYear10 5.06%
American Century Asset Allocation Portfolio | ONE CHOICE IN RETIREMENT PORTFOLIO | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARTAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [5]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.76%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [2]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.04%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.02%) [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.02%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 673
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 886
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,115
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,771
Label rr_AverageAnnualReturnLabel A Class1 Return Before Taxes [6]
1 Year rr_AverageAnnualReturnYear01 (0.44%) [6]
5 Years rr_AverageAnnualReturnYear05 4.73% [6]
10 Years rr_AverageAnnualReturnYear10 3.97% [6]
American Century Asset Allocation Portfolio | ONE CHOICE IN RETIREMENT PORTFOLIO | C Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ATTCX
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 0.76%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [2]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.79%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.02%) [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.77%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 180
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 562
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 969
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,101
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 4.86%
5 Years rr_AverageAnnualReturnYear05 5.19%
10 Years rr_AverageAnnualReturnYear10 3.81% [7]
American Century Asset Allocation Portfolio | ONE CHOICE IN RETIREMENT PORTFOLIO | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARSRX
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 0.76%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [2]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.29%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.02%) [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.27%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 130
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 408
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 706
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,554
Label rr_AverageAnnualReturnLabel R Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.39%
5 Years rr_AverageAnnualReturnYear05 5.72%
10 Years rr_AverageAnnualReturnYear10 4.33%
American Century Asset Allocation Portfolio | ONE CHOICE IN RETIREMENT PORTFOLIO | R6 Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARDTX
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 0.52%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [2]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.55%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.13%) [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.42%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 43
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 163
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 295
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 677
American Century Asset Allocation Portfolio | ONE CHOICE 2020 PORTFOLIO  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading One Choice® 2020 Portfolio
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks the highest total return consistent with its asset mix.
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 and hold shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 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 64 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 Expenses3 (expenses that you pay each year as a percentage of the value of your investment) [8]
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination July 30, 2018
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Because the fund buys and sells shares of other American Century mutual funds (the underlying funds) directly from the issuers, the fund is not expected to incur transaction costs directly. However, as a shareholder in the underlying funds, the fund indirectly pays transaction costs, such as commissions, when the underlying funds buy and sell securities (or “turn over” their portfolios). 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 12% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 12.00%
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 $50,000 in American Century Investments funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
Acquired Fund Fees and Expenses, Based on Estimates [Text] rr_AcquiredFundFeesAndExpensesBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
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. You may be required to pay brokerage commissions on your purchases of Investor or I Class shares of the fund, which are not reflected in the example.  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
One Choice 2020 Portfolio is a “fund of funds,” meaning that it seeks to achieve its objective by investing in other American Century mutual funds (the underlying funds) that represent a variety of asset classes and investment styles. The underlying stock funds draw on growth, value and quantitative investment techniques and diversify investments among small, medium and large U.S. and foreign companies. The underlying bond funds invest in fixed-income securities that vary by issuer type (corporate and government), credit quality (investment-grade and high-yield or “junk bonds”) and geographic exposure (domestic and international). The following table indicates the fund’s neutral mix; that is, how the fund’s investments generally will be allocated among the major asset classes. The table also shows the neutral weightings of each underlying fund currently being used within the various asset classes. This information is as of December 1, 2016, except the allocation to NT High Income Fund was changed from an equivalent allocation to High-Yield Fund on May 19, 2017.
Equity Securities (Stock Funds)
47.90
%
NT Core Equity Plus Fund
3.00
%
NT Disciplined Growth Fund
1.73
%
NT Emerging Markets Fund
0.75
%
NT Equity Growth Fund
9.75
%
NT Global Real Estate Fund
1.15
%
NT Growth Fund
5.01
%
NT Heritage Fund
2.71
%
NT International Growth Fund
4.63
%
NT International Small-Mid Cap Fund
0.19
%
NT International Value Fund
2.63
%
NT Large Company Value Fund
9.50
%
NT Mid Cap Value Fund
5.00
%
NT Small Company Fund
1.85
%
 
Fixed-Income Securities (Bond Funds)
43.60
%
 
Global Bond Fund
6.63
%
 
NT High Income Fund
3.75
%
 
Inflation-Adjusted Bond Fund
2.35
%
 
International Bond Fund
4.75
%
 
NT Diversified Bond Fund
20.97
%
 
Short Duration Inflation Protection Bond Fund
5.15
%
 
 
 
 
Cash Equivalents (Money Market Fund)
8.50
%
 
U.S. Government Money Market Fund
8.50
%
 
 
 
 
 
 
 
 
 
 
 
 
The target date in the fund name (2020) refers to the approximate year an investor plans to retire and likely would stop making new investments in the fund. The fund assumes a retirement age of 65 and may not be appropriate for an investor who plans to retire at or near the target date, but at an age well before or after 65. As the target date approaches, the fund’s neutral mix will become more conservative by decreasing the allocation to stocks and increasing the allocation to bonds and cash. By the time the fund reaches its target date, the neutral mix will become fixed and match that of One Choice In Retirement Portfolio, which is currently 45% stock funds, 45% bond funds and 10% money market funds. The fund is designed for investors who plan to withdraw the value of their account gradually after retirement. The following chart shows how the neutral mix is expected to change over time according to a predetermined glide path.
glidepathimagea31.gif
The portfolio managers regularly review the fund’s allocations to determine whether rebalancing is appropriate. In order to better balance risks in changing market environments, the portfolio managers may make modest deviations from the neutral mix in light of prevailing market conditions. We reserve the right to modify the neutral mix and underlying funds from time to time should circumstances warrant a change.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Allocation Risk – The fund’s performance and risks depend in part on the managers’ skill in determining the fund’s neutral mix, selecting and weighting the underlying funds, and implementing any deviations from the neutral mix. The managers’ evaluations and assumptions regarding asset classes or underlying funds may differ from actual market conditions.
•
Fund of Funds Risks – The fund’s performance and risks reflect the performance and risks of the underlying American Century Investments funds in which it invests. The fund’s investment in other American Century Investments funds may create a conflict of interest for the fund’s advisor.
•
“Growth” and “Value” Style Risks – The underlying funds represent a mix of investment styles, each of which has risks associated with it. Growth stocks can be volatile and may lack dividends that can cushion share prices during market declines. Value stocks may continue to be undervalued by the market for long periods of time.
•
Small- and Mid-Cap Stock Risks – Stocks of smaller companies may be more volatile than larger-company stocks. Smaller companies may have limited financial resources, product lines and markets, and their securities may trade less frequently and in more limited volumes than the securities of larger companies, which could lead to higher transaction costs. To the extent an underlying fund invests in these companies, it may take on more risk.
•
Interest Rate Risk – Generally, when interest rates rise, the value of an underlying fund’s fixed-income securities will decline. The opposite is true when interest rates decline. Underlying funds with longer weighted average maturities are more sensitive to interest rate changes. A period of rising interest rates may negatively affect the performance of underlying fixed-income funds.
•
Credit Risk – The value of an underlying fund’s fixed-income securities will be affected adversely by any erosion in the ability of the issuers of these securities to make interest and principal payments as they become due. Changes in the credit rating of a fixed-income security held by an underlying fund could have a similar effect.
•
Foreign Securities Risk – Some of the underlying funds invest in foreign securities, which are generally riskier than U.S. securities. Securities of foreign issuers may be less liquid, more volatile and harder to value than U.S. securities. Fluctuations in currency exchange rates also may affect an underlying fund’s share price.
•
High-Yield Securities Risk – Some of the underlying funds may invest in high-yield securities, which are considered to have speculative characteristics and are more likely to be negatively affected by changes in economic conditions.
•
Tobacco Exclusion – The underlying funds do not invest in securities issued by companies assigned the Global Industry Classification Standard (GICS) or the Bloomberg Industry Classification Standard (BICS) for the tobacco industry. This exclusion may cause an underlying fund to forego profitable investment opportunities.
•
Market Risk – The value of the fund’s shares will go up and down based on the performance of the underlying funds in which it invests. The value of the underlying funds’ shares will, in turn, fluctuate based on the performance of the securities they own and other factors generally affecting the securities market.
•
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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
Highest Performance Quarter (3Q 2009): 11.07% Lowest Performance Quarter (4Q 2008): -11.97%
As of June 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 5.42%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2016
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 Asset Allocation Portfolio | ONE CHOICE 2020 PORTFOLIO | S&P Target Date To 2020 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 S&P Target Date To 2020 Index (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 6.52%
5 Years rr_AverageAnnualReturnYear05 6.48%
Since Inception rr_AverageAnnualReturnSinceInception 4.35%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2020 PORTFOLIO | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARBVX
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 0.77%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [9]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [9]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.80%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [10]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.77%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 79
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 253
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 442
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 987
Annual Return 2009 rr_AnnualReturn2009 20.11%
Annual Return 2010 rr_AnnualReturn2010 11.70%
Annual Return 2011 rr_AnnualReturn2011 2.50%
Annual Return 2012 rr_AnnualReturn2012 11.47%
Annual Return 2013 rr_AnnualReturn2013 12.58%
Annual Return 2014 rr_AnnualReturn2014 6.61%
Annual Return 2015 rr_AnnualReturn2015 (1.61%)
Annual Return 2016 rr_AnnualReturn2016 6.07%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 5.42%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 11.07%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (11.97%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.07%
5 Years rr_AverageAnnualReturnYear05 6.90%
Since Inception rr_AverageAnnualReturnSinceInception 4.82%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2020 PORTFOLIO | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 5.13%
5 Years rr_AverageAnnualReturnYear05 5.85%
Since Inception rr_AverageAnnualReturnSinceInception 3.96%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2020 PORTFOLIO | 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 3.98%
5 Years rr_AverageAnnualReturnYear05 5.19%
Since Inception rr_AverageAnnualReturnSinceInception 3.59%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2020 PORTFOLIO | INSTITUTIONAL CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARBSX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [11]
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [11]
Maximum Account Fee rr_MaximumAccountFee none [11]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.59%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [9]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [9]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.62%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [10]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.57%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 58
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 194
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 341
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 770
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.19%
5 Years rr_AverageAnnualReturnYear05 7.09%
Since Inception rr_AverageAnnualReturnSinceInception 5.02%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2020 PORTFOLIO | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARBMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [12]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.77%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [9]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [9]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.05%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [10]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.02%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 673
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 888
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,119
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,781
Label rr_AverageAnnualReturnLabel A Class1 Return Before Taxes [13]
1 Year rr_AverageAnnualReturnYear01 (0.35%) [13]
5 Years rr_AverageAnnualReturnYear05 5.35% [13]
Since Inception rr_AverageAnnualReturnSinceInception 3.84% [13]
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008 [13]
American Century Asset Allocation Portfolio | ONE CHOICE 2020 PORTFOLIO | C Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARNCX
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 0.77%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [9]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [9]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.80%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [10]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.77%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 180
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 564
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 973
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,111
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 4.90%
5 Years rr_AverageAnnualReturnYear05 5.81%
Since Inception rr_AverageAnnualReturnSinceInception 3.78% [14]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010
American Century Asset Allocation Portfolio | ONE CHOICE 2020 PORTFOLIO | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARBRX
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 0.77%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [9]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [9]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.30%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [10]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.27%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 130
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 410
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 711
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,564
Label rr_AverageAnnualReturnLabel R Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.45%
5 Years rr_AverageAnnualReturnYear05 6.34%
Since Inception rr_AverageAnnualReturnSinceInception 4.29%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2020 PORTFOLIO | R6 Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARBDX
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 0.52%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [9]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [9]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.55%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.13%) [10]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.42%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 43
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 163
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 295
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 677
American Century Asset Allocation Portfolio | ONE CHOICE 2025 PORTFOLIO  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading One Choice® 2025 Portfolio
Objective [Heading] rr_ObjectiveHeading Investment Objective 
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks the highest total return consistent with its asset mix.
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 and hold shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 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 64 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 Expenses3 (expenses that you pay each year as a percentage of the value of your investment) [15]
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination July 30, 2018
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Because the fund buys and sells shares of other American Century mutual funds (the underlying funds) directly from the issuers, the fund is not expected to incur transaction costs directly. However, as a shareholder in the underlying funds, the fund indirectly pays transaction costs, such as commissions, when the underlying funds buy and sell securities (or “turn over” their portfolios). 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 11% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 11.00%
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 $50,000 in American Century Investments funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
Acquired Fund Fees and Expenses, Based on Estimates [Text] rr_AcquiredFundFeesAndExpensesBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
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. You may be required to pay brokerage commissions on your purchases of Investor or I Class shares of the fund, which are not reflected in the example.  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
One Choice 2025 Portfolio is a “fund of funds,” meaning that it seeks to achieve its objective by investing in other American Century mutual funds (the underlying funds) that represent a variety of asset classes and investment styles. The underlying stock funds draw on growth, value and quantitative investment techniques and diversify investments among small, medium and large U.S. and foreign companies. The underlying bond funds invest in fixed-income securities that vary by issuer type (corporate and government), credit quality (investment-grade and high-yield or “junk bonds”) and geographic exposure (domestic and international). The following table indicates the fund’s neutral mix; that is, how the fund’s investments generally will be allocated among the major asset classes. The table also shows the neutral weightings of each underlying fund currently being used within the various asset classes. This information is as of December 1, 2016, except the allocation to NT High Income Fund was changed from an equivalent allocation to High-Yield Fund on May 19, 2017.
Equity Securities (Stock Funds)
52.90
%
NT Core Equity Plus Fund
3.00
%
NT Disciplined Growth Fund
2.10
%
NT Emerging Markets Fund
1.75
%
NT Equity Growth Fund
9.50
%
NT Global Real Estate Fund
1.40
%
NT Growth Fund
5.65
%
NT Heritage Fund
3.65
%
NT International Growth Fund
5.00
%
NT International Small-Mid Cap Fund
0.50
%
NT International Value Fund
3.25
%
NT Large Company Value Fund
9.75
%
NT Mid Cap Value Fund
5.75
%
NT Small Company Fund
1.60
%
 
Fixed-Income Securities (Bond Funds)
41.10
%
 
Global Bond Fund
6.00
%
 
NT High Income Fund
3.55
%
 
Inflation-Adjusted Bond Fund
3.60
%
 
International Bond Fund
4.20
%
 
NT Diversified Bond Fund
20.20
%
 
Short Duration Inflation Protection Bond Fund
3.55
%
 
 
 
 
Cash Equivalents (Money Market Fund)
6.00
%
 
U.S. Government Money Market Fund
6.00
%
 
 
 
 
 
 
 
 
 
 
 
 
The target date in the fund name (2025) refers to the approximate year an investor plans to retire and likely would stop making new investments in the fund. The fund assumes a retirement age of 65 and may not be appropriate for an investor who plans to retire at or near the target date, but at an age well before or after 65. As the target date approaches, the fund’s neutral mix will become more conservative by decreasing the allocation to stocks and increasing the allocation to bonds and cash. By the time the fund reaches its target date, the neutral mix will become fixed and match that of One Choice In Retirement Portfolio, which is currently 45% stock funds, 45% bond funds and 10% money market funds. The fund is designed for investors who plan to withdraw the value of their account gradually after retirement. The following chart shows how the neutral mix is expected to change over time according to a predetermined glide path.
glidepathimagea31.gif
The portfolio managers regularly review the fund’s allocations to determine whether rebalancing is appropriate. In order to better balance risks in changing market environments, the portfolio managers may make modest deviations from the neutral mix in light of prevailing market conditions. We reserve the right to modify the neutral mix and underlying funds from time to time should circumstances warrant a change.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Allocation Risk – The fund’s performance and risks depend in part on the managers’ skill in determining the fund’s neutral mix, selecting and weighting the underlying funds, and implementing any deviations from the neutral mix. The managers’ evaluations and assumptions regarding asset classes or underlying funds may differ from actual market conditions.
•
Fund of Funds Risks – The fund’s performance and risks reflect the performance and risks of the underlying American Century Investments funds in which it invests. The fund’s investment in other American Century Investments funds may create a conflict of interest for the fund’s advisor.
•
“Growth” and “Value” Style Risks – The underlying funds represent a mix of investment styles, each of which has risks associated with it. Growth stocks can be volatile and may lack dividends that can cushion share prices during market declines. Value stocks may continue to be undervalued by the market for long periods of time.
•
Small- and Mid-Cap Stock Risks – Stocks of smaller companies may be more volatile than larger-company stocks. Smaller companies may have limited financial resources, product lines and markets, and their securities may trade less frequently and in more limited volumes than the securities of larger companies, which could lead to higher transaction costs. To the extent an underlying fund invests in these companies, it may take on more risk.
•
Interest Rate Risk – Generally, when interest rates rise, the value of an underlying fund’s fixed-income securities will decline. The opposite is true when interest rates decline. Underlying funds with longer weighted average maturities are more sensitive to interest rate changes. A period of rising interest rates may negatively affect the performance of underlying fixed-income funds.
•
Credit Risk – The value of an underlying fund’s fixed-income securities will be affected adversely by any erosion in the ability of the issuers of these securities to make interest and principal payments as they become due. Changes in the credit rating of a fixed-income security held by an underlying fund could have a similar effect.
•
Foreign Securities Risk – Some of the underlying funds invest in foreign securities, which are generally riskier than U.S. securities. Securities of foreign issuers may be less liquid, more volatile and harder to value than U.S. securities. Fluctuations in currency exchange rates also may affect an underlying fund’s share price.
•
High-Yield Securities Risk – Some of the underlying funds may invest in high-yield securities, which are considered to have speculative characteristics and are more likely to be negatively affected by changes in economic conditions.
•
Tobacco Exclusion – The underlying funds do not invest in securities issued by companies assigned the Global Industry Classification Standard (GICS) or the Bloomberg Industry Classification Standard (BICS) for the tobacco industry. This exclusion may cause an underlying fund to forego profitable investment opportunities.
•
Market Risk – The value of the fund’s shares will go up and down based on the performance of the underlying funds in which it invests. The value of the underlying funds’ shares will, in turn, fluctuate based on the performance of the securities they own and other factors generally affecting the securities market.
•
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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
Highest Performance Quarter (3Q 2009): 11.70% Lowest Performance Quarter (4Q 2008): -13.92%
As of June 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 6.15%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2016
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 Asset Allocation Portfolio | ONE CHOICE 2025 PORTFOLIO | S&P Target Date To 2025 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 S&P Target Date To 2025 Index3 (reflects no deduction for fees, expenses or taxes) [16]
1 Year rr_AverageAnnualReturnYear01 7.17% [16]
5 Years rr_AverageAnnualReturnYear05 7.24% [16]
American Century Asset Allocation Portfolio | ONE CHOICE 2025 PORTFOLIO | S&P Target Date 2025 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 S&P Target Date 2025 Index (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 7.82%
5 Years rr_AverageAnnualReturnYear05 8.37%
10 Years rr_AverageAnnualReturnYear10 4.78%
American Century Asset Allocation Portfolio | ONE CHOICE 2025 PORTFOLIO | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARWIX
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 0.79%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [17]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [17]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.82%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [18]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.79%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 81
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 259
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 453
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,011
Annual Return 2007 rr_AnnualReturn2007 9.29%
Annual Return 2008 rr_AnnualReturn2008 (25.02%)
Annual Return 2009 rr_AnnualReturn2009 21.24%
Annual Return 2010 rr_AnnualReturn2010 12.57%
Annual Return 2011 rr_AnnualReturn2011 1.77%
Annual Return 2012 rr_AnnualReturn2012 12.14%
Annual Return 2013 rr_AnnualReturn2013 14.04%
Annual Return 2014 rr_AnnualReturn2014 6.87%
Annual Return 2015 rr_AnnualReturn2015 (1.52%)
Annual Return 2016 rr_AnnualReturn2016 6.20%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 6.15%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 11.70%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (13.92%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.20%
5 Years rr_AverageAnnualReturnYear05 7.40%
10 Years rr_AverageAnnualReturnYear10 4.98%
American Century Asset Allocation Portfolio | ONE CHOICE 2025 PORTFOLIO | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 5.29%
5 Years rr_AverageAnnualReturnYear05 6.26%
10 Years rr_AverageAnnualReturnYear10 4.02%
American Century Asset Allocation Portfolio | ONE CHOICE 2025 PORTFOLIO | 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 4.08%
5 Years rr_AverageAnnualReturnYear05 5.59%
10 Years rr_AverageAnnualReturnYear10 3.69%
American Century Asset Allocation Portfolio | ONE CHOICE 2025 PORTFOLIO | INSTITUTIONAL CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARWFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [19]
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [19]
Maximum Account Fee rr_MaximumAccountFee none [19]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.61%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [17]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [17]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.64%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [18]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.59%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 60
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 200
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 352
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 794
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.42%
5 Years rr_AverageAnnualReturnYear05 7.61%
10 Years rr_AverageAnnualReturnYear10 5.18%
American Century Asset Allocation Portfolio | ONE CHOICE 2025 PORTFOLIO | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARWAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [20]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.79%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [17]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [17]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.07%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [18]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.04%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 675
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 893
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,129
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,803
Label rr_AverageAnnualReturnLabel A Class1 Return Before Taxes [21]
1 Year rr_AverageAnnualReturnYear01 (0.08%) [21]
5 Years rr_AverageAnnualReturnYear05 5.88% [21]
10 Years rr_AverageAnnualReturnYear10 4.10% [21]
American Century Asset Allocation Portfolio | ONE CHOICE 2025 PORTFOLIO | C Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARWCX
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 0.79%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [17]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [17]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.82%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [18]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.79%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 182
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 571
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 983
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,132
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.13%
5 Years rr_AverageAnnualReturnYear05 6.32%
10 Years rr_AverageAnnualReturnYear10 3.94% [22]
American Century Asset Allocation Portfolio | ONE CHOICE 2025 PORTFOLIO | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARWRX
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 0.79%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [17]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [17]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.32%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [18]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.29%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 132
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 416
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 721
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,587
Label rr_AverageAnnualReturnLabel R Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.68%
5 Years rr_AverageAnnualReturnYear05 6.86%
10 Years rr_AverageAnnualReturnYear10 4.46%
American Century Asset Allocation Portfolio | ONE CHOICE 2025 PORTFOLIO | R6 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARWDX
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 none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [17]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [17]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.57%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.13%) [18]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.44%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 45
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 170
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 306
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 702
American Century Asset Allocation Portfolio | ONE CHOICE 2030 PORTFOLIO  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading One Choice® 2030 Portfolio
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks the highest total return consistent with its asset mix.
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 and hold shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 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 64 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 Expenses3 (expenses that you pay each year as a percentage of the value of your investment) [23]
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination July 30, 2018
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Because the fund buys and sells shares of other American Century mutual funds (the underlying funds) directly from the issuers, the fund is not expected to incur transaction costs directly. However, as a shareholder in the underlying funds, the fund indirectly pays transaction costs, such as commissions, when the underlying funds buy and sell securities (or “turn over” their portfolios). 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 10% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 10.00%
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 $50,000 in American Century Investments funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
Acquired Fund Fees and Expenses, Based on Estimates [Text] rr_AcquiredFundFeesAndExpensesBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
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. You may be required to pay brokerage commissions on your purchases of Investor or I Class shares of the fund, which are not reflected in the example.  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
One Choice 2030 Portfolio is a “fund of funds,” meaning that it seeks to achieve its objective by investing in other American Century mutual funds (the underlying funds) that represent a variety of asset classes and investment styles. The underlying stock funds draw on growth, value and quantitative investment techniques and diversify investments among small, medium and large U.S. and foreign companies. The underlying bond funds invest in fixed-income securities that vary by issuer type (corporate and government), credit quality (investment-grade and high-yield or “junk bonds”) and geographic exposure (domestic and international). The following table indicates the fund’s neutral mix; that is, how the fund’s investments generally will be allocated among the major asset classes. The table also shows the neutral weightings of each underlying fund currently being used within the various asset classes. This information is as of December 1, 2016, except the allocation to NT High Income Fund was changed from an equivalent allocation to High-Yield Fund on May 19, 2017.
Equity Securities (Stock Funds)
58.60
%
NT Core Equity Plus Fund
3.00
%
NT Disciplined Growth Fund
2.48
%
NT Emerging Markets Fund
2.55
%
NT Equity Growth Fund
9.35
%
NT Global Real Estate Fund
1.65
%
NT Growth Fund
6.76
%
NT Heritage Fund
4.34
%
NT International Growth Fund
5.48
%
NT International Small-Mid Cap Fund
0.81
%
NT International Value Fund
3.88
%
NT Large Company Value Fund
10.10
%
NT Mid Cap Value Fund
6.00
%
NT Small Company Fund
2.20
%
 
Fixed-Income Securities (Bond Funds)
36.40
%
 
Global Bond Fund
5.38
%
 
NT High Income Fund
3.30
%
 
Inflation-Adjusted Bond Fund
4.60
%
 
International Bond Fund
2.80
%
 
NT Diversified Bond Fund
18.32
%
 
Short Duration Inflation Protection Bond Fund
2.00
%
 
 
 
 
Cash Equivalents (Money Market Fund)
5.00
%
 
U.S. Government Money Market Fund
5.00
%
 
 
 
 
 
 
 
 
 
 
 
 
The target date in the fund name (2030) refers to the approximate year an investor plans to retire and likely would stop making new investments in the fund. The fund assumes a retirement age of 65 and may not be appropriate for an investor who plans to retire at or near the target date, but at an age well before or after 65. As the target date approaches, the fund’s neutral mix will become more conservative by decreasing the allocation to stocks and increasing the allocation to bonds and cash. By the time the fund reaches its target date, the neutral mix will become fixed and match that of One Choice In Retirement Portfolio, which is currently 45% stock funds, 45% bond funds and 10% money market funds. The fund is designed for investors who plan to withdraw the value of their account gradually after retirement. The following chart shows how the neutral mix is expected to change over time according to a predetermined glide path.
glidepathimagea31.gif
The portfolio managers regularly review the fund’s allocations to determine whether rebalancing is appropriate. In order to better balance risks in changing market environments, the portfolio managers may make modest deviations from the neutral mix in light of prevailing market conditions. We reserve the right to modify the neutral mix and underlying funds from time to time should circumstances warrant a change.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Allocation Risk – The fund’s performance and risks depend in part on the managers’ skill in determining the fund’s neutral mix, selecting and weighting the underlying funds, and implementing any deviations from the neutral mix. The managers’ evaluations and assumptions regarding asset classes or underlying funds may differ from actual market conditions.
•
Fund of Funds Risks – The fund’s performance and risks reflect the performance and risks of the underlying American Century Investments funds in which it invests. The fund’s investment in other American Century Investments funds may create a conflict of interest for the fund’s advisor.
•
“Growth” and “Value” Style Risks – The underlying funds represent a mix of investment styles, each of which has risks associated with it. Growth stocks can be volatile and may lack dividends that can cushion share prices during market declines. Value stocks may continue to be undervalued by the market for long periods of time.
•
Small- and Mid-Cap Stock Risks – Stocks of smaller companies may be more volatile than larger-company stocks. Smaller companies may have limited financial resources, product lines and markets, and their securities may trade less frequently and in more limited volumes than the securities of larger companies, which could lead to higher transaction costs. To the extent an underlying fund invests in these companies, it may take on more risk.
•
Interest Rate Risk – Generally, when interest rates rise, the value of an underlying fund’s fixed-income securities will decline. The opposite is true when interest rates decline. Underlying funds with longer weighted average maturities are more sensitive to interest rate changes. A period of rising interest rates may negatively affect the performance of underlying fixed-income funds.
•
Credit Risk – The value of an underlying fund’s fixed-income securities will be affected adversely by any erosion in the ability of the issuers of these securities to make interest and principal payments as they become due. Changes in the credit rating of a fixed-income security held by an underlying fund could have a similar effect.
•
Foreign Securities Risk – Some of the underlying funds invest in foreign securities, which are generally riskier than U.S. securities. Securities of foreign issuers may be less liquid, more volatile and harder to value than U.S. securities. Fluctuations in currency exchange rates also may affect an underlying fund’s share price. Investing in securities of companies located in emerging market countries is generally riskier than investing in securities of companies located in developed foreign countries.
•
High-Yield Securities Risk – Some of the underlying funds may invest in high-yield securities, which are considered to have speculative characteristics and are more likely to be negatively affected by changes in economic conditions.
•
Tobacco Exclusion – The underlying funds do not invest in securities issued by companies assigned the Global Industry Classification Standard (GICS) or the Bloomberg Industry Classification Standard (BICS) for the tobacco industry. This exclusion may cause an underlying fund to forego profitable investment opportunities.
•
Market Risk – The value of the fund’s shares will go up and down based on the performance of the underlying funds in which it invests. The value of the underlying funds’ shares will, in turn, fluctuate based on the performance of the securities they own and other factors generally affecting the securities market.
•
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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
Highest Performance Quarter (3Q 2009): 12.53% Lowest Performance Quarter (3Q 2011): -10.33%
As of June 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 6.62%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2016
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 Asset Allocation Portfolio | ONE CHOICE 2030 PORTFOLIO | S&P Target Date To 2030 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 S&P Target Date To 2030 Index (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 7.75%
5 Years rr_AverageAnnualReturnYear05 7.95%
Since Inception rr_AverageAnnualReturnSinceInception 4.53%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2030 PORTFOLIO | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARCVX
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 0.82%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [24]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [24]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.85%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.81%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 83
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 268
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 468
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,046
Annual Return 2009 rr_AnnualReturn2009 22.88%
Annual Return 2010 rr_AnnualReturn2010 13.39%
Annual Return 2011 rr_AnnualReturn2011 1.04%
Annual Return 2012 rr_AnnualReturn2012 12.79%
Annual Return 2013 rr_AnnualReturn2013 15.86%
Annual Return 2014 rr_AnnualReturn2014 7.22%
Annual Return 2015 rr_AnnualReturn2015 (1.37%)
Annual Return 2016 rr_AnnualReturn2016 6.41%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 6.62%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 12.53%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (10.33%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.41%
5 Years rr_AverageAnnualReturnYear05 8.01%
Since Inception rr_AverageAnnualReturnSinceInception 4.96%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2030 PORTFOLIO | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 5.54%
5 Years rr_AverageAnnualReturnYear05 6.92%
Since Inception rr_AverageAnnualReturnSinceInception 4.14%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2030 PORTFOLIO | 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 4.21%
5 Years rr_AverageAnnualReturnYear05 6.11%
Since Inception rr_AverageAnnualReturnSinceInception 3.74%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2030 PORTFOLIO | INSTITUTIONAL CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARCSX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [26]
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [26]
Maximum Account Fee rr_MaximumAccountFee none [26]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.63%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [24]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [24]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.66%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.61%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 62
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 207
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 363
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 818
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.63%
5 Years rr_AverageAnnualReturnYear05 8.23%
Since Inception rr_AverageAnnualReturnSinceInception 5.16%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2030 PORTFOLIO | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARCMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [27]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.82%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [24]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [24]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.10%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.06%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 677
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 901
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,143
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,835
Label rr_AverageAnnualReturnLabel A Class1 Return Before Taxes [28]
1 Year rr_AverageAnnualReturnYear01 (0.06%) [28]
5 Years rr_AverageAnnualReturnYear05 6.46% [28]
Since Inception rr_AverageAnnualReturnSinceInception 3.96% [28]
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008 [28]
American Century Asset Allocation Portfolio | ONE CHOICE 2030 PORTFOLIO | C Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARWOX
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 0.82%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [24]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [24]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.85%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.81%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 184
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 579
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 998
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,163
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.34%
5 Years rr_AverageAnnualReturnYear05 6.93%
Since Inception rr_AverageAnnualReturnSinceInception 3.91% [29]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010
American Century Asset Allocation Portfolio | ONE CHOICE 2030 PORTFOLIO | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARCRX
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 0.82%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [24]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [24]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.35%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.31%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 134
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 424
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 736
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,620
Label rr_AverageAnnualReturnLabel R Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.89%
5 Years rr_AverageAnnualReturnYear05 7.47%
Since Inception rr_AverageAnnualReturnSinceInception 4.42%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2030 PORTFOLIO | R6 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARCUX
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 0.55%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [24]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [24]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.58%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.12%) [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.46%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 47
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 174
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 312
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 715
American Century Asset Allocation Portfolio | ONE CHOICE 2035 PORTFOLIO  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading One Choice® 2035 Portfolio
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks the highest total return consistent with its asset mix.
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 and hold shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 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 64 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 Expenses3 (expenses that you pay each year as a percentage of the value of your investment) [30]
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination July 30, 2018
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover 
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Because the fund buys and sells shares of other American Century mutual funds (the underlying funds) directly from the issuers, the fund is not expected to incur transaction costs directly. However, as a shareholder in the underlying funds, the fund indirectly pays transaction costs, such as commissions, when the underlying funds buy and sell securities (or “turn over” their portfolios). 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 8% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 8.00%
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 $50,000 in American Century Investments funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
Acquired Fund Fees and Expenses, Based on Estimates [Text] rr_AcquiredFundFeesAndExpensesBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
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. You may be required to pay brokerage commissions on your purchases of Investor or I Class shares of the fund, which are not reflected in the example.  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
One Choice 2035 Portfolio is a “fund of funds,” meaning that it seeks to achieve its objective by investing in other American Century mutual funds (the underlying funds) that represent a variety of asset classes and investment styles. The underlying stock funds draw on growth, value and quantitative investment techniques and diversify investments among small, medium and large U.S. and foreign companies. The underlying bond funds invest in fixed-income securities that vary by issuer type (corporate and government), credit quality (investment-grade and high-yield or “junk bonds”) and geographic exposure (domestic and international). The following table indicates the fund’s neutral mix; that is, how the fund’s investments generally will be allocated among the major asset classes. The table also shows the neutral weightings of each underlying fund currently being used within the various asset classes. This information is as of December 1, 2016, except the allocation to NT High Income Fund was changed from an equivalent allocation to High-Yield Fund on May 19, 2017.
Equity Securities (Stock Funds)
64.50
%
NT Core Equity Plus Fund
3.25
%
NT Disciplined Growth Fund
2.85
%
NT Emerging Markets Fund
3.00
%
NT Equity Growth Fund
9.25
%
NT Global Real Estate Fund
1.90
%
NT Growth Fund
8.39
%
NT Heritage Fund
4.53
%
NT International Growth Fund
6.25
%
NT International Small-Mid Cap Fund
1.13
%
NT International Value Fund
4.50
%
NT Large Company Value Fund
10.50
%
NT Mid Cap Value Fund
6.00
%
NT Small Company Fund
2.95
%
 
Fixed-Income Securities (Bond Funds)
30.50
%
 
Global Bond Fund
4.75
%
 
NT High Income Fund
3.00
%
 
Inflation-Adjusted Bond Fund
5.25
%
 
International Bond Fund
0.80
%
 
NT Diversified Bond Fund
16.05
%
 
Short Duration Inflation Protection Bond Fund
0.65
%
 
 
 
 
Cash Equivalents (Money Market Fund)
5.00
%
 
U.S. Government Money Market Fund
5.00
%
 
 
 
 
 
 
 
 
 
 
 
 
The target date in the fund name (2035) refers to the approximate year an investor plans to retire and likely would stop making new investments in the fund. The fund assumes a retirement age of 65 and may not be appropriate for an investor who plans to retire at or near the target date, but at an age well before or after 65. As the target date approaches, the fund’s neutral mix will become more conservative by decreasing the allocation to stocks and increasing the allocation to bonds and cash. By the time the fund reaches its target date, the neutral mix will become fixed and match that of One Choice In Retirement Portfolio, which is currently 45% stock funds, 45% bond funds and 10% money market funds. The fund is designed for investors who plan to withdraw the value of their account gradually after retirement. The following chart shows how the neutral mix is expected to change over time according to a predetermined glide path.glidepathimagea31.gifThe portfolio managers regularly review the fund’s allocations to determine whether rebalancing is appropriate. In order to better balance risks in changing market environments, the portfolio managers may make modest deviations from the neutral mix in light of prevailing market conditions. We reserve the right to modify the neutral mix and underlying funds from time to time should circumstances warrant a change.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Allocation Risk – The fund’s performance and risks depend in part on the managers’ skill in determining the fund’s neutral mix, selecting and weighting the underlying funds, and implementing any deviations from the neutral mix. The managers’ evaluations and assumptions regarding asset classes or underlying funds may differ from actual market conditions.
•
Fund of Funds Risks – The fund’s performance and risks reflect the performance and risks of the underlying American Century Investments funds in which it invests. The fund’s investment in other American Century Investments funds may create a conflict of interest for the fund’s advisor.
•
“Growth” and “Value” Style Risks – The underlying funds represent a mix of investment styles, each of which has risks associated with it. Growth stocks can be volatile and may lack dividends that can cushion share prices during market declines. Value stocks may continue to be undervalued by the market for long periods of time.
•
Small- and Mid-Cap Stock Risks – Stocks of smaller companies may be more volatile than larger-company stocks. Smaller companies may have limited financial resources, product lines and markets, and their securities may trade less frequently and in more limited volumes than the securities of larger companies, which could lead to higher transaction costs. To the extent an underlying fund invests in these companies, it may take on more risk.
•
Interest Rate Risk – Generally, when interest rates rise, the value of an underlying fund’s fixed-income securities will decline. The opposite is true when interest rates decline. Underlying funds with longer weighted average maturities are more sensitive to interest rate changes. A period of rising interest rates may negatively affect the performance of underlying fixed-income funds.
•
Credit Risk – The value of an underlying fund’s fixed-income securities will be affected adversely by any erosion in the ability of the issuers of these securities to make interest and principal payments as they become due. Changes in the credit rating of a fixed-income security held by an underlying fund could have a similar effect.
•
Foreign Securities Risk – Some of the underlying funds invest in foreign securities, which are generally riskier than U.S. securities. Securities of foreign issuers may be less liquid, more volatile and harder to value than U.S. securities. Fluctuations in currency exchange rates also may affect an underlying fund’s share price. Investing in securities of companies located in emerging market countries is generally riskier than investing in securities of companies located in developed foreign countries.
•
Emerging Market Risk - Investing in securities of companies located in emerging market countries generally is also riskier than investing in securities of companies located in foreign developed countries. Emerging market countries may have unstable governments and/or economies that are subject to sudden change. These changes may be magnified by the countries’ emergent financial markets, resulting in significant volatility to investments in these countries.
•
Real Estate Investing - An investment in the fund may be subject to many of the same risks as a direct investment in real estate. These risks include changes in economic conditions, interest rates, property values, property tax increases, overbuilding and increased competition, environmental contamination, zoning and natural disasters. This is due to the fact that the value of the fund’s investments may be affected by the value of the real estate owned by the companies in which it invests.
•
Tobacco Exclusion – The underlying funds do not invest in securities issued by companies assigned the Global Industry Classification Standard (GICS) or the Bloomberg Industry Classification Standard (BICS) for the tobacco industry. This exclusion may cause an underlying fund to forego profitable investment opportunities.
•
Market Risk – The value of the fund’s shares will go up and down based on the performance of the underlying funds in which it invests. The value of the underlying funds’ shares will, in turn, fluctuate based on the performance of the securities they own and other factors generally affecting the securities market.
•
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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
Highest Performance Quarter (3Q 2009): 13.46% Lowest Performance Quarter (4Q 2008): -17.42%
As of June 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 7.20%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2016
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 Asset Allocation Portfolio | ONE CHOICE 2035 PORTFOLIO | S&P Target Date To 2035 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 S&P Target Date To 2035 Index3 (reflects no deduction for fees, expenses or taxes) [31]
1 Year rr_AverageAnnualReturnYear01 8.27% [31]
5 Years rr_AverageAnnualReturnYear05 8.55% [31]
American Century Asset Allocation Portfolio | ONE CHOICE 2035 PORTFOLIO | S&P Target Date 2035 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 S&P Target Date 2035 Index (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 8.85%
5 Years rr_AverageAnnualReturnYear05 9.59%
Since Inception rr_AverageAnnualReturnSinceInception 4.86%
American Century Asset Allocation Portfolio | ONE CHOICE 2035 PORTFOLIO | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARYIX
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 0.84%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [32]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [32]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.87%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [33]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.84%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 86
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 275
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 480
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,070
Annual Return 2007 rr_AnnualReturn2007 10.36%
Annual Return 2008 rr_AnnualReturn2008 (30.58%)
Annual Return 2009 rr_AnnualReturn2009 24.31%
Annual Return 2010 rr_AnnualReturn2010 14.28%
Annual Return 2011 rr_AnnualReturn2011 0.37%
Annual Return 2012 rr_AnnualReturn2012 13.62%
Annual Return 2013 rr_AnnualReturn2013 17.92%
Annual Return 2014 rr_AnnualReturn2014 7.56%
Annual Return 2015 rr_AnnualReturn2015 (1.23%)
Annual Return 2016 rr_AnnualReturn2016 6.54%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 7.20%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 13.46%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (17.42%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.54%
5 Years rr_AverageAnnualReturnYear05 8.68%
Since Inception rr_AverageAnnualReturnSinceInception 5.17%
American Century Asset Allocation Portfolio | ONE CHOICE 2035 PORTFOLIO | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 5.61%
5 Years rr_AverageAnnualReturnYear05 7.48%
Since Inception rr_AverageAnnualReturnSinceInception 4.25%
American Century Asset Allocation Portfolio | ONE CHOICE 2035 PORTFOLIO | 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 4.36%
5 Years rr_AverageAnnualReturnYear05 6.65%
Since Inception rr_AverageAnnualReturnSinceInception 3.90%
American Century Asset Allocation Portfolio | ONE CHOICE 2035 PORTFOLIO | INSTITUTIONAL CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARLIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [34]
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [34]
Maximum Account Fee rr_MaximumAccountFee none [34]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.65%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [32]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [32]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.68%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [33]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.64%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 66
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 214
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 375
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 843
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.75%
5 Years rr_AverageAnnualReturnYear05 8.89%
Since Inception rr_AverageAnnualReturnSinceInception 5.38%
American Century Asset Allocation Portfolio | ONE CHOICE 2035 PORTFOLIO | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARYAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [35]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.84%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [32]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [32]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.12%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [33]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.09%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 680
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 908
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,154
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,857
Label rr_AverageAnnualReturnLabel A Class1 Return Before Taxes [36]
1 Year rr_AverageAnnualReturnYear01 0.13% [36]
5 Years rr_AverageAnnualReturnYear05 7.13% [36]
Since Inception rr_AverageAnnualReturnSinceInception 4.29% [36]
American Century Asset Allocation Portfolio | ONE CHOICE 2035 PORTFOLIO | C Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARLCX
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 0.84%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [32]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [32]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.87%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [33]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.84%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 187
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 586
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,009
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,185
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.46%
5 Years rr_AverageAnnualReturnYear05 7.59%
Since Inception rr_AverageAnnualReturnSinceInception 4.12% [37]
American Century Asset Allocation Portfolio | ONE CHOICE 2035 PORTFOLIO | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARYRX
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 0.84%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [32]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [32]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.37%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [33]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.34%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 137
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 432
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 748
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,643
Label rr_AverageAnnualReturnLabel R Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.08%
5 Years rr_AverageAnnualReturnYear05 8.15%
Since Inception rr_AverageAnnualReturnSinceInception 4.65%
American Century Asset Allocation Portfolio | ONE CHOICE 2035 PORTFOLIO | R6 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARLDX
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 0.57%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [32]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [32]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.60%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.11%) [33]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.49%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 50
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 181
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 324
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 740
American Century Asset Allocation Portfolio | ONE CHOICE 2040 PORTFOLIO  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading One Choice® 2040 Portfolio
Objective [Heading] rr_ObjectiveHeading Investment Objective 
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks the highest total return consistent with its asset mix.
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 and hold shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 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 64 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 Expenses3 (expenses that you pay each year as a percentage of the value of your investment) [38]
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination July 30, 2018
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Because the fund buys and sells shares of other American Century mutual funds (the underlying funds) directly from the issuers, the fund is not expected to incur transaction costs directly. However, as a shareholder in the underlying funds, the fund indirectly pays transaction costs, such as commissions, when the underlying funds buy and sell securities (or “turn over” their portfolios). 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 8% of the average value of its portfolio. 
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 8.00%
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 $50,000 in American Century Investments funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
Acquired Fund Fees and Expenses, Based on Estimates [Text] rr_AcquiredFundFeesAndExpensesBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
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. You may be required to pay brokerage commissions on your purchases of Investor or I Class shares of the fund, which are not reflected in the example.  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
One Choice 2040 Portfolio is a “fund of funds,” meaning that it seeks to achieve its objective by investing in other American Century mutual funds (the underlying funds) that represent a variety of asset classes and investment styles. The underlying stock funds draw on growth, value and quantitative investment techniques and diversify investments among small, medium and large U.S. and foreign companies. The underlying bond funds invest in fixed-income securities that vary by issuer type (corporate and government), credit quality (investment-grade and high-yield or “junk bonds”) and geographic exposure (domestic and international). The following table indicates the fund’s neutral mix; that is, how the fund’s investments generally will be allocated among the major asset classes. The table also shows the neutral weightings of each underlying fund currently being used within the various asset classes. This information is as of December 1, 2016, except the allocation to NT High Income Fund was changed from an equivalent allocation to High-Yield Fund on May 19, 2017.
Equity Securities (Stock Funds)
70.80
%
NT Core Equity Plus Fund
3.25
%
NT Disciplined Growth Fund
3.08
%
NT Emerging Markets Fund
3.75
%
NT Equity Growth Fund
9.75
%
NT Global Real Estate Fund
2.15
%
NT Growth Fund
9.38
%
NT Heritage Fund
5.46
%
NT International Growth Fund
6.68
%
NT International Small-Mid Cap Fund
1.44
%
NT International Value Fund
4.86
%
NT Large Company Value Fund
11.54
%
NT Mid Cap Value Fund
6.31
%
NT Small Company Fund
3.15
%
 
Fixed-Income Securities (Bond Funds)
25.70
%
 
Global Bond Fund
4.28
%
 
NT High Income Fund
2.55
%
 
Inflation-Adjusted Bond Fund
5.15
%
 
NT Diversified Bond Fund
13.72
%
 
 
 
 
Cash Equivalents (Money Market Fund)
3.50
%
 
U.S. Government Money Market Fund
3.50
%
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
The target date in the fund name (2040) refers to the approximate year an investor plans to retire and likely would stop making new investments in the fund. The fund assumes a retirement age of 65 and may not be appropriate for an investor who plans to retire at or near the target date, but at an age well before or after 65. As the target date approaches, the fund’s neutral mix will become more conservative by decreasing the allocation to stocks and increasing the allocation to bonds and cash. By the time the fund reaches its target date, the neutral mix will become fixed and match that of One Choice In Retirement Portfolio, which is currently 45% stock funds, 45% bond funds and 10% money market funds. The fund is designed for investors who plan to withdraw the value of their account gradually after retirement. The following chart shows how the neutral mix is expected to change over time according to a predetermined glide path.
glidepathimagea31.gif
The portfolio managers regularly review the fund’s allocations to determine whether rebalancing is appropriate. In order to better balance risks in changing market environments, the portfolio managers may make modest deviations from the neutral mix in light of prevailing market conditions. We reserve the right to modify the neutral mix and underlying funds from time to time should circumstances warrant a change.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Allocation Risk – The fund’s performance and risks depend in part on the managers’ skill in determining the fund’s neutral mix, selecting and weighting the underlying funds, and implementing any deviations from the neutral mix. The managers’ evaluations and assumptions regarding asset classes or underlying funds may differ from actual market conditions.
•
Fund of Funds Risks – The fund’s performance and risks reflect the performance and risks of the underlying American Century Investments funds in which it invests. The fund’s investment in other American Century Investments funds may create a conflict of interest for the fund’s advisor.
•
“Growth” and “Value” Style Risks – The underlying funds represent a mix of investment styles, each of which has risks associated with it. Growth stocks can be volatile and may lack dividends that can cushion share prices during market declines. Value stocks may continue to be undervalued by the market for long periods of time.
•
Small- and Mid-Cap Stock Risks – Stocks of smaller companies may be more volatile than larger-company stocks. Smaller companies may have limited financial resources, product lines and markets, and their securities may trade less frequently and in more limited volumes than the securities of larger companies, which could lead to higher transaction costs. To the extent an underlying fund invests in these companies, it may take on more risk.
•
Interest Rate Risk – Generally, when interest rates rise, the value of an underlying fund’s fixed-income securities will decline. The opposite is true when interest rates decline. Underlying funds with longer weighted average maturities are more sensitive to interest rate changes. A period of rising interest rates may negatively affect the performance of underlying fixed-income funds.
•
Credit Risk – The value of an underlying fund’s fixed-income securities will be affected adversely by any erosion in the ability of the issuers of these securities to make interest and principal payments as they become due. Changes in the credit rating of a fixed-income security held by an underlying fund could have a similar effect.
•
Foreign Securities Risk – Some of the underlying funds invest in foreign securities, which are generally riskier than U.S. securities. Securities of foreign issuers may be less liquid, more volatile and harder to value than U.S. securities. Fluctuations in currency exchange rates also may affect an underlying fund’s share price. Investing in securities of companies located in emerging market countries is generally riskier than investing in securities of companies located in developed foreign countries.
•
Emerging Market Risk - Investing in securities of companies located in emerging market countries generally is also riskier than investing in securities of companies located in foreign developed countries. Emerging market countries may have unstable governments and/or economies that are subject to sudden change. These changes may be magnified by the countries’ emergent financial markets, resulting in significant volatility to investments in these countries.
•
Real Estate Investing - An investment in the fund may be subject to many of the same risks as a direct investment in real estate. These risks include changes in economic conditions, interest rates, property values, property tax increases, overbuilding and increased competition, environmental contamination, zoning and natural disasters. This is due to the fact that the value of the fund’s investments may be affected by the value of the real estate owned by the companies in which it invests.
•
Tobacco Exclusion – The underlying funds do not invest in securities issued by companies assigned the Global Industry Classification Standard (GICS) or the Bloomberg Industry Classification Standard (BICS) for the tobacco industry. This exclusion may cause an underlying fund to forego profitable investment opportunities.
•
Market Risk – The value of the fund’s shares will go up and down based on the performance of the underlying funds in which it invests. The value of the underlying funds’ shares will, in turn, fluctuate based on the performance of the securities they own and other factors generally affecting the securities market.
•
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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
Highest Performance Quarter (2Q 2009): 14.38% Lowest Performance Quarter (3Q 2011): -12.68%
As of June 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 7.81%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2016
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 Asset Allocation Portfolio | ONE CHOICE 2040 PORTFOLIO | S&P Target Date To 2040 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 S&P Target Date To 2040 Index (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 8.77%
5 Years rr_AverageAnnualReturnYear05 9.09%
Since Inception rr_AverageAnnualReturnSinceInception 4.71%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2040 PORTFOLIO | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARDVX
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 0.86%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [39]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [39]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.89%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [40]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.86%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 88
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 281
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 491
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,094
Annual Return 2009 rr_AnnualReturn2009 25.95%
Annual Return 2010 rr_AnnualReturn2010 14.99%
Annual Return 2011 rr_AnnualReturn2011 (0.27%)
Annual Return 2012 rr_AnnualReturn2012 14.50%
Annual Return 2013 rr_AnnualReturn2013 19.69%
Annual Return 2014 rr_AnnualReturn2014 8.03%
Annual Return 2015 rr_AnnualReturn2015 (1.32%)
Annual Return 2016 rr_AnnualReturn2016 6.80%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 7.81%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 14.38%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (12.68%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.80%
5 Years rr_AverageAnnualReturnYear05 9.29%
Since Inception rr_AverageAnnualReturnSinceInception 5.41%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2040 PORTFOLIO | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 5.87%
5 Years rr_AverageAnnualReturnYear05 8.17%
Since Inception rr_AverageAnnualReturnSinceInception 4.60%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2040 PORTFOLIO | 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 4.55%
5 Years rr_AverageAnnualReturnYear05 7.17%
Since Inception rr_AverageAnnualReturnSinceInception 4.14%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2040 PORTFOLIO | INSTITUTIONAL CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARDSX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [41]
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [41]
Maximum Account Fee rr_MaximumAccountFee none [41]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.67%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [39]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [39]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.70%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [40]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.66%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 68
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 220
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 386
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 867
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.11%
5 Years rr_AverageAnnualReturnYear05 9.52%
Since Inception rr_AverageAnnualReturnSinceInception 5.62%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2040 PORTFOLIO | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARDMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [42]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.86%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [39]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [39]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.14%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [40]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.11%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 682
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 914
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,164
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,879
Label rr_AverageAnnualReturnLabel A Class1 Return Before Taxes [43]
1 Year rr_AverageAnnualReturnYear01 0.41% [43]
5 Years rr_AverageAnnualReturnYear05 7.74% [43]
Since Inception rr_AverageAnnualReturnSinceInception 4.42% [43]
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008 [43]
American Century Asset Allocation Portfolio | ONE CHOICE 2040 PORTFOLIO | C Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARNOX
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 0.86%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [39]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [39]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.89%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [40]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.86%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 189
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 592
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,019
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,206
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.72%
5 Years rr_AverageAnnualReturnYear05 8.21%
Since Inception rr_AverageAnnualReturnSinceInception 4.35% [44]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010
American Century Asset Allocation Portfolio | ONE CHOICE 2040 PORTFOLIO | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARDRX
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 0.86%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [39]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [39]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.39%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [40]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.36%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 139
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 438
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 758
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,665
Label rr_AverageAnnualReturnLabel R Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.36%
5 Years rr_AverageAnnualReturnYear05 8.75%
Since Inception rr_AverageAnnualReturnSinceInception 4.88%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2040 PORTFOLIO | R6 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARDUX
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 0.58%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [39]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [39]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.61%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.10%) [40]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.51%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 52
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 186
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 331
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 753
American Century Asset Allocation Portfolio | ONE CHOICE 2045 PORTFOLIO  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading One Choice® 2045 Portfolio
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks the highest total return consistent with its asset mix.
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 and hold shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 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 64 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 Expenses3 (expenses that you pay each year as a percentage of the value of your investment) [45]
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination July 30, 2018
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover 
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Because the fund buys and sells shares of other American Century mutual funds (the underlying funds) directly from the issuers, the fund is not expected to incur transaction costs directly. However, as a shareholder in the underlying funds, the fund indirectly pays transaction costs, such as commissions, when the underlying funds buy and sell securities (or “turn over” their portfolios). 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 7% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 7.00%
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 $50,000 in American Century Investments funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
Acquired Fund Fees and Expenses, Based on Estimates [Text] rr_AcquiredFundFeesAndExpensesBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
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. You may be required to pay brokerage commissions on your purchases of Investor or I Class shares of the fund, which are not reflected in the example. 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
One Choice 2045 Portfolio is a “fund of funds,” meaning that it seeks to achieve its objective by investing in other American Century mutual funds (the underlying funds) that represent a variety of asset classes and investment styles. The underlying stock funds draw on growth, value and quantitative investment techniques and diversify investments among small, medium and large U.S. and foreign companies. The underlying bond funds invest in fixed-income securities that vary by issuer type (corporate and government), credit quality (investment-grade and high-yield or “junk bonds”) and geographic exposure (domestic and international). The following table indicates the fund’s neutral mix; that is, how the fund’s investments generally will be allocated among the major asset classes. The table also shows the neutral weightings of each underlying fund currently being used within the various asset classes. This information is as of December 1, 2016, except the allocation to NT High Income Fund was changed from an equivalent allocation to High-Yield Fund on May 19, 2017.
Equity Securities (Stock Funds)
77.15
%
NT Core Equity Plus Fund
3.75
%
NT Disciplined Growth Fund
3.20
%
NT Emerging Markets Fund
4.75
%
NT Equity Growth Fund
10.25
%
NT Global Real Estate Fund
2.40
%
NT Growth Fund
10.20
%
NT Heritage Fund
6.40
%
NT International Growth Fund
6.80
%
NT International Small-Mid Cap Fund
1.75
%
NT International Value Fund
5.05
%
NT Large Company Value Fund
12.60
%
NT Mid Cap Value Fund
7.00
%
NT Small Company Fund
3.00
%
 
Fixed-Income Securities (Bond Funds)
21.85
%
 
Global Bond Fund
3.90
%
 
NT High Income Fund
2.15
%
 
Inflation-Adjusted Bond Fund
4.30
%
 
NT Diversified Bond Fund
11.50
%
 
 
 
 
Cash Equivalents (Money Market Fund)
1.00
%
 
U.S. Government Money Market Fund
1.00
%
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
The target date in the fund name (2045) refers to the approximate year an investor plans to retire and likely would stop making new investments in the fund. The fund assumes a retirement age of 65 and may not be appropriate for an investor who plans to retire at or near the target date, but at an age well before or after 65. As the target date approaches, the fund’s neutral mix will become more conservative by decreasing the allocation to stocks and increasing the allocation to bonds and cash. By the time the fund reaches its target date, the neutral mix will become fixed and match that of One Choice In Retirement Portfolio, which is currently 45% stock funds, 45% bond funds and 10% money market funds. The fund is designed for investors who plan to withdraw the value of their account gradually after retirement. The following chart shows how the neutral mix is expected to change over time according to a predetermined glide path.
glidepathimagea31.gif
The portfolio managers regularly review the fund’s allocations to determine whether rebalancing is appropriate. In order to better balance risks in changing market environments, the portfolio managers may make modest deviations from the neutral mix in light of prevailing market conditions. We reserve the right to modify the neutral mix and underlying funds from time to time should circumstances warrant a change.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Allocation Risk – The fund’s performance and risks depend in part on the managers’ skill in determining the fund’s neutral mix, selecting and weighting the underlying funds, and implementing any deviations from the neutral mix. The managers’ evaluations and assumptions regarding asset classes or underlying funds may differ from actual market conditions.
•
Fund of Funds Risks – The fund’s performance and risks reflect the performance and risks of the underlying American Century Investments funds in which it invests. The fund’s investment in other American Century Investments funds may create a conflict of interest for the fund’s advisor.
•
“Growth” and “Value” Style Risks – The underlying funds represent a mix of investment styles, each of which has risks associated with it. Growth stocks can be volatile and may lack dividends that can cushion share prices during market declines. Value stocks may continue to be undervalued by the market for long periods of time.
•
Small- and Mid-Cap Stock Risks – Stocks of smaller companies may be more volatile than larger-company stocks. Smaller companies may have limited financial resources, product lines and markets, and their securities may trade less frequently and in more limited volumes than the securities of larger companies, which could lead to higher transaction costs. To the extent an underlying fund invests in these companies, it may take on more risk.
•
Interest Rate Risk – Generally, when interest rates rise, the value of an underlying fund’s fixed-income securities will decline. The opposite is true when interest rates decline. Underlying funds with longer weighted average maturities are more sensitive to interest rate changes. A period of rising interest rates may negatively affect the performance of underlying fixed-income funds.
•
Credit Risk – The value of an underlying fund’s fixed-income securities will be affected adversely by any erosion in the ability of the issuers of these securities to make interest and principal payments as they become due. Changes in the credit rating of a fixed-income security held by an underlying fund could have a similar effect.
•
Foreign Securities Risk – Some of the underlying funds invest in foreign securities, which are generally riskier than U.S. securities. Securities of foreign issuers may be less liquid, more volatile and harder to value than U.S. securities. Fluctuations in currency exchange rates also may affect an underlying fund’s share price. Investing in securities of companies located in emerging market countries is generally riskier than investing in securities of companies located in developed foreign countries.
•
Emerging Market Risk - Investing in securities of companies located in emerging market countries generally is also riskier than investing in securities of companies located in foreign developed countries. Emerging market countries may have unstable governments and/or economies that are subject to sudden change. These changes may be magnified by the countries’ emergent financial markets, resulting in significant volatility to investments in these countries.
•
Real Estate Investing - An investment in the fund may be subject to many of the same risks as a direct investment in real estate. These risks include changes in economic conditions, interest rates, property values, property tax increases, overbuilding and increased competition, environmental contamination, zoning and natural disasters. This is due to the fact that the value of the fund’s investments may be affected by the value of the real estate owned by the companies in which it invests.
•
Tobacco Exclusion – The underlying funds do not invest in securities issued by companies assigned the Global Industry Classification Standard (GICS) or the Bloomberg Industry Classification Standard (BICS) for the tobacco industry. This exclusion may cause an underlying fund to forego profitable investment opportunities.
•
Market Risk – The value of the fund’s shares will go up and down based on the performance of the underlying funds in which it invests. The value of the underlying funds’ shares will, in turn, fluctuate based on the performance of the securities they own and other factors generally affecting the securities market.
•
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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
Highest Performance Quarter (2Q 2009): 14.89% Lowest Performance Quarter (4Q 2008): -19.49%
As of June 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 8.47%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2016
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 Asset Allocation Portfolio | ONE CHOICE 2045 PORTFOLIO | S&P Target Date To 2045 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 S&P Target Date To 2045 Index3 (reflects no deduction for fees, expenses or taxes) [46]
1 Year rr_AverageAnnualReturnYear01 9.14% [46]
5 Years rr_AverageAnnualReturnYear05 9.55% [46]
American Century Asset Allocation Portfolio | ONE CHOICE 2045 PORTFOLIO | S&P Target Date 2045 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 S&P Target Date 2045 Index (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 9.54%
5 Years rr_AverageAnnualReturnYear05 10.31%
Since Inception rr_AverageAnnualReturnSinceInception 4.89%
American Century Asset Allocation Portfolio | ONE CHOICE 2045 PORTFOLIO | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
AROIX
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 0.89%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [47]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [47]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.92%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [48]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.89%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 91
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 291
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 507
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,129
Annual Return 2007 rr_AnnualReturn2007 10.74%
Annual Return 2008 rr_AnnualReturn2008 (33.64%)
Annual Return 2009 rr_AnnualReturn2009 26.36%
Annual Return 2010 rr_AnnualReturn2010 15.50%
Annual Return 2011 rr_AnnualReturn2011 (0.78%)
Annual Return 2012 rr_AnnualReturn2012 15.00%
Annual Return 2013 rr_AnnualReturn2013 21.08%
Annual Return 2014 rr_AnnualReturn2014 8.40%
Annual Return 2015 rr_AnnualReturn2015 (1.38%)
Annual Return 2016 rr_AnnualReturn2016 7.15%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 8.47%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 14.89%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (19.49%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.15%
5 Years rr_AverageAnnualReturnYear05 9.78%
Since Inception rr_AverageAnnualReturnSinceInception 5.43%
American Century Asset Allocation Portfolio | ONE CHOICE 2045 PORTFOLIO | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 6.14%
5 Years rr_AverageAnnualReturnYear05 8.54%
Since Inception rr_AverageAnnualReturnSinceInception 4.52%
American Century Asset Allocation Portfolio | ONE CHOICE 2045 PORTFOLIO | 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 4.84%
5 Years rr_AverageAnnualReturnYear05 7.57%
Since Inception rr_AverageAnnualReturnSinceInception 4.13%
American Century Asset Allocation Portfolio | ONE CHOICE 2045 PORTFOLIO | INSTITUTIONAL CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
AOOIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [49]
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [49]
Maximum Account Fee rr_MaximumAccountFee none [49]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [47]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [47]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.73%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [48]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.69%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 71
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 230
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 403
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 903
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.43%
5 Years rr_AverageAnnualReturnYear05 10.01%
Since Inception rr_AverageAnnualReturnSinceInception 5.64%
American Century Asset Allocation Portfolio | ONE CHOICE 2045 PORTFOLIO | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
AROAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [50]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.89%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [47]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [47]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.17%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [48]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.14%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 685
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 923
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,180
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,911
Label rr_AverageAnnualReturnLabel A Class1 Return Before Taxes [51]
1 Year rr_AverageAnnualReturnYear01 0.84% [51]
5 Years rr_AverageAnnualReturnYear05 8.22% [51]
Since Inception rr_AverageAnnualReturnSinceInception 4.54% [51]
American Century Asset Allocation Portfolio | ONE CHOICE 2045 PORTFOLIO | C Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
AROCX
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 0.89%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [47]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [47]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.92%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [48]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.89%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 192
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 601
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,035
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,238
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.14%
5 Years rr_AverageAnnualReturnYear05 8.69%
Since Inception rr_AverageAnnualReturnSinceInception 4.38% [52]
American Century Asset Allocation Portfolio | ONE CHOICE 2045 PORTFOLIO | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARORX
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 0.89%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [47]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [47]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.42%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [48]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.39%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 142
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 447
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 774
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,698
Label rr_AverageAnnualReturnLabel R Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.68%
5 Years rr_AverageAnnualReturnYear05 9.24%
Since Inception rr_AverageAnnualReturnSinceInception 4.91%
American Century Asset Allocation Portfolio | ONE CHOICE 2045 PORTFOLIO | R6 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARDOX
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 0.60%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [47]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03% [47]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.63%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.09%) [48]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.54%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 55
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 193
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 343
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 778
American Century Asset Allocation Portfolio | ONE CHOICE 2050 PORTFOLIO  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading One Choice® 2050 Portfolio
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks the highest total return consistent with its asset mix.
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 and hold shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 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 64 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 Expenses3 (expenses that you pay each year as a percentage of the value of your investment) [53]
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination July 30, 2018
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Because the fund buys and sells shares of other American Century mutual funds (the underlying funds) directly from the issuers, the fund is not expected to incur transaction costs directly. However, as a shareholder in the underlying funds, the fund indirectly pays transaction costs, such as commissions, when the underlying funds buy and sell securities (or “turn over” their portfolios). 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 7% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 7.00%
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 $50,000 in American Century Investments funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
Acquired Fund Fees and Expenses, Based on Estimates [Text] rr_AcquiredFundFeesAndExpensesBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
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. You may be required to pay brokerage commissions on your purchases of Investor or I Class shares of the fund, which are not reflected in the example.  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
One Choice 2050 Portfolio is a “fund of funds,” meaning that it seeks to achieve its objective by investing in other American Century mutual funds (the underlying funds) that represent a variety of asset classes and investment styles. The underlying stock funds draw on growth, value and quantitative investment techniques and diversify investments among small, medium and large U.S. and foreign companies. The underlying bond funds invest in fixed-income securities that vary by issuer type (corporate and government), credit quality (investment-grade and high-yield or “junk bonds”) and geographic exposure (domestic and international). The following table indicates the fund’s neutral mix; that is, how the fund’s investments generally will be allocated among the major asset classes. The table also shows the neutral weightings of each underlying fund currently being used within the various asset classes. This information is as of December 1, 2016, except the allocation to NT High Income Fund was changed from an equivalent allocation to High-Yield Fund on May 19, 2017.
Equity Securities (Stock Funds)
81.40
%
NT Core Equity Plus Fund
4.50
%
NT Disciplined Growth Fund
3.33
%
NT Emerging Markets Fund
5.75
%
NT Equity Growth Fund
10.25
%
NT Global Real Estate Fund
2.65
%
NT Growth Fund
10.75
%
NT Heritage Fund
6.59
%
NT International Growth Fund
6.68
%
NT International Small-Mid Cap Fund
2.06
%
NT International Value Fund
5.24
%
NT Large Company Value Fund
13.41
%
NT Mid Cap Value Fund
6.94
%
NT Small Company Fund
3.25
%
 
Fixed-Income Securities (Bond Funds)
18.60
%
 
Global Bond Fund
3.53
%
 
NT High Income Fund
1.85
%
 
Inflation-Adjusted Bond Fund
3.70
%
 
NT Diversified Bond Fund
9.52
%
 
 
 
 
Cash Equivalents (Money Market Fund)
0.00
%
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
The target date in the fund name (2050) refers to the approximate year an investor plans to retire and likely would stop making new investments in the fund. The fund assumes a retirement age of 65 and may not be appropriate for an investor who plans to retire at or near the target date, but at an age well before or after 65. As the target date approaches, the fund’s neutral mix will become more conservative by decreasing the allocation to stocks and increasing the allocation to bonds and cash. By the time the fund reaches its target date, the neutral mix will become fixed and match that of One Choice In Retirement Portfolio, which is currently 45% stock funds, 45% bond funds and 10% money market funds. The fund is designed for investors who plan to withdraw the value of their account gradually after retirement. The following chart shows how the neutral mix is expected to change over time according to a predetermined glide path.
glidepathimagea31.gif
The portfolio managers regularly review the fund’s allocations to determine whether rebalancing is appropriate. In order to better balance risks in changing market environments, the portfolio managers may make modest deviations from the neutral mix in light of prevailing market conditions. We reserve the right to modify the neutral mix and underlying funds from time to time should circumstances warrant a change.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Allocation Risk – The fund’s performance and risks depend in part on the managers’ skill in determining the fund’s neutral mix, selecting and weighting the underlying funds, and implementing any deviations from the neutral mix. The managers’ evaluations and assumptions regarding asset classes or underlying funds may differ from actual market conditions.
•
Fund of Funds Risks – The fund’s performance and risks reflect the performance and risks of the underlying American Century Investments funds in which it invests. The fund’s investment in other American Century Investments funds may create a conflict of interest for the fund’s advisor.
•
“Growth” and “Value” Style Risks – The underlying funds represent a mix of investment styles, each of which has risks associated with it. Growth stocks can be volatile and may lack dividends that can cushion share prices during market declines. Value stocks may continue to be undervalued by the market for long periods of time.
•
Small- and Mid-Cap Stock Risks – Stocks of smaller companies may be more volatile than larger-company stocks. Smaller companies may have limited financial resources, product lines and markets, and their securities may trade less frequently and in more limited volumes than the securities of larger companies, which could lead to higher transaction costs. To the extent an underlying fund invests in these companies, it may take on more risk.
•
Interest Rate Risk – Generally, when interest rates rise, the value of an underlying fund’s fixed-income securities will decline. The opposite is true when interest rates decline. Underlying funds with longer weighted average maturities are more sensitive to interest rate changes. A period of rising interest rates may negatively affect the performance of underlying fixed-income funds.
•
Credit Risk – The value of an underlying fund’s fixed-income securities will be affected adversely by any erosion in the ability of the issuers of these securities to make interest and principal payments as they become due. Changes in the credit rating of a fixed-income security held by an underlying fund could have a similar effect.
•
Foreign Securities Risk – Some of the underlying funds invest in foreign securities, which are generally riskier than U.S. securities. Securities of foreign issuers may be less liquid, more volatile and harder to value than U.S. securities. Fluctuations in currency exchange rates also may affect an underlying fund’s share price. Investing in securities of companies located in emerging market countries is generally riskier than investing in securities of companies located in developed foreign countries.
•
Emerging Market Risk - Investing in securities of companies located in emerging market countries generally is also riskier than investing in securities of companies located in foreign developed countries. Emerging market countries may have unstable governments and/or economies that are subject to sudden change. These changes may be magnified by the countries’ emergent financial markets, resulting in significant volatility to investments in these countries.
•
Real Estate Investing - An investment in the fund may be subject to many of the same risks as a direct investment in real estate. These risks include changes in economic conditions, interest rates, property values, property tax increases, overbuilding and increased competition, environmental contamination, zoning and natural disasters. This is due to the fact that the value of the fund’s investments may be affected by the value of the real estate owned by the companies in which it invests.
•
Tobacco Exclusion – The underlying funds do not invest in securities issued by companies assigned the Global Industry Classification Standard (GICS) or the Bloomberg Industry Classification Standard (BICS) for the tobacco industry. This exclusion may cause an underlying fund to forego profitable investment opportunities.
•
Market Risk – The value of the fund’s shares will go up and down based on the performance of the underlying funds in which it invests. The value of the underlying funds’ shares will, in turn, fluctuate based on the performance of the securities they own and other factors generally affecting the securities market.
•
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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
Highest Performance Quarter (2Q 2009): 15.07% Lowest Performance Quarter (3Q 2011): -14.04%
As of June 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 8.86%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2016
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 Asset Allocation Portfolio | ONE CHOICE 2050 PORTFOLIO | S&P Target Date To 2050 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 S&P Target Date To 2050 Index (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 9.43%
5 Years rr_AverageAnnualReturnYear05 9.98%
Since Inception rr_AverageAnnualReturnSinceInception 4.99%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2050 PORTFOLIO | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARFVX
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 0.92%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [54]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [54]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.96%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [55]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.92%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 94
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 302
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 528
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,174
Annual Return 2009 rr_AnnualReturn2009 26.66%
Annual Return 2010 rr_AnnualReturn2010 15.70%
Annual Return 2011 rr_AnnualReturn2011 (0.96%)
Annual Return 2012 rr_AnnualReturn2012 15.39%
Annual Return 2013 rr_AnnualReturn2013 21.58%
Annual Return 2014 rr_AnnualReturn2014 8.60%
Annual Return 2015 rr_AnnualReturn2015 (1.59%)
Annual Return 2016 rr_AnnualReturn2016 7.40%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 8.86%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 15.07%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (14.04%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.40%
5 Years rr_AverageAnnualReturnYear05 9.98%
Since Inception rr_AverageAnnualReturnSinceInception 5.36%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2050 PORTFOLIO | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 6.45%
5 Years rr_AverageAnnualReturnYear05 8.86%
Since Inception rr_AverageAnnualReturnSinceInception 4.59%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2050 PORTFOLIO | 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 4.98%
5 Years rr_AverageAnnualReturnYear05 7.76%
Since Inception rr_AverageAnnualReturnSinceInception 4.12%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2050 PORTFOLIO | INSTITUTIONAL CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARFSX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [56]
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [56]
Maximum Account Fee rr_MaximumAccountFee none [56]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.72%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [54]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [54]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.76%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [55]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.72%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 74
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 239
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 419
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 939
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.60%
5 Years rr_AverageAnnualReturnYear05 10.19%
Since Inception rr_AverageAnnualReturnSinceInception 5.58%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2050 PORTFOLIO | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARFMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [57]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.92%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [54]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [54]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.21%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [55]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.17%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 688
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 934
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,199
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,953
Label rr_AverageAnnualReturnLabel A Class1 Return Before Taxes [58]
1 Year rr_AverageAnnualReturnYear01 0.96% [58]
5 Years rr_AverageAnnualReturnYear05 8.43% [58]
Since Inception rr_AverageAnnualReturnSinceInception 4.37% [58]
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008 [58]
American Century Asset Allocation Portfolio | ONE CHOICE 2050 PORTFOLIO | C Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARFDX
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 0.92%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [54]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [54]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.96%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [55]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.92%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 195
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 612
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,054
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,279
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.30%
5 Years rr_AverageAnnualReturnYear05 8.90%
Since Inception rr_AverageAnnualReturnSinceInception 4.32% [59]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010
American Century Asset Allocation Portfolio | ONE CHOICE 2050 PORTFOLIO | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARFWX
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 0.92%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [54]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [54]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.46%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [55]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.42%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 145
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 459
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 794
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,742
Label rr_AverageAnnualReturnLabel R Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.85%
5 Years rr_AverageAnnualReturnYear05 9.42%
Since Inception rr_AverageAnnualReturnSinceInception 4.84%
Inception Date rr_AverageAnnualReturnInceptionDate May 30, 2008
American Century Asset Allocation Portfolio | ONE CHOICE 2050 PORTFOLIO | R6 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARFEX
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 0.62%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [54]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [54]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.66%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.09%) [55]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.57%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 58
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 203
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 359
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 814
American Century Asset Allocation Portfolio | ONE CHOICE 2055 PORTFOLIO  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading One Choice® 2055 Portfolio
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks the highest total return consistent with its asset mix.
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 and hold shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 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 64 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 Expenses3 (expenses that you pay each year as a percentage of the value of your investment) [60]
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination July 30, 2018
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Because the fund buys and sells shares of other American Century mutual funds (the underlying funds) directly from the issuers, the fund is not expected to incur transaction costs directly. However, as a shareholder in the underlying funds, the fund indirectly pays transaction costs, such as commissions, when the underlying funds buy and sell securities (or “turn over” their portfolios). 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 6% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 6.00%
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 $50,000 in American Century Investments funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
Acquired Fund Fees and Expenses, Based on Estimates [Text] rr_AcquiredFundFeesAndExpensesBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
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. You may be required to pay brokerage commissions on your purchases of Investor or I Class shares of the fund, which are not reflected in the example.  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
One Choice 2055 Portfolio is a “fund of funds,” meaning that it seeks to achieve its objective by investing in other American Century mutual funds (the underlying funds) that represent a variety of asset classes and investment styles. The underlying stock funds draw on growth, value and quantitative investment techniques and diversify investments among small, medium and large U.S. and foreign companies. The underlying bond funds invest in fixed-income securities that vary by issuer type (corporate and government), credit quality (investment-grade and high-yield or “junk bonds”) and geographic exposure (domestic and international). The following table indicates the fund’s neutral mix; that is, how the fund’s investments generally will be allocated among the major asset classes. The table also shows the neutral weightings of each underlying fund currently being used within the various asset classes. This information is as of December 1, 2016, except the allocation to NT High Income Fund was changed from an equivalent allocation to High-Yield Fund on May 19, 2017.
Equity Securities (Stock Funds)
83.90
%
NT Core Equity Plus Fund
4.50
%
NT Disciplined Growth Fund
3.45
%
NT Emerging Markets Fund
6.25
%
NT Equity Growth Fund
10.50
%
NT Global Real Estate Fund
2.90
%
NT Growth Fund
10.80
%
NT Heritage Fund
6.78
%
NT International Growth Fund
6.30
%
NT International Small-Mid Cap Fund
2.38
%
NT International Value Fund
5.43
%
NT Large Company Value Fund
13.98
%
NT Mid Cap Value Fund
6.88
%
NT Small Company Fund
3.75
%
 
Fixed-Income Securities (Bond Funds)
16.10
%
 
Global Bond Fund
3.15
%
 
NT High Income Fund
1.60
%
 
Inflation-Adjusted Bond Fund
3.20
%
 
NT Diversified Bond Fund
8.15
%
 
 
 
 
Cash Equivalents (Money Market Fund)
0.00
%
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
The target date in the fund name (2055) refers to the approximate year an investor plans to retire and likely would stop making new investments in the fund. The fund assumes a retirement age of 65 and may not be appropriate for an investor who plans to retire at or near the target date, but at an age well before or after 65. As the target date approaches, the fund’s neutral mix will become more conservative by decreasing the allocation to stocks and increasing the allocation to bonds and cash. By the time the fund reaches its target date, the neutral mix will become fixed and match that of One Choice In Retirement Portfolio, which is currently 45% stock funds, 45% bond funds and 10% money market funds. The fund is designed for investors who plan to withdraw the value of their account gradually after retirement. The following chart shows how the neutral mix is expected to change over time according to a predetermined glide path.
glidepathimagea31.gif
The portfolio managers regularly review the fund’s allocations to determine whether rebalancing is appropriate. In order to better balance risks in changing market environments, the portfolio managers may make modest deviations from the neutral mix in light of prevailing market conditions. We reserve the right to modify the neutral mix and underlying funds from time to time should circumstances warrant a change.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Allocation Risk – The fund’s performance and risks depend in part on the managers’ skill in determining the fund’s neutral mix, selecting and weighting the underlying funds, and implementing any deviations from the neutral mix. The managers’ evaluations and assumptions regarding asset classes or underlying funds may differ from actual market conditions.
•
Fund of Funds Risks – The fund’s performance and risks reflect the performance and risks of the underlying American Century Investments funds in which it invests. The fund’s investment in other American Century Investments funds may create a conflict of interest for the fund’s advisor.
•
“Growth” and “Value” Style Risks – The underlying funds represent a mix of investment styles, each of which has risks associated with it. Growth stocks can be volatile and may lack dividends that can cushion share prices during market declines. Value stocks may continue to be undervalued by the market for long periods of time.
•
Small- and Mid-Cap Stock Risks – Stocks of smaller companies may be more volatile than larger-company stocks. Smaller companies may have limited financial resources, product lines and markets, and their securities may trade less frequently and in more limited volumes than the securities of larger companies, which could lead to higher transaction costs. To the extent an underlying fund invests in these companies, it may take on more risk.
•
Interest Rate Risk – Generally, when interest rates rise, the value of an underlying fund’s fixed-income securities will decline. The opposite is true when interest rates decline. Underlying funds with longer weighted average maturities are more sensitive to interest rate changes. A period of rising interest rates may negatively affect the performance of underlying fixed-income funds.
•
Credit Risk – The value of an underlying fund’s fixed-income securities will be affected adversely by any erosion in the ability of the issuers of these securities to make interest and principal payments as they become due. Changes in the credit rating of a fixed-income security held by an underlying fund could have a similar effect.
•
Foreign Securities Risk – Some of the underlying funds invest in foreign securities, which are generally riskier than U.S. securities. Securities of foreign issuers may be less liquid, more volatile and harder to value than U.S. securities. Fluctuations in currency exchange rates also may affect an underlying fund’s share price. Investing in securities of companies located in emerging market countries is generally riskier than investing in securities of companies located in developed foreign countries.
•
Emerging Market Risk - Investing in securities of companies located in emerging market countries generally is also riskier than investing in securities of companies located in foreign developed countries. Emerging market countries may have unstable governments and/or economies that are subject to sudden change. These changes may be magnified by the countries’ emergent financial markets, resulting in significant volatility to investments in these countries.
•
Real Estate Investing - An investment in the fund may be subject to many of the same risks as a direct investment in real estate. These risks include changes in economic conditions, interest rates, property values, property tax increases, overbuilding and increased competition, environmental contamination, zoning and natural disasters. This is due to the fact that the value of the fund’s investments may be affected by the value of the real estate owned by the companies in which it invests.
•
Tobacco Exclusion – The underlying funds do not invest in securities issued by companies assigned the Global Industry Classification Standard (GICS) or the Bloomberg Industry Classification Standard (BICS) for the tobacco industry. This exclusion may cause an underlying fund to forego profitable investment opportunities.
•
Market Risk – The value of the fund’s shares will go up and down based on the performance of the underlying funds in which it invests. The value of the underlying funds’ shares will, in turn, fluctuate based on the performance of the securities they own and other factors generally affecting the securities market.
•
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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
Highest Performance Quarter (1Q 2012): 11.54% Lowest Performance Quarter (3Q 2015): -7.42%
As of June 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 9.10%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2016
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 Asset Allocation Portfolio | ONE CHOICE 2055 PORTFOLIO | S&P Target Date To 2055 Plus 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 S&P Target Date To 2055+ Index (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 9.63%
5 Years rr_AverageAnnualReturnYear05 10.32%
Since Inception rr_AverageAnnualReturnSinceInception 7.39%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 31, 2011
American Century Asset Allocation Portfolio | ONE CHOICE 2055 PORTFOLIO | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
AREVX
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 0.93%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [61]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [61]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.97%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [62]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.92%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 94
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 305
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 532
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,185
Annual Return 2012 rr_AnnualReturn2012 15.51%
Annual Return 2013 rr_AnnualReturn2013 22.21%
Annual Return 2014 rr_AnnualReturn2014 8.80%
Annual Return 2015 rr_AnnualReturn2015 (1.64%)
Annual Return 2016 rr_AnnualReturn2016 7.60%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 9.10%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2012
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 11.54%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2015
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (7.42%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.60%
5 Years rr_AverageAnnualReturnYear05 10.19%
Since Inception rr_AverageAnnualReturnSinceInception 7.75%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 31, 2011
American Century Asset Allocation Portfolio | ONE CHOICE 2055 PORTFOLIO | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 6.78%
5 Years rr_AverageAnnualReturnYear05 9.27%
Since Inception rr_AverageAnnualReturnSinceInception 6.92%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 31, 2011
American Century Asset Allocation Portfolio | ONE CHOICE 2055 PORTFOLIO | 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 4.97%
5 Years rr_AverageAnnualReturnYear05 7.94%
Since Inception rr_AverageAnnualReturnSinceInception 5.99%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 31, 2011
American Century Asset Allocation Portfolio | ONE CHOICE 2055 PORTFOLIO | INSTITUTIONAL CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARENX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [63]
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [63]
Maximum Account Fee rr_MaximumAccountFee none [63]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.73%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [61]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [61]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.77%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [62]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.72%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 74
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 241
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 423
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 950
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.82%
5 Years rr_AverageAnnualReturnYear05 10.41%
Since Inception rr_AverageAnnualReturnSinceInception 7.97%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 31, 2011
American Century Asset Allocation Portfolio | ONE CHOICE 2055 PORTFOLIO | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
AREMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [64]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.93%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [61]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [61]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.22%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [62]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.17%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 688
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 936
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,203
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,963
Label rr_AverageAnnualReturnLabel A Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.07%
5 Years rr_AverageAnnualReturnYear05 8.63%
Since Inception rr_AverageAnnualReturnSinceInception 6.37%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 31, 2011
American Century Asset Allocation Portfolio | ONE CHOICE 2055 PORTFOLIO | C CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
AREFX
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 0.93%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [61]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [61]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.97%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [62]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.92%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 195
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 614
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,059
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,289
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.44%
5 Years rr_AverageAnnualReturnYear05 9.09%
Since Inception rr_AverageAnnualReturnSinceInception 6.67%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 31, 2011
American Century Asset Allocation Portfolio | ONE CHOICE 2055 PORTFOLIO | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
AREOX
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 0.93%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [61]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [61]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.47%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [62]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.42%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 145
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 461
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 799
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,752
Label rr_AverageAnnualReturnLabel R Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.06%
5 Years rr_AverageAnnualReturnYear05 9.65%
Since Inception rr_AverageAnnualReturnSinceInception 7.22%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 31, 2011
American Century Asset Allocation Portfolio | ONE CHOICE 2055 PORTFOLIO | R6 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
AREUX
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 0.63%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [61]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [61]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.67%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.10%) [62]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.57%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 58
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 205
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 364
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 826
American Century Asset Allocation Portfolio | ONE CHOICE 2060 PORTFOLIO  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading One Choice® 2060 Portfolio
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks the highest total return consistent with its asset mix.
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 and hold shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 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 64 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 Expenses3 (expenses that you pay each year as a percentage of the value of your investment) [65]
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination July 30, 2018
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
Because the fund buys and sells shares of other American Century mutual funds (the underlying funds) directly from the issuers, the fund is not expected to incur transaction costs directly. However, as a shareholder in the underlying funds, the fund indirectly pays transaction costs, such as commissions, when the underlying funds buy and sell securities (or “turn over” their portfolios). 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 period from September 30, 2015 (fund inception) to July 31, 2016, the fund’s portfolio turnover rate was 13% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 13.00%
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 $50,000 in American Century Investments funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
Acquired Fund Fees and Expenses, Based on Estimates [Text] rr_AcquiredFundFeesAndExpensesBasedOnEstimates Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
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. You may be required to pay brokerage commissions on your purchases of Investor or I Class shares of the fund, which are not reflected in the example.  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
One Choice 2060 Portfolio is a “fund of funds,” meaning that it seeks to achieve its objective by investing in other American Century mutual funds (the underlying funds) that represent a variety of asset classes and investment styles. The underlying stock funds draw on growth, value and quantitative investment techniques and diversify investments among small, medium and large U.S. and foreign companies. The underlying bond funds invest in fixed-income securities that vary by issuer type (corporate and government), credit quality (investment-grade and high-yield or “junk bonds”) and geographic exposure (domestic and international). The following table indicates the fund’s neutral mix; that is, how the fund’s investments generally will be allocated among the major asset classes. The table also shows the neutral weightings of each underlying fund currently being used within the various asset classes. This information is as of December 1, 2016, except the allocation to NT High Income Fund was changed from an equivalent allocation to High-Yield Fund on May 19, 2017.
Equity Securities (Stock Funds)
85.00
%
NT Core Equity Plus Fund
4.50
%
NT Disciplined Growth Fund
3.50
%
NT Emerging Markets Fund
6.50
%
NT Equity Growth Fund
10.75
%
NT Global Real Estate Fund
3.00
%
NT Growth Fund
11.00
%
NT Heritage Fund
6.75
%
NT International Growth Fund
6.00
%
NT International Small-Mid Cap Fund
2.50
%
NT International Value Fund
5.50
%
NT Large Company Value Fund
14.25
%
NT Mid Cap Value Fund
6.75
%
NT Small Company Fund
4.00
%
 
Fixed-Income Securities (Bond Funds)
15.00
%
 
Global Bond Fund
3.00
%
 
NT High Income Fund
1.50
%
 
Inflation-Adjusted Bond Fund
3.00
%
 
NT Diversified Bond Fund
7.50
%
 
 
 
 
Cash Equivalents (Money Market Fund)
0.00
%
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
The target date in the fund name (2060) refers to the approximate year an investor plans to retire and likely would stop making new investments in the fund. The fund assumes a retirement age of 65 and may not be appropriate for an investor who plans to retire at or near the target date, but at an age well before or after 65. As the target date approaches, the fund’s neutral mix will become more conservative by decreasing the allocation to stocks and increasing the allocation to bonds and cash. By the time the fund reaches its target date, the neutral mix will become fixed and match that of One Choice In Retirement Portfolio, which is currently 45% stock funds, 45% bond funds and 10% money market funds. The fund is designed for investors who plan to withdraw the value of their account gradually after retirement. The following chart shows how the neutral mix is expected to change over time according to a predetermined glide path.
glidepathimagea31.gif
The portfolio managers regularly review the fund’s allocations to determine whether rebalancing is appropriate. In order to better balance risks in changing market environments, the portfolio managers may make modest deviations from the neutral mix in light of prevailing market conditions. We reserve the right to modify the neutral mix and underlying funds from time to time should circumstances warrant a change.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Allocation Risk – The fund’s performance and risks depend in part on the managers’ skill in determining the fund’s neutral mix, selecting and weighting the underlying funds, and implementing any deviations from the neutral mix. The managers’ evaluations and assumptions regarding asset classes or underlying funds may differ from actual market conditions.
•
Fund of Funds Risks – The fund’s performance and risks reflect the performance and risks of the underlying American Century Investments funds in which it invests. The fund’s investment in other American Century Investments funds may create a conflict of interest for the fund’s advisor.
•
“Growth” and “Value” Style Risks – The underlying funds represent a mix of investment styles, each of which has risks associated with it. Growth stocks can be volatile and may lack dividends that can cushion share prices during market declines. Value stocks may continue to be undervalued by the market for long periods of time.
•
Small- and Mid-Cap Stock Risks – Stocks of smaller companies may be more volatile than larger-company stocks. Smaller companies may have limited financial resources, product lines and markets, and their securities may trade less frequently and in more limited volumes than the securities of larger companies, which could lead to higher transaction costs. To the extent an underlying fund invests in these companies, it may take on more risk.
•
Interest Rate Risk – Generally, when interest rates rise, the value of an underlying fund’s fixed-income securities will decline. The opposite is true when interest rates decline. Underlying funds with longer weighted average maturities are more sensitive to interest rate changes. A period of rising interest rates may negatively affect the performance of underlying fixed-income funds.
•
Credit Risk – The value of an underlying fund’s fixed-income securities will be affected adversely by any erosion in the ability of the issuers of these securities to make interest and principal payments as they become due. Changes in the credit rating of a fixed-income security held by an underlying fund could have a similar effect.
•
Foreign Securities Risk – Some of the underlying funds invest in foreign securities, which are generally riskier than U.S. securities. Securities of foreign issuers may be less liquid, more volatile and harder to value than U.S. securities. Fluctuations in currency exchange rates also may affect an underlying fund’s share price. Investing in securities of companies located in emerging market countries is generally riskier than investing in securities of companies located in developed foreign countries.
•
Emerging Market Risk - Investing in securities of companies located in emerging market countries generally is also riskier than investing in securities of companies located in foreign developed countries. Emerging market countries may have unstable governments and/or economies that are subject to sudden change. These changes may be magnified by the countries’ emergent financial markets, resulting in significant volatility to investments in these countries.
•
Real Estate Investing - An investment in the fund may be subject to many of the same risks as a direct investment in real estate. These risks include changes in economic conditions, interest rates, property values, property tax increases, overbuilding and increased competition, environmental contamination, zoning and natural disasters. This is due to the fact that the value of the fund’s investments may be affected by the value of the real estate owned by the companies in which it invests.
•
Tobacco Exclusion – The underlying funds do not invest in securities issued by companies assigned the Global Industry Classification Standard (GICS) or the Bloomberg Industry Classification Standard (BICS) for the tobacco industry. This exclusion may cause an underlying fund to forego profitable investment opportunities.
•
Market Risk – The value of the fund’s shares will go up and down based on the performance of the underlying funds in which it invests. The value of the underlying funds’ shares will, in turn, fluctuate based on the performance of the securities they own and other factors generally affecting the securities market.
•
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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, including losses near to, at, or after retirement. There is no guarantee that the fund will provide adequate income at or through your retirement.
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
Highest Performance Quarter (3Q 2016): 9.30% Lowest Performance Quarter (1Q 2016): 0.49%
As of June 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 9.13%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2016
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 Asset Allocation Portfolio | ONE CHOICE 2060 PORTFOLIO | S&P Target Date To 2055 Plus 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 S&P Target Date To 2055+ Index (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 9.63%
Since Inception rr_AverageAnnualReturnSinceInception 11.27%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 30, 2015
American Century Asset Allocation Portfolio | ONE CHOICE 2060 PORTFOLIO | INVESTOR CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARGVX
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 0.93%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [66]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [66]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.97%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [67]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.92%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 94
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 305
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 532
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,185
Annual Return 2016 rr_AnnualReturn2016 7.71%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 9.13%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 9.30%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.49%
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.71%
Since Inception rr_AverageAnnualReturnSinceInception 9.34%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 30, 2015
American Century Asset Allocation Portfolio | ONE CHOICE 2060 PORTFOLIO | INVESTOR CLASS | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 7.42%
Since Inception rr_AverageAnnualReturnSinceInception 8.80%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 30, 2015
American Century Asset Allocation Portfolio | ONE CHOICE 2060 PORTFOLIO | 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 4.54%
Since Inception rr_AverageAnnualReturnSinceInception 7.02%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 30, 2015
American Century Asset Allocation Portfolio | ONE CHOICE 2060 PORTFOLIO | INSTITUTIONAL CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARGNX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [68]
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [68]
Maximum Account Fee rr_MaximumAccountFee none [68]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.73%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [66]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [66]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.77%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [67]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.72%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 74
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 241
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 423
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 950
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.92%
Since Inception rr_AverageAnnualReturnSinceInception 9.55%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 30, 2015
American Century Asset Allocation Portfolio | ONE CHOICE 2060 PORTFOLIO | A CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARGMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [69]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.93%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [66]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [66]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.22%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [67]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.17%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 688
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 936
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,203
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,963
Label rr_AverageAnnualReturnLabel A Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.23%
Since Inception rr_AverageAnnualReturnSinceInception 4.04%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 30, 2015
American Century Asset Allocation Portfolio | ONE CHOICE 2060 PORTFOLIO | C CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARGHX
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 0.93%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [66]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [66]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.97%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [67]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.92%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 195
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 614
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,059
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,289
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.70%
Since Inception rr_AverageAnnualReturnSinceInception 8.30%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 30, 2015
American Century Asset Allocation Portfolio | ONE CHOICE 2060 PORTFOLIO | R CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARGRX
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 0.93%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [66]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [66]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.47%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [67]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.42%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 145
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 461
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 799
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,752
Label rr_AverageAnnualReturnLabel R Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.17%
Since Inception rr_AverageAnnualReturnSinceInception 8.79%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 30, 2015
American Century Asset Allocation Portfolio | ONE CHOICE 2060 PORTFOLIO | R6 CLASS  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol
ARGDX
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 0.63%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none [66]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04% [66]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.67%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.10%) [67]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.57%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 58
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 205
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 364
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 826
[1] The expense information in the table has been restated to reflect current fees.
[2] Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
[3] The advisor has agreed to waive a portion of the fund’s management fee. The advisor expects this waiver to continue until July 30, 2018 and cannot terminate it prior to such date without the approval of the Board of Directors.
[4] Prior to April 10, 2017, this class was referred to as the Institutional Class.
[5] 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 the purchase.
[6] 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.
[7] Historical performance for C Class prior to its inception 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.
[8] The expense information in the table has been restated to reflect current fees.
[9] Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
[10] The advisor has agreed to waive a portion of the fund’s management fee. The advisor expects this waiver to continue until July 30, 2018 and cannot terminate it prior to such date without the approval of the Board of Directors.
[11] Prior to April 10, 2017, this class was referred to as the Institutional Class.
[12] 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 the purchase.
[13] 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.
[14] Historical performance for C Class prior to its inception 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.
[15] The expense information in the table has been restated to reflect current fees.
[16] Because the S&P Target Date To 2025 Index total return data is first available as of May 31, 2007, returns for the S&P Target Date 2025 Index are also shown to cover the 10-year period.
[17] Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
[18] The advisor has agreed to waive a portion of the fund’s management fee. The advisor expects this waiver to continue until July 30, 2018 and cannot terminate it prior to such date without the approval of the Board of Directors.
[19] Prior to April 10, 2017, this class was referred to as the Institutional Class.
[20] 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 the purchase.
[21] 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.
[22] Historical performance for C Class prior to its inception 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.
[23] The expense information in the table has been restated to reflect current fees.
[24] Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
[25] The advisor has agreed to waive a portion of the fund’s management fee. The advisor expects this waiver to continue until July 30, 2018 and cannot terminate it prior to such date without the approval of the Board of Directors.
[26] Prior to April 10, 2017, this class was referred to as the Institutional Class.
[27] 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 the purchase.
[28] 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.
[29] Historical performance for C Class prior to its inception 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.
[30] The expense information in the table has been restated to reflect current fees.
[31] Because the S&P Target Date To 2035 Index total return data is first available as of May 31, 2007, returns for the S&P Target Date 2035 Index are also shown to cover the 10-year period.
[32] Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
[33] The advisor has agreed to waive a portion of the fund’s management fee. The advisor expects this waiver to continue until July 30, 2018 and cannot terminate it prior to such date without the approval of the Board of Directors.
[34] Prior to April 10, 2017, this class was referred to as the Institutional Class.
[35] 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 the purchase.
[36] 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.
[37] Historical performance for C Class prior to its inception 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.
[38] The expense information in the table has been restated to reflect current fees.
[39] Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
[40] The advisor has agreed to waive a portion of the fund’s management fee. The advisor expects this waiver to continue until July 30, 2018 and cannot terminate it prior to such date without the approval of the Board of Directors.
[41] Prior to April 10, 2017, this class was referred to as the Institutional Class.
[42] 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 the purchase.
[43] 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.
[44] Historical performance for C Class prior to its inception 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.
[45] The expense information in the table has been restated to reflect current fees.
[46] Because the S&P Target Date To 2045 Index total return data is first available as of May 31, 2007, returns for the S&P Target Date 2045 Index are also shown to cover the 10-year period.
[47] Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
[48] The advisor has agreed to waive a portion of the fund’s management fee. The advisor expects this waiver to continue until July 30, 2018 and cannot terminate it prior to such date without the approval of the Board of Directors.
[49] Prior to April 10, 2017, this class was referred to as the Institutional Class.
[50] 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 the purchase.
[51] 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.
[52] Historical performance for C Class prior to its inception 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.
[53] The expense information in the table has been restated to reflect current fees.
[54] Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
[55] The advisor has agreed to waive a portion of the fund’s management fee. The advisor expects this waiver to continue until July 30, 2018 and cannot terminate it prior to such date without the approval of the Board of Directors.
[56] Prior to April 10, 2017, this class was referred to as the Institutional Class.
[57] 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 the purchase.
[58] 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.
[59] Historical performance for C Class prior to its inception 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.
[60] The expense information in the table has been restated to reflect current fees.
[61] Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
[62] The advisor has agreed to waive a portion of the fund’s management fee. The advisor expects this waiver to continue until July 30, 2018 and cannot terminate it prior to such date without the approval of the Board of Directors.
[63] Prior to April 10, 2017, this class was referred to as the Institutional Class.
[64] 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 the purchase.
[65] The expense information in the table has been restated to reflect current fees.
[66] Other Expenses and Acquired Fund Fees and Expenses are based on estimated amounts for the current fiscal year.
[67] The advisor has agreed to waive a portion of the fund’s management fee. The advisor expects this waiver to continue until July 30, 2018 and cannot terminate it prior to such date without the approval of the Board of Directors.
[68] Prior to April 10, 2017, this class was referred to as the Institutional Class.
[69] 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 the purchase.