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Label Element Value
Prospectus: rr_ProspectusTable  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Aug. 31, 2017
Entity Registrant Name dei_EntityRegistrantName American Century California Tax Free & Municipal Funds
Central Index Key dei_EntityCentralIndexKey 0000717316
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Dec. 29, 2017
Document Effective Date dei_DocumentEffectiveDate Jan. 01, 2018
Prospectus Date rr_ProspectusDate Jan. 01, 2018
American Century California Tax-Free and Municipal Funds | California High-Yield Municipal Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading California High-Yield Municipal Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks high current income that is exempt from federal and California income taxes.
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 A Class sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in Calculation of Sales Charges on page 12 of the fund’s prospectus, Appendix A of the fund’s prospectus and Sales Charges in Appendix B of the statement of additional information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 50% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 50.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for A Class sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in Calculation of Sales Charges on page 12 of the fund’s prospectus, Appendix A of the fund’s prospectus and Sales Charges in Appendix B of the statement of additional information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
The example below is intended to help you compare the costs of investing in the fund with the costs of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods, that you earn a 5% return each year, and that the fund’s operating expenses remain the same. You may be required to pay brokerage commissions on your purchases of Investor, I or Y 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
The fund invests in California municipal and other debt securities with an emphasis on high-yield securities. A high-yield security is one that has been rated below investment-grade, or determined by the investment advisor to be of similar quality. Under normal market conditions, the portfolio managers invest at least 80% of the fund’s net assets in municipal securities with income payments exempt from federal and California income taxes. Cities, counties and other municipalities in California and U.S. territories usually issue these securities for public projects, such as schools, roads, and water and sewer systems. Some of these investments are not necessarily exempt from the federal alternative minimum tax. 
The portfolio managers seek to invest in securities that will result in a high yield for the fund. To accomplish this, the portfolio managers buy securities that are rated below investment-grade, including so-called junk bonds and bonds that are in technical or monetary default. Issuers of these securities often have short financial histories or have questionable credit or have had and may continue to have problems making interest and principal payments. 
The portfolio managers also may buy unrated securities if they determine such securities meet the investment objectives of the fund. 
Although the fund invests primarily for income, it also employs techniques designed to realize capital appreciation. For example, the portfolio managers may select bonds with maturities and coupon rates that position the fund for potential capital appreciation for a variety of reasons, including their view on the direction of future interest-rate movements and the potential for a credit upgrade.
When determining whether to sell a security, the portfolio managers consider, among other things, current and anticipated changes in interest rates, the credit quality of a particular issuer, comparable alternatives, general market conditions and any other factor deemed relevant by the portfolio managers. 
Risk [Heading] rr_RiskHeading Principal Risks 
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Credit Risk – Debt securities, even investment-grade debt securities, are subject to credit risk. Credit risk is the risk that the inability or perceived inability of the issuer to make interest and principal payments will cause the value of the securities to decrease. As a result, the fund’s share price could also decrease. Changes in the credit rating of a debt security held by the fund could have a similar effect. The fund’s investments often have high credit risk, which helps the fund pursue a higher yield than more conservatively managed bond funds.
•
Below Investment-Grade Securities Risk – Issuers of lower rated, high-yield securities are more vulnerable to real or perceived economic changes (such as an economic downturn or a prolonged period of rising interest rates), political changes, or adverse developments specific to the issuer. Adverse economic, political and other developments may be more likely to cause an issuer of low-quality bonds to default on its obligation to pay interest and principal due under its securities. The fund invests a significant part of its assets in securities rated below investment-grade or that are unrated, including bonds that are in technical or monetary default. By definition, the issuers of many of these securities have had and may continue to have problems making interest and principal payments.
•
Interest Rate Risk – When interest rates change, the fund’s share value will be affected. Generally, the value of debt securities and the funds that hold them decline as interest rates rise. Because the fund typically invests in intermediate-term and long-term bonds, the fund’s interest rate risk is generally higher than for funds with shorter-weighted average maturities, such as money market and short-term bond funds. A period of rising interest rates may negatively affect the fund’s performance.
•
California Economic Risk – The fund will be sensitive to events that affect California’s economy. Significant political or economic developments in California will likely impact virtually all municipal securities issued in the state. Because the fund invests principally in California municipal securities, it may have a higher level of risk than funds that invest in a larger universe of securities.
•
Municipal Securities Risk – Because the fund invests principally in municipal securities, it will be sensitive to events that affect municipal markets, including legislative or political changes and the financial condition of the issuers of municipal securities. The fund may have a higher level of risk than funds that invest in a larger universe of securities.
•
Liquidity Risk – The fund may also be subject to liquidity risk. During periods of market turbulence or unusually low trading activity, in order to meet redemptions, it may be necessary for the fund to sell securities at prices that could have an adverse effect on the fund’s share price. Changing regulatory and market conditions, including increases in interest rates and credit spreads may adversely affect the liquidity of the fund’s investments.
•
Tax Risk – Some or all of the fund’s income may be subject to the federal alternative minimum tax. There is no guarantee that all of the fund’s income will remain exempt from federal or state income taxes. Income from municipal bonds held by a fund could be declared taxable because of unfavorable changes in tax laws, adverse interpretations by the Internal Revenue Service or state tax authorities, or non-compliant conduct of a bond issuer. The fund may sell securities that lose their tax-exempt statuses at inopportune times, which may cause tax consequences or a decrease in the fund’s value.
•
Market Risk – The value of securities owned by the fund may go up and down, sometimes rapidly or unpredictably.
•
Principal Loss – At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.
An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency. 
Risk Lose Money [Text] rr_RiskLoseMoney Principal Loss – At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency. 
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Fund Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, including yields, please visit americancentury.com. 
Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown. 
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress americancentury.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Calendar Year Total Returns
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown. 
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest Performance Quarter (3Q 2009): 12.08% Lowest Performance Quarter (4Q 2008): -9.36%
As of September 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 6.64%.
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 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
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 California Tax-Free and Municipal Funds | California High-Yield Municipal Fund | Barclays Municipal Bond Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses and taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays Municipal Bond Index    (reflects no deduction for fees, expenses and taxes)
1 Year rr_AverageAnnualReturnYear01 0.25%
5 Years rr_AverageAnnualReturnYear05 3.28%
10 Years rr_AverageAnnualReturnYear10 4.24%
American Century California Tax-Free and Municipal Funds | California High-Yield Municipal Fund | S&P Municipal Bond California 50% Investment Grade/50% High Yield Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses and taxes)
Label rr_AverageAnnualReturnLabel S&P Municipal Bond California 50% Investment Grade/50% High Yield Index1    (reflects no deduction for fees, expenses and taxes) [1]
1 Year rr_AverageAnnualReturnYear01 1.78% [1]
5 Years rr_AverageAnnualReturnYear05 6.82% [1]
American Century California Tax-Free and Municipal Funds | California High-Yield Municipal Fund | Investor Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol BCHYX
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 0.49%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 51
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 161
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 280
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 629
Annual Return 2007 rr_AnnualReturn2007 (0.33%)
Annual Return 2008 rr_AnnualReturn2008 (13.52%)
Annual Return 2009 rr_AnnualReturn2009 20.43%
Annual Return 2010 rr_AnnualReturn2010 4.29%
Annual Return 2011 rr_AnnualReturn2011 11.02%
Annual Return 2012 rr_AnnualReturn2012 11.09%
Annual Return 2013 rr_AnnualReturn2013 (3.17%)
Annual Return 2014 rr_AnnualReturn2014 13.76%
Annual Return 2015 rr_AnnualReturn2015 5.08%
Annual Return 2016 rr_AnnualReturn2016 0.33%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 6.64%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 12.08%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (9.36%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 0.33%
5 Years rr_AverageAnnualReturnYear05 5.22%
10 Years rr_AverageAnnualReturnYear10 4.48%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 1986
American Century California Tax-Free and Municipal Funds | California High-Yield Municipal Fund | Investor Class | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 0.33%
5 Years rr_AverageAnnualReturnYear05 5.22%
10 Years rr_AverageAnnualReturnYear10 4.48%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 1986
American Century California Tax-Free and Municipal Funds | California High-Yield Municipal Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 1.72%
5 Years rr_AverageAnnualReturnYear05 4.98%
10 Years rr_AverageAnnualReturnYear10 4.46%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 1986
American Century California Tax-Free and Municipal Funds | California High-Yield Municipal Fund | I Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol BCHIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [2]
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [2]
Maximum Account Fee rr_MaximumAccountFee none [2]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.29%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.30%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 31
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 97
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 169
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 381
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 0.63%
5 Years rr_AverageAnnualReturnYear05 5.43%
Since Inception rr_AverageAnnualReturnSinceInception 5.94%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010
American Century California Tax-Free and Municipal Funds | California High-Yield Municipal Fund | Y Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol ACYHX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.26%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.27%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 28
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 87
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 152
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 344
American Century California Tax-Free and Municipal Funds | California High-Yield Municipal Fund | A Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol CAYAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [3]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.49%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.75%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 523
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 679
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 849
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,339
Label rr_AverageAnnualReturnLabel A Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (4.46%)
5 Years rr_AverageAnnualReturnYear05 4.01%
10 Years rr_AverageAnnualReturnYear10 3.74%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 31, 2003
American Century California Tax-Free and Municipal Funds | California High-Yield Municipal Fund | C Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol CAYCX
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 0.49%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.50%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 153
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 475
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 819
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,789
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (0.66%)
5 Years rr_AverageAnnualReturnYear05 4.18%
10 Years rr_AverageAnnualReturnYear10 3.44%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 31, 2003
American Century California Tax-Free and Municipal Funds | California Intermediate-Term Tax-Free Bond Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading California Intermediate-Term Tax-Free Bond FundCalifornia Tax-Free Money Market Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective 
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks safety of principal and high current income that is exempt from federal and California income taxes. 
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 A Class sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in Calculation of Sales Charges on page 12 of the fund’s prospectus, Appendix A of the fund’s prospectus and Sales Charges in Appendix B of the statement of additional information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 52% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 52.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for A Class sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in American Century Investments funds. More information about these and other discounts is available from your financial professional and in Calculation of Sales Charges on page 12 of the fund’s prospectus, Appendix A of the fund’s prospectus and Sales Charges in Appendix B of the statement of additional information.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
The example below is intended to help you compare the costs of investing in the fund with the costs of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods, that you earn a 5% return each year, and that the fund’s operating expenses remain the same. You may be required to pay brokerage commissions on your purchases of Investor, I or Y 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
The portfolio managers primarily buy investment-grade debt securities and, under normal market conditions, will invest at least 80% of the fund’s net assets in debt securities that have interest payments exempt from federal and California income taxes. Cities, counties and other municipalities in California and U.S. territories, such as Puerto Rico, issue these securities.
The fund’s weighted average maturity will be not less than three years nor more than ten years. However, there is no maturity limit on individual securities. 
Although the fund invests primarily in investment-grade securities, up to 20% of the value of the fund’s net assets may be invested in below investment-grade securities, also known as junk bonds. The fund also may invest in securities which, while not rated, are determined by the portfolio managers to be of comparable credit quality to those rated below investment-grade. 
When determining whether to sell a security, portfolio managers consider, among other things, current and anticipated changes in interest rates, the credit quality of a particular issuer, comparable alternatives, general market conditions and any other factor deemed relevant by the portfolio managers. 
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Credit Risk – Debt securities, even investment-grade debt securities, are subject to credit risk. Credit risk is the risk that the inability or perceived inability of the issuer to make interest and principal payments will cause the value of the securities to decrease. As a result, the fund’s share price could also decrease. Changes in the credit rating of a debt security held by the fund could have a similar effect.
•
Below Investment-Grade Securities Risk – Issuers of lower rated, high-yield securities are more vulnerable to real or perceived economic changes (such as an economic downturn or a prolonged period of rising interest rates), political changes or adverse developments specific to an issuer. These factors may be more likely to cause an issuer of low quality bonds to default on its obligations.
•
Interest Rate Risk – Investments in debt securities are sensitive to interest rate changes. Generally, the value of debt securities and the funds that hold them decline as interest rates rise. The fund’s interest rate risk is moderate under normal market conditions, but it may fluctuate as the portfolio managers reposition the fund in response to changing market conditions. A period of rising interest rates may negatively affect the fund’s performance.
•
California Economic Risk – The fund will be sensitive to events that affect California’s economy. Significant political or economic developments in California will likely impact virtually all municipal securities issued in the state. Because the fund invests principally in California municipal securities, it may have a higher level of risk than funds that invest in a larger universe of securities.
•
Municipal Securities Risk – The fund invests principally in municipal securities, so it will be sensitive to events that affect municipal markets, including legislative or political changes and the financial condition of the issuers of municipal securities. By investing primarily in municipal securities, the fund may have a higher level of risk than funds that invest in a larger universe of securities.
•
Loss of Tax Exemptions Risk – There is no guarantee that all of the fund’s income will be exempt from federal or state income taxes. Income from municipal bonds held by the fund could be declared taxable because of unfavorable changes in tax laws, adverse interpretations by the Internal Revenue Service or state tax authorities, or non-compliant conduct of a bond issuer. The fund may sell securities that lose their tax-exempt statuses at inopportune times, which may cause tax consequences or a decrease in the fund’s value.
•
Liquidity Risk – The fund may also be subject to liquidity risk. During periods of market turbulence or unusually low trading activity, to meet redemptions, it may be necessary for the fund to sell securities at prices that could have an adverse effect on the fund’s share price. Changing regulatory and market conditions, including increases in interest rates and credit spreads may adversely affect the liquidity of the fund’s investments.
•
Market Risk – The value of securities owned by the fund may go up and down, sometimes rapidly or unpredictably.
•
Principal Loss – At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.
An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.
Risk Lose Money [Text] rr_RiskLoseMoney Principal Loss – At any given time your shares may be worth less than the price you paid for them. In other words, it is possible to lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a bank deposit, and it is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Fund Performance 
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance. The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. For current performance information, including yields, please visit americancentury.com.
Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Investor Class shares. The table shows how the fund’s average annual returns for the periods shown compared with those of a broad measure of market performance.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress americancentury.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Calendar Year Total Returns
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest Performance Quarter (3Q 2009): 6.57% Lowest Performance Quarter (4Q 2010): -4.11%
As of September 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 4.14%.
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 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
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 California Tax-Free and Municipal Funds | California Intermediate-Term Tax-Free Bond Fund | Barclays 7 Year Municipal Bond Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes  (reflects no deduction for fees, expenses and taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays 7 Year Municipal Bond Index    (reflects no deduction for fees, expenses and taxes)
1 Year rr_AverageAnnualReturnYear01 (0.50%)
5 Years rr_AverageAnnualReturnYear05 2.38%
10 Years rr_AverageAnnualReturnYear10 4.36%
American Century California Tax-Free and Municipal Funds | California Intermediate-Term Tax-Free Bond Fund | S&P Intermediate Term California AMT-Free Municipal Bond Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses and taxes)
Label rr_AverageAnnualReturnLabel S&P Intermediate Term California AMT-Free Municipal Bond Index2    (reflects no deduction for fees, expenses and taxes) [4]
1 Year rr_AverageAnnualReturnYear01 (0.15%) [4]
5 Years rr_AverageAnnualReturnYear05 2.93% [4]
American Century California Tax-Free and Municipal Funds | California Intermediate-Term Tax-Free Bond Fund | Investor Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol BCITX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Maximum Account Fee rr_MaximumAccountFee $ 25
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.46%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.47%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 48
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 151
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 264
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 592
Annual Return 2007 rr_AnnualReturn2007 2.64%
Annual Return 2008 rr_AnnualReturn2008 (0.58%)
Annual Return 2009 rr_AnnualReturn2009 9.78%
Annual Return 2010 rr_AnnualReturn2010 2.09%
Annual Return 2011 rr_AnnualReturn2011 10.19%
Annual Return 2012 rr_AnnualReturn2012 5.94%
Annual Return 2013 rr_AnnualReturn2013 (1.31%)
Annual Return 2014 rr_AnnualReturn2014 6.21%
Annual Return 2015 rr_AnnualReturn2015 2.68%
Annual Return 2016 rr_AnnualReturn2016 (0.29%)
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 4.14%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 6.57%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2010
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (4.11%)
Label rr_AverageAnnualReturnLabel Investor Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (0.29%)
5 Years rr_AverageAnnualReturnYear05 2.60%
10 Years rr_AverageAnnualReturnYear10 3.66%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 09, 1983
American Century California Tax-Free and Municipal Funds | California Intermediate-Term Tax-Free Bond Fund | Investor Class | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (0.29%)
5 Years rr_AverageAnnualReturnYear05 2.60%
10 Years rr_AverageAnnualReturnYear10 3.66%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 09, 1983
American Century California Tax-Free and Municipal Funds | California Intermediate-Term Tax-Free Bond Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 0.87%
5 Years rr_AverageAnnualReturnYear05 2.59%
10 Years rr_AverageAnnualReturnYear10 3.57%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 09, 1983
American Century California Tax-Free and Municipal Funds | California Intermediate-Term Tax-Free Bond Fund | I Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol BCTIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none [5]
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [5]
Maximum Account Fee rr_MaximumAccountFee none [5]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.26%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.27%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 28
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 87
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 152
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 344
Label rr_AverageAnnualReturnLabel I Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (0.09%)
5 Years rr_AverageAnnualReturnYear05 2.80%
Since Inception rr_AverageAnnualReturnSinceInception 3.66%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010
American Century California Tax-Free and Municipal Funds | California Intermediate-Term Tax-Free Bond Fund | Y Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol ACYTX
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 0.23%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.24%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 25
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 77
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 135
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 306
American Century California Tax-Free and Municipal Funds | California Intermediate-Term Tax-Free Bond Fund | A Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol BCIAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none [6]
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.46%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.72%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 520
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 670
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 833
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,305
Label rr_AverageAnnualReturnLabel A Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (4.98%)
5 Years rr_AverageAnnualReturnYear05 1.40%
10 Years rr_AverageAnnualReturnYear10 2.92% [1]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010
American Century California Tax-Free and Municipal Funds | California Intermediate-Term Tax-Free Bond Fund | C Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol BCIYX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Maximum Account Fee rr_MaximumAccountFee none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.46%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.47%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 150
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 466
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 803
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,756
Label rr_AverageAnnualReturnLabel C Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (1.27%)
5 Years rr_AverageAnnualReturnYear05 1.58%
10 Years rr_AverageAnnualReturnYear10 2.64% [1]
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 01, 2010
American Century California Tax-Free and Municipal Funds | California Tax-Free Money Market Fund  
Prospectus: rr_ProspectusTable  
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The fund seeks safety of principal and high current income that is exempt from federal and California income taxes.
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.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Maximum Account Fee rr_MaximumAccountFee $ 25
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.49%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.50%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
The example below is intended to help you compare the costs of investing in the fund with the costs of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods, that you earn a 5% return each year, and that the fund’s operating expenses remain the same. You may be required to pay brokerage commissions on your purchases of Investor 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
The fund is a retail money market fund that invests in municipal money market securities. The securities purchased by the fund are subject to the maturity, quality, diversification, and other requirements of Rule 2a-7 under the Investment Company Act of 1940, as amended. Although the fund seeks to maintain a $1.00 share price, there is no guarantee it will be able to do so. Under normal market conditions, the fund invests in cash-equivalent, high-quality debt securities, at least 80% of which have interest payments exempt from federal and California income taxes. Cities, counties, other municipalities in California and U.S. territories may issue the securities. A high-quality debt security is one an independent rating agency rates in its top two credit quality categories or that the advisor determines to be of comparable credit quality.
Some of the securities in which the fund invests are guaranteed by certain U.S. government agencies or instrumentalities such as the Federal Home Loan Bank (FHLB), the Federal National Mortgage Association (Fannie Mae), and the Federal Home Loan Mortgage Corporation (Freddie Mac). Such securities are not guaranteed by the U.S. Treasury or supported by the full faith and credit of the U.S. government. However, these agencies are authorized to borrow from the U.S. Treasury to meet their obligations. 
When determining whether to buy or sell a security, portfolio managers may consider, among other things, current and anticipated changes in interest rates, issuer credit quality, comparable alternatives, diversification limits, general market conditions and any other factor deemed relevant by the portfolio managers.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
•
Low Yield – Because high-quality debt securities are among the safest securities available, the interest they pay is among the lowest for income-paying securities. Accordingly, the yield on this fund will likely be lower than the yield on funds that invest in lower-quality or longer-term securities.
•
California Economic Risk – The fund will be sensitive to events that affect California’s economy. Significant political or economic developments in California will likely impact virtually all municipal securities issued in the state. Because the fund invests principally in California municipal securities, it may have a higher level of risk than funds that invest in a larger universe of securities.
•
Municipal Securities Risk – Because the fund invests principally in municipal securities, it will be sensitive to events that affect municipal markets, including legislative or political changes and the financial condition of the issuers of municipal securities. By investing primarily in municipal securities, the fund may have a higher level of risk than funds that invest in a larger universe of securities.
•
Interest Rate Risk – Interest rate risk means that the value of debt securities and the funds that hold them decline as interest rates rise. A period of rising interest rates may negatively affect the fund’s performance.
•
Credit Risk – Credit risk is the risk that the inability or perceived inability of the issuer to make interest and principal payments will cause the value of the securities to decrease.
•
Liquidity Risk – Liquidity risk means that during periods of market turbulence or unusually low trading activity, to meet redemptions it may be necessary for the fund to sell securities at prices that could have an adverse effect on the fund’s share price. Changing regulatory and market conditions may adversely affect the liquidity of the fund’s investments. If liquidity decreases too much, the fund may impose a fee on the sale of shares or temporarily suspend redemptions.
•
Loss of Tax Exemptions Risk – There is no guarantee that all of the fund’s income will be exempt from federal or state income taxes. Income from municipal bonds held by the fund could be declared taxable because of unfavorable changes in tax laws, adverse interpretations by the Internal Revenue Service or state tax authorities, or non-compliant conduct of a bond issuer. The fund may sell securities that lose their tax-exempt statuses at inopportune times, which may cause tax consequences or a decrease in the fund’s value.
•
Principal Loss – You could lose money by investing in the fund. Although the fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. The fund may impose a fee upon sale of your shares or may temporarily suspend your ability to sell shares if the fund’s liquidity falls below required minimums because of market conditions or other factors. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The fund’s sponsor has no legal obligation to provide financial support to the fund, and you should not expect that the sponsor will provide financial support to the fund at any time.
Risk Lose Money [Text] rr_RiskLoseMoney Principal Loss – You could lose money by investing in the fund. Although the fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. The fund may impose a fee upon sale of your shares or may temporarily suspend your ability to sell shares if the fund’s liquidity falls below required minimums because of market conditions or other factors. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The fund’s sponsor has no legal obligation to provide financial support to the fund, and you should not expect that the sponsor will provide financial support to the fund at any time.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The fund’s sponsor has no legal obligation to provide financial support to the fund, and you should not expect that the sponsor will provide financial support to the fund at any time.
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. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. For current performance information, including yields, please visit americancentury.com. 
Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress americancentury.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance is not necessarily an indication of how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Calendar Year Total Returns
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales charges and account fees, if applicable, are not reflected in the bar chart. If those charges were included, returns would be less than those shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest Performance Quarter (3Q 2007): 0.82% Lowest Performance Quarter (1Q 2010): 0.00%
As of September 30, 2017, the most recent calendar quarter end, the fund’s Investor Class year-to-date return was 0.27%.
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns For the calendar year ended December 31, 2016
American Century California Tax-Free and Municipal Funds | California Tax-Free Money Market Fund | Investor Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol BCTXX
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 51
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 161
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 280
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 629
Annual Return 2007 rr_AnnualReturn2007 3.22%
Annual Return 2008 rr_AnnualReturn2008 1.92%
Annual Return 2009 rr_AnnualReturn2009 0.18%
Annual Return 2010 rr_AnnualReturn2010 0.01%
Annual Return 2011 rr_AnnualReturn2011 0.01%
Annual Return 2012 rr_AnnualReturn2012 0.01%
Annual Return 2013 rr_AnnualReturn2013 0.01%
Annual Return 2014 rr_AnnualReturn2014 0.01%
Annual Return 2015 rr_AnnualReturn2015 0.01%
Annual Return 2016 rr_AnnualReturn2016 0.13%
Year to Date Return, Label rr_YearToDateReturnLabel Investor Class year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.27%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Performance Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2007
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 0.82%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Performance Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2010
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn
Label rr_AverageAnnualReturnLabel Investor Class
1 Year rr_AverageAnnualReturnYear01 0.13%
5 Years rr_AverageAnnualReturnYear05 0.03%
10 Years rr_AverageAnnualReturnYear10 0.54%
[1] Historical performance for A and C Classes prior to their inception is based on the performance of Investor Class shares. A and C Class performance has been adjusted to reflect differences in sales charges, if applicable, and expenses between classes.
[2] Prior to April 10, 2017, this class was referred to as the Institutional Class.
[3] 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.
[4] Effective December 31, 2017, the fund’s investment advisor selected a different benchmark for comparison purposes. The advisor believes the S&P Intermediate Term California AMT-Free Municipal Bond Index is more reflective of the fund’s strategy. Because the S&P Intermediate Term California AMT-Free Municipal Bond Index total return data is first available as of June 30, 2010, returns for the Bloomberg Barclays 7 Year Municipal Bond Index are also shown to cover the 10 year period.
[5] Prior to April 10, 2017, this class was was referred to as the Institutional Class.
[6] Purchases of $1 million or more may be subject to a contingent deferred sales charge of 1.00% if the shares are redeemed within one year of the date of the purchase.