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Investment Risks - AMERICAN CENTURY MUNICIPAL TRUST
Oct. 01, 2025
HIGH-YIELD MUNICIPAL FUND | Credit Risk1 Member  
Prospectus [Line Items]  
Risk [Text Block] 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.
HIGH-YIELD MUNICIPAL FUND | Below Investment-Grade Securities Risk Member  
Prospectus [Line Items]  
Risk [Text Block] 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. High-yield securities are speculative.
HIGH-YIELD MUNICIPAL FUND | Interest Rate Risk1 Member  
Prospectus [Line Items]  
Risk [Text Block] 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.
HIGH-YIELD MUNICIPAL FUND | Liquidity Risk Member  
Prospectus [Line Items]  
Risk [Text Block] 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.
HIGH-YIELD MUNICIPAL FUND | Municipal Securities Risk Member  
Prospectus [Line Items]  
Risk [Text Block] 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.
HIGH-YIELD MUNICIPAL FUND | Tax Risk Member  
Prospectus [Line Items]  
Risk [Text Block] 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 noncompliant 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.
HIGH-YIELD MUNICIPAL FUND | Market Risk Member  
Prospectus [Line Items]  
Risk [Text Block] Market Risk – The risk that the value of securities owned by the fund may go up and down, sometimes rapidly or unpredictably. Market risks, including political, regulatory, economic and social developments, can affect the value of the fund’s investments. Natural disasters, public health emergencies, war, terrorism and other unforeseeable events may lead to increased market volatility and may have adverse long-term effects on world economies and markets generally.
HIGH-YIELD MUNICIPAL FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] Principal Loss Risk – 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.
HIGH-YIELD MUNICIPAL FUND | Risk Not Insured Depository Institution [Member]  
Prospectus [Line Items]  
Risk [Text Block]
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.
INTERMEDIATE-TERM TAX-FREE BOND FUND | Credit Risk1 Member  
Prospectus [Line Items]  
Risk [Text Block] 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.
INTERMEDIATE-TERM TAX-FREE BOND FUND | Below Investment-Grade Securities Risk Member  
Prospectus [Line Items]  
Risk [Text Block] 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.
INTERMEDIATE-TERM TAX-FREE BOND FUND | Interest Rate Risk1 Member  
Prospectus [Line Items]  
Risk [Text Block] Interest Rate Risk – Investments in debt securities are also 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.
INTERMEDIATE-TERM TAX-FREE BOND FUND | Liquidity Risk Member  
Prospectus [Line Items]  
Risk [Text Block] 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.
INTERMEDIATE-TERM TAX-FREE BOND FUND | Municipal Securities Risk Member  
Prospectus [Line Items]  
Risk [Text Block] Municipal Securities Risk – The fund invests principally in municipal securities and 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.
INTERMEDIATE-TERM TAX-FREE BOND FUND | Market Risk Member  
Prospectus [Line Items]  
Risk [Text Block] Market Risk – The value of securities owned by the fund may go up and down, sometimes rapidly or unpredictably. Market risks, including political, regulatory, economic and social developments, can affect the value of the fund’s investments. Natural disasters, public health emergencies, war, terrorism and other unforeseeable events may lead to increased market volatility and may have adverse long-term effects on world economies and markets generally.
INTERMEDIATE-TERM TAX-FREE BOND FUND | Loss Of Tax-Exemptions Risk Member  
Prospectus [Line Items]  
Risk [Text Block] 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 noncompliant 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.
INTERMEDIATE-TERM TAX-FREE BOND FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] Principal Loss Risk – 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.
INTERMEDIATE-TERM TAX-FREE BOND FUND | Risk Not Insured Depository Institution [Member]  
Prospectus [Line Items]  
Risk [Text Block]
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.
TAX-FREE MONEY MARKET FUND | Credit Risk1 Member  
Prospectus [Line Items]  
Risk [Text Block] 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.
TAX-FREE MONEY MARKET FUND | Interest Rate Risk1 Member  
Prospectus [Line Items]  
Risk [Text Block] 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.
TAX-FREE MONEY MARKET FUND | Liquidity Risk Member  
Prospectus [Line Items]  
Risk [Text Block] 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.
TAX-FREE MONEY MARKET FUND | Municipal Securities Risk Member  
Prospectus [Line Items]  
Risk [Text Block] 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.
TAX-FREE MONEY MARKET FUND | Loss Of Tax-Exemptions Risk Member  
Prospectus [Line Items]  
Risk [Text Block] 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 noncompliant 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.
TAX-FREE MONEY MARKET FUND | Low Yield Risk Member  
Prospectus [Line Items]  
Risk [Text Block] Low Yield Risk – 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.
TAX-FREE MONEY MARKET FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] Principal Loss Risk – 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.
TAX-FREE MONEY MARKET FUND | Risk Not Insured Depository Institution [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the fund is not a bank account and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.