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Label Element Value
Prospectus: rr_ProspectusTable  
Document Type dei_DocumentType 497
Document Period End Date dei_DocumentPeriodEndDate Nov. 28, 2017
Entity Registrant Name dei_EntityRegistrantName AMERICAN CENTURY MUTUAL FUNDS, INC.
Central Index Key dei_EntityCentralIndexKey 0000100334
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Nov. 28, 2017
Document Effective Date dei_DocumentEffectiveDate Apr. 10, 2017
Prospectus Date rr_ProspectusDate Apr. 10, 2017
American Century Mutual Funds, Inc | SELECT FUND  
Prospectus: rr_ProspectusTable  
Supplement [Text Block] ck0000100334_SupplementTextBlock
American Century Mutual Funds, Inc.
Summary Prospectus and Prospectus Supplement
Select Fund

 
Supplement dated November 28, 2017
Summary Prospectus dated April 10, 2017 (as revised August 1, 2017) and Prospectus dated April 10, 2017

The following is added as the last paragraph under the Principal Investment Strategies section on page 2 of the summary prospectus and page 3 of the prospectus.
The fund may write covered calls on a portion of the fund’s holdings in common stock when the portfolio managers believe call premiums are attractive relative to the price of the underlying security.

The following is added as the fourth bullet point under the Principal Risks section on pages 2 and 3 of the summary prospectus and page 3 of the prospectus.
•
Covered Call Risk – Writing covered calls may limit the fund’s ability to participate in price increases of the underlying securities and could lower the fund’s return.