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Label Element Value
Prospectus: rr_ProspectusTable  
Document Type dei_DocumentType 497
Document Period End Date dei_DocumentPeriodEndDate Oct. 31, 2015
Entity Registrant Name dei_EntityRegistrantName PRINCIPAL FUNDS INC.
Central Index Key dei_EntityCentralIndexKey 0000898745
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Dec. 16, 2016
Document Effective Date dei_DocumentEffectiveDate Dec. 16, 2016
Prospectus Date rr_ProspectusDate Jun. 28, 2016
Supplement [Text Block] ck0000898745_SupplementTextBlock
Principal Funds, Inc.

Supplement dated December 16, 2016
to the Statutory Prospectus dated June 28, 2016
(as supplemented on July 29, 2016)

This supplement updates information currently in the Statutory Prospectus. Please retain this supplement for future reference.
Principal Funds Inc | Principal LifeTime Hybrid 2060 Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading PRINCIPAL LIFETIME HYBRID 2060 FUND
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
In the Average Annual Total Returns table, change “S&P Target Date 2055+ Index” to “S&P Target Date 2055 Index”.
Effective December 31, 2016, insert a row above “S&P Target Date 2055 Index”, and add the following:
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
Effective December 31, 2016, add the following after the paragraph that begins, “After-tax returns are calculated . . .”:
Effective December 31, 2016, the Fund’s primary benchmark changed from S&P Target Date 2055 Index to the S&P Target Date 2060+ Index because of the recent availability of the index which more closely aligns with the investment approach of the Fund.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns for the periods ended December 31, 2015
Principal Funds Inc | Principal LifeTime Hybrid 2060 Fund | S&P target date 2060 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 2060+ Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 (0.66%)
Since Inception rr_AverageAnnualReturnSinceInception 1.11%