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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType Other
Document Period End Date dei_DocumentPeriodEndDate Jan. 09, 2015
Registrant Name dei_EntityRegistrantName PRINCIPAL FUNDS INC
Central Index Key dei_EntityCentralIndexKey 0000898745
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Jan. 09, 2015
Document Effective Date dei_DocumentEffectiveDate Jan. 09, 2015
Prospectus Date rr_ProspectusDate Dec. 31, 2014
Bond Market Index Fund [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading BOND MARKET INDEX FUND
Supplement [Text Block] ck0000898745_SupplementTextBlock
Supplement dated January 9, 2015
to the Classes A, C, J, P, Institutional, R-1, R-2, R-3, R-4, R-5, R-6 and S Shares Prospectus
for Principal Funds, Inc.
dated December 31, 2014

This supplement updates information currently in the Prospectus. Retain this supplement with the Prospectus.

FUND SUMMARIES


Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
Delete Footnote 1 to the Annual Fund Operating Expenses table and substitute:
(1)
Expense information in the table has been restated to reflect current fees. Effective December 31, 2013, Distribution and/or Service (12b-1) Fees for Class J shares were reduced.
Bond Market Index Fund [Member] | Class J  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PBIJX