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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType Other
Document Period End Date dei_DocumentPeriodEndDate Dec. 13, 2013
Registrant Name dei_EntityRegistrantName PRINCIPAL FUNDS INC
Central Index Key dei_EntityCentralIndexKey 0000898745
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Dec. 13, 2013
Document Effective Date dei_DocumentEffectiveDate Dec. 13, 2013
Prospectus Date rr_ProspectusDate Mar. 01, 2013
PFI Prospectus - Class J
  
Risk/Return: rr_RiskReturnAbstract  
Supplement [Text Block] ck0000898745_SupplementTextBlock
Supplement dated December 13, 2013
to the Class J Shares Prospectus
for Principal Funds, Inc.
dated March 1, 2013

(as supplemented on March 28, 2013, April 17, 2103, May 9, 2013, June 14, 2013,
November 4, 2013, and November 22, 2013)

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

FUND SUMMARIES
PFI Prospectus - Class J | SmallCap Growth Fund I [Member]
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading SmallCap Growth Fund I
Supplement [Text Block] ck0000898745_SupplementTextBlock
On December 10, 2013, the Board of Directors of Principal Funds, Inc. approved the acquisition of the assets of the SmallCap Growth Fund II by the SmallCap Growth Fund I. This proposal will be submitted for shareholder vote at a Special Meeting of Shareholders of SmallCap Growth Fund II tentatively scheduled for April 18, 2014. Additional information about this proposal will be provided in the Proxy Statement/Prospectus that is expected to be mailed to record date shareholders of SmallCap Growth Fund II in February 2014. If shareholders approve this proposal, the acquisition is expected to occur on or about April 25, 2014. Additionally, if shareholders approve this proposal, Emerald Advisers, Inc. will become an additional sub-advisor to the SmallCap Growth Fund I.
PFI Prospectus - Class J | SmallCap Growth Fund II [Member]
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading SmallCap Growth Fund II
Supplement [Text Block] ck0000898745_SupplementTextBlock
On December 10, 2013, the Board of Directors of Principal Funds, Inc. approved the acquisition of the assets of the SmallCap Growth Fund II by the SmallCap Growth Fund I. This proposal will be submitted for shareholder vote at a Special Meeting of Shareholders of SmallCap Growth Fund II tentatively scheduled for April 18, 2014. Additional information about this proposal will be provided in the Proxy Statement/Prospectus that is expected to be mailed to record date shareholders of SmallCap Growth Fund II in February 2014. If shareholders approve this proposal, the acquisition is expected to occur on or about April 25, 2014. Additionally, if shareholders approve this proposal, Emerald Advisers, Inc. will become an additional sub-advisor to the SmallCap Growth Fund I.