Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	Other
Document Period End Date	dei_DocumentPeriodEndDate	Nov. 04, 2013
Registrant Name	dei_EntityRegistrantName	PRINCIPAL FUNDS INC
Central Index Key	dei_EntityCentralIndexKey	0000898745
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Nov. 04, 2013
Document Effective Date	dei_DocumentEffectiveDate	Nov. 04, 2013
Prospectus Date	rr_ProspectusDate	Mar. 01, 2013
PFI Prospectus - Institutional, R-1, R-2, R-3, R-4, and R-5 Class Shares [Member]
Risk/Return:	rr_RiskReturnAbstract
Supplement [Text Block]	ck0000898745_SupplementTextBlock	Supplement dated November 4, 2013 to the Classes Institutional, R-1, R-2, R-3, R-4, and R-5 Shares Prospectus for Principal Funds, Inc. dated March 1, 2013 (as supplemented on March 28, 2013, April 2, 2013, April 17, 2013, May 9, 2013, June 14, 2013, September 13, 2013 and September 20, 2013) This supplement updates information currently in the Prospectus. Retain this supplement with the Prospectus. FUND SUMMARIES
PFI Prospectus - Institutional, R-1, R-2, R-3, R-4, and R-5 Class Shares [Member] \| SmallCap Growth Fund I [Member]
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SmallCap Growth Fund I
Strategy [Heading]	rr_StrategyHeading	Under the Principal Investment Strategies heading, delete the first paragraph and substitute:
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies with small market capitalizations at the time of each purchase. For this Fund, companies with small market capitalizations are those with market capitalizations equal to or smaller than the greater of: 1) $6.0 billion or 2) the highest market capitalization of the companies in the Russell 2000^® Growth Index (as of December 31, 2012, the range was between approximately $27.9 million and $4.7 billion). The Fund invests in growth equity securities; growth orientation emphasizes buying equity securities of companies whose potential for growth of capital and earnings is expected to be above average.

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Document Type

dei_DocumentType

Other

Document Period End Date

dei_DocumentPeriodEndDate

Nov. 04, 2013

Registrant Name

dei_EntityRegistrantName

PRINCIPAL FUNDS INC

Central Index Key

dei_EntityCentralIndexKey

0000898745

Amendment Flag

dei_AmendmentFlag

false

Document Creation Date

dei_DocumentCreationDate

Nov. 04, 2013

Document Effective Date

dei_DocumentEffectiveDate

Nov. 04, 2013

Prospectus Date

rr_ProspectusDate

Mar. 01, 2013

PFI Prospectus - Institutional, R-1, R-2, R-3, R-4, and R-5 Class Shares [Member]

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

ck0000898745_SupplementTextBlock

Supplement dated November 4, 2013

to the Classes Institutional, R-1, R-2, R-3, R-4, and R-5 Shares Prospectus

for Principal Funds, Inc.

dated March 1, 2013

(as supplemented on March 28, 2013, April 2, 2013, April 17, 2013, May 9, 2013, June 14, 2013,

September 13, 2013 and September 20, 2013)

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

FUND SUMMARIES

PFI Prospectus - Institutional, R-1, R-2, R-3, R-4, and R-5 Class Shares [Member] | SmallCap Growth Fund I [Member]

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

SmallCap Growth Fund I

Strategy [Heading]

rr_StrategyHeading

Under the Principal Investment Strategies heading, delete the first paragraph and substitute:

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies with small market capitalizations at the time of each purchase. For this Fund, companies with small market capitalizations are those with market capitalizations equal to or smaller than the greater of: 1) $6.0 billion or 2) the highest market capitalization of the companies in the Russell 2000^® Growth Index (as of December 31, 2012, the range was between approximately $27.9 million and $4.7 billion). The Fund invests in growth equity securities; growth orientation emphasizes buying equity securities of companies whose potential for growth of capital and earnings is expected to be above average.