Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	Other
Document Period End Date	dei_DocumentPeriodEndDate	Sep. 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	Sep. 13, 2013
Document Effective Date	dei_DocumentEffectiveDate	Sep. 13, 2013
Prospectus Date	rr_ProspectusDate	Dec. 28, 2012
PFI Prospectus - Institutional Class Shares
Risk/Return:	rr_RiskReturnAbstract
Supplement [Text Block]	ck0000898745_SupplementTextBlock	Supplement dated September 13, 2013 to the Classes Institutional, R-1, R-2, R-3, R-4 and R-5 Shares Prospectus for Principal Funds, Inc. dated December 28, 2013 (as supplemented on February 8, 2013, March 15, 2013, April 29, 2013, June 14, 2013 and July 31, 2013) This supplement updates information currently in the Prospectus. Retain this supplement with the Prospectus. FUND SUMMARIES
PFI Prospectus - Institutional Class Shares \| Blue Chip Fund [Member]
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Blue Chip Fund
Risk [Heading]	rr_RiskHeading	Under the Principal Risks heading, after the Growth Stock Risk, add the following:
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.
PFI Prospectus - Institutional Class Shares \| Small-MidCap Dividend Income Fund [Member]
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Small-MidCap Dividend Income Fund
Strategy [Heading]	rr_StrategyHeading	Under the Principal Investment Strategies heading, delete the 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 dividend-paying equity securities of companies with small to medium market capitalizations at the time of each purchase. For this Fund, companies with small to medium market capitalizations are those with market capitalizations similar to companies in the Russell 2500 Value Index (as of June 30, 2013, the range of the index was between approximately $29.4 million and $13.0 billion). The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund invests in the securities of foreign issuers, real estate investment trusts, preferred securities, convertible securities, fixed-income securities, master limited partnerships, and royalty trusts.

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Document Type

dei_DocumentType

Other

Document Period End Date

dei_DocumentPeriodEndDate

Sep. 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

Sep. 13, 2013

Document Effective Date

dei_DocumentEffectiveDate

Sep. 13, 2013

Prospectus Date

rr_ProspectusDate

Dec. 28, 2012

PFI Prospectus - Institutional Class Shares

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

ck0000898745_SupplementTextBlock

Supplement dated September 13, 2013

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

for Principal Funds, Inc.

dated December 28, 2013

(as supplemented on February 8, 2013, March 15, 2013, April 29, 2013,

June 14, 2013 and July 31, 2013)

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

FUND SUMMARIES

PFI Prospectus - Institutional Class Shares | Blue Chip Fund [Member]

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Blue Chip Fund

Risk [Heading]

rr_RiskHeading

Under the Principal Risks heading, after the Growth Stock Risk, add the following:

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.

PFI Prospectus - Institutional Class Shares | Small-MidCap Dividend Income Fund [Member]

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Small-MidCap Dividend Income Fund

Strategy [Heading]

rr_StrategyHeading

Under the Principal Investment Strategies heading, delete the 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 dividend-paying equity securities of companies with small to medium market capitalizations at the time of each purchase. For this Fund, companies with small to medium market capitalizations are those with market capitalizations similar to companies in the Russell 2500 Value Index (as of June 30, 2013, the range of the index was between approximately $29.4 million and $13.0 billion). The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund invests in the securities of foreign issuers, real estate investment trusts, preferred securities, convertible securities, fixed-income securities, master limited partnerships, and royalty trusts.