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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType Other
Document Period End Date dei_DocumentPeriodEndDate Mar. 14, 2013
Registrant Name dei_EntityRegistrantName PRINCIPAL FUNDS INC
Central Index Key dei_EntityCentralIndexKey 0000898745
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Mar. 14, 2013
Document Effective Date dei_DocumentEffectiveDate Mar. 14, 2013
Prospectus Date rr_ProspectusDate Mar. 01, 2013
PFI Prospectus - Class A, B, C, P
  
Risk/Return: rr_RiskReturnAbstract  
Supplement [Text Block] ck0000898745_SupplementTextBlock
Supplement dated March 14, 2013
to the Class A, Class B, Class C, and Class P Shares Prospectus
for Principal Funds, Inc.
dated March 1, 2013

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

FUND SUMMARIES
PFI Prospectus - Class A, B, C, P | High Yield Fund I [Member]
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading High Yield Fund I
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Under the Performance heading, delete the first paragraph and substitute:
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund's Class A shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). These annual returns do not reflect sales charges; if they did, results would be lower. The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund's average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principal.com or by calling 1-800-222-5852.
PFI Prospectus - Class A, B, C, P | High Yield Fund I [Member] | High Yield I Fund, Class A
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PYHAX
PFI Prospectus - Class A, B, C, P | LargeCap Growth Fund I [Member]
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading LargeCap Growth Fund I
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Under the Performance heading, delete the first paragraph and substitute:
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund's Class A shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). These annual returns do not reflect sales charges; if they did, results would be lower. The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund's average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principal.com or by calling 1-800-222-5852.
PFI Prospectus - Class A, B, C, P | LargeCap Growth Fund I [Member] | LargeCap Growth I Fund, Class A
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PLGAX