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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType Other
Document Period End Date dei_DocumentPeriodEndDate Jun. 16, 2014
Registrant Name dei_EntityRegistrantName PRINCIPAL FUNDS INC
Central Index Key dei_EntityCentralIndexKey 0000898745
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Jun. 16, 2014
Document Effective Date dei_DocumentEffectiveDate Jun. 16, 2014
Prospectus Date rr_ProspectusDate Jun. 03, 2014
PFI Prospectus - Class A,P
  
Risk/Return: rr_RiskReturnAbstract  
Supplement [Text Block] ck0000898745_SupplementTextBlock
Supplement dated June 16, 2014
to the Classes A and P Shares Prospectus
for Principal Funds, Inc.
dated June 3, 2014

This supplement updates information currently in the Prospectus. Retain this supplement with the Prospectus.
FUND SUMMARIES
PFI Prospectus - Class A,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 Performance Delete the Average Annual Total Returns table and the text below it, and substitute:
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2013
PFI Prospectus - Class A,P | LargeCap Growth Fund I [Member] | Russell 1000 Growth Index [Member]
  
Risk/Return: rr_RiskReturnAbstract  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Russell 1000 Growth Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 33.48%
5 Years rr_AverageAnnualReturnYear05 20.39%
10 Years rr_AverageAnnualReturnYear10 7.83%
PFI Prospectus - Class A,P | LargeCap Growth Fund I [Member] | LargeCap Growth Fund I, Class P
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Class P Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 36.44%
5 Years rr_AverageAnnualReturnYear05 23.53%
10 Years rr_AverageAnnualReturnYear10 8.70%
PFI Prospectus - Class A,P | LargeCap Growth Fund I [Member] | LargeCap Growth Fund I, Class P | After Taxes on Distributions
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Class P Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 34.49%
5 Years rr_AverageAnnualReturnYear05 22.85%
10 Years rr_AverageAnnualReturnYear10 8.16%
PFI Prospectus - Class A,P | LargeCap Growth Fund I [Member] | LargeCap Growth Fund I, Class P | After Taxes on Distributions and Sales
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Class P Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 22.17%
5 Years rr_AverageAnnualReturnYear05 19.48%
10 Years rr_AverageAnnualReturnYear10 7.13%
PFI Prospectus - Class A,P | MidCap Value Fund III [Member]
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading MIDCAP VALUE FUND III
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Delete the Average Annual Total Returns table and the text below it, and substitute:
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Class A shares only and would be different for Class P shares.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2013
PFI Prospectus - Class A,P | MidCap Value Fund III [Member] | Russell Midcap Value Index [Member]
  
Risk/Return: rr_RiskReturnAbstract  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Russell Midcap Value Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 33.46%
5 Years rr_AverageAnnualReturnYear05 21.16%
10 Years rr_AverageAnnualReturnYear10 10.25%
PFI Prospectus - Class A,P | MidCap Value Fund III [Member] | MidCap Value Fund III, Class A
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 28.51%
5 Years rr_AverageAnnualReturnYear05 18.74%
10 Years rr_AverageAnnualReturnYear10 8.34%
PFI Prospectus - Class A,P | MidCap Value Fund III [Member] | MidCap Value Fund III, Class A | After Taxes on Distributions
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 27.03%
5 Years rr_AverageAnnualReturnYear05 18.16%
10 Years rr_AverageAnnualReturnYear10 7.21%
PFI Prospectus - Class A,P | MidCap Value Fund III [Member] | MidCap Value Fund III, Class A | After Taxes on Distributions and Sales
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 16.65%
5 Years rr_AverageAnnualReturnYear05 15.06%
10 Years rr_AverageAnnualReturnYear10 6.48%
PFI Prospectus - Class A,P | MidCap Value Fund III [Member] | MidCap Value Fund III, Class P
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Class P Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 36.06%
5 Years rr_AverageAnnualReturnYear05 20.14%
10 Years rr_AverageAnnualReturnYear10 9.02%