Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Prospectus Date	rr_ProspectusDate	Feb. 29, 2012
Principal LifeTime 2055 Fund (Prospectus Summary): \| Principal LifeTime 2055 Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return, Heading	rr_RiskReturnHeading	PRINCIPAL LIFETIME 2055 FUND
Supplement Text	ck0000898745_SupplementTextBlock	Supplement dated April 23, 2012 to the Class R-1, Class R-2, Class R-3, Class R-4 and Class R-5 Shares Prospectus for Principal Funds, Inc. dated February 29, 2012 (as supplemented on March 16, 2012) This supplement updates information currently in the Prospectus. Retain this supplement with the Prospectus. FUND SUMMARIES PRINCIPAL LIFETIME 2055 FUND Under the Annual Fund Operating Expenses table, delete the footnote and substitute: (1) Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund’s expenses attributable to Class R-1, R-2, R-3, R-4, and R-5 shares and, if necessary, pay expenses normally payable by the Fund, excluding interest expense and Acquired Fund Fees and Expenses, through the period ending February 28, 2013. The expense limit will maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.96% for Class R-1, 0.83% for Class R-2, 0.65% for Class R-3, 0.46% for Class R-4, and 0.34% for Class R-5. It is expected that the expense limit will continue through the period disclosed; however, Principal Funds, Inc. and Principal, the parties to the agreement, may agree to terminate the expense limit prior to the end of the period.
Principal LifeTime 2055 Fund \| R-1
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	LTFGX
Principal LifeTime 2055 Fund \| R-2
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	LTFSX
Principal LifeTime 2055 Fund \| R-3
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	LTFDX
Principal LifeTime 2055 Fund \| R-4
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	LTFLX
Principal LifeTime 2055 Fund \| R-5
Risk/Return:	rr_RiskReturnAbstract
Trading Symbol	dei_TradingSymbol	LTFPX

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Prospectus Date

rr_ProspectusDate

Feb. 29, 2012

Principal LifeTime 2055 Fund (Prospectus Summary): | Principal LifeTime 2055 Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return, Heading

rr_RiskReturnHeading

PRINCIPAL LIFETIME 2055 FUND

Supplement Text

ck0000898745_SupplementTextBlock

Supplement dated April 23, 2012

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

for Principal Funds, Inc.

dated February 29, 2012

(as supplemented on March 16, 2012)

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

FUND SUMMARIES

PRINCIPAL LIFETIME 2055 FUND

Under the Annual Fund Operating Expenses table, delete the footnote and substitute:

(1) Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund’s expenses attributable to Class R-1, R-2, R-3, R-4, and R-5 shares and, if necessary, pay expenses normally payable by the Fund, excluding interest expense and Acquired Fund Fees and Expenses, through the period ending February 28, 2013. The expense limit will maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.96% for Class R-1, 0.83% for Class R-2, 0.65% for Class R-3, 0.46% for Class R-4, and 0.34% for Class R-5. It is expected that the expense limit will continue through the period disclosed; however, Principal Funds, Inc. and Principal, the parties to the agreement, may agree to terminate the expense limit prior to the end of the period.

Principal LifeTime 2055 Fund | R-1

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

LTFGX

Principal LifeTime 2055 Fund | R-2

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

LTFSX