Label

Element

Value

Prospectus:

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Supplement [Text Block]

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Principal Funds, Inc.

Supplement dated December 15, 2017

to the Statutory Prospectus dated March 1, 2017, as revised May 2, 2017

(as supplemented June 16, 2017, July 1, 2017, July 31, 2017, September 15, 2017 and October 2, 2017)

This supplement updates information currently in the Statutory Prospectus. Please retain this supplement for future reference.

Document Type

dei_DocumentType

497

Document Period End Date

dei_DocumentPeriodEndDate

Oct. 31, 2016

Entity Registrant Name

dei_EntityRegistrantName

PRINCIPAL FUNDS INC

Central Index Key

dei_EntityCentralIndexKey

0000898745

Amendment Flag

dei_AmendmentFlag

false

Document Creation Date

dei_DocumentCreationDate

Dec. 15, 2017

Document Effective Date

dei_DocumentEffectiveDate

Dec. 15, 2017

Prospectus Date

rr_ProspectusDate

Dec. 15, 2017

Money Market Fund [Member]

Prospectus:

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Supplement [Text Block]

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FUND SUMMARY FOR MONEY MARKET

On December 12, 2017, the Board of Directors of Principal Funds, Inc. (“PFI”) approved the forced redemptions and terminations of Class C and Institutional Class Shares of the Money Market Fund (the “Fund”). Effective January 18, 2018, Class C and Institutional Class Shares of the Fund will no longer be available for purchase or for exchanges from other PFI series. Following the close of business on or about March 23, 2018, Class C and Institutional Class Shares of the Fund held within a retirement plan account under the custodianship of Principal Life Insurance Company will automatically convert into Class A Shares of the Fund on the basis of the share classes’ relative net asset values on such date without the imposition of a sales charge or any other charge; the Fund’s remaining outstanding Class C and Institutional Class Shares will be redeemed at net asset value without the imposition of a sales charge or any other charge, proceeds will be sent to shareholders of record, and these share classes of the Fund will terminate. At such time, delete references to Class C and Institutional Class Shares of the Fund from the prospectus.