Label

Element

Value

Prospectus:

rr_ProspectusTable

Document Type

dei_DocumentType

497

Document Period End Date

dei_DocumentPeriodEndDate

Aug. 31, 2015

Entity Registrant Name

dei_EntityRegistrantName

PRINCIPAL FUNDS INC

Central Index Key

dei_EntityCentralIndexKey

0000898745

Amendment Flag

dei_AmendmentFlag

false

Document Creation Date

dei_DocumentCreationDate

Mar. 18, 2016

Document Effective Date

dei_DocumentEffectiveDate

Mar. 18, 2016

Prospectus Date

rr_ProspectusDate

Dec. 31, 2015

Supplement [Text Block]

ck0000898745_SupplementTextBlock

Principal Funds, Inc.

Supplement dated March 18, 2016

to the Statutory Prospectus dated December 31, 2015

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

Diversified Real Asset Fund [Member]

Prospectus:

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Risk/Return [Heading]

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DIVERSIFIED REAL ASSET

Strategy [Heading]

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Effective on or about May 31, 2016, replace the first paragraph in the Principal Investment Strategies section with the following:

Strategy Narrative [Text Block]

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Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in investments related to real assets and real asset companies. The Fund seeks to achieve its investment objective by allocating its assets among general investment categories related to real assets and real asset companies (which include tangible assets and investments that are expected to perform well in periods of high inflation) such as the following: inflation-indexed bonds, securities of real estate companies, commodity-linked derivatives and commodity index-linked notes, U.S. treasury and agency notes and bonds, foreign currency, securities of natural resource companies, master limited partnerships (MLPs), publicly-listed infrastructure companies, floating rate debt, securities of U.S. and non-U.S. agriculture companies, and securities of U.S. and non-U.S. timber companies. The Fund purchases derivative instruments. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index.