Label

Element

Value

Prospectus:

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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

Mar. 27, 2017

Document Effective Date

dei_DocumentEffectiveDate

Mar. 27, 2017

Prospectus Date

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Mar. 01, 2017

Supplement [Text Block]

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Principal Funds, Inc.

Supplement dated March 27, 2017

to the Statutory Prospectus dated March 1, 2017

(as supplemented on March 17, 2017 and March 24, 2017)

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

PFI Prospectus [Member] | MidCap Value Fund I

Prospectus:

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Risk/Return [Heading]

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MIDCAP VALUE FUND I

Strategy [Heading]

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In the Principal Investment Strategies section, replace the first and second paragraphs 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 equity securities of companies with medium market capitalizations at the time of purchase. For this Fund, companies with medium market capitalizations are those with market capitalizations within the range of companies comprising the Russell Midcap^®Value Index (as of December 31, 2016, the range was between approximately $394.9 million and $38.8 billion). The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund also invests in real estate investment trusts, and actively trades portfolio securities.

Principal Management Corporation invests between 10% and 30% of the Fund's assets in equity securities in an attempt to match or exceed the performance of the Russell Midcap^®Value Index by purchasing securities in the index while slightly overweighting and underweighting certain individual equity securities relative to their weight in the index. The Fund's remaining assets are managed by the sub-advisors.