Label	Element	Value
Prospectus:	rr_ProspectusTable
Document Type	dei_DocumentType	497
Document Period End Date	dei_DocumentPeriodEndDate	Aug. 31, 2017
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. 16, 2018
Document Effective Date	dei_DocumentEffectiveDate	Mar. 16, 2018
Prospectus Date	rr_ProspectusDate	Dec. 31, 2017
Supplement [Text Block]	ck0000898745_SupplementTextBlock	Principal Funds, Inc. Supplement dated March 16, 2018 to the Statutory Prospectus dated December 31, 2017 (as supplemented on January 8, 2018 and January 30, 2018) This supplement updates information currently in the Statutory Prospectus. Please retain this supplement for future reference.
Principal Funds Inc \| Real Estate Debt Income Fund
Prospectus:	rr_ProspectusTable
Risk/Return [Heading]	rr_RiskReturnHeading	REAL ESTATE DEBT INCOME FUND
Strategy [Heading]	rr_StrategyHeading	Under Principal Investment Strategies, delete the third paragraph.
Risk [Heading]	rr_RiskHeading	Under Principal Risks, delete Non-Diversification Risk.

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Value

Prospectus:

rr_ProspectusTable

Document Type

dei_DocumentType

497

Document Period End Date

dei_DocumentPeriodEndDate

Aug. 31, 2017

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. 16, 2018

Document Effective Date

dei_DocumentEffectiveDate

Mar. 16, 2018

Prospectus Date

rr_ProspectusDate

Dec. 31, 2017

Supplement [Text Block]

ck0000898745_SupplementTextBlock

Principal Funds, Inc.

Supplement dated March 16, 2018

to the Statutory Prospectus dated December 31, 2017

(as supplemented on January 8, 2018 and January 30, 2018)

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

Principal Funds Inc | Real Estate Debt Income Fund

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

REAL ESTATE DEBT INCOME FUND

Strategy [Heading]

rr_StrategyHeading

Under Principal Investment Strategies, delete the third paragraph.

Risk [Heading]

rr_RiskHeading

Under Principal Risks, delete Non-Diversification Risk.

- Definition

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The date the document was made available and submitted, in CCYY-MM-DD format. The date of submission, date of acceptance by the recipient, and the document effective date are all potentially different.

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- Definition

The date when a document, upon receipt and acceptance, becomes officially effective, in CCYY-MM-DD format. Usually it is a system-assigned date time value, but it may be declared by the submitter in some cases.

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The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented. If there is no historical data in the report, use the filing date. The format of the date is CCYY-MM-DD.

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- Definition

The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word "Other".

+ References

No definition available.

+ Details

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- Definition

A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation 12B
-Number 240
-Section 12b
-Subsection 1

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The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.

+ References

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-Publisher SEC
-Name Regulation 12B
-Number 240
-Section 12b
-Subsection 1

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The date of the prospectus.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 1
-Subsection a
-Paragraph 3

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- Definition

Prospectus Table.

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-Chapter A

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- Definition

Narrative Risk Disclosure.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 4
-Subsection b
-Paragraph 1

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- Definition

Risk/Return Summary Investment Objectives/Goals Include the following information, in plain English under rule 421(d) under the Securities Act, in the order and subject matter indicated

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 2

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- Definition

Principal investment strategies of the Fund. Summarize how the Fund intends to achieve its investment objectives by identifying the Fund's principal investment strategies (including the type or types of securities in which the Fund invests or will invest principally) and any policy to concentrate in securities of issuers in a particular industry or group of industries.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 4
-Subsection a

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