Label	Element	Value
Prospectus:	rr_ProspectusTable
Document Type	dei_DocumentType	497
Document Period End Date	dei_DocumentPeriodEndDate	Aug. 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	May 02, 2017
Document Effective Date	dei_DocumentEffectiveDate	May 02, 2017
Prospectus Date	rr_ProspectusDate	Apr. 07, 2017
Supplement [Text Block]	ck0000898745_SupplementTextBlock	Principal Funds, Inc. Supplement dated May 2, 2017 to the Statutory Prospectus dated April 7, 2017 This supplement updates information currently in the Statutory Prospectus. Please retain this supplement for future reference.
PFI Prospectus [Member] \| Multi-Manager Equity Long/Short Fund
Prospectus:	rr_ProspectusTable
Risk/Return [Heading]	rr_RiskReturnHeading	MULTI-MANAGER EQUITY LONG/SHORT FUND
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	In the Principal Investment Strategies section, delete the paragraph for "Global Thematic."
PFI Prospectus [Member] \| SystematEx Large Value Fund
Prospectus:	rr_ProspectusTable
Risk/Return [Heading]	rr_RiskReturnHeading	SYSTEMATEX LARGE VALUE FUND
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	In the Performance section, within the Average Annual Total Returns table, delete the row description for the third line (Class R-6 Return Before Taxes) and substitute: Class R-6 Return After Taxes on Distributions and Sale of Fund Shares

Label

Element

Value

Prospectus:

rr_ProspectusTable

Document Type

dei_DocumentType

497

Document Period End Date

dei_DocumentPeriodEndDate

Aug. 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

May 02, 2017

Document Effective Date

dei_DocumentEffectiveDate

May 02, 2017

Prospectus Date

rr_ProspectusDate

Apr. 07, 2017

Supplement [Text Block]

ck0000898745_SupplementTextBlock

Principal Funds, Inc.

Supplement dated May 2, 2017

to the Statutory Prospectus dated April 7, 2017

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

PFI Prospectus [Member] | Multi-Manager Equity Long/Short Fund

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

MULTI-MANAGER EQUITY LONG/SHORT FUND

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

In the Principal Investment Strategies section, delete the paragraph for "Global Thematic."

PFI Prospectus [Member] | SystematEx Large Value Fund

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

SYSTEMATEX LARGE VALUE FUND

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

In the Performance section, within the Average Annual Total Returns table, delete the row description for the third line (Class R-6 Return Before Taxes) and substitute:

Class R-6 Return After Taxes on Distributions and Sale of Fund Shares

- Definition

Supplement [Text Block]

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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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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

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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

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

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Namespace Prefix:	dei_
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Balance Type:	na
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- Definition

If the Fund has annual returns for at least one calendar year, provide a table showing the Fund's (A) average annual total return; (B) average annual total return (after taxes on distributions); and (C) average annual total return (after taxes on distributions and redemption). A Money Market Fund should show only the returns described in clause (A) of the preceding sentence. All returns should be shown for 1-, 5-, and 10- calendar year periods ending on the date of the most recently completed calendar year (or for the life of the Fund, if shorter), but only for periods subsequent to the effective date of the Fund's registration statement. The table also should show the returns of an appropriate broad-based securities market index as defined in Instruction 5 to Item 22(b)(7) for the same periods. A Fund that has been in existence for more than 10 years also may include returns for the life of the Fund. A Money Market Fund may provide the Fund's 7-day yield ending on the date of the most recent calendar year or disclose a toll-free (or collect) telephone number that investors can use to obtain the Fund's current 7-day yield. For a Fund (other than a Money Market Fund or a Fund described in General Instruction C.3.(d)(iii)), provide the information in the following table with the specified captions AVERAGE ANNUAL TOTAL RETURNS (For the periods ended December 31, _____). For a Fund that provides annual total returns for only one calendar year or for a Fund that does not include the bar chart because it does not have annual returns for a full calendar year, modify, as appropriate, the narrative explanation required by paragraph (c)(2)(i) (e.g., by stating that the information gives some indication of the risks of an investment in the Fund by comparing the Fund's performance with a broad measure of market performance).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 4
-Subsection b
-Paragraph 2
-Subparagraph iv

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- Definition

The date of the prospectus.

+ References

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-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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-Publisher SEC
-Name Form
-Number N-1A
-Chapter A

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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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