2.4.0.8010000 - Document - Risk/Return Summary {Unlabeled}falsefalsefalse1false falsefalseD2013Q1Sept13_dei_DocumentInformationDocumentAxis_ck0000898745_PFIProspectusInstitutionalClassSharesMemberhttp://www.sec.gov/CIK0000898745duration2013-09-13T00:00:002013-09-13T00:00:001false 2ck0000898745_SupplementTextBlockck0000898745_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;text-align:center;font-size:10pt;"><font style="font-family:Arial;font-size:10pt;font-weight:bold;">Supplement dated September 13, 2013</font></div><div style="line-height:120%;text-align:center;font-size:10pt;"><font style="font-family:Arial;font-size:10pt;font-weight:bold;">to the Classes Institutional, R-1, R-2, R-3, R-4 and R-5 Shares Prospectus</font></div><div style="line-height:120%;text-align:center;font-size:10pt;"><font style="font-family:Arial;font-size:10pt;font-weight:bold;">for Principal Funds, Inc.</font></div><div style="line-height:120%;text-align:center;font-size:10pt;"><font style="font-family:Arial;font-size:10pt;font-weight:bold;">dated December 28, 2013</font></div><div style="line-height:120%;text-align:left;text-indent:48px;font-size:10pt;"><font style="font-family:Arial;font-size:10pt;">&#160;&#160;&#160;&#160;</font></div><div style="line-height:120%;text-align:center;font-size:10pt;"><font style="font-family:Arial;font-size:10pt;">(as supplemented on February 8, 2013, March 15, 2013, April 29, 2013, </font></div><div style="line-height:120%;padding-bottom:8px;text-align:center;font-size:10pt;"><font style="font-family:Arial;font-size:10pt;">June 14, 2013 and July 31, 2013)</font></div><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:Arial;font-size:10pt;">This supplement updates information currently in the Prospectus. Retain this supplement with the Prospectus.</font></div><div style="line-height:120%;text-align:center;font-size:10pt;"><font style="font-family:Arial;font-size:10pt;"><br clear="none"/></font></div><div style="line-height:120%;padding-bottom:16px;text-align:left;font-size:10pt;"><font style="font-family:Arial;font-size:10pt;font-weight:bold;">FUND SUMMARIES</font></div></div>falsefalsefalseus-types:textBlockItemTypestringSupplement [Text Block]No definition available.false0Supplement [Text Block]2false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00Blue Chip Fund [Member]falsefalsefalse2false truefalseD2013Q1Sept13_dei_DocumentInformationDocumentAxis_ck0000898745_PFIProspectusInstitutionalClassSharesMember_dei_LegalEntityAxis_ck0000898745_S000037378Memberhttp://www.sec.gov/CIK0000898745duration2013-09-13T00:00:002013-09-13T00:00:00falsefalsePFI Prospectus - Institutional Class Sharesdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_PFIProspectusInstitutionalClassSharesMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBlue Chip Fund [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000037378Memberdei_LegalEntityAxisexplicitMembernanafalse0Blue Chip Fund [Member]3false 2rr_RiskReturnHeadingrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Blue Chip Fund falsefalsefalsexbrli:stringItemTypestringRisk/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 indicatedReference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 false0Risk/Return [Heading]4false 2rr_RiskHeadingrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Under the Principal Risks heading, after the Growth Stock Risk, add the following:falsefalsefalsexbrli:stringItemTypestringNarrative Risk Disclosure.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 1 -Subsection b false0Risk [Heading]5false 2rr_RiskNarrativeTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;padding-bottom:8px;text-align:left;font-size:10pt;"><font style="font-family:Arial;font-size:10pt;font-weight:bold;">Risk of Being an Underlying Fund. </font><font style="font-family:Arial;font-size:10pt;">A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.</font></div></div>falsefalsefalseus-types:textBlockItemTypestringNarrative Risk Disclosure. A Fund may, in responding to this Item, describe the types of investors for whom the Fund is intended or the types of investment goals that may be consistent with an investment in the Fund.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 1 -Subparagraph i -Clause instruction -Subsection b false0Risk Narrative [Text Block]6false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00Small-MidCap Dividend Income Fund [Member]falsefalsefalse3false truefalseD2013Q1Sept13_dei_DocumentInformationDocumentAxis_ck0000898745_PFIProspectusInstitutionalClassSharesMember_dei_LegalEntityAxis_ck0000898745_S000032942Memberhttp://www.sec.gov/CIK0000898745duration2013-09-13T00:00:002013-09-13T00:00:00falsefalsePFI Prospectus - Institutional Class Sharesdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_PFIProspectusInstitutionalClassSharesMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseSmall-MidCap Dividend Income Fund [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000032942Memberdei_LegalEntityAxisexplicitMembernanafalse0Small-MidCap Dividend Income Fund [Member]7false 2rr_RiskReturnHeadingrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Small-MidCap Dividend Income Fundfalsefalsefalsexbrli:stringItemTypestringRisk/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 indicatedReference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 false0Risk/Return [Heading]8false 2rr_StrategyHeadingrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Under the Principal Investment Strategies heading, delete the paragraph and substitute:falsefalsefalsexbrli:stringItemTypestringPrincipal 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.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection a false0Strategy [Heading]9false 2rr_StrategyNarrativeTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:Arial;font-size:10pt;">Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in dividend-paying equity securities of companies with small to medium market capitalizations at the time of each purchase. For this Fund, companies with small to medium market capitalizations are those with market capitalizations similar to companies in the Russell 2500 Value Index (as of June 30, 2013, the range of the index was between approximately $29.4 million and $13.0 billion). The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund invests in the securities of foreign issuers, real estate investment trusts, preferred securities, convertible securities, fixed-income securities, master limited partnerships, and royalty trusts.</font></div></div>falsefalsefalseus-types:textBlockItemTypestringPrincipal 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.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection a false0Strategy Narrative [Text Block]falseRisk/Return Summary (PFI Prospectus - Institutional Class Shares)UnKnownUnKnownUnKnownUnKnowntruefalsefalseSheethttp://xbrl.sec.gov/rr/role/RiskReturn19