2.4.0.8010000 - Document - Risk/Return Summary {Unlabeled}falsefalsefalse1false falsefalseD2013Q1Sept13_dei_DocumentInformationDocumentAxis_ck0000898745_PFIProspectusClassACPMemberhttp://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 A, C, and P 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%;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;"><br clear="none"/></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:left;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 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00Small-MidCap Dividend Income Fund [Member]falsefalsefalse2false truefalseD2013Q1Sept13_dei_DocumentInformationDocumentAxis_ck0000898745_PFIProspectusClassACPMember_dei_LegalEntityAxis_ck0000898745_S000032942Memberhttp://www.sec.gov/CIK0000898745duration2013-09-13T00:00:002013-09-13T00:00:00falsefalsePFI Prospectus Class ACPdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_PFIProspectusClassACPMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseSmall-MidCap Dividend Income Fund [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000032942Memberdei_LegalEntityAxisexplicitMembernanafalse0Small-MidCap Dividend Income Fund [Member]3false 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]4false 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]5false 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 Class ACP)UnKnownUnKnownUnKnownUnKnowntruefalsefalseSheethttp://xbrl.sec.gov/rr/role/RiskReturn15