2.2.0.25truefalse061210 - Document - Risk/Return Summary {Unlabeled} (Bond & Mortgage Securities Fund)falsefalsetrue1falsefalsetruefalse{dei_LegalEntityAxis} : S000006952 Member 3/1/2011 - 3/1/2011 eol_0000898745-11-000041_STD_1_20110301_0_396770x-9996807http://www.sec.gov/CIK0000898745duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseck0000898745_S000006952Memberdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberpureStandardhttp://www.xbrl.org/2003/instancepure0iso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421703false0rr_AnnualReturnCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00Total Returns as of December 31 each year (Class A shares)falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. Provide annual total returns beginning with the earliest calendar year. Calculate annual returns using the Instructions to Item 8(a), except that the calculations should be based on calendar years. If a Fund's shares are sold subject to a sales load or account fees, state that sales loads or account fees are not reflected in the bar chart and that, if these amounts were reflected, returns would be less than those shown. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets). When a Multiple Class Fund offering one or more Classes offers a new Class in a prospectus that does not offer the shares of any other Class, include the bar chart with annual total returns for any other existing Class for the first year that the Class is offered. Explain in a footnote that the returns are for a Class that is not offered in the prospectus that would have substantially similar annual returns because the shares are invested in the same portfolio of securities and the annual returns would differ only to the extent that the Classes do not have the same expenses. Include return information for the other Class reflected in the bar chart in the performance table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit b -Subsection b falsefalseAnnual Return, Caption4false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.principal.com/role/riskreturn_s000006952member1falsefalsefalse00Bond & Mortgage Securities Fund (Prospectus Summary) | Bond & Mortgage Securities FundBond & Mortgage Securities Fund (Prospectus Summary) | Bond & Mortgage Securities Fundfalsefalsefalsefalsefalse2falsefalseUSDtruefalse{dei_DocumentInformationDocumentAxis} : SummaryS000006952 Member {dei_LegalEntityAxis} : S000006952 Member 3/1/2011 - 3/1/2011 USD ($) $eol_0000898745-11-000041_STD_1_20110301_0_396770x-9996807_396840x-9995145http://www.sec.gov/CIK0000898745duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseck0000898745_SummaryS000006952Memberdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_SummaryS000006952Memberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseck0000898745_S000006952Memberdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberpureStandardhttp://www.xbrl.org/2003/instancepure0iso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseBond & Mortgage Securities Fund (Prospectus Summary) | Bond & Mortgage Securities Fund6false0rr_RiskReturnHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00BOND & MORTGAGE SECURITIES FUNDfalsefalsefalsefalsefalseOtherxbrli: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 falsefalseRisk/Return, Heading7false0rr_ObjectiveHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Objective: falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringInvestment Objectives/Goals. Disclose the Fund's investment objectives or goals. A Fund also may identify its type or category (e.g., that it is a Money Market Fund or a balanced fund).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 -Subsection a falsefalseInvestment Objective, Heading8false0rr_ObjectivePrimaryTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<pre>The Fund seeks to provide current income.</pre>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringInvestment Objectives/Goals. Disclose the Fund's investment objectives or goals. A Fund also may identify its type or category (e.g., that it is a Money Market Fund or a balanced fund).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 -Subsection a falsefalseinvestment Objective, Primary9false0rr_ExpenseHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Fees and Expenses of the FundfalsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Summary Fee Table Includes the following information, in plain English under rule 421(d) under the Securities Act, after Item 2 Fees and expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold shared of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $[_____] in [name of fund family] funds. Shareholder Fees (fees paid directly from your investment) Example This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be You would pay the following expenses if you did not redeem your shares The Example does not reflect sales charges (loads) on reinvested dividends [and other distributions]. If these sales charges (loads) were included, your costs would be higher. Portfolio Turnover The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was __% of the average value of its whole portfolio. Instructions. A.3.instructions.6 New Funds. For purposes of this Item, a "New Fund" is a Fund that does not include in Form N-1A financial statements reporting operating results or that includes financial statements for the Fund's initial fiscal year reporting operating results for a period of 6 months or less. The following Instructions apply to New Funds.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph d -Subsection instructions falsefalseExpense, Heading10false0rr_ExpenseNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<pre>This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in Principal Funds, Inc. More information about these and other discounts is available from your financial professional and in "Choosing a Share Class" and "The Costs of Investing" beginning on pages 214 and 221, respectively, of the Fund's prospectus and "Multiple Class Structure" beginning on page 103 of the Fund's Statement of Additional Information.</pre>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringThis table describes the fees and expenses that you may pay if you buy and hold shared of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $[_____] in [name of fund family] funds. Include the narrative explanations in the order indicated. A Fund may modify the narrative explanations if the explanation contains comparable information to that shown.The narrative explanation regarding sales charge discounts is only required by a Fund that offers such discounts and should specify the minimum level of investment required to qualify for a discount. Modify the narrative explanation to state that Fund shares are sold on a national securities exchange at the end of the time periods indicated, and that brokerage commissions for buying and selling Fund shares through a broker are not reflected.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph b -Subsection instructions falsefalseExpense, Narrative11false0rr_ShareholderFeesCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Shareholder Fees (fees paid directly from your investment)falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringShareholder Fees (fees paid directly from your investment).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subsection table falsefalseShareholder Fees, Caption12false0rr_ShareholderFeesTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div style="display:none">~ http://www.principal.com/role/ShareholderFeesData_S000006952Member column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>falsefalse<div style="display:none">~ http://www.principal.com/role/ShareholderFeesData_S000006952Member column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>falsehttp://www.principal.com/role/ShareholderFeesData_S000006952Memberfalsefalse061211 - Schedule - Shareholder Feestruefalsefalse1falseColumnperiodPeriod*Columndei_LegalEntityAxisAxis*Columnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - A Classrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000018963Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - A Classiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$2falseColumnperiodPeriod*Columndei_LegalEntityAxisAxis*Columnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - B Classrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000018964Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - B Classiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$3falseColumnperiodPeriod*Columndei_LegalEntityAxisAxis*Columnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - Class Crr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000038772Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - Class Ciso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowprimaryElement*4false0rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPricerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truetruetrue0.03750.0375falsefalsefalsetruefalse2truetruetrue0.00000.0000falsefalsefalsetruefalse3truetruetrue0.00000.0000falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureMaximum Deferred Sales Charge (Load) (as a percentage of ____) A.3.instructions.2.a.i "Maximum Deferred Sales Charge (Load)" includes the maximum total deferred sales charge (load) payable upon redemption, in installments, or both, expressed as a percentage of the amount or amounts stated in response to Item 7(a), except that, for a sales charge (load) based on net asset value at the time of purchase, show the sales charge (load) as a percentage of the offering price at the time of purchase. A Fund may include in a footnote to the table, if applicable, a tabular presentation showing the amount of deferred sales charges (loads) over time or a narrative explanation of the sales charges (loads) (e.g., __% in the first year after purchase, declining to __% in the __ year and eliminated thereafter). A.3.instructions.2.a.ii If more than one type of sales charge (load) is imposed (e.g., a deferred sales charge (load) and a front-end sales charge (load)), the first caption in the table should read "Maximum Sales Charge (Load)" and show the maximum cumulative percentage. Show the percentage amounts and the terms of each sales charge (load) comprising that figure on separate lines below.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 1 -Subsection table falsefalseMaximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)0rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPricetruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.03750.0375falsefalsefalsetruefalse2truetruetrue0.00000.0000falsefalsefalsetruefalse3truetruetrue0.00000.0000falsefalsefalsetruefalseOthernanafalsefalseMaximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)2falseRowprimaryElement*5false0rr_MaximumDeferredSalesChargeOverOfferingPricerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truetruetrue0.01000.0100falsefalsefalsetruefalse2truetruetrue0.05000.0500falsefalsefalsetruefalse3truetruetrue0.01000.0100falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureMaximum Deferred Sales Charge (Load) (as a percentage of ____) A.3.instructions.2.a.i "Maximum Deferred Sales Charge (Load)" includes the maximum total deferred sales charge (load) payable upon redemption, in installments, or both, expressed as a percentage of the amount or amounts stated in response to Item 7(a), except that, for a sales charge (load) based on net asset value at the time of purchase, show the sales charge (load) as a percentage of the offering price at the time of purchase. A Fund may include in a footnote to the table, if applicable, a tabular presentation showing the amount of deferred sales charges (loads) over time or a narrative explanation of the sales charges (loads) (e.g., __% in the first year after purchase, declining to __% in the __ year and eliminated thereafter). A.3.instructions.2.a.ii If more than one type of sales charge (load) is imposed (e.g., a deferred sales charge (load) and a front-end sales charge (load)), the first caption in the table should read "Maximum Sales Charge (Load)" and show the maximum cumulative percentage. Show the percentage amounts and the terms of each sales charge (load) comprising that figure on separate lines below.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph a -Clause i -Subsection instructions falsefalseMaximum Deferred Sales Charge (Load) (as a percentage of dollars subject to charge)0rr_MaximumDeferredSalesChargeOverOfferingPricetruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.01000.0100falsefalsefalsetruefalse2truetruetrue0.05000.0500falsefalsefalsetruefalse3truetruetrue0.01000.0100falsefalsefalsetruefalseOthernanafalsefalseMaximum Deferred Sales Charge (Load) (as a percentage of dollars subject to charge)32Shareholder Fees Bond & Mortgage Securities FundUnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*Columndei_LegalEntityAxisAxis*Columnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*RowprimaryElement*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to ShareholderFeesData.No authoritative reference available.falsefalseShareholder Fees [Table]13false0rr_OperatingExpensesCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment) falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringAnnual Fund Operating Expenses (ongoing expenses that you pay each year as a percentage of the value of your investment)Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 7 -Subsection table falsefalseOperating Expenses, Caption14false0rr_AnnualFundOperatingExpensesTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div style="display:none">~ http://www.principal.com/role/OperatingExpensesData_S000006952Member column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>falsefalse<div style="display:none">~ http://www.principal.com/role/OperatingExpensesData_S000006952Member column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>falsehttp://www.principal.com/role/OperatingExpensesData_S000006952Memberfalsefalse061212 - Schedule - Annual Fund Operating Expensestruefalsefalse1falseColumnperiodPeriod*Columndei_LegalEntityAxisAxis*Columnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - A Classrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000018963Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - A Classiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$2falseColumnperiodPeriod*Columndei_LegalEntityAxisAxis*Columnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - B Classrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000018964Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - B Classiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$3falseColumnperiodPeriod*Columndei_LegalEntityAxisAxis*Columnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - Class Crr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000038772Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - Class Ciso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowprimaryElement*3false0rr_ManagementFeesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00520.0052falsefalsefalsetruefalse2truetruetrue0.00520.0052falsefalsefalsetruefalse3truetruetrue0.00520.0052falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureManagement Fees include investment advisory fees (including any fees based on the Fund's performance), any other management fees payable to the investment adviser or its affiliates, and administrative fees payable to the investment adviser or its affiliates that are not included as "Other Expenses."Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph a -Subsection instructions falsefalseManagement Fees0rr_ManagementFeesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00520.0052falsefalsefalsetruefalse2truetruetrue0.00520.0052falsefalsefalsetruefalse3truetruetrue0.00520.0052falsefalsefalsetruefalseOthernanafalsefalseManagement Fees2falseRowprimaryElement*4false0rr_DistributionAndService12b1FeesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00250.0025falsefalsefalsetruefalse2truetruetrue0.01000.0100falsefalsefalsetruefalse3truetruetrue0.01000.0100falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureDistribution [and/or Service] (12b-1) Fees" include all distribution or other expenses incurred during the most recent fiscal year under a plan adopted pursuant to rule 12b-1 [17 CFR 270.12b-1]. Under an appropriate caption or a subcaption of "Other Expenses," disclose the amount of any distribution or similar expenses deducted from the Fund's assets other than pursuant to a rule 12b-1 plan.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 9 -Subsection table falsefalseDistribution and/or Service (12b-1) Fees0rr_DistributionAndService12b1FeesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00250.0025falsefalsefalsetruefalse2truetruetrue0.01000.0100falsefalsefalsetruefalse3truetruetrue0.01000.0100falsefalsefalsetruefalseOthernanafalsefalseDistribution and/or Service (12b-1) Fees3falseRowprimaryElement*5false0rr_OtherExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00270.0027falsefalsefalsetruefalse2truetruetrue0.00630.0063falsefalsefalsetruefalse3truetruetrue0.00600.0060falsefalsefalsetruefalseOtherrr:NonNegativePure4Typepure"Other Expenses" include all expenses not otherwise disclosed in the table that are deducted from the Fund's assets or charged to all shareholder accounts. The amount of expenses deducted from the Fund's assets are the amounts shown as expenses in the Fund's statement of operations (including increases resulting from complying with paragraph 2(g) of rule 6-07 of Regulation S-X [17 CFR 210.6-07]). "Other Expenses" do not include extraordinary expenses as determined under generally accepted accounting principles (see Accounting Principles Board Opinion No. 30). If extraordinary expenses were incurred that materially affected the Fund's "Other Expenses," disclose in a footnote to the table what "Other Expenses" would have been had the extraordinary expenses been included.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph c -Clause i -Subsection instructions falsefalseOther Expenses0rr_OtherExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00270.0027falsefalsefalsetruefalse2truetruetrue0.00630.0063falsefalsefalsetruefalse3truetruetrue0.00600.0060falsefalsefalsetruefalseOthernanafalsefalseOther Expenses4falseRowprimaryElement*7false0rr_ExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.01040.0104falsefalsefalsetruefalse2truetruetrue0.02150.0215falsefalsefalsetruefalse3truetruetrue0.02120.0212falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureTotal Annual Fund Operating Expenses. If the Fund is a Feeder Fund, reflect the aggregate expenses of the Feeder Fund and the Master Fund in a single fee table using the captions provided. In a footnote to the fee table, state that the table and Example reflect the expenses of both the Feeder and Master Funds. If the prospectus offers more than one Class of a Multiple Class Fund or more than one Feeder Fund that invests in the same Master Fund, provide a separate response for each Class or Feeder Fund. Base the percentages of "Annual Fund Operating Expenses" on amounts incurred during the Fund's most recent fiscal year, but include in expenses amounts that would have been incurred absent expense reimbursement or fee waiver arrangements. If the Fund has changed its fiscal year and, as a result, the most recent fiscal year is less than three months, use the fiscal year prior to the most recent fiscal year as the basis for determining "Annual Fund Operating Expenses."Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph d -Subsection instructions falsefalseTotal Annual Fund Operating Expenses0rr_ExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.01040.0104falsefalsefalsetruefalse2truetruetrue0.02150.0215falsefalsefalsetruefalse3truetruetrue0.02120.0212falsefalsefalsetruefalseOthernanafalsefalseTotal Annual Fund Operating Expenses5falseRowprimaryElement*8false0rr_FeeWaiverOrReimbursementOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue-0.0010-0.0010falsefalsefalsetruefalse2truetruetrue-0.0055-0.0055falsefalsefalsetruefalse3truetruetrue-0.0037-0.0037falsefalsefalsetruefalseOtherrr:NonPositivePure4TypepureTotal Annual Fund Operating Expenses. If there were expense reimbursement or fee waiver arrangements that reduced any Fund operating expenses and will continue to reduce them for no less than one year from the effective date of the Fund's registration statement, a Fund may add two captions to the table one caption showing the amount of the expense reimbursement or fee waiver, and a second caption showing the Fund's net expenses after subtracting the fee reimbursement or expense waiver from the total fund operating expenses. The Fund should place these additional captions directly below the "Total Annual Fund Operating Expenses" caption of the table and should use appropriate descriptive captions, such as "Fee Waiver [and/or Expense Reimbursement]" and "Total Annual Fund Operating Expenses After Fee Waiver [and/or Expense Reimbursement]," respectively. If the Fund provides this disclosure, also disclose the period for which the expense reimbursement or fee waiver arrangement is expected to continue, and briefly describe who can terminate the arrangement and under what circumstances.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 11 -Subsection table falsefalseExpense Reimbursement0rr_FeeWaiverOrReimbursementOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue-0.0010-0.0010falsefalsefalsetruefalse2truetruetrue-0.0055-0.0055falsefalsefalsetruefalse3truetruetrue-0.0037-0.0037falsefalsefalsetruefalseOthernanafalsefalseExpense Reimbursement6falseRowprimaryElement*9false0rr_NetExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00940.0094falsefalsefalsetruefalse2truetruetrue0.01600.0160falsefalsefalsetruefalse3truetruetrue0.01750.0175falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureTotal Annual Fund Operating Expenses.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 11 -Subsection table falsefalseTotal Annual Fund Operating Expenses after Expense Reimbursement0rr_NetExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00940.0094falsefalsefalsetruefalse2truetruetrue0.01600.0160falsefalsefalsetruefalse3truetruetrue0.01750.0175falsefalsefalsetruefalseOthernanafalsefalseTotal Annual Fund Operating Expenses after Expense Reimbursement36Annual Fund Operating Expenses Bond & Mortgage Securities FundUnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*Columndei_LegalEntityAxisAxis*Columnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*RowprimaryElement*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to OperatingExpensesData.No authoritative reference available.falsefalseAnnual Fund Operating Expenses [Table]15false0ck0000898745_ExpenseClosingTextBlockck0000898745falsenadurationThis Closing Text Block is to include information not included in the Expenses Narrative.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<pre>Principal Management Corporation has contractually agreed to limit the Fund's expenses attributable to Class A, Class B, and Class C shares and, if necessary, pay expenses normally payable by the Fund, excluding interest expense, through the period ending February 29, 2012. The expense limit will maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.94% for Class A, 1.60% for Class B, and 1.75% for Class C shares. This agreement can be terminated by mutual agreement of the parties (Principal Funds, Inc. and Principal Management Corporation). </pre>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringThis Closing Text Block is to include information not included in the Expenses Narrative.No authoritative reference available.falsefalseOperating Expense, Closing16false0rr_ExpenseExampleHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Example falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringHeading for Expense Example.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subsection instructions falsefalseExpense Example, Heading17false0rr_ExpenseExampleNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<pre>This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example assumes conversion of the Class B shares to Class A shares after the eighth year. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be: </pre>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringThe Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 1 -Subsection example falsefalseExpense Example, Narrative18false0rr_ExpenseExampleWithRedemptionTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div style="display:none">~ http://www.principal.com/role/ExpenseExample_S000006952Member column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>falsefalse<div style="display:none">~ http://www.principal.com/role/ExpenseExample_S000006952Member column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>truehttp://www.principal.com/role/ExpenseExample_S000006952Memberfalsefalse061213 - Schedule - Expense Example {Transposed}truefalsefalse1falseColumnprimaryElement*3false0rr_ExpenseExampleYear01rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue467467falsefalsefalsetruefalse2truefalsetrue663663falsefalsefalsetruefalse3truefalsetrue278278falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subsection instructions falsefalseExpense Example, With Redemption, 1 YearfalseUSDfalsefalse$2falseColumnprimaryElement*4false0rr_ExpenseExampleYear03rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue682682falsefalsefalsetruefalse2truefalsetrue10111011falsefalsefalsetruefalse3truefalsetrue622622falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalseExpense Example, With Redemption, 3 YearsfalseUSDfalsefalse$3falseColumnprimaryElement*5false0rr_ExpenseExampleYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue917917falsefalsefalsetruefalse2truefalsetrue12951295falsefalsefalsetruefalse3truefalsetrue10991099falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalseExpense Example, With Redemption, 5 YearsfalseUSDfalsefalse$4falseColumnprimaryElement*6false0rr_ExpenseExampleYear10rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue15881588falsefalsefalsetruefalse2truefalsetrue21472147falsefalsefalsetruefalse3truefalsetrue24172417falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalseExpense Example, With Redemption, 10 YearsfalseUSDfalsefalse$1falseRowperiodPeriod*Rowdei_LegalEntityAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - A Classrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000018963Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - A Classiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue467467falsefalsefalsetruefalse2truefalsetrue682682falsefalsefalsetruefalse3truefalsetrue917917falsefalsefalsetruefalse4truefalsetrue15881588falsefalsefalsetruefalseOthernanafalsefalseBond & Mortgage Securities Fund - A Class2falseRowperiodPeriod*Rowdei_LegalEntityAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - B Classrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000018964Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - B Classiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue663663falsefalsefalsetruefalse2truefalsetrue10111011falsefalsefalsetruefalse3truefalsetrue12951295falsefalsefalsetruefalse4truefalsetrue21472147falsefalsefalsetruefalseOthernanafalsefalseBond & Mortgage Securities Fund - B Class3falseRowperiodPeriod*Rowdei_LegalEntityAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - Class Crr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000038772Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - Class Ciso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue278278falsefalsefalsetruefalse2truefalsetrue622622falsefalsefalsetruefalse3truefalsetrue10991099falsefalsefalsetruefalse4truefalsetrue24172417falsefalsefalsetruefalseOthernanafalsefalseBond & Mortgage Securities Fund - Class C43Expense Example Bond & Mortgage Securities Fund (USD $)UnKnownUnKnownUnKnownUnKnownfalsetrueColumnprimaryElement*RowperiodPeriod*Rowdei_LegalEntityAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to ExpenseExample.No authoritative reference available.falsefalseExpense Example, With Redemption [Table]19false0rr_ExpenseExampleNoRedemptionByYearCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00You would pay the following expenses if you did not redeem your shares:falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph 1 -Subsection example falsefalseExpense Example, No Redemption, By Year, Caption20false0rr_ExpenseExampleNoRedemptionTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div style="display:none">~ http://www.principal.com/role/ExpenseExampleNoRedemption_S000006952Member column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>falsefalse<div style="display:none">~ http://www.principal.com/role/ExpenseExampleNoRedemption_S000006952Member column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>truehttp://www.principal.com/role/ExpenseExampleNoRedemption_S000006952Memberfalsefalse061214 - Schedule - Expense Example, No Redemption {Transposed}truefalsefalse1falseColumnprimaryElement*3false0rr_ExpenseExampleNoRedemptionYear01rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue467467falsefalsefalsetruefalse2truefalsetrue163163falsefalsefalsetruefalse3truefalsetrue178178falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph 1 -Subsection example falsefalseExpense Example, No Redemption, 1 YearfalseUSDfalsefalse$2falseColumnprimaryElement*4false0rr_ExpenseExampleNoRedemptionYear03rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue682682falsefalsefalsetruefalse2truefalsetrue611611falsefalsefalsetruefalse3truefalsetrue622622falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph 1 -Subsection example falsefalseExpense Example, No Redemption, 3 YearsfalseUSDfalsefalse$3falseColumnprimaryElement*5false0rr_ExpenseExampleNoRedemptionYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue917917falsefalsefalsetruefalse2truefalsetrue10951095falsefalsefalsetruefalse3truefalsetrue10991099falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subparagraph f -Subsection instructions falsefalseExpense Example, No Redemption, 5 YearsfalseUSDfalsefalse$4falseColumnprimaryElement*6false0rr_ExpenseExampleNoRedemptionYear10rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue15881588falsefalsefalsetruefalse2truefalsetrue21472147falsefalsefalsetruefalse3truefalsetrue24172417falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subparagraph f -Subsection instructions falsefalseExpense Example, No Redemption, 10 YearsfalseUSDfalsefalse$1falseRowperiodPeriod*Rowdei_LegalEntityAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - A Classrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000018963Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - A Classiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue467467falsefalsefalsetruefalse2truefalsetrue682682falsefalsefalsetruefalse3truefalsetrue917917falsefalsefalsetruefalse4truefalsetrue15881588falsefalsefalsetruefalseOthernanafalsefalseBond & Mortgage Securities Fund - A Class2falseRowperiodPeriod*Rowdei_LegalEntityAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - B Classrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000018964Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - B Classiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue163163falsefalsefalsetruefalse2truefalsetrue611611falsefalsefalsetruefalse3truefalsetrue10951095falsefalsefalsetruefalse4truefalsetrue21472147falsefalsefalsetruefalseOthernanafalsefalseBond & Mortgage Securities Fund - B Class3falseRowperiodPeriod*Rowdei_LegalEntityAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - Class Crr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000038772Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - Class Ciso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue178178falsefalsefalsetruefalse2truefalsetrue622622falsefalsefalsetruefalse3truefalsetrue10991099falsefalsefalsetruefalse4truefalsetrue24172417falsefalsefalsetruefalseOthernanafalsefalseBond & Mortgage Securities Fund - Class C43Expense Example, No Redemption Bond & Mortgage Securities Fund (USD $)UnKnownUnKnownUnKnownUnKnownfalsetrueColumnprimaryElement*RowperiodPeriod*Rowdei_LegalEntityAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to ExpenseExampleNoRedemption.No authoritative reference available.falsefalseExpense Example, No Redemption [Table]21false0rr_PortfolioTurnoverHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Portfolio TurnoverfalsefalsefalsefalsefalseOtherxbrli:stringItemTypestringDisclose the portfolio turnover rate provided in response to Item 14(a) for the most recent fiscal year (or for such shorter period as the Fund has been in operation). Disclose the period for which the information is provided if less than a full fiscal year. A Fund that is a Money Market Fund may omit the portfolio turnover information required by this Item.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 5 -Subsection instructions falsefalsePortfolio Turnover, Heading22false0rr_PortfolioTurnoverTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<pre>The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 357.4% of the average value of its portfolio.</pre>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDisclose the portfolio turnover rate provided in response to Item 14(a) for the most recent fiscal year (or for such shorter period as the Fund has been in operation). Disclose the period for which the information is provided if less than a full fiscal year. A Fund that is a Money Market Fund may omit the portfolio turnover information required by this Item.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subsection example falsefalsePortfolio Turnover23false0rr_StrategyHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Principal Investment StrategiesfalsefalsefalsefalsefalseOtherxbrli: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 falsefalseInvestment Strategy, Heading24false0rr_StrategyNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<pre>Under normal circumstances, the Fund invests at least 80% of its net assets in intermediate maturity fixed-income or debt securities rated BBB- or higher by Standard &amp; Poor's Rating Service ("S&amp;P") or Baa3 or higher by Moody's Investors Service, Inc. ("Moody's") at the time of purchase, including securities issued or guaranteed by the U.S. government or its agencies or instrumentalities; asset-backed securities or mortgage-backed securities representing an interest in a pool of mortgage loans or other assets; debt securities and taxable municipal bonds; and debt securities issued or guaranteed by foreign governments payable in U.S. dollars. The Fund may also invest in foreign securities, and up to 20% of its assets in non-investment grade securities ("junk bonds) which are securities rated BB+ or lower by S&amp;P or Ba1 or lower by Moody's at the time of purchase. Under normal circumstances, the Fund maintains an average portfolio duration that is within &#xB1;15% or &#xB1;0.75 year (whichever is greater) of the duration of the Barclays Capital Aggregate Bond Index, which as of December 31, 2010 was 4.8 years. The Fund may actively trade securities to achieve its investment objective, enter into dollar roll transactions which may involve leverage, and utilize derivative strategies including certain options transactions, financial futures contracts, swaps, currency forwards, and related options for purposes such as earning income and enhancing returns, managing or adjusting the risk profile of the Fund, replacing more traditional direct investments, or obtaining exposure to certain markets. During the fiscal year ended October 31, 2010, the average ratings of the Fund's fixed-income assets, based on market value at each month-end, were as follows (all ratings are by Moody's): 52.11% in securities rated 6.88% in securities rated 0.04% in securities Aaa Ba rated C 6.10% in securities rated 5.59% in securities rated 0.03% in securities Aa B rated D 1.87% in securities rated 1.38% in securities 9.97% in securities rated A Caa not rated 15.87% in securities rated 0.16% in securities rated Baa Ca </pre>falsefalsefalsefalsefalseOtherus-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 falsefalseInvestment Strategy, Narrative25false0rr_RiskHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Principal RisksfalsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNarrative Risk Disclosure.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 1 -Subsection b falsefalseRisk, Heading26false0rr_RiskNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<pre>The Fund may be an appropriate investment for investors seeking diversification by investing in a fixed-income mutual fund. The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are: Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs. Counterparty Risk. Counterparty risk is the risk that the counterparty to a derivatives contract or repurchase agreement, the borrower of a portfolio's securities, or other obligation, will be unable or unwilling to make timely principal, interest, or settlement payments, or otherwise to honor its obligations. Derivatives Risk. Transactions in derivatives (such as options, futures, and swaps) may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses. Fixed-Income Securities Risk. Fixed-income securities are subject to interest rate risk and credit quality risk. The market value of fixed-income securities generally declines when interest rates rise, and an issuer of fixed-income securities could default on its payment obligations. Foreign Securities Risk. The risks of foreign securities include loss of value as a result of: political or economic instability; nationalization, expropriation or confiscatory taxation; changes in foreign exchange rates and foreign exchange restrictions; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies). High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative. Leverage Risk. Leverage created by borrowing or certain types of transactions or investments, such as reverse repurchase agreements, loans of portfolio securities, and the use of when-issued, delayed delivery or forward commitment transactions, or derivative instruments, may impair the Fund's liquidity, cause it to liquidate positions at an unfavorable time, increase volatility of the Fund's net asset value, or diminish the Fund's performance. Municipal Securities Risk. Principal and interest payments on municipal securities may not be guaranteed by the issuing body and may be payable only from a particular source. That source may not perform as expected and payment obligations may not be made or made on time. Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates. Prepayment Risk. Unscheduled prepayments on mortgage-backed and asset-backed securities may have to be reinvested at lower rates. A reduction in prepayments may increase the effective maturities of these securities, exposing them to the risk of decline in market value over time (extension risk). Real Estate Securities Risk. Real estate securities are subject to the risks associated with direct ownership of real estate, including declines in value, adverse economic conditions, increases in expenses, regulatory changes and environmental problems. Underlying Fund Risk. As of the date of this prospectus, this fund was being used as an underlying fund of a fund of funds, and 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. U.S. Government Securities Risk. Yields available from U.S. government securities are generally lower than yields from many other fixed-income securities. U.S. Government Sponsored Securities Risk. Securities issued by U.S. government-sponsored or -chartered enterprises such as the Federal Home Loan Mortgage Corporation, the Federal National Mortgage Association, and the Federal Home Loan Banks are not issued or guaranteed by the U.S. Treasury. </pre>falsefalsefalsefalsefalseOtherus-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 falsefalseRisk, Narrative27false0rr_BarChartAndPerformanceTableHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Performance falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Bar Chart and Table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subsection b falsefalseBar Chart and Performance Table, Heading28false0rr_PerformanceNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<pre>The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund's Class A shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). These annual returns do not reflect sales charges; if they did, results would be lower. The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund's average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principalfunds.com or by calling 1-800-222-5852. Class A and B shares commenced operations on June 28, 2005, and Class C shares were first sold on January 16, 2007. The returns for Class A, B, and C shares, for the periods prior to those dates, are based on the performance of the R-3 Class shares adjusted to reflect the fees and expenses of Class A, B, and C shares. The adjustments result in performance for such periods that is no higher than the historical performance of the R-3 Class shares. R-3 Class shares were first sold on December 6, 2000.</pre>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringRisk/Return Bar Chart and Table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subsection b falsefalsePerformance, Narrative29false0rr_BarChartNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<pre>The bar chart shows the investment returns of the Fund's Class A shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). These annual returns do not reflect sales charges; if they did, results would be lower.</pre>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringProvide a brief explanation of how the information illustrates the variability of the Fund's returns (e.g., by stating that the information provides some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual returns for 1, 5, and 10 years compare with those of a broad measure of market performance). Provide a statement to the effect that the Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph i -Subsection b falsefalseBar Chart, Narrative30false0rr_BarChartTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div style="display:none">~ http://www.principal.com/role/BarChartData_S000006952Member column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>falsefalseBarChart27.jpg<div style="display:none">~ http://www.principal.com/role/BarChartData_S000006952Member column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>falsehttp://www.principal.com/role/BarChartData_S000006952Memberfalsefalse061215 - Schedule - Annual Total Returnstruefalsefalse1falseColumnperiodPeriod*Columndei_LegalEntityAxisAxis*Columnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMembertruefalseShare Classesrr_ProspectusShareClassAxisrr_ShareClassDomainrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundShare ClassesStandard0falseUSDfalsefalse$2falseColumnperiodPeriod*Columndei_LegalEntityAxisAxis*Columnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - A Classrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000018963Memberrr_ProspectusShareClassAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - A Classiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowprimaryElement*3false0rr_AnnualReturnCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00Total Returns as of December 31 each year (Class A shares)falsefalsefalsetruefalse2falsetruefalse00falsefalsefalsetruefalseOtherxbrli:stringItemTypestringIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. Provide annual total returns beginning with the earliest calendar year. Calculate annual returns using the Instructions to Item 8(a), except that the calculations should be based on calendar years. If a Fund's shares are sold subject to a sales load or account fees, state that sales loads or account fees are not reflected in the bar chart and that, if these amounts were reflected, returns would be less than those shown. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets). When a Multiple Class Fund offering one or more Classes offers a new Class in a prospectus that does not offer the shares of any other Class, include the bar chart with annual total returns for any other existing Class for the first year that the Class is offered. Explain in a footnote that the returns are for a Class that is not offered in the prospectus that would have substantially similar annual returns because the shares are invested in the same portfolio of securities and the annual returns would differ only to the extent that the Classes do not have the same expenses. Include return information for the other Class reflected in the bar chart in the performance table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit b -Subsection b falsefalseAnnual Return, Caption0rr_AnnualReturnCaptiontruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00Total Returns as of December 31 each year (Class A shares)Total Returns as of December 31 each year (Class A shares)falsefalsefalsetruefalse2falsefalsefalse00falsefalsefalsefalsefalseOthernanafalsefalseAnnual Return, Caption2falseRowprimaryElement*4false0rr_AnnualReturn2001rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalsetruefalse2truetruefalse0.06920.0692falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 20010rr_AnnualReturn2001truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2truetruefalse0.06920.0692falsefalsefalsetruefalseOthernanafalsefalseAnnual Return 20013falseRowprimaryElement*5false0rr_AnnualReturn2002rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalsetruefalse2truetruefalse0.08570.0857falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 20020rr_AnnualReturn2002truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2truetruefalse0.08570.0857falsefalsefalsetruefalseOthernanafalsefalseAnnual Return 20024falseRowprimaryElement*6false0rr_AnnualReturn2003rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalsetruefalse2truetruefalse0.03560.0356falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a -Subsection b falsefalseAnnual Return 20030rr_AnnualReturn2003truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2truetruefalse0.03560.0356falsefalsefalsetruefalseOthernanafalsefalseAnnual Return 20035falseRowprimaryElement*7false0rr_AnnualReturn2004rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalsetruefalse2truetruefalse0.04090.0409falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a -Subsection b falsefalseAnnual Return 20040rr_AnnualReturn2004truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2truetruefalse0.04090.0409falsefalsefalsetruefalseOthernanafalsefalseAnnual Return 20046falseRowprimaryElement*8false0rr_AnnualReturn2005rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalsetruefalse2truetruefalse0.02170.0217falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 20050rr_AnnualReturn2005truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2truetruefalse0.02170.0217falsefalsefalsetruefalseOthernanafalsefalseAnnual Return 20057falseRowprimaryElement*9false0rr_AnnualReturn2006rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalsetruefalse2truetruefalse0.04220.0422falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 20060rr_AnnualReturn2006truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2truetruefalse0.04220.0422falsefalsefalsetruefalseOthernanafalsefalseAnnual Return 20068falseRowprimaryElement*10false0rr_AnnualReturn2007rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalsetruefalse2truetruefalse0.02680.0268falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a -Subsection b falsefalseAnnual Return 20070rr_AnnualReturn2007truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2truetruefalse0.02680.0268falsefalsefalsetruefalseOthernanafalsefalseAnnual Return 20079falseRowprimaryElement*11false0rr_AnnualReturn2008rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalsetruefalse2truetruefalse-0.1466-0.1466falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 20080rr_AnnualReturn2008truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2truetruefalse-0.1466-0.1466falsefalsefalsetruefalseOthernanafalsefalseAnnual Return 200810falseRowprimaryElement*12false0rr_AnnualReturn2009rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalsetruefalse2truetruefalse0.19410.1941falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a -Subsection b falsefalseAnnual Return 20090rr_AnnualReturn2009truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2truetruefalse0.19410.1941falsefalsefalsetruefalseOthernanafalsefalseAnnual Return 200911falseRowprimaryElement*13false0rr_AnnualReturn2010rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00falsefalsefalsetruefalse2truetruefalse0.10950.1095falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 20100rr_AnnualReturn2010truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2truetruefalse0.10950.1095falsefalsefalsetruefalseOthernanafalsefalseAnnual Return 2010211Annual Total Returns UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*Columndei_LegalEntityAxisAxis*Columnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*RowprimaryElement*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to BarChartData.No authoritative reference available.falsefalseBar Chart [Table]31false0rr_BarChartClosingTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<pre>Highest return for a quarter during the period of the bar chart above: Q3 '09 9.08% Lowest return for a quarter during the period of the bar chart above: Q4 '08 -6.25% </pre>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseBar Chart, Closing32false0rr_PerformanceTableNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<pre>After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Class A shares only and would be different for Class B and Class C shares. </pre>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringIf 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 shouldshow the returns of an appropriate broadbased 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).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iv -Subsection b falsefalsePerformance Table, Narrative33false0rr_AverageAnnualReturnCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00Average Annual Total Returns For the periods ended December 31, 2010falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringThis item represents Average Anuual Total Returns. If a Multiple Class Fund offers a Class in the prospectus that converts into another Class after a stated period, compute average annual total returns in the table by using the returns of the other Class for the period after conversion.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 5 -Subsection b falsefalseAverage Annual Returns, Caption34false0rr_PerformanceTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div style="display:none">~ http://www.principal.com/role/PerformanceTableData_S000006952Member column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * row primary compact * ~</div>falsefalse<div style="display:none">~ http://www.principal.com/role/PerformanceTableData_S000006952Member column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * row primary compact * ~</div>truehttp://www.principal.com/role/PerformanceTableData_S000006952Memberfalsefalse061216 - Schedule - Average Annual Total Returns {Transposed}truefalsefalse1falseColumnprimaryElement*3false0rr_AverageAnnualReturnLabelrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00Class A Return Before Taxesfalsefalsefalsetruefalse2falsetruefalse00Class A Return After Taxes on Distributionsfalsefalsefalsetruefalse3falsetruefalse00Class A Return After Taxes on Distribution and Sale of Fund Sharesfalsefalsefalsetruefalse4falsetruefalse00Class B Return Before Taxesfalsefalsefalsetruefalse5falsetruefalse00Class C Return Before Taxesfalsefalsefalsetruefalse6falsetruefalse00Barclays Capital Aggregate Bond IndexfalsefalsefalsetruefalseOtherxbrli:stringItemTypestringThis item represents Average Anuual Total Returns. If a Multiple Class Fund offers a Class in the prospectus that converts into another Class after a stated period, compute average annual total returns in the table by using the returns of the other Class for the period after conversion.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 -Subsection b falsefalseAverage Annual Returns, LabelfalseUSDfalsefalse$2falseColumnprimaryElement*4false0rr_AverageAnnualReturnYear01rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.06750.0675falsefalsefalsetruefalse2truetruetrue0.05530.0553falsefalsefalsetruefalse3truetruetrue0.04360.0436falsefalsefalsetruefalse4truetruetrue0.05200.0520falsefalsefalsetruefalse5truetruetrue0.09060.0906falsefalsefalsetruefalse6truetruetrue0.06540.0654falsefalsefalsetruefalseOtherxbrli:pureItemTypepureReturn Before Taxes.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 -Subsection b falsefalseAverage Annual Returns, 1 YearfalseUSDfalsefalse$3falseColumnprimaryElement*5false0rr_AverageAnnualReturnYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.03090.0309falsefalsefalsetruefalse2truetruetrue0.01500.0150falsefalsefalsetruefalse3truetruetrue0.01670.0167falsefalsefalsetruefalse4truetruetrue0.02870.0287falsefalsefalsetruefalse5truetruetrue0.03060.0306falsefalsefalsetruefalse6truetruetrue0.05800.0580falsefalsefalsetruefalseOtherxbrli:pureItemTypepureReturn Before Taxes.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 -Subsection b falsefalseAverage Annual Returns, 5 YearsfalseUSDfalsefalse$4falseColumnprimaryElement*6false0rr_AverageAnnualReturnYear10rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.04060.0406falsefalsefalsetruefalse2truetruetrue0.02500.0250falsefalsefalsetruefalse3truetruetrue0.02520.0252falsefalsefalsetruefalse4truetruetrue0.03870.0387falsefalsefalsetruefalse5truetruetrue0.03690.0369falsefalsefalsetruefalse6truetruetrue0.05840.0584falsefalsefalsetruefalseOtherxbrli:pureItemTypepureReturn Before Taxes.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 -Subsection b falsefalseAverage Annual Returns, 10 YearsfalseUSDfalsefalse$1falseRowperiodPeriod*Rowdei_LegalEntityAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - A Classrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_C000018963Memberrr_ProspectusShareClassAxisexplicitMembertruefalseBefore Taxesrr_PerformanceMeasureAxisrr_PerformanceMeasureDomainrr_PerformanceMeasureAxisexplicitMemberBond & Mortgage Securities FundBond & Mortgage Securities Fund - A ClassBefore Taxesiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00Class A Return Before TaxesClass A Return Before Taxesfalsefalsefalsetruefalse2truetruetrue0.06750.0675falsefalsefalsetruefalse3truetruetrue0.03090.0309falsefalsefalsetruefalse4truetruetrue0.04060.0406falsefalsefalsetruefalseOthernanafalsefalseBond & Mortgage Securities Fund - A Class2falseRowperiodPeriod*Rowdei_LegalEntityAxisAxis*Rowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*duration2011-03-01T00:00:002011-03-01T00:00:00falsefalseBond & Mortgage Securities Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000898745_S000006952Memberdei_LegalEntityAxisexplicitMemberfalsefalseBond & Mortgage Securities Fund - 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