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Label Element Value
Prospectus: rr_ProspectusTable  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Aug. 31, 2017
Entity Registrant Name dei_EntityRegistrantName PRINCIPAL FUNDS INC
Central Index Key dei_EntityCentralIndexKey 0000898745
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Dec. 31, 2017
Document Effective Date dei_DocumentEffectiveDate Dec. 31, 2017
Prospectus Date rr_ProspectusDate Dec. 31, 2017
Principal Funds Inc | Blue Chip Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading BLUE CHIP FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks long-term growth of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 $50,000 in Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 27.1% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 27.10%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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 also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption With respect to Class C and J shares, you would pay the following expenses if you did not redeem your shares (all other classes would be the same as in the above example):
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies with large market capitalizations at the time of purchase that, in Principal Global Investors, LLC’s (“PGI’s”) (the Fund’s investment advisor) opinion, display characteristics of a “blue chip” company.  For this Fund, companies with large market capitalizations are those with market capitalizations similar to companies in the Russell 1000 Growth® Index (as of November 30, 2017, this range was between approximately $1.2 billion and $896.0 billion). In PGI’s view, “blue chip” companies typically display some or all of the following characteristics:  (1) large, well-established and financially sound companies; (2) issuers with market capitalizations in the billions; (3) are considered market leaders or among the top three companies in its sector; and (4) commonly considered  household names. The Fund tends to focus on securities of companies that show potential for growth of capital as well as an expectation for above average earnings. The Fund invests in securities of foreign companies.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.
•
Small and Medium Market Capitalization Companies Risk. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.
Foreign Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.
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; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Classes A, C, and J - www.principalfunds.com.
•
For Institutional Class and Classes R-3, R-4, R-5, and R-6 - www.principal.com.
Using the historical performance of the Fund's Institutional Class shares, adjusted as described below, 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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (June 14, 2012).
For periods prior to the inception date of Classes A and C shares (September 30, 2013), Classes R-3, R-4, and R-5 shares (March 29, 2016), Class R-6 shares (January 3, 2017), and Class J shares (September 11, 2017), the performance shown in the bar chart for Class A shares and the table for Classes A, C, J, R-3, R-4, R-5 and R-6 shares is that of the Fund's Institutional Class shares, adjusted to reflect the respective fees and expenses of each class. However, where this adjustment for fees and expenses results in performance for a newer class that is higher than the historical performance of the Institutional Class shares, the historical performance of the Institutional Class shares is used. These adjustments for these newer classes result in performance for such periods that is no higher than the historical performance of the Institutional Class shares, which were first sold June 14, 2012.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Classes A, C, and J - www.principalfunds.com.•For Institutional Class and Classes R-3, R-4, R-5, and R-6 - www.principal.com.Using the historical performance of the Fund's Institutional Class shares, adjusted as described below, 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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [1]
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q1 '13
10.03%
Lowest return for a quarter during the period of the bar chart above:
Q3 '15
(4.58)%

(1) The year-to-date return as of September 30, 2017 was 20.21% for Class A shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class A shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Blue Chip Fund | Russell 1000 Growth Index [Member]  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Russell 1000 Growth Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 7.08%
Since Inception rr_AverageAnnualReturnSinceInception 14.19%
Principal Funds Inc | Blue Chip Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PBLAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.68%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.22% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.15%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.15%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 661
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 895
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,148
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,871
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Annual Return 2013 rr_AnnualReturn2013 28.67%
Annual Return 2014 rr_AnnualReturn2014 9.96%
Annual Return 2015 rr_AnnualReturn2015 4.79%
Annual Return 2016 rr_AnnualReturn2016 8.23%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 20.21%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2013
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 10.03%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2015
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (4.58%)
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.25%
Since Inception rr_AverageAnnualReturnSinceInception 11.94%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 14, 2012
Principal Funds Inc | Blue Chip Fund | Class A | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 2.12%
Since Inception rr_AverageAnnualReturnSinceInception 11.55%
Principal Funds Inc | Blue Chip Fund | Class A | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 1.39%
Since Inception rr_AverageAnnualReturnSinceInception 9.42%
Principal Funds Inc | Blue Chip Fund | Class C  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PBLCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.68%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.26% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.94%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.94%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 297
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 609
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,047
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,264
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 197
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 609
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,047
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,264
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Label rr_AverageAnnualReturnLabel Class C Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 6.44%
Since Inception rr_AverageAnnualReturnSinceInception 12.49%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 14, 2012
Principal Funds Inc | Blue Chip Fund | Class J  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PBCJX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.68%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.21% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.04%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.04%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 206
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 331
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 574
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,271
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 106
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 331
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 574
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,271
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Label rr_AverageAnnualReturnLabel Class J Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.49%
Since Inception rr_AverageAnnualReturnSinceInception 13.66%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 14, 2012
Principal Funds Inc | Blue Chip Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PBCKX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.68%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.69%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.69%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 70
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 221
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 384
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 859
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 8.87%
Since Inception rr_AverageAnnualReturnSinceInception 14.06%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 14, 2012
Principal Funds Inc | Blue Chip Fund | R-3  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGBEX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.68%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.32% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.25%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.25%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 127
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 397
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 686
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,511
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-3 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 8.29%
Since Inception rr_AverageAnnualReturnSinceInception 13.41%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 14, 2012
Principal Funds Inc | Blue Chip Fund | R-4  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGBFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.68%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.10%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.28% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.06%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.06%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 108
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 337
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 585
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,294
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-4 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 8.48%
Since Inception rr_AverageAnnualReturnSinceInception 13.62%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 14, 2012
Principal Funds Inc | Blue Chip Fund | R-5  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGBGX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.68%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.26% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.94%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.94%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 96
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 300
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 520
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,155
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-5 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 8.62%
Since Inception rr_AverageAnnualReturnSinceInception 13.76%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 14, 2012
Principal Funds Inc | Blue Chip Fund | R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGBHX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.68%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.69%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.69%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 70
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 221
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 384
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 859
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-6 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 8.81%
Since Inception rr_AverageAnnualReturnSinceInception 13.99%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 14, 2012
Principal Funds Inc | Bond Market Index Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading BOND MARKET INDEX FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks to provide current income.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 117.8% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 117.80%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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 also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption With respect to Class J shares, you would pay the following expenses if you did not redeem your shares (all other classes would be the same as in the above example):
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund uses a passive investment approach known as "sampling" to invest at least 80% of its net assets, plus any borrowings for investment purposes, in investments designed to track the Bloomberg Barclays U.S. Aggregate Bond Index (the "Index") at the time of purchase. The Index is composed of investment grade, fixed rate debt issues with maturities of one year or more, including government securities, corporate securities, and asset-backed and mortgage-backed securities (securitized products). The Index is rebalanced monthly to reflect securities that have dropped out of or entered the Index in the preceding month. Because of the practical difficulties and expense of purchasing all of the securities in the Index, the Fund does not purchase all of the securities in the Index. Instead, the Fund uses a sampling methodology to purchase securities with generally the same risk and return characteristics of the Index. Under normal circumstances, the Fund maintains an average portfolio duration that is in line with the duration of the Index, which as of August 31, 2017 was 5.93 years. The Fund will not concentrate (invest more than 25% of its assets) its investments in a particular industry except to the extent the Index is so concentrated. Because the Fund's portfolio turnover rate during the most recent fiscal year was more than 100%, the Fund is considered actively traded.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
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.
Index Fund Risk. An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.
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.
Portfolio Turnover (Active Trading) Risk. High portfolio turnover (more than 100%) caused by actively trading portfolio securities may result in accelerating the realization of taxable gains and losses, lower fund performance and increased brokerage costs.
Real Estate Securities Risk. Investing in real estate securities subjects the fund to the risks associated with the real estate market (which are similar to the risks associated with direct ownership in real estate), including declines in real estate values, loss due to casualty or condemnation, property taxes, interest rate changes, increased expenses, cash flow of underlying real estate assets, regulatory changes (including zoning, land use and rents), and environmental problems, as well as to the risks related to the management skill and creditworthiness of the issuer.
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
Securitized Products Risk. Investments in securitized products are subject to risks similar to traditional fixed income securities, such as credit, interest rate, liquidity, prepayment, extension, and default risk, as well as additional risks associated with the nature of the assets and the servicing of those assets. Unscheduled prepayments on securitized products 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).
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.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Class J - www.principalfunds.com.
•
For Institutional Class and Classes R-1, R-2, R-3, R-4, and R-5 - www.principal.com.
The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (December 30, 2009).
For periods prior to the inception date of Class J shares (March 16, 2010), the performance shown in the table for Class J shares is that of the Fund's Institutional Class shares, adjusted to reflect the fees and expenses of the Class J shares. These adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares, which were first sold on December 30, 2009.
During 2014, the Institutional Class experienced a significant withdrawal of monies by an affiliate. As the remaining shareholders held relatively small positions, the total return amounts expressed herein are greater than those that would have been experienced without the withdrawal.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Class J - www.principalfunds.com.•For Institutional Class and Classes R-1, R-2, R-3, R-4, and R-5 - www.principal.com.The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 (1) [4]
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q3 '11
3.76%
Lowest return for a quarter during the period of the bar chart above:
Q4 '16
(3.12)%

(1) The year-to-date return as of September 30, 2017 was 2.95% for Institutional Class shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Institutional Class shares only and would be different for the other share classes
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 Institutional Class shares only and would be different for the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Bond Market Index Fund | Bloomberg Barclays U.S. Aggregate Bond Index [Member]  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays U.S. Aggregate Bond Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 2.65%
5 Years rr_AverageAnnualReturnYear05 2.23%
Since Inception rr_AverageAnnualReturnSinceInception 4.34%
Principal Funds Inc | Bond Market Index Fund | Class J  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PBIJX
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.30%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.71%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.10%) [5],[6]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.61%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 162
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 217
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 385
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 873
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 62
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 217
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 385
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 873
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Label rr_AverageAnnualReturnLabel Class J Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 0.64%
5 Years rr_AverageAnnualReturnYear05 1.30% [7]
Since Inception rr_AverageAnnualReturnSinceInception 2.54% [7]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | Bond Market Index Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PNIIX
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.01%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.27%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.10%) [5],[6]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.17%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 17
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 77
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 142
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 333
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Annual Return 2010 rr_AnnualReturn2010 5.90%
Annual Return 2011 rr_AnnualReturn2011 7.45%
Annual Return 2012 rr_AnnualReturn2012 3.89%
Annual Return 2013 rr_AnnualReturn2013 (2.44%)
Annual Return 2014 rr_AnnualReturn2014 6.63%
Annual Return 2015 rr_AnnualReturn2015 0.23%
Annual Return 2016 rr_AnnualReturn2016 2.17%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 2.95%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2011
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 3.76%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.12%)
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.17%
5 Years rr_AverageAnnualReturnYear05 2.05% [7]
Since Inception rr_AverageAnnualReturnSinceInception 3.34% [7]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | Bond Market Index Fund | Institutional Class | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Institutional Class Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 1.39%
5 Years rr_AverageAnnualReturnYear05 1.17% [7]
Since Inception rr_AverageAnnualReturnSinceInception 2.47% [7]
Principal Funds Inc | Bond Market Index Fund | Institutional Class | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Institutional Class Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 1.23%
5 Years rr_AverageAnnualReturnYear05 1.19% [7]
Since Inception rr_AverageAnnualReturnSinceInception 2.22% [7]
Principal Funds Inc | Bond Market Index Fund | R-1  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PBIMX
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.35%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.54%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.15%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.10%) [5],[6]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.05%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 107
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 355
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 623
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,389
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-1 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.30%
5 Years rr_AverageAnnualReturnYear05 0.95%
Since Inception rr_AverageAnnualReturnSinceInception 2.27%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | Bond Market Index Fund | R-2  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PBINX
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.30%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.46%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.02%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.10%) [5],[6]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.92%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 94
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 315
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 554
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,239
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-2 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.41%
5 Years rr_AverageAnnualReturnYear05 1.08%
Since Inception rr_AverageAnnualReturnSinceInception 2.41%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | Bond Market Index Fund | R-3  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PBOIX
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.33%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.84%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.10%) [5],[6]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.74%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 76
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 258
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 456
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,028
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-3 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.59%
5 Years rr_AverageAnnualReturnYear05 1.27%
Since Inception rr_AverageAnnualReturnSinceInception 2.59%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | Bond Market Index Fund | R-4  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PBIPX
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.10%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.29%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.65%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.10%) [5],[6]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.55%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 56
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 198
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 352
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 801
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-4 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.83%
5 Years rr_AverageAnnualReturnYear05 1.46%
Since Inception rr_AverageAnnualReturnSinceInception 2.80%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | Bond Market Index Fund | R-5  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PBIQX
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.27%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.53%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.10%) [5],[6]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.43%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 44
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 160
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 286
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 655
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-5 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.95%
5 Years rr_AverageAnnualReturnYear05 1.57%
Since Inception rr_AverageAnnualReturnSinceInception 2.91%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | Capital Securities Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading CAPITAL SECURITIES FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks to provide current income.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 8.4% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 8.40%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in capital securities at the time of purchase. Capital securities include Tier 2 subordinated debt securities issued by U.S. and non-U.S. financial institutions (including, but not limited to, banks and insurance companies), contingent convertible securities (“Cocos”), as well as preferred securities, including preferred stock and junior subordinated debt, issued by U.S. and non-U.S. corporations, financial institutions, and other issuers for purposes of satisfying regulatory capital requirements or obtaining rating agency credit. Capital securities may pay fixed rate or adjustable rate distributions and generally have a payment "preference" over common stock, but are junior to the issuer's senior debt in a liquidation of the issuer’s assets. Cocos are hybrid debt securities typically issued by banking institutions that have contractual equity conversion or principal write-down features that are triggered by regulatory capital thresholds or regulatory actions calling into question the issuing banking institution’s continued viability as a going-concern if the conversion trigger were not exercised.
Tier 2 and preferred securities purchased by the Fund are issued by companies with senior debt rated at the time of purchase BBB- or higher by S&P Global Ratings ("S&P Global") or Baa3 or higher by Moody's Investors Service, Inc. ("Moody's"). The Fund may invest up to 100% of its assets in below investment grade (sometimes called “junk”) preferred securities which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P Global (if the preferred security has been rated by only one of those agencies, that rating will determine whether the preferred security is below investment grade; if the preferred security has not been rated by either of those agencies, those selecting such investments will determine whether the preferred security is of a quality comparable to those rated below investment grade), provided that the issuer of such below investment grade preferred securities has senior debt outstanding that is rated at the time of purchase BBB- or higher by S&P Global or Baa3 or higher by Moody's. The Fund is not managed to a particular maturity or duration.
The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the U.S. and non-U.S. (foreign) financial services (i.e., banking, insurance and commercial finance) industry.
During the fiscal year ended August 31, 2017, 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):
0.00% in securities rated Aaa
64.22% in securities rated Baa
0.00% in securities rated Caa
0.00% in securities rated D
0.00% in securities rated Aa
20.48% in securities rated Ba
0.00% in securities rated Ca
1.01% in securities not rated
11.38% in securities rated A
2.91% in securities rated B
0.00% in securities rated C
 
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the U.S. and non-U.S. (foreign) financial services (i.e., banking, insurance and commercial finance) industry.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Contingent Convertible Securities Risk. In addition to the general risks associated with fixed-income securities and convertible securities, the risks of investing in contingent convertible securities (“CoCos”) include the risk that a CoCo may be written down, written off or converted into an equity security when the issuer’s capital ratio falls below a specified trigger level, or in a regulator’s discretion depending on the regulator’s judgment about the issuer’s solvency prospects. Due to these features, CoCos may have substantially greater risk than other securities in times of financial stress. If the trigger level is breached, the issuer’s decision to write down, write off or convert a CoCo may result in the fund's complete loss on an investment in CoCos with no chance of recovery even if the issuer remains in existence.
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; 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.
Industry Concentration Risk. A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries.
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Financial Services. A fund concentrating in financial services companies may be more susceptible to adverse economic or regulatory occurrences affecting financial services companies. Financial companies may be adversely affected in certain market cycles, including periods of rising interest rates, which may restrict the availability and increase the cost of capital, and declining economic conditions, which may cause credit losses due to financial difficulties of borrowers. Because many types of financial companies are especially vulnerable to these economic cycles, the Fund's investments in these companies may lose significant value during such periods.
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.
Preferred Securities Risk. Because preferred securities have a lower priority claim on assets or earnings than senior bonds and other debt instruments in a company's capital structure, they are subject to greater credit and liquidation risk than more senior debt instruments. In addition, preferred securities are subject to other risks, such as limited or no voting rights, deferring or skipping distributions, interest rate risk, and redeeming the security prior to any stated maturity date.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at www.principal.com.
The bar chart shows the investment returns of the Fund’s Class S shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (March 14, 2014).
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at www.principal.com.The bar chart shows the investment returns of the Fund’s Class S shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [8]
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q3 '16
4.20%
Lowest return for a quarter during the period of the bar chart above:
Q1 '16
(0.81)%

(1) The year-to-date return as of September 30, 2017 was 10.20% for Class S shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class S shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 S shares only and would be different for the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Capital Securities Fund | BofA Merrill Lynch U.S. All Capital Securities Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel ICE BofA Merrill Lynch U.S. All Capital Securities Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 3.81%
Since Inception rr_AverageAnnualReturnSinceInception 5.93%
Principal Funds Inc | Capital Securities Fund | Class S  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PCSFX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.07%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.08%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.07%) [9]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.01% [10]
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 1
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 3
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 6
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 13
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Annual Return 2015 rr_AnnualReturn2015 3.70%
Annual Return 2016 rr_AnnualReturn2016 5.67%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 10.20%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.20%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (0.81%)
Label rr_AverageAnnualReturnLabel Class S Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.67%
Since Inception rr_AverageAnnualReturnSinceInception 4.68%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 14, 2014
Principal Funds Inc | Capital Securities Fund | Class S | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class S Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 3.93%
Since Inception rr_AverageAnnualReturnSinceInception 2.62%
Principal Funds Inc | Capital Securities Fund | Class S | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class S Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 3.74%
Since Inception rr_AverageAnnualReturnSinceInception 2.79%
Principal Funds Inc | Diversified Real Asset Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading DIVERSIFIED REAL ASSET FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks a long-term total return in excess of inflation.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 65.1% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 65.10%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts 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 Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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 also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption With respect to Class C shares, you would pay the following expenses if you did not redeem your shares (all other classes would be the same as in the above example):
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in investments related to real assets and real asset companies. The Fund seeks to achieve its investment objective by allocating its assets among general investment categories related to real assets and real asset companies (which include tangible assets and investments that are expected to perform well in periods of rising or high inflation) such as the following: infrastructure, natural resources and timber, commodities, real estate companies, foreign currency, and certain bonds and fixed income securities (such as inflation-indexed bonds, U.S. treasury and agency notes and bonds, and floating rate debt). The Fund purchases derivative instruments. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index.

In managing the Fund, Principal Global Investors, LLC (“PGI”), the Fund’s investment advisor, determines the Fund's strategic asset allocation among strategies that are executed by multiple sub-advisors. The allocations will vary from time to time, and the Fund may add additional investment categories. The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the real estate and energy/natural resources industries. Except for the foregoing concentration policy, the Fund retains considerable latitude in allocating its assets. The Fund invests in U.S. and foreign securities. The Fund may invest in equity securities regardless of market capitalization size (small, medium, or large) and style (growth or value). The fixed income portion of the Fund is not managed to a particular maturity or duration.
The Fund invests in domestic and foreign publicly-listed infrastructure companies. Publicly-listed infrastructure equity securities trade on an exchange and include, but are not limited to, companies involved in the ownership and/or operations of infrastructure assets within the transportation, communications, water, electricity transmission and distribution, and oil and gas storage, processing and transportation industries. The Fund invests in MLPs, and in particular, in the mid-stream category of MLPs, which is generally comprised of pipelines used to gather, process, transport, and distribute natural resources such as natural gas, crude oil, and refined petroleum products.
Natural resources generally include precious metals, such as gold, silver and platinum, ferrous and nonferrous metals, such as iron, aluminum and copper, strategic metals such as uranium and titanium, hydrocarbons such as coal, oil and natural gas, timberland, and undeveloped real property. The Fund invests in securities of companies that primarily own, explore, mine, process or otherwise develop natural resources, timber and wood products, or agricultural commodities and products, or that supply goods and services to such companies. These include companies contributing to and/or profiting from, these sectors, especially those active in production, processing and supply chain services. Part of the natural resources strategy is managed by PGI using a passive management strategy in which PGI purchases all of the securities in the S&P Global Natural Resources Index, and weighs them equally, in an attempt to match or exceed the performance of the index.
Commodities are assets that have tangible properties, such as oil, coal, natural gas, agricultural products, industrial metals, livestock and precious metals. To gain exposure to the commodities markets without investing directly in physical commodities, the Fund invests in a combination of commodity index-linked notes and fixed-income securities. Commodity index-linked notes are derivative debt instruments with principal and/or coupon payments linked to the performance of commodity indices. These notes are sometimes referred to as "structured notes" because the terms of these notes may be structured by the issuer and the purchaser of the note. The value of these notes will rise or fall in response to changes in the underlying commodity index and will be subject to credit and interest rate risks that typically affect debt securities. The fixed income securities are primarily short-term U.S. Treasury and Agency notes and bonds.
The Fund invests in a wholly-owned subsidiary of the Fund organized under the laws of the Cayman Islands (the “Cayman Subsidiary”). The Fund invests in the Cayman Subsidiary to gain exposure to the commodity markets within the limitations of the federal tax law requirements applicable to regulated investment companies (“RICs”) under the Internal Revenue Code (the “Code”). The Cayman Subsidiary invests in commodity-linked derivatives, including commodity-linked swaps, commodity futures contracts and/or options on commodities, as well as instruments such as fixed income securities, cash and cash equivalents and/or U.S. government securities, either as investments or to serve as margin or collateral for the Cayman Subsidiary's derivatives positions.
The Fund invests in equity securities of companies that have at least 50% of its assets, income or profits derived from products or services related to the real estate industry ("real estate companies"). Real estate companies include real estate investment trusts ("REITs"), REIT-like entities, and companies with substantial real estate holdings such as paper, lumber, hotel and entertainment companies as well as building supply manufacturers, mortgage lenders, and mortgage servicing companies.
The Fund invests in currency forward contracts and options for the purpose of hedging risk and providing total return. This portion of the Fund invests in currencies of economically and politically stable industrialized nations, and approximately 20 of the most liquid emerging market currencies. To help preserve purchasing power, when domestic inflation increases, the Fund seeks to invest in currencies in countries where inflation remains low and stable.
The Fund invests in inflation-indexed bonds issued by the U.S. and non-U.S. governments, their agencies or instrumentalities and U.S. and non-U.S. corporations. Inflation-indexed bonds are fixed-income securities that are structured to provide protection against inflation. The value of the bond's principal or the interest income paid on the bond is adjusted to track changes in an official inflation measure.
The Fund invests in below-investment-grade (sometimes called “junk”) or comparable unrated floating rate debt (also known as bank loans, syndicated loans, leveraged loans or senior floating rate interests). Floating rate debt has a variable coupon that resets periodically, with interest payments determined by a representative interest rate index (e.g. LIBOR or the federal funds rate) plus a fixed spread. As a result, the coupon payments vary, or “float” with prevailing market interest rates.
During the fiscal year ended August 31, 2017, 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):
41.56% in securities rated Aaa
5.84% in securities rated Baa
3.24% in securities rated Caa
0.10% in securities rated D
0.00% in securities rated Aa
23.93% in securities rated Ba
0.05% in securities rated Ca
6.86% in securities not rated
0.65% in securities rated A
17.77% in securities rated B
0.00% in securities rated C
 
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the real estate and energy/natural resources industries.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Asset Allocation Risk. A fund's selection and weighting of asset classes and allocation among sub-advisors may cause it to underperform other funds with a similar investment objective.
Bank Loans Risk. Changes in economic conditions are likely to cause issuers of bank loans (also known as senior floating rate interests) to be unable to meet their obligations. In addition, the value of the collateral securing the loan (if any) may decline, causing a loan to be substantially unsecured. Underlying credit agreements governing the bank loans, reliance on market makers, priority of repayment and overall market volatility may harm the liquidity of loans.
Cayman Subsidiary Risk. A fund is subject to the particular risks associated with the investments of the Fund’s wholly-owned Cayman Subsidiary, namely Commodity-Related Investments Risk, Counterparty Risk and Derivatives Risk. The Cayman Subsidiary is not registered under the Investment Company Act and is not subject to all the investor protections of the Investment Company Act. The laws of the Cayman Islands and/or the United States (including the IRS position on income earned from wholly-owned subsidiaries described in past IRS private letter rulings) may change, resulting in the inability of the fund and/or the Cayman Subsidiary to operate as described in this Prospectus.
Commodity-Related Investments Risk. The value of commodities investments will generally be affected by overall market movements and factors specific to a particular industry or commodity, which may include weather, embargoes, tariffs, and economic health, political, international regulatory and other developments. Exposure to the commodities markets may subject the fund to greater volatility than investments in traditional securities.
Counterparty Risk. Counterparty risk is the risk that the counterparty to a contract or other obligation will be unable or unwilling to honor its obligations.
Derivatives Risk. Derivatives may not move in the direction anticipated by the portfolio manager. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and result in disproportionate losses that may be substantially greater than a fund's initial investment.
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Commodity Index-Linked Notes. Commodity index-linked notes expose the fund to movements in commodity prices. They are also subject to credit, counterparty, and interest rate risk. Commodity index-linked notes are often leveraged. At the maturity of the note, the fund may receive more or less principal than it originally invested. The fund may also receive interest payments on the note that are less than the stated coupon interest payments.
•
Currency Contracts. Derivatives related to currency contracts involve the specific risk of government action through exchange controls that would restrict the ability of the fund to deliver or receive currency.
•
Forward Contracts, Futures and Swaps. Forward contracts, futures, and swaps involve specific risks, including: the imperfect correlation between the change in market value of the instruments held by the fund and the price of the forward contract, future or swap; possible lack of a liquid secondary market for a forward contract, future or swap and the resulting inability to close a forward contract, future or swap when desired; counterparty risk; and if the fund has insufficient cash, it may have to sell securities from its portfolio to meet daily variation margin requirements.
•
Options. Options involve specific risks, including: imperfect correlation between the change in market value of the instruments held by the fund and the price of the options, counterparty risk, difference in trading hours for the options markets and the markets for the underlying securities (rate movements can take place in the underlying markets that cannot be reflected in the options markets), and an insufficient liquid secondary market for particular options.
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.
•
Small and Medium Market Capitalization Companies Risk. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.
•
Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.
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 Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.
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; 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.
Industry Concentration Risk. A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries.
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Energy/Natural Resources. A fund concentrating in energy/natural resource companies may be affected by numerous factors, including events occurring in nature, inflationary pressures, international politics, the success of exploration projects, commodity prices, energy conservation, taxes and other government regulations. In addition, interest rates and general economic conditions may affect the demand for energy/natural resources. For example, events occurring in nature (such as earthquakes or fires in prime energy/natural resource areas) and political events (such as coups, military confrontations or acts of terrorism) can affect overall supply of energy/natural resources and the value of companies involved in energy/natural resources.
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Real Estate. A fund concentrating in the real estate industry is subject to the risks associated with direct ownership of real estate, securities of companies in the real estate industry, and/or real estate investment trusts.
Leverage Risk. Leverage created by borrowing or certain types of transactions or investments 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.
Master Limited Partnership ("MLP") Risk. MLPs are publicly-traded limited partnership interests or units. An MLP that invests in a particular industry (e.g., oil and gas) will be harmed by detrimental economic events within that industry. As partnerships, MLPs may be subject to less regulation (and less protection for investors) under state laws than corporations. In addition, MLPs may be subject to state taxation in certain jurisdictions, which may reduce the amount of income an MLP pays to its investors.
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.
Real Estate Investment Trusts (“REITs”) Risk. In addition to risks associated with investing in real estate securities, REITs are dependent upon management skills, are not diversified, and are subject to heavy cash flow dependency, risks of default by borrowers, and self-liquidation. Investment in REITs also involves risks similar to risks of investing in small market capitalization companies, such as limited financial resources, less frequent and limited volume trading, and may be subject to more abrupt or erratic price movements than larger company securities. A REIT could fail to qualify for tax-free pass-through of income under the Internal Revenue Code. Fund shareholders will indirectly bear their proportionate share of the expenses of REITs in which the fund invests.
Real Estate Securities Risk. Investing in real estate securities subjects the fund to the risks associated with the real estate market (which are similar to the risks associated with direct ownership in real estate), including declines in real estate values, loss due to casualty or condemnation, property taxes, interest rate changes, increased expenses, cash flow of underlying real estate assets, regulatory changes (including zoning, land use and rents), and environmental problems, as well as to the risks related to the management skill and creditworthiness of the issuer.
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
U.S. Government Securities Risk. Yields available from U.S. government securities are generally lower than yields from many other fixed-income securities.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Classes A and C - www.principalfunds.com.
•
For Institutional Class and Classes R-3, R-4, R-5, and R-6 - www.principal.com.
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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (March 16, 2010).
For periods prior to the inception date of Class R-6 shares (December 31, 2014), and Classes R-3, R-4, and R-5 shares (March 29, 2016), the performance shown in the table for these newer classes is that of the Fund's Institutional Class shares, adjusted to reflect the respective fees and expenses of each class. However, where this adjustment for fees and expenses results in performance for a newer class that is higher than the historical performance of the Institutional Class shares, the historical performance of the Institutional Class shares is used. These adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares, which were first sold March 16, 2010.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Classes A and C - www.principalfunds.com.•For Institutional Class and Classes R-3, R-4, R-5, and R-6 - www.principal.com.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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex Performance of a blended index shows how the Fund’s performance compares to a blend of indices with similar investment objectives. Performance of the components of the blended index are also shown. The weightings of the Diversified Real Asset Strategic Index are as follows: 35% Bloomberg Barclays U.S. Treasury TIPS Index, 20% S&P Global Infrastructure Index, 20% S&P Global Natural Resources Index, 15% Bloomberg Commodity Index, and 10% FTSE EPRA/NAREIT Developed Markets Index.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [11]
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q4 '11
7.04%
Lowest return for a quarter during the period of the bar chart above:
Q3 '15
(10.42)%

(1) The year-to-date return as of September 30, 2017 was 7.13% for Class A shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class A shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 the other share classes.
Performance of a blended index shows how the Fund’s performance compares to a blend of indices with similar investment objectives. Performance of the components of the blended index are also shown. The weightings of the Diversified Real Asset Strategic Index are as follows: 35% Bloomberg Barclays U.S. Treasury TIPS Index, 20% S&P Global Infrastructure Index, 20% S&P Global Natural Resources Index, 15% Bloomberg Commodity Index, and 10% FTSE EPRA/NAREIT Developed Markets Index. The blended index returns reflect the allocation described in the preceding sentence.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Diversified Real Asset Fund | Diversified Real Asset Strategic Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Diversified Real Asset Strategic Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 12.40%
5 Years rr_AverageAnnualReturnYear05 1.31%
Since Inception rr_AverageAnnualReturnSinceInception 2.28%
Principal Funds Inc | Diversified Real Asset Fund | Bloomberg Barclays US Treasury TIPS Index [Member]  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays U.S. Treasury TIPS Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 4.68%
5 Years rr_AverageAnnualReturnYear05 0.89%
Since Inception rr_AverageAnnualReturnSinceInception 3.32%
Principal Funds Inc | Diversified Real Asset Fund | S&P Global Infrastructure Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel S&P Global Infrastructure Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 11.45%
5 Years rr_AverageAnnualReturnYear05 6.77%
Since Inception rr_AverageAnnualReturnSinceInception 5.54%
Principal Funds Inc | Diversified Real Asset Fund | S&P Global Natural Resources Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel S&P Global Natural Resources Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 31.45%
5 Years rr_AverageAnnualReturnYear05 (0.82%)
Since Inception rr_AverageAnnualReturnSinceInception (1.29%)
Principal Funds Inc | Diversified Real Asset Fund | Bloomberg Commodity Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Commodity Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 11.77%
5 Years rr_AverageAnnualReturnYear05 (8.95%)
Since Inception rr_AverageAnnualReturnSinceInception (5.86%)
Principal Funds Inc | Diversified Real Asset Fund | FTSE EPRA/NAREIT Developed Markets Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel FTSE EPRA/NAREIT Developed Markets Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 4.06%
5 Years rr_AverageAnnualReturnYear05 9.48%
Since Inception rr_AverageAnnualReturnSinceInception 8.15%
Principal Funds Inc | Diversified Real Asset Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PRDAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 3.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.48%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.54%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.31%) [12],[13]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.23%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 496
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 814
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,155
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,115
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Annual Return 2011 rr_AnnualReturn2011 0.41%
Annual Return 2012 rr_AnnualReturn2012 7.23%
Annual Return 2013 rr_AnnualReturn2013 4.96%
Annual Return 2014 rr_AnnualReturn2014 2.14%
Annual Return 2015 rr_AnnualReturn2015 (12.66%)
Annual Return 2016 rr_AnnualReturn2016 5.40%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 7.13%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2011
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 7.04%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2015
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (10.42%)
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.44%
5 Years rr_AverageAnnualReturnYear05 0.36%
Since Inception rr_AverageAnnualReturnSinceInception 2.46%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 16, 2010
Principal Funds Inc | Diversified Real Asset Fund | Class A | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 0.57%
5 Years rr_AverageAnnualReturnYear05 (0.18%)
Since Inception rr_AverageAnnualReturnSinceInception 1.94%
Principal Funds Inc | Diversified Real Asset Fund | Class A | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 0.96%
5 Years rr_AverageAnnualReturnYear05 0.19%
Since Inception rr_AverageAnnualReturnSinceInception 1.83%
Principal Funds Inc | Diversified Real Asset Fund | Class C  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PRDCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.30%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.11%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.13%) [12],[13]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.98%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 301
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 648
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,122
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,431
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 201
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 648
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,122
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,431
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Label rr_AverageAnnualReturnLabel Class C Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 3.58%
5 Years rr_AverageAnnualReturnYear05 0.36%
Since Inception rr_AverageAnnualReturnSinceInception 2.28%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 16, 2010
Principal Funds Inc | Diversified Real Asset Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PDRDX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.12%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.93%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.07%) [12],[13]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.86%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 88
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 289
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 508
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,137
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.86%
5 Years rr_AverageAnnualReturnYear05 1.52%
Since Inception rr_AverageAnnualReturnSinceInception 3.45%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 16, 2010
Principal Funds Inc | Diversified Real Asset Fund | R-3  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGDRX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.33%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.39%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [12],[13]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.36%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 138
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 437
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 758
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,666
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-3 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.34%
5 Years rr_AverageAnnualReturnYear05 1.00%
Since Inception rr_AverageAnnualReturnSinceInception 2.92%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 16, 2010
Principal Funds Inc | Diversified Real Asset Fund | R-4  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGDSX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.10%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.29%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.20%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [12],[13]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.17%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 119
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 378
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 657
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,452
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-4 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.53%
5 Years rr_AverageAnnualReturnYear05 1.19%
Since Inception rr_AverageAnnualReturnSinceInception 3.11%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 16, 2010
Principal Funds Inc | Diversified Real Asset Fund | R-5  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGDTX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.27%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.08%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [12],[13]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.05%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 107
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 340
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 593
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,314
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-5 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.67%
5 Years rr_AverageAnnualReturnYear05 1.31%
Since Inception rr_AverageAnnualReturnSinceInception 3.24%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 16, 2010
Principal Funds Inc | Diversified Real Asset Fund | R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PDARX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.03%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.84%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [12],[13]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.80%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 82
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 264
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 462
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,033
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-6 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 5.86%
5 Years rr_AverageAnnualReturnYear05 1.52%
Since Inception rr_AverageAnnualReturnSinceInception 3.44%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 16, 2010
Principal Funds Inc | Dynamic Floating Rate High Income Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading DYNAMIC FLOATING RATE HIGH INCOME FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks to provide a high level of current income.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 104.0% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 104.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts 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 Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in floating rate debt securities, including bank loans and corporate bonds, and other investment companies that provide investment exposure to such floating rate securities. Floating interest rates vary with and are periodically adjusted to reflect changes in a generally recognized base interest rate such as LIBOR (London Interbank Offered Rate) or the prime rate. Floating rate debt securities are often below investment grade rated securities (sometimes called “high yield” or “junk”) which are rated at the time of purchase Ba1 or lower by Moody’s Investors Services, Inc. (“Moody’s”) and BB+ or lower by S&P Global Ratings (“S&P Global”) (if the security has not been rated by either of those agencies, the Sub-Advisor will determine whether the security is of a quality comparable to those rated below investment grade). The Fund also invests in US and non-US fixed-rate loans, investment grade and below investment grade corporate bonds. Under normal circumstances, the Fund maintains an average portfolio duration that is within 0 to 2 years. The Fund actively trades portfolio securities. From time to time, the Fund borrows to purchase securities prior to the settlement of bank loan sales transactions.
The Fund uses derivative instruments for hedging, managing fixed income exposure, managing foreign currency exposure, and/or mitigating volatility. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. Specifically, the Fund invests in futures contracts (including Treasury, sovereign bond and volatility futures) and/or interest rate swaps to manage the fixed-income exposure (including for hedging purposes) and credit default swaps to increase or decrease, in an efficient manner, exposure to certain sectors or individual issuers. The Fund uses forwards to manage its foreign currency exposure.
During the fiscal year ended August 31, 2017, 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):
0.00% in securities rated Aaa
13.42% in securities rated Baa
4.29% in securities rated Caa
0.00% in securities rated D
0.00% in securities rated Aa
49.46% in securities rated Ba
0.05% in securities rated Ca
1.07% in securities not rated
0.00% in securities rated A
31.71% in securities rated B
0.00% in securities rated C
 
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Bank Loans Risk. Changes in economic conditions are likely to cause issuers of bank loans (also known as senior floating rate interests) to be unable to meet their obligations. In addition, the value of the collateral securing the loan (if any) may decline, causing a loan to be substantially unsecured. Underlying credit agreements governing the bank loans, reliance on market makers, priority of repayment and overall market volatility may harm the liquidity of loans.
Borrowing Risk. Borrowing can increase fund expenses due to interest payments to lenders and related expenses. Such borrowing also might reduce the fund’s return if the yield on the investments purchased is less than the borrowing costs.
Counterparty Risk. Counterparty risk is the risk that the counterparty to a contract or other obligation will be unable or unwilling to honor its obligations.
Derivatives Risk. Derivatives may not move in the direction anticipated by the portfolio manager. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and result in disproportionate losses that may be substantially greater than a fund's initial investment.
•
Credit Default Swaps. Credit default swaps involve special risks in addition to those associated with swaps generally because they are difficult to value, are highly susceptible to liquidity and credit risk, and generally pay a return to the party that has paid the premium only in the event of an actual default by the issuer of the underlying obligation (as opposed to a credit downgrade or other indication of financial difficulty). The protection “buyer” in a credit default contract may be obligated to pay the protection “seller” an up front payment or a periodic stream of payments over the term of the contract provided generally that no credit event on a reference obligation has occurred. If a credit event occurs, the seller generally must pay the buyer the “par value” (full notional value) of the swap in exchange for an equal face amount of deliverable obligations of the reference entity described in the swap, or the seller may be required to deliver the related net cash amount, if the swap is cash settled. The Fund may be either the buyer or seller in the transaction.
•
Currency Contracts. Derivatives related to currency contracts involve the specific risk of government action through exchange controls that would restrict the ability of the fund to deliver or receive currency.
•
Forward Contracts, Futures and Swaps. Forward contracts, futures, and swaps involve specific risks, including: the imperfect correlation between the change in market value of the instruments held by the fund and the price of the forward contract, future or swap; possible lack of a liquid secondary market for a forward contract, future or swap and the resulting inability to close a forward contract, future or swap when desired; counterparty risk; and if the fund has insufficient cash, it may have to sell securities from its portfolio to meet daily variation margin requirements.
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; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).
Hedging Risk. A fund that implements a hedging strategy using derivatives and/or securities could expose the fund to the risk that can arise when a change in the value of a hedge does not match a change in the value of the asset it hedges. In other words, the change in value of the hedge could move in a direction that does not match the change in value of the underlying asset, resulting in a risk of loss to the fund.
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 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.
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.
Portfolio Turnover (Active Trading) Risk. High portfolio turnover (more than 100%) caused by actively trading portfolio securities may result in accelerating the realization of taxable gains and losses, lower fund performance and increased brokerage costs.
Volatility Mitigation Risk.  Volatility mitigation strategies may increase fund transaction costs, which could increase losses or reduce gains.  These strategies may not protect the fund from market declines and may reduce the fund’s participation in market gains.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Class A - www.principalfunds.com.
•
For Institutional Class - www.principal.com.
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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (September 10, 2014).
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Class A - www.principalfunds.com.•For Institutional Class - www.principal.com.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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex Effective June 6, 2017, the Fund's primary benchmark changed from Bloomberg Barclays High Yield 2% Issuer Constrained Index to S&P/LSTA Leveraged Loan 100 Index because S&P/LSTA Leveraged Loan 100 Index is more representative of the Fund's strategy.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [14]
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q3 '16
4.35%
Lowest return for a quarter during the period of the bar chart above:
Q4 '15
(3.74)%
(1) The year-to-date return as of September 30, 2017 was 2.55% for Class A shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class A shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 the other share classes.
Effective June 6, 2017, the Fund's primary benchmark changed from Bloomberg Barclays High Yield 2% Issuer Constrained Index to S&P/LSTA Leveraged Loan 100 Index because S&P/LSTA Leveraged Loan 100 Index is more representative of the Fund's strategy.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Dynamic Floating Rate High Income Fund | Bloomberg Barclays High Yield 2% Issuer Constrained Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays High Yield 2% Issuer Constrained Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 17.13%
Since Inception rr_AverageAnnualReturnSinceInception 4.00%
Principal Funds Inc | Dynamic Floating Rate High Income Fund | S&P/LSTA Leveraged Loan 100 Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel S&P/LSTA Leveraged Loan 100 Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 10.88%
Since Inception rr_AverageAnnualReturnSinceInception 2.78%
Principal Funds Inc | Dynamic Floating Rate High Income Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PDYAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 3.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.65%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.89%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.02%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.81%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.69%) [15]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.12%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 485
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 858
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,256
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,367
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Annual Return 2015 rr_AnnualReturn2015 (3.79%)
Annual Return 2016 rr_AnnualReturn2016 12.15%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 2.55%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.35%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2015
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (3.74%)
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 7.95%
Since Inception rr_AverageAnnualReturnSinceInception 0.18%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 10, 2014
Principal Funds Inc | Dynamic Floating Rate High Income Fund | Class A | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 5.63%
Since Inception rr_AverageAnnualReturnSinceInception (1.88%)
Principal Funds Inc | Dynamic Floating Rate High Income Fund | Class A | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 4.44%
Since Inception rr_AverageAnnualReturnSinceInception (0.82%)
Principal Funds Inc | Dynamic Floating Rate High Income Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PDYIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.65%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.75%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.02%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.42%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.65%) [15]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.77%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 79
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 385
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 714
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,646
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 12.63%
Since Inception rr_AverageAnnualReturnSinceInception 2.24%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 10, 2014
Principal Funds Inc | EDGE MidCap Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading EDGE MIDCAP FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks long-term growth of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment):
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 11.9% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 11.90%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies with medium market capitalizations at the time of purchase. For this Fund, companies with medium market capitalizations are those with market capitalizations within the range of companies comprising the Russell Midcap® Index (as of November 30, 2017, this range was between approximately $632.6 million and $35.5 billion). The Fund invests in real estate investment trust ("REIT") securities. The Fund invests in foreign securities.
The Fund invests in equity securities with value and/or growth characteristics and constructs an investment portfolio that has a "blend" of equity securities with these characteristics. Investing in value equity securities is an investment strategy that emphasizes buying equity securities that appear to be undervalued. The growth orientation selection emphasizes buying equity securities of companies whose potential for growth of capital and earnings is expected to be above average. The Fund does not have a policy of preferring one of these categories over the other.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.
•
Small and Medium Market Capitalization Companies Risk. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.
•
Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.
Foreign Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.
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; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).
Real Estate Investment Trusts (“REITs”) Risk. In addition to risks associated with investing in real estate securities, REITs are dependent upon management skills, are not diversified, and are subject to heavy cash flow dependency, risks of default by borrowers, and self-liquidation. Investment in REITs also involves risks similar to risks of investing in small market capitalization companies, such as limited financial resources, less frequent and limited volume trading, and may be subject to more abrupt or erratic price movements than larger company securities. A REIT could fail to qualify for tax-free pass-through of income under the Internal Revenue Code. Fund shareholders will indirectly bear their proportionate share of the expenses of REITs in which the fund invests.
Real Estate Securities Risk. Investing in real estate securities subjects the fund to the risks associated with the real estate market (which are similar to the risks associated with direct ownership in real estate), including declines in real estate values, loss due to casualty or condemnation, property taxes, interest rate changes, increased expenses, cash flow of underlying real estate assets, regulatory changes (including zoning, land use and rents), and environmental problems, as well as to the risks related to the management skill and creditworthiness of the issuer.
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Institutional Class and Class R-6 - www.principal.com.
The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (September 28, 2015).
For periods prior to the inception date of Class R-6 shares (January 3, 2017), the performance shown in the table for Class R-6 shares is that of the Fund's Institutional Class shares, adjusted to reflect the fees and expenses of Class R-6 shares. However, where this adjustment for fees and expenses results in performance for Class R-6 shares that is higher than the historical performance of the Institutional Class shares, the historical performance of the Institutional Class shares is used. These adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares, which were first sold September 28, 2015.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Institutional Class and Class R-6 - www.principal.com.The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [16]
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q1 '16
9.58%
Lowest return for a quarter during the period of the bar chart above:
Q3 '16
2.54%
(1) The year-to-date return as of September 30, 2017 was 8.86% for Institutional Class shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Institutional Class shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 Institutional Class shares only and would be different for the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | EDGE MidCap Fund | Russell Midcap Index [Member]  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Russell MidCap Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 13.80%
Since Inception rr_AverageAnnualReturnSinceInception 15.54%
Principal Funds Inc | EDGE MidCap Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PEDGX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.03%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.78%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [17]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.78%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 80
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 249
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 433
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 966
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Annual Return 2016 rr_AnnualReturn2016 24.44%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 8.86%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 9.58%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 2.54%
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 24.44%
Since Inception rr_AverageAnnualReturnSinceInception 20.60%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 28, 2015
Principal Funds Inc | EDGE MidCap Fund | Institutional Class | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Institutional Class Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 22.44%
Since Inception rr_AverageAnnualReturnSinceInception 18.96%
Principal Funds Inc | EDGE MidCap Fund | Institutional Class | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Institutional Class Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 14.14%
Since Inception rr_AverageAnnualReturnSinceInception 15.20%
Principal Funds Inc | EDGE MidCap Fund | R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PEDMX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.06%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.81%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [17]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.77%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 79
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 255
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 446
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 998
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-6 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 24.38%
Since Inception rr_AverageAnnualReturnSinceInception 20.56%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 28, 2015
Principal Funds Inc | Global Multi-Strategy Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading GLOBAL MULTI-STRATEGY FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks to achieve long-term capital appreciation with an emphasis on positive total returns and managing volatility.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 317.6% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 317.60%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts 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 Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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 also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption With respect to Class C shares, you would pay the following expenses if you did not redeem your shares (all other classes would be the same as in the above example):
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Principal Global Investors, LLC ("PGI"), the Fund's investment advisor, seeks to combine diversified investment strategies efficiently and systematically so that the Fund generates a positive total return with relatively low volatility and low sensitivity or correlation to market indices. In managing the Fund, PGI allocates the Fund’s assets among the investment strategies described below, which one or more of the Fund's sub-advisors execute. PGI has considerable latitude in allocating the Fund's assets. Depending upon market conditions, the Fund may use the strategies to varying degrees, discontinue using a strategy, or add strategies.
The Fund invests in a broad range of instruments including, but not limited to, equities, bonds, currencies, commodities, convertible securities, and bank loans. Under normal market conditions, the Fund invests in securities of issuers located throughout the world, including the U.S., invests at least 30% of its net assets in foreign and emerging market securities, and holds investments tied economically to at least twenty countries.
The Fund invests in equity securities regardless of market capitalization size (small, medium, or large) and style (growth or value). The Fund invests in investment-grade and below investment-grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's Investors Service, Inc. ("Moody's") and BB+ or lower by S&P Global Ratings ("S&P Global") (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, those selecting such investments will determine whether the bond is of a quality comparable to those rated below investment grade). The fixed income portion of the Fund is not managed to a particular maturity or duration. The Fund actively trades portfolio securities.
The Fund invests in derivative instruments. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The strategies use different types of derivative instruments for various purposes, including to gain exposure to securities and to attempt to reduce risk. The Fund may invest in money market funds in order to provide collateral for certain derivative positions and other financial instruments and to provide asset coverage for certain derivative positions and other financial instruments that create obligations to make future payments to third parties.
The Fund takes long and short positions in securities and derivative instruments. When taking a short position, the Fund may sell an instrument that it does not own and then borrow to meet its settlement obligations. Short positions benefit from a decrease in price of the underlying instrument and lose value if the price of the underlying instrument increases. Long positions profit if the value of the instrument increases. Simultaneously engaging in long investing and short selling reduces the net exposure to general market movements. The Fund also takes relative value positions in an effort capitalize on price differences between similar securities or relative value among securities of the same company.
Credit/Distressed. This strategy uses a flexible approach to invest primarily in fixed income securities and instruments related to credit, currencies and interest rates, while employing risk management strategies. This strategy uses a variety of techniques to obtain market exposure, such as derivative instruments, including options, futures, forwards and swaps (including credit default swaps); entering into a series of purchase and sale contracts; purchasing securities on a when-issued, delayed delivery or forward commitment basis; and engaging in short sales. This strategy may obtain investment exposure substantially through derivatives instruments, may use such instruments in an effort to minimize volatility, and may use equity futures for hedging purposes.
A portion of this strategy takes long and short positions in selected emerging market issuers when those selecting such investments identify factors (such as macro-economic factors, country-specific factors, or credit-specific factors) that they believe will drive substantial appreciation or depreciation of the particular exposure. The strategy's geographic focus is derived from economic and political developments and the specific nature of local jurisdictions in the emerging markets.
Equity Long/Short. This strategy provides long and short exposure to a diversified portfolio of U.S. and foreign, including emerging market, equity securities. Those selecting such investments simultaneously invest long in equities they expect to increase in value and either short sells equities they expect to decrease in value, or hedges equity market exposure another way (for example, by using derivatives such as futures or options). This strategy uses two methods of analysis: fundamental analysis, which examines a company's financial statements and operations, especially sales, earnings, products, management and competition; and quantitative analysis, which uses mathematical models to evaluate a company's measurable characteristics such as revenue, earnings, margins and market share.
Event-Driven. This strategy invests in securities on the basis that a specific event or catalyst will affect future prices. This strategy attempts to capitalize on price discrepancies and returns generated by corporate activity, such as merger arbitrage, where the Fund holds a long/short portfolio of stocks of companies involved in mergers.
Global Macro. This strategy provides long and short exposure to a broad spectrum of global assets (including equities, currencies, fixed income securities, bonds, commodities, and interest rates) in an effort to profit from movement in the prices of securities that are highly sensitive to macroeconomic conditions. The managed futures portion of this strategy uses quantitative selection models to help predict movements in these markets. In pursuing this strategy, the Fund, either directly or through its wholly-owned subsidiary organized under the laws of the Cayman Islands (the “Cayman Subsidiary”) invests in commodity-linked derivatives and in instruments such as fixed income securities, cash and cash equivalents and/or U.S. government securities, either as investments or to serve as margin or collateral for derivative positions.
Commodities are assets that have tangible properties, such as oil, coal, natural gas, agricultural products, industrial metals, livestock and precious metals. In pursuing certain commodity strategies, the Fund invests its assets in the Cayman Subsidiary to gain exposure to the commodity markets within the limitations of the federal tax law requirements applicable to regulated investment companies (“RICs”) under the Internal Revenue Code (the “Code”). The Fund's investments in its Cayman Subsidiary at any time will not exceed 25% of the Fund's net assets.
Market Neutral. This strategy invests in long and short positions across different asset classes (including equity and fixed income securities) in an effort to neutralize market risk exposure. The fixed income portion seeks product types that have attractive return characteristics with low volatility. This strategy uses arbitrage, which is the simultaneous purchase and sale of assets in an effort to exploit price differences of identical or similar securities on different markets or in different forms. The fixed-income arbitrage portion seeks to exploit mispricing of various, liquid fixed income or interest rate sensitive securities and provides long and short exposure to developed country bond and currency markets, investment grade and high yield credit markets, and forward mortgage-backed securities trading in the to-be-announced ("TBA") markets. The convertible arbitrage portion structures trades using multiple securities within a convertible bond issuer's capital structure. This strategy may also use derivatives to hedge against a decline in interest rates or credit exposure.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Arbitrage Trading Risk. The underlying relationships between securities in which the fund takes arbitrage investment positions may change in an adverse manner, in which case the fund may realize losses.
Asset Allocation Risk. A fund’s selection and weighting of asset classes and allocation among sub-advisors may cause it to underperform other funds with a similar investment objective.
Bank Loans Risk. Changes in economic conditions are likely to cause issuers of bank loans (also known as senior floating rate interests) to be unable to meet their obligations. In addition, the value of the collateral securing the loan (if any) may decline, causing a loan to be substantially unsecured. Underlying credit agreements governing the bank loans, reliance on market makers, priority of repayment and overall market volatility may harm the liquidity of loans.
Cayman Subsidiary Risk. A fund is subject to the particular risks associated with the investments of the Fund’s wholly-owned Cayman Subsidiary, namely Commodity-Related Investments Risk, Counterparty Risk and Derivatives Risk. The Cayman Subsidiary is not registered under the Investment Company Act and is not subject to all the investor protections of the Investment Company Act. The laws of the Cayman Islands and/or the United States (including the IRS position on income earned from wholly-owned subsidiaries described in past IRS private letter rulings) may change, resulting in the inability of the fund and/or the Cayman Subsidiary to operate as described in this Prospectus.
Commodity-Related Investments Risk. The value of commodities investments will generally be affected by overall market movements and factors specific to a particular industry or commodity, which may include weather, embargoes, tariffs, and economic health, political, international regulatory and other developments. Exposure to the commodities markets may subject the fund to greater volatility than investments in traditional securities.
Convertible Securities Risk. Convertible securities are bonds, notes, debentures, preferred stock or other securities which are convertible into common stock. Convertible securities are subject to the credit and interest rate risks associated with fixed income securities and to the stock market risk associated with equity securities.
Counterparty Risk. Counterparty risk is the risk that the counterparty to a contract or other obligation will be unable or unwilling to honor its obligations.
Derivatives Risk. Derivatives may not move in the direction anticipated by the portfolio manager. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and result in disproportionate losses that may be substantially greater than a fund's initial investment.
•
Credit Default Swaps. Credit default swaps involve special risks in addition to those associated with swaps generally because they are difficult to value, are highly susceptible to liquidity and credit risk, and generally pay a return to the party that has paid the premium only in the event of an actual default by the issuer of the underlying obligation (as opposed to a credit downgrade or other indication of financial difficulty). The protection “buyer” in a credit default contract may be obligated to pay the protection “seller” an up-front payment or a periodic stream of payments over the term of the contract provided generally that no credit event on a reference obligation has occurred. If a credit event occurs, the seller generally must pay the buyer the “par value” (i.e., full notional value) of the swap in exchange for an equal face amount of deliverable obligations of the reference entity described in the swap, or the seller may be required to deliver the related net cash amount, if the swap is cash settled. The Fund may be either the buyer or seller in the transaction.
•
Currency Contracts. Derivatives related to currency contracts involve the specific risk of government action through exchange controls that would restrict the ability of the fund to deliver or receive currency.
•
Forward Contracts, Futures and Swaps. Forward contracts, futures, and swaps involve specific risks, including: the imperfect correlation between the change in market value of the instruments held by the fund and the price of the forward contract, future or swap; possible lack of a liquid secondary market for a forward contract, future or swap and the resulting inability to close a forward contract, future or swap when desired; counterparty risk; and if the fund has insufficient cash, it may have to sell securities from its portfolio to meet daily variation margin requirements.
•
Options. Options involve specific risks, including: imperfect correlation between the change in market value of the instruments held by the fund and the price of the options, counterparty risk, difference in trading hours for the options markets and the markets for the underlying securities (rate movements can take place in the underlying markets that cannot be reflected in the options markets), and an insufficient liquid secondary market for particular options.
Emerging Markets Risk. Investments in emerging market countries may have more risk than those in developed market countries because the emerging markets are less developed and more illiquid. Emerging market countries can also be subject to increased social, economic, regulatory, and political uncertainties and can be extremely volatile.
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.
•
Small and Medium Market Capitalization Companies Risk. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.
•
Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.
Event-Driven Trading Risk. Event-driven trading involves the risk that the special situation may not occur as anticipated, if at all, and that the market price of a stock declines.
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 Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.
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; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).
Hedging Risk. A fund that implements a hedging strategy using derivatives and/or securities could expose the fund to the risk that can arise when a change in the value of a hedge does not match a change in the value of the asset it hedges. In other words, the change in value of the hedge could move in a direction that does not match the change in value of the underlying asset, resulting in a risk of loss to the fund.
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.
Investment Company Securities Risk. A fund that invests in another investment company (for example, another fund or an exchange-traded fund (“ETF”)) is subject to the risks associated with direct ownership of the securities in which such investment company invests. Fund shareholders indirectly bear their proportionate share of the expenses of each such investment company.
Leverage Risk. Leverage created by borrowing or certain types of transactions or investments 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.
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.
Portfolio Turnover (Active Trading) Risk. High portfolio turnover (more than 100%) caused by actively trading portfolio securities may result in accelerating the realization of taxable gains and losses, lower fund performance and increased brokerage costs.
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
Securitized Products Risk. Investments in securitized products are subject to risks similar to traditional fixed income securities, such as credit, interest rate, liquidity, prepayment, extension, and default risk, as well as additional risks associated with the nature of the assets and the servicing of those assets. Unscheduled prepayments on securitized products 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). With respect to securities that are delivered in TBA transactions, there is a risk that the actual securities received by the portfolio may be less favorable than what was anticipated when entering into the transaction.
Short Sale Risk. A short sale involves the sale by the fund of a security that it does not own with the hope of purchasing the same security at a later date at a lower price. A fund may also enter into a short derivative position through a futures contract or swap agreement. If the price of the security or derivative has increased during this time, then the fund will incur a loss equal to the increase in price from the time that the short sale was entered into plus any premiums and interest paid to the third party. Therefore, short sales involve the risk that losses may be exaggerated, potentially losing more money than the actual cost of the investment. Also, there is the risk that the third party to the short sale may fail to honor its contract terms, causing a loss to the fund.
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.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Classes A and C - www.principalfunds.com.
•
For Institutional Class and Class R-6 - www.principal.com.
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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (October 24, 2011).
For periods prior to the inception date of Class C shares (June 14, 2012) and Class R-6 shares (June 12, 2017), the performance shown in the table for Classes C and R-6 shares is that of the Fund's Institutional Class shares, adjusted to reflect the respective fees and expenses of each class. However, where this adjustment for fees and expenses results in performance for a newer class that is higher than the historical performance of the Institutional Class shares, the historical performance of the Institutional Class shares is used. These adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares, which were first sold on October 24, 2011.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Classes A and C - www.principalfunds.com.•For Institutional Class and Class R-6 - www.principal.com.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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [18]
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q1 '12
2.81%
Lowest return for a quarter during the period of the bar chart above:
Q3 '15
(1.99)%

(1) The year-to-date return as of September 30, 2017 was 4.71% for Class A shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class A shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Global Multi-Strategy Fund | HFRI (Hedge Fund Research Inc.) Funds-of-Funds Composite Index [Member]  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel HFRI (Hedge Fund Research Inc.) Fund-of-Funds Composite Index (reflects no deduction for taxes)
1 Year rr_AverageAnnualReturnYear01 0.51%
5 Years rr_AverageAnnualReturnYear05 3.42%
Since Inception rr_AverageAnnualReturnSinceInception 3.20%
Principal Funds Inc | Global Multi-Strategy Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PMSAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 3.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.56%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.54%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 0.04%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.13% [19]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.71%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.56%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [20],[21]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.52%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 621
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,138
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,681
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 3,159
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Annual Return 2012 rr_AnnualReturn2012 5.56%
Annual Return 2013 rr_AnnualReturn2013 4.96%
Annual Return 2014 rr_AnnualReturn2014 3.36%
Annual Return 2015 rr_AnnualReturn2015 (0.94%)
Annual Return 2016 rr_AnnualReturn2016 2.85%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 4.71%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2012
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 2.81%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2015
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (1.99%)
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (1.01%)
5 Years rr_AverageAnnualReturnYear05 2.34%
Since Inception rr_AverageAnnualReturnSinceInception 2.16%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 24, 2011
Principal Funds Inc | Global Multi-Strategy Fund | Class A | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (1.01%)
5 Years rr_AverageAnnualReturnYear05 1.99%
Since Inception rr_AverageAnnualReturnSinceInception 1.82%
Principal Funds Inc | Global Multi-Strategy Fund | Class A | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 (0.57%)
5 Years rr_AverageAnnualReturnYear05 1.78%
Since Inception rr_AverageAnnualReturnSinceInception 1.64%
Principal Funds Inc | Global Multi-Strategy Fund | Class C  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PMSCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.56%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.54%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 0.04%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.19% [19]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.77%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 3.37%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [20],[21]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 3.33%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 436
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,032
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,752
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 3,655
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 336
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 1,032
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,752
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 3,655
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Label rr_AverageAnnualReturnLabel Class C Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.03%
5 Years rr_AverageAnnualReturnYear05 2.39%
Since Inception rr_AverageAnnualReturnSinceInception 2.16%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 24, 2011
Principal Funds Inc | Global Multi-Strategy Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PSMIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.56%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.54%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 0.04%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.07% [19]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.65%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.25%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [20],[21]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.21%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 224
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 699
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,201
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,582
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 3.27%
5 Years rr_AverageAnnualReturnYear05 3.52%
Since Inception rr_AverageAnnualReturnSinceInception 3.29%
Inception Date rr_AverageAnnualReturnInceptionDate Oct. 24, 2011
Principal Funds Inc | Global Multi-Strategy Fund | Class R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGLSX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.56%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.54%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 0.04%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.01% [19]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.59%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.19%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [20],[21]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.15%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 218
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 681
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,171
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,521
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-6 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 3.27%
5 Years rr_AverageAnnualReturnYear05 3.51%
Since Inception rr_AverageAnnualReturnSinceInception 3.26%
Principal Funds Inc | Global Opportunities Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading GLOBAL OPPORTUNITIES FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks long-term growth of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 $50,000 in Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 117.1% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 117.10%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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 also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption With respect to Class C shares, you would pay the following expenses if you did not redeem your shares (all other classes would be the same as in the above example):
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal market circumstances, the Fund invests in equity securities of issuers located throughout the world, including the U.S., invests at least 30% of its net assets in foreign and emerging market securities, and holds investments tied economically to at least ten countries. The Fund has a flexible investment strategy and may invest in equity securities regardless of market capitalization (small, medium, or large) and style (growth or value). The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund also invests in growth equity securities, an investment strategy that emphasizes buying equity securities of companies whose potential for growth of capital and earnings is expected to be above average. The Fund actively trades portfolio securities.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Emerging Markets Risk. Investments in emerging market countries may have more risk than those in developed market countries because the emerging markets are less developed and more illiquid. Emerging market countries can also be subject to increased social, economic, regulatory, and political uncertainties and can be extremely volatile.
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.
•
Small and Medium Market Capitalization Companies. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.
•
Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.
Foreign Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.
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; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).
Portfolio Turnover (Active Trading) Risk. High portfolio turnover (more than 100%) caused by actively trading portfolio securities may result in accelerating the realization of taxable gains and losses, lower fund performance and increased brokerage costs.
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Classes A and C - www.principalfunds.com.
•
For Institutional Class - www.principal.com.
Using the historical performance of the Fund's Institutional Class shares, adjusted as described below, 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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (December 28, 2012).
For periods prior to the inception date of Classes A and C shares (September 30, 2013), the performance shown in the bar chart for Class A shares and the table for Classes A and C shares is that of the Fund's Institutional Class shares, adjusted to reflect the respective fees and expenses of each class. These adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares, which were first sold December 28, 2012.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Classes A and C - www.principalfunds.com.•For Institutional Class - www.principal.com.Using the historical performance of the Fund's Institutional Class shares, adjusted as described below, 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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [22]
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q4 '13
9.11%
Lowest return for a quarter during the period of the bar chart above:
Q3 '15
(6.80)%

(1) The year-to-date return as of September 30, 2017 was 16.08% for Class A shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class A shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Global Opportunities Fund | MSCI All Country World Index (ACWI)  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel MSCI All Country World Index (ACWI) (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 7.86%
Since Inception rr_AverageAnnualReturnSinceInception 7.92%
Principal Funds Inc | Global Opportunities Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGLAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.83%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.90%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.98%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.48%) [23]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.50%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 694
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,093
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,517
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,693
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Annual Return 2013 rr_AnnualReturn2013 23.48%
Annual Return 2014 rr_AnnualReturn2014 3.71%
Annual Return 2015 rr_AnnualReturn2015 0.20%
Annual Return 2016 rr_AnnualReturn2016 0.12%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 16.08%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2013
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 9.11%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2015
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (6.80%)
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (5.42%)
Since Inception rr_AverageAnnualReturnSinceInception 5.12%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2012
Principal Funds Inc | Global Opportunities Fund | Class A | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (5.67%)
Since Inception rr_AverageAnnualReturnSinceInception 4.03%
Principal Funds Inc | Global Opportunities Fund | Class A | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 (2.87%)
Since Inception rr_AverageAnnualReturnSinceInception 3.71%
Principal Funds Inc | Global Opportunities Fund | Class C  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGOCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.83%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 2.08%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 3.91%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (1.66%) [23]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.25%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 328
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,040
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,870
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 4,026
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 228
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 1,040
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,870
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 4,026
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Label rr_AverageAnnualReturnLabel Class C Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (1.68%)
Since Inception rr_AverageAnnualReturnSinceInception 5.80%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2012
Principal Funds Inc | Global Opportunities Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGOIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.83%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.02%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.85%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [23]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.85%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 87
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 271
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 471
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,049
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 0.79%
Since Inception rr_AverageAnnualReturnSinceInception 7.34%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 28, 2012
Principal Funds Inc | International Equity Index Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading INTERNATIONAL EQUITY INDEX FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks long-term growth of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment):
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 24.7% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 24.70%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in securities that compose the MSCI EAFE NR Index (the "Index") at the time of purchase. The Index is a market-weighted equity index designed to measure the equity performance of developed markets (Europe, Australia, New Zealand, and Far East, which includes Hong Kong, Japan and Singapore), excluding the United States and Canada. The Index includes growth and value stocks and is rebalanced semi-annually. The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a replication strategy which involves investing in the securities that make up the Index, in the same approximate proportions as the Index. The Fund utilizes exchange-traded funds ("ETFs") and derivative strategies (including index futures) on a daily basis to gain exposure to the Index in an effort to minimize tracking error relative to the benchmark. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Derivatives Risk. Derivatives may not move in the direction anticipated by the portfolio manager. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and result in disproportionate losses that may be substantially greater than a fund's initial investment.
•
Futures. Futures involve specific risks, including: the imperfect correlation between the change in market value of the instruments held by the fund and the price of the future; possible lack of a liquid secondary market for a future and the resulting inability to close a future when desired; counterparty risk; and if the fund has insufficient cash, it may have to sell securities from its portfolio to meet daily variation margin requirements.
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.
•
Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.
Foreign Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.
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; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).
Index Fund Risk. An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.
Investment Company Securities Risk. A fund that invests in another investment company (for example, another fund or an exchange-traded fund (“ETF”)) is subject to the risks associated with direct ownership of the securities in which such investment company invests. Fund shareholders indirectly bear their proportionate share of the expenses of each such investment company.
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at www.principal.com.
The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (December 30, 2009).
For periods prior to the inception date of Class R-6 shares (January 3, 2017), the performance shown in the table for Class R-6 shares is that of the Fund's Institutional Class shares, adjusted to reflect the fees and expenses of Class R-6 shares. However, where this adjustment for fees and expenses results in performance for Class R-6 shares that is higher than the historical performance of the Institutional Class shares, the historical performance of the Institutional Class shares is used. These adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares, which were first sold December 30, 2009.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at www.principal.com.The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [24]
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q3 '10
17.39%
Lowest return for a quarter during the period of the bar chart above:
Q3 '11
(20.25)%

(1) The year-to-date return as of September 30, 2017 was 20.42% for Institutional Class shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Institutional Class shares only and would be different for the other classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 Institutional Class shares only and would be different for the other classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | International Equity Index Fund | MSCI EAFE NR Index [Member]  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel MSCI EAFE NR Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 1.00%
5 Years rr_AverageAnnualReturnYear05 6.53%
Since Inception rr_AverageAnnualReturnSinceInception 0.75%
Principal Funds Inc | International Equity Index Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PIDIX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.07%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.33%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.01%) [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.32%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 33
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 105
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 184
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 417
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Annual Return 2010 rr_AnnualReturn2010 6.24%
Annual Return 2011 rr_AnnualReturn2011 (12.39%)
Annual Return 2012 rr_AnnualReturn2012 18.04%
Annual Return 2013 rr_AnnualReturn2013 21.37%
Annual Return 2014 rr_AnnualReturn2014 (5.98%)
Annual Return 2015 rr_AnnualReturn2015 (1.00%)
Annual Return 2016 rr_AnnualReturn2016 0.82%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 20.42%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 17.39%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (20.25%)
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 0.82%
5 Years rr_AverageAnnualReturnYear05 6.10%
Since Inception rr_AverageAnnualReturnSinceInception 3.26%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | International Equity Index Fund | Institutional Class | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Institutional Class Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 0.27%
5 Years rr_AverageAnnualReturnYear05 4.83%
Since Inception rr_AverageAnnualReturnSinceInception 2.30%
Principal Funds Inc | International Equity Index Fund | Institutional Class | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Institutional Class Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 1.12%
5 Years rr_AverageAnnualReturnYear05 4.92%
Since Inception rr_AverageAnnualReturnSinceInception 2.69%
Principal Funds Inc | International Equity Index Fund | R-1  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PILIX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.35%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.59%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.20%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.20%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 122
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 381
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 660
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,455
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-1 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (0.13%)
5 Years rr_AverageAnnualReturnYear05 5.18%
Since Inception rr_AverageAnnualReturnSinceInception 2.35%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | International Equity Index Fund | R-2  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PINEX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.30%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.51%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.07%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.07%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 109
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 340
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 590
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,306
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-2 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 0.10%
5 Years rr_AverageAnnualReturnYear05 5.33%
Since Inception rr_AverageAnnualReturnSinceInception 2.48%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | International Equity Index Fund | R-3  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PIIOX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.38%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.89%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.89%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 91
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 284
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 493
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,096
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-3 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 0.17%
5 Years rr_AverageAnnualReturnYear05 5.53%
Since Inception rr_AverageAnnualReturnSinceInception 2.68%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | International Equity Index Fund | R-4  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PIIPX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.10%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.34%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.70%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.70%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 72
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 224
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 390
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 871
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-4 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 0.48%
5 Years rr_AverageAnnualReturnYear05 5.72%
Since Inception rr_AverageAnnualReturnSinceInception 2.88%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | International Equity Index Fund | R-5  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PIIQX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.32%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.58%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.58%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 59
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 186
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 324
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 726
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-5 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 0.56%
5 Years rr_AverageAnnualReturnYear05 5.84%
Since Inception rr_AverageAnnualReturnSinceInception 2.99%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | International Equity Index Fund | R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PFIEX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.07%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.33%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [25]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.28%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 29
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 101
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 180
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 413
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-6 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 0.75%
5 Years rr_AverageAnnualReturnYear05 6.03%
Since Inception rr_AverageAnnualReturnSinceInception 3.19%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 30, 2009
Principal Funds Inc | International Small Company Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading INTERNATIONAL SMALL COMPANY FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks long-term growth of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 $50,000 in Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 58.8% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 58.80%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies with small market capitalizations at the time of purchase. For this Fund, companies with small market capitalizations are those with market capitalizations within the range of companies comprising the MSCI World ex-USA Small Cap Index (as of November 30, 2017, this range was between approximately $1.0 million and $12.5 billion). The Fund may invest in equity securities regardless of style (growth or value). The Fund invests primarily in foreign equity securities. The Fund typically invests in foreign securities of more than 10 countries but has no limitation on the percentage of assets that is invested in each country or denominated in any currency. Primary consideration is given to securities of corporations of developed areas, such as Japan, Western Europe, Canada, Australia, and New Zealand.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.
•
Small and Medium Market Capitalization Companies Risk. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.
•
Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.
Foreign Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.
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; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Class A - www.principalfunds.com.
•
For Institutional Class and Class R-6 - www.principal.com.
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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (June 11, 2014).
For periods prior to the inception date of Institutional Class shares (December 31, 2014) and Class R-6 shares (January 3, 2017), the performance shown in the table for these newer classes is that of the Fund's Class A shares, adjusted to reflect the respective fees and expenses of each class. However, where this adjustment for fees and expenses results in performance for a newer class that is higher than the historical performance of the Class A shares, the historical performance of the Class A shares is used (without respect to sales charges, which do not apply to Institutional Class or Class R-6 shares). These adjustments result in performance for such periods that is no higher than the historical performance of the Class A shares, which were first sold June 11, 2014.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Class A - www.principalfunds.com.•For Institutional Class and Class R-6 - www.principal.com.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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 (1)  [24]
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q3 '16
8.43%
Lowest return for a quarter during the period of the bar chart above:
Q3 '15
(6.44)%

(1) The year-to-date return as of September 30, 2017 was 28.60% for Class A shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class A shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | International Small Company Fund | MSCI World ex USA Small Cap Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel MSCI World ex USA Small Cap Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 4.32%
Since Inception rr_AverageAnnualReturnSinceInception (0.53%)
Principal Funds Inc | International Small Company Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PICAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.04%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.63%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.93%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (1.32%) [26]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.61%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 705
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,289
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,898
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 3,534
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Annual Return 2015 rr_AnnualReturn2015 7.73%
Annual Return 2016 rr_AnnualReturn2016 0.81%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 28.60%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 8.43%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2015
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (6.44%)
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (4.72%)
Since Inception rr_AverageAnnualReturnSinceInception (2.56%)
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 11, 2014
Principal Funds Inc | International Small Company Fund | Class A | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (4.72%)
Since Inception rr_AverageAnnualReturnSinceInception (2.65%)
Principal Funds Inc | International Small Company Fund | Class A | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 (2.64%)
Since Inception rr_AverageAnnualReturnSinceInception (1.87%)
Principal Funds Inc | International Small Company Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PISMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.04%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.04%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.09%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [26]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.09%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 111
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 347
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 601
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,329
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.33%
Since Inception rr_AverageAnnualReturnSinceInception (0.13%)
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 11, 2014
Principal Funds Inc | International Small Company Fund | R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PFISX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.04%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.05%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.10%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [26]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.07%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 109
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 347
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 603
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,338
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-6 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 0.81%
Since Inception rr_AverageAnnualReturnSinceInception (0.49%)
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 11, 2014
Principal Funds Inc | Multi-Manager Equity Long/Short Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading MULTI-MANAGER EQUITY LONG/SHORT FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks long-term growth of capital with lower volatility than the global equity markets.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 $50,000 in Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 301.2% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 301.20%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities and derivatives on equity securities, at the time of purchase. Principal Global Investors, LLC (“PGI"), the Fund’s investment advisor, strategically allocates the Fund's assets among investment strategies, which one or more of the Fund’s sub-advisors execute using various methods such as fundamental analysis and systematic framework. PGI retains considerable latitude in allocating the Fund's assets. Depending upon market conditions, the Fund may use the strategies to varying degrees at any time, discontinue using a strategy, or add strategies.
The Fund has a flexible investment strategy and invests in a broad range of equity securities, exchange-traded funds, and derivatives instruments. The Fund invests in U.S. and foreign, including emerging market, securities, particularly in Europe. Although the Fund focuses on securities of mid- to large-capitalization companies, it may invest in equity securities regardless of market capitalization size (small, medium or large). The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund also invests in growth equity securities, an investment strategy that emphasizes buying equity securities of companies whose potential for growth of capital and earnings is expected to be above average. The Fund uses derivative instruments, including swaps, futures and options, to gain exposure to a variety of securities or mitigate volatility and forwards to manage its foreign currency exposure. The Fund uses hedging techniques to attempt to reduce the risk of investment positions. The Fund actively trades portfolio securities.
The Fund takes long and short positions in equity securities, exchange-traded funds, and derivative instruments. When taking a short position, the Fund may sell an instrument that it does not own and then borrow to meet its settlement obligations. A short position will benefit from a decrease in price of the underlying instrument and loses value if the price of the underlying instrument increases. The Fund also invests a portion of the proceeds it receives from short sales into long positions. Long positions profit if the price of the instrument increases. Simultaneously engaging in long investing and short selling seeks to reduce the net exposure of the overall portfolio to general market movements.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Asset Allocation Risk. A fund's selection and weighting of asset classes and allocation among sub-advisors may cause it to underperform other funds with a similar investment objective.
Counterparty Risk. Counterparty risk is the risk that the counterparty to a contract or other obligation will be unable or unwilling to honor its obligations.
Derivatives Risk. Derivatives may not move in the direction anticipated by the portfolio manager. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and result in disproportionate losses that may be substantially greater than a fund's initial investment.
•
Currency Contracts. Derivatives related to currency contracts involve the specific risk of government action through exchange controls that would restrict the ability of the fund to deliver or receive currency.
•
Forward Contracts, Futures and Swaps. Forward contracts, futures, and swaps involve specific risks, including: the imperfect correlation between the change in market value of the instruments held by the fund and the price of the forward contract, future or swap; possible lack of a liquid secondary market for a forward contract, future or swap and the resulting inability to close a forward contract, future or swap when desired; counterparty risk; and if the fund has insufficient cash, it may have to sell securities from its portfolio to meet daily variation margin requirements.
•
Options. Options involve specific risks, including: imperfect correlation between the change in market value of the instruments held by the fund and the price of the options, counterparty risk, difference in trading hours for the options markets and the markets for the underlying securities (rate movements can take place in the underlying markets that cannot be reflected in the options markets), and an insufficient liquid secondary market for particular options.
Emerging Markets Risk. Investments in emerging market countries may have more risk than those in developed market countries because the emerging markets are less developed and more illiquid. Emerging market countries can also be subject to increased social, economic, regulatory, and political uncertainties and can be extremely volatile.
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.
•
Small and Medium Market Capitalization Companies. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.
•
Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.
European Focus Risk. A fund that focuses its investments in securities of European companies may be particularly susceptible to economic, political, regulatory or other events or conditions affecting issuers and countries in Europe. Currency devaluations could occur or could continue to occur. Debt problems of the private or public sectors in a single European Union (EU) country can pose significant economic risks to the EU as a whole. Additionally, the United Kingdom's vote to leave the EU, commonly known as “Brexit,” may have significant political and financial consequences for European markets and the broader global economy, including greater market volatility and illiquidity, currency fluctuations, and deterioration in economic activity. As a result, the fund’s performance may be more volatile than the performance of a more geographically diversified fund.
Foreign Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.
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; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).
Hedging Risk. A fund that implements a hedging strategy using derivatives and/or securities could expose the fund to the risk that can arise when a change in the value of a hedge does not match a change in the value of the asset it hedges. In other words, the change in value of the hedge could move in a direction that does not match the change in value of the underlying asset, resulting in a risk of loss to the fund.
Investment Company Securities Risk. A fund that invests in another investment company (for example, another fund or an exchange-traded fund (“ETF”)) is subject to the risks associated with direct ownership of the securities in which such investment company invests. Fund shareholders indirectly bear their proportionate share of the expenses of each such investment company.
Leverage Risk. Leverage created by borrowing or certain types of transactions or investment 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. In particular, investing the proceeds of short sales may amplify leverage risk.
Portfolio Turnover (Active Trading) Risk. High portfolio turnover (more than 100%) caused by actively trading portfolio securities may result in accelerating the realization of taxable gains and losses, lower fund performance and increased brokerage costs.
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
Short Sale Risk. A short sale involves the sale by the fund of a security that it does not own with the hope of purchasing the same security at a later date at a lower price. A fund may also enter into a short derivative position through a futures contract or swap agreement. If the price of the security or derivative has increased during this time, then the fund will incur a loss equal to the increase in price from the time that the short sale was entered into plus any premiums and interest paid to the third party. Therefore, short sales involve the risk that losses may be exaggerated, potentially losing more money than the actual cost of the investment. Also, there is the risk that the third party to the short sale may fail to honor its contract terms, causing a loss to the fund.
By investing the proceeds received from selling securities short, a fund could be deemed to be employing a form of leverage, which creates special risks. The use of leverage may increase a fund’s exposure to long securities positions and make any change in the fund’s NAV greater than it would be without the use of leverage. This could result in increased volatility of returns. There is no guarantee that any leveraging strategy a fund employs will be successful during any period in which it is employed.
Volatility Mitigation Risk.  Volatility mitigation strategies may increase fund transaction costs, which could increase losses or reduce gains.  These strategies may not protect the fund from market declines and may reduce the fund’s participation in market gains.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
No performance information is shown below because the Fund has not yet had a calendar year of performance. The Fund's performance is benchmarked against the HFRX Equity Hedge Index. Performance information provides an indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Class A - www.principalfunds.com.
•
For Institutional Class and Class R-6 - www.principal.com.
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess No performance information is shown below because the Fund has not yet had a calendar year of performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Principal Funds Inc | Multi-Manager Equity Long/Short Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGMMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.57%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.82%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 28.04%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 28.86%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 30.72%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (27.84%) [27]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.88%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 825
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 5,327
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 7,811
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 10,178
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Principal Funds Inc | Multi-Manager Equity Long/Short Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGPIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.57%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.82%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 29.56%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 30.38%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 31.99%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (29.46%) [27]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.53%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 256
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 5,162
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 7,777
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 10,143
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Principal Funds Inc | Multi-Manager Equity Long/Short Fund | R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PGPMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.57%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.82%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 0.06%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.88%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.49%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [27]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.45%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 248
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 772
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,322
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,823
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Principal Funds Inc | Opportunistic Municipal Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading OPPORTUNISTIC MUNICIPAL FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks to provide a high level of income that is exempt from federal income tax while protecting investors’ capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 67.9% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 67.90%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts 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 Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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 also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption With respect to Class C shares, you would pay the following expenses if you did not redeem your shares (all other classes would be the same as in the above example):
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in municipal obligations (securities issued by or on behalf of state or local governments and other public authorities). Municipal obligations pay interest that is exempt from federal income tax. The Fund has a flexible investment strategy and invests in obligations of any duration and credit quality, including below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's Investors Service, Inc. ("Moody's") and BB+ or lower by S&P Global Ratings ("S&P Global") (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, those selecting such investments will determine whether the bond is of a quality comparable to those rated below investment grade). The Fund is not managed to a particular maturity or duration.
The Fund invests in other debt obligations, including (but not limited to) taxable municipal obligations, U.S. Treasury securities, obligations of the U.S. Government, its agencies and instrumentalities (“Agency Securities”) and exchange-traded funds ("ETFs") to gain exposure to the municipal market.
The Fund uses derivative instruments. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The Fund invests in futures contracts to hedge against changes in interest rates or as a substitute for the purchase of portfolio securities. The Fund also invests in inverse floating rate instruments, which are generally more volatile than other types of municipal obligations and may involve leverage, to enhance investment income.
During the fiscal year ended August 31, 2017, 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):
 1.77% in securities rated Aaa
26.84% in securities rated Baa
1.05% in securities rated Caa
0.00% in securities rated D
13.02% in securities rated Aa
9.14% in securities rated Ba
0.00% in securities rated Ca
20.24% in securities not rated
19.77% in securities rated A
8.17% in securities rated B
0.00% in securities rated C
 
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Counterparty Risk. Counterparty risk is the risk that the counterparty to a contract or other obligation will be unable or unwilling to honor its obligations.
Derivatives Risk. Derivatives may not move in the direction anticipated by the portfolio manager. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and result in disproportionate losses that may be substantially greater than a fund's initial investment.
•
Futures. Futures involve specific risks, including: the imperfect correlation between the change in market value of the instruments held by the fund and the price of the future; possible lack of a liquid secondary market for a future and the resulting inability to close a future when desired; counterparty risk; and if the fund has insufficient cash, it may have to sell securities from its portfolio to meet daily variation margin requirements.
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.
Hedging Risk. A fund that implements a hedging strategy using derivatives and/or securities could expose the fund to the risk that can arise when a change in the value of a hedge does not match a change in the value of the asset it hedges. In other words, the change in value of the hedge could move in a direction that does not match the change in value of the underlying asset, resulting in a risk of loss to the fund.
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.
Inverse Floating Rate Investments Risk. Inverse floating rate investments are extremely sensitive to changes in interest rates and in some cases their market value may be extremely volatile.
Investment Company Securities Risk. A fund that invests in another investment company (for example, another fund or an exchange-traded fund (“ETF”)) is subject to the risks associated with direct ownership of the securities in which such investment company invests. Fund shareholders indirectly bear their proportionate share of the expenses of each such investment company.
Leverage Risk. Leverage created by borrowing or certain types of transactions or investments 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 Obligations 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.
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.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Classes A and C - www.principalfunds.com.
•
For Institutional Class - www.principal.com.
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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (June 14, 2012).
For periods prior to the inception date of Institutional Class shares (March 10, 2015), the performance shown in the table for Institutional Class shares is that of the Fund's Class A shares, adjusted to reflect the fees and expenses of Institutional Class shares. However, where this adjustment for fees and expenses results in performance for the Institutional Class that is higher than the historical performance of the Class A shares, the historical performance of the Class A shares is used (without respect to sales charges, which does not apply to Institutional Class). These adjustments result in performance for such periods that is no higher than the historical performance of the Class A shares, which were first sold June 14, 2012.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Classes A and C - www.principalfunds.com.•For Institutional Class - www.principal.com.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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [28]
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q1 '14
6.17%
Lowest return for a quarter during the period of the bar chart above:
Q4 '16
(6.58)%

(1) The year-to-date return as of September 30, 2017 was 7.80% for Class A shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class A shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Opportunistic Municipal Fund | Bloomberg Barclays Municipal Bond Index [Member]  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 0.25%
Since Inception rr_AverageAnnualReturnSinceInception 2.83%
Principal Funds Inc | Opportunistic Municipal Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PMOAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 3.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.50%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.06%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 0.14%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.20%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.95%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [29]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.95%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 468
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 666
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 881
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,498
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Annual Return 2013 rr_AnnualReturn2013 (7.76%)
Annual Return 2014 rr_AnnualReturn2014 16.17%
Annual Return 2015 rr_AnnualReturn2015 6.29%
Annual Return 2016 rr_AnnualReturn2016 (0.30%)
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 7.80%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2014
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 6.17%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (6.58%)
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (4.05%)
Since Inception rr_AverageAnnualReturnSinceInception 3.44%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 14, 2012
Principal Funds Inc | Opportunistic Municipal Fund | Class A | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (4.05%)
Since Inception rr_AverageAnnualReturnSinceInception 3.42%
Principal Funds Inc | Opportunistic Municipal Fund | Class A | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 (0.83%)
Since Inception rr_AverageAnnualReturnSinceInception 3.55%
Principal Funds Inc | Opportunistic Municipal Fund | Class C  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PMODX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.50%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.06%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.31%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.81%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.10%) [29]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.71%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 274
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 560
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 971
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,118
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 174
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 560
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 971
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,118
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Label rr_AverageAnnualReturnLabel Class C Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (2.01%)
Since Inception rr_AverageAnnualReturnSinceInception 3.52%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 14, 2012
Principal Funds Inc | Opportunistic Municipal Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol POMFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.50%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.06%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 0.23%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.29%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.79%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.11%) [29]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.68%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 69
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 241
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 428
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 968
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (0.06%)
Since Inception rr_AverageAnnualReturnSinceInception 4.37%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 14, 2012
Principal Funds Inc | Origin Emerging Markets Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading ORIGIN EMERGING MARKETS FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks long-term growth of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 $50,000 in Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 66.3% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 66.30%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of emerging market companies at the time of purchase. The Fund considers a security to be tied economically to an emerging market country (an “emerging market security”) if the issuer of the security has its principal place of business or principal office in an emerging market country, has its principal securities trading market in an emerging market country, or derives a majority of its revenue from emerging market countries.
"Emerging market country" means any country which is considered to be an emerging country by the international financial community (including the MSCI Emerging Markets Index or Bloomberg Barclays Emerging Markets USD Aggregate Bond Index). The Fund invests in equity securities of small, medium, and large market capitalization companies and in growth and value stocks.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Emerging Markets Risk. Investments in emerging market countries may have more risk than those in developed market countries because the emerging markets are less developed and more illiquid. Emerging market countries can also be subject to increased social, economic, regulatory, and political uncertainties and can be extremely volatile.
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.
•
Small and Medium Market Capitalization Companies Risk. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.
•
Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.
Foreign Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.
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; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Class A - www.principalfunds.com.
•
For Institutional Class and Class R-6 - www.principal.com.
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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (January 23, 2015).
During 2015, Class A experienced a significant withdrawal of monies by an affiliate. As the remaining shareholders held relatively small positions, the total return amounts expressed herein are greater than those that would have been experienced without the withdrawal.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Class A - www.principalfunds.com.•For Institutional Class and Class R-6 - www.principal.com.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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [30]
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q3 '16
8.79%
Lowest return for a quarter during the period of the bar chart above:
Q4 '16
(9.91)%
(1) The year-to-date return as of September 30, 2017 was 41.30% for Class A shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class A shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Origin Emerging Markets Fund | MSCI Emerging Markets NR Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel MSCI Emerging Markets NR Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 11.19%
Since Inception rr_AverageAnnualReturnSinceInception (4.60%)
Principal Funds Inc | Origin Emerging Markets Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol POEYX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.19%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 4.22%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 5.67%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (3.91%) [31]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.76%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 719
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,818
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 2,902
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 5,550
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Annual Return 2016 rr_AnnualReturn2016 1.46%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 41.30%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 8.79%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (9.91%)
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (4.12%)
Since Inception rr_AverageAnnualReturnSinceInception (11.04%) [32]
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 23, 2015
Principal Funds Inc | Origin Emerging Markets Fund | Class A | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (3.97%)
Since Inception rr_AverageAnnualReturnSinceInception (11.05%) [32]
Principal Funds Inc | Origin Emerging Markets Fund | Class A | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 (2.03%)
Since Inception rr_AverageAnnualReturnSinceInception (8.18%) [32]
Principal Funds Inc | Origin Emerging Markets Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol POEIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.19%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.05%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.25%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [31]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.25%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 127
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 397
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 686
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,511
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.00%
Since Inception rr_AverageAnnualReturnSinceInception (8.79%)
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 23, 2015
Principal Funds Inc | Origin Emerging Markets Fund | R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol POEFX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.19%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.04%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.24%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.02%) [31]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.22%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 124
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 391
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 679
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,498
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-6 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.10%
Since Inception rr_AverageAnnualReturnSinceInception (8.80%)
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 23, 2015
Principal Funds Inc | Preferred Securities Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading PREFERRED SECURITIES FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks to provide current income.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 16.1% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 16.10%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts 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 Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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 also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption With respect to Classes C and J shares, you would pay the following expenses if you did not redeem your shares (all other classes would be the same as in the above example):
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowing for investment purposes, in preferred securities at the time of purchase. Preferred securities typically include preferred stock and various types of junior subordinated debt and trust preferred securities. Preferred securities may pay fixed rate or adjustable rate distributions and generally have a payment "preference" over common stock, but are junior to the issuer's senior debt in a liquidation of the issuer’s assets.
The Fund also invests in contingent convertible securities (“Cocos”), which are hybrid debt securities typically issued by non-US banking institutions that have contractual equity conversion or principal write-down features that are triggered by regulatory capital thresholds or regulatory actions calling into question the issuing banking institution’s continued viability as a going-concern if the conversion trigger were not exercised.
Preferred securities purchased by the Fund are of companies with senior debt rated at the time of purchase BBB- or higher by S&P Global Ratings ("S&P Global") or Baa3 or higher by Moody's Investors Service, Inc. ("Moody's") or, if unrated, of comparable quality in the opinion of those selecting such investments. The Fund also invests up to 40% of its assets in below investment grade preferred securities and bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P Global (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, those selecting such investments will determine whether the bond is of a quality comparable to those rated below investment grade). The Fund invests in other debt obligations, including (but not limited to) U.S. Treasury securities and obligations of the U.S. Government, its agencies and instrumentalities. The Fund invests in foreign securities.
The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the financial services (i.e., banking, insurance and commercial finance) industry.
During the fiscal year ended August 31, 2017, 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):
0.00% in securities rated Aaa
65.05% in securities rated Baa
0.00% in securities rated Caa
0.00% in securities rated D
0.18% in securities rated Aa
20.84% in securities rated Ba
0.00% in securities rated Ca
1.04% in securities not rated
10.00% in securities rated A
2.89% in securities rated B
0.00% in securities rated C
 
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the financial services (i.e., banking, insurance and commercial finance) industry.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Contingent Convertible Securities Risk. In addition to the general risks associated with fixed-income securities and convertible securities, the risks of investing in contingent convertible securities (“CoCos”) include the risk that a CoCo may be written down, written off or converted into an equity security when the issuer’s capital ratio falls below a specified trigger level, or in a regulator’s discretion depending on the regulator’s judgment about the issuer’s solvency prospects. Due to these features, CoCos may have substantially greater risk than other securities in times of financial stress. If the trigger level is breached, the issuer’s decision to write down, write off or convert a CoCo may result in the fund's complete loss on an investment in CoCos with no chance of recovery even if the issuer remains in existence.
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; 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.
Industry Concentration Risk. A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries.
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Financial Services. A fund concentrating in financial services companies may be more susceptible to adverse economic or regulatory occurrences affecting financial services companies. Financial companies may be adversely affected in certain market cycles, including periods of rising interest rates, which may restrict the availability and increase the cost of capital, and declining economic conditions, which may cause credit losses due to financial difficulties of borrowers. Because many types of financial companies are especially vulnerable to these economic cycles, the Fund’s investments in these companies may lose significant value during such periods.
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.
Preferred Securities Risk. Because preferred securities have a lower priority claim on assets or earnings than senior bonds and other debt instruments in a company's capital structure, they are subject to greater credit and liquidation risk than more senior debt instruments. In addition, preferred securities are subject to other risks, such as limited or no voting rights, deferring or skipping distributions, interest rate risk, and redeeming the security prior to any stated maturity date.
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
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.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Classes A, C, and J - www.principalfunds.com.
•
For Institutional Class and Classes R-1, R-2, R-3, R-4, R-5 and R-6 - www.principal.com.
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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
For periods prior to the inception date of Class C shares (January 16, 2007) and Class R-6 shares (January 3, 2017), the performance shown in the table for these newer classes is that of the Fund's Institutional Class shares, adjusted to reflect the respective fees and expenses of each class. However, where this adjustment for fees and expenses results in performance for a newer class that is higher than the historical performance of the Institutional Class shares, the historical performance of the Institutional Class shares is used. These adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares, which were first sold May 1, 2002.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Classes A, C, and J - www.principalfunds.com.•For Institutional Class and Classes R-1, R-2, R-3, R-4, R-5 and R-6 - www.principal.com.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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [33]
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q2 '09
38.89%
Lowest return for a quarter during the period of the bar chart above:
Q3 '08
(20.97)%

(1) The year-to-date return as of September 30, 2017 was 9.36% for Class A shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class A shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Preferred Securities Fund | BofA Merrill Lynch U.S. All Capital Securities Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel ICE BofA Merrill Lynch U.S. All Capital Securities Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 3.81%
5 Years rr_AverageAnnualReturnYear05 none
10 Years rr_AverageAnnualReturnYear10 none
Principal Funds Inc | Preferred Securities Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PPSAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 3.75%
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.11%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.06%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [34]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.06%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 479
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 700
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 938
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,621
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Annual Return 2007 rr_AnnualReturn2007 (8.29%)
Annual Return 2008 rr_AnnualReturn2008 (22.42%)
Annual Return 2009 rr_AnnualReturn2009 46.15%
Annual Return 2010 rr_AnnualReturn2010 16.04%
Annual Return 2011 rr_AnnualReturn2011 1.17%
Annual Return 2012 rr_AnnualReturn2012 18.87%
Annual Return 2013 rr_AnnualReturn2013 1.47%
Annual Return 2014 rr_AnnualReturn2014 11.24%
Annual Return 2015 rr_AnnualReturn2015 4.69%
Annual Return 2016 rr_AnnualReturn2016 3.39%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 9.36%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 38.89%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (20.97%)
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (0.53%)
5 Years rr_AverageAnnualReturnYear05 6.92%
10 Years rr_AverageAnnualReturnYear10 5.49%
Principal Funds Inc | Preferred Securities Fund | Class A | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (2.09%)
5 Years rr_AverageAnnualReturnYear05 4.77%
10 Years rr_AverageAnnualReturnYear10 3.36%
Principal Funds Inc | Preferred Securities Fund | Class A | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 0.44%
5 Years rr_AverageAnnualReturnYear05 4.73%
10 Years rr_AverageAnnualReturnYear10 3.52%
Principal Funds Inc | Preferred Securities Fund | Class C  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PRFCX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.11%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.81%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [34]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.81%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 284
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 569
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 980
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,127
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 184
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 569
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 980
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,127
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Label rr_AverageAnnualReturnLabel Class C Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.74%
5 Years rr_AverageAnnualReturnYear05 6.93%
10 Years rr_AverageAnnualReturnYear10 5.10%
Principal Funds Inc | Preferred Securities Fund | Class J  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PPSJX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.18%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.03%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [34]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.03%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 205
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 328
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 569
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,259
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 105
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 328
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 569
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,259
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Label rr_AverageAnnualReturnLabel Class J Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.51%
5 Years rr_AverageAnnualReturnYear05 7.63%
10 Years rr_AverageAnnualReturnYear10 5.63%
Principal Funds Inc | Preferred Securities Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PPSIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.07%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.77%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [34]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.77%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 79
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 246
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 428
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 954
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 3.72%
5 Years rr_AverageAnnualReturnYear05 8.08%
10 Years rr_AverageAnnualReturnYear10 6.21%
Principal Funds Inc | Preferred Securities Fund | R-1  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PUSAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.35%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.53%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.58%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [34]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.58%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 161
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 499
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 860
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,878
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-1 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.89%
5 Years rr_AverageAnnualReturnYear05 7.18%
10 Years rr_AverageAnnualReturnYear10 5.32%
Principal Funds Inc | Preferred Securities Fund | R-2  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PPRSX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.30%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.45%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.45%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [34]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.45%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 148
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 459
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 792
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,735
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-2 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 3.05%
5 Years rr_AverageAnnualReturnYear05 7.31%
10 Years rr_AverageAnnualReturnYear10 5.45%
Principal Funds Inc | Preferred Securities Fund | R-3  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PNARX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.32%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.27%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [34]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.27%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 129
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 403
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 697
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,534
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-3 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 3.32%
5 Years rr_AverageAnnualReturnYear05 7.52%
10 Years rr_AverageAnnualReturnYear10 5.65%
Principal Funds Inc | Preferred Securities Fund | R-4  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PQARX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.10%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.28%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.08%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [34]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.08%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 110
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 343
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 595
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,317
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-4 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 3.52%
5 Years rr_AverageAnnualReturnYear05 7.71%
10 Years rr_AverageAnnualReturnYear10 5.83%
Principal Funds Inc | Preferred Securities Fund | R-5  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PPARX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.26%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.96%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [34]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.96%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 98
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 306
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 531
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,178
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-5 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 3.52%
5 Years rr_AverageAnnualReturnYear05 7.86%
10 Years rr_AverageAnnualReturnYear10 5.96%
Principal Funds Inc | Preferred Securities Fund | R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PPREX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.02%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.72%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [34]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.72%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 74
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 230
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 401
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 894
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-6 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 3.63%
5 Years rr_AverageAnnualReturnYear05 7.97%
10 Years rr_AverageAnnualReturnYear10 6.11%
Principal Funds Inc | Real Estate Allocation Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading REAL ESTATE ALLOCATION FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks to provide total return with income.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 $50,000 in Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 44.4% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 44.40%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in mutual funds that invest in the real estate industry at the time of purchase. The Fund operates as a fund of funds and currently invests in the following underlying funds of Principal Funds, Inc.: Global Real Estate Securities Fund and Real Estate Debt Income Fund. The underlying funds invest in equity and debt real estate securities of U.S. and non-U.S. issuers and are both concentrated in the real estate industry; therefore, the Real Estate Allocation Fund is considered concentrated in the real estate industry as well. A real estate company has at least 50% of its assets, income or profits derived from products or services related to the real estate industry. Real estate companies include real estate investment trusts ("REITs") and companies with substantial real estate holdings such as paper, lumber, hotel and entertainment companies as well as those whose products and services relate to the real estate industry include building supply manufacturers, mortgage lenders and mortgage servicing companies.
The Fund allocates its investments between the underlying funds, 25% to 75% in each underlying fund, based on qualitative and quantitative analysis. The Fund, without shareholder approval, may add, remove or substitute underlying funds when it deems appropriate.
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration The underlying funds invest in equity and debt real estate securities of U.S. and non-U.S. issuers and are both concentrated in the real estate industry; therefore, the Real Estate Allocation Fund is considered concentrated in the real estate industry as well.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The diversification of the Fund is designed to moderate overall price volatility. However, the Fund is subject to the particular risks of the underlying funds in the proportions in which the Fund invests in them, and its share prices will fluctuate as the prices of underlying fund shares rise or fall with changing market conditions. If you sell your shares when their value is less than the price you paid, you will lose money. The Fund operates as a fund of funds and thus bears both its own expenses and, indirectly, its proportionate share of the expenses of the underlying funds in which it invests. 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.
Fund of Funds Risk
Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the Fund invests ("underlying funds"). The Fund's selection and weighting of asset classes and allocation of investments in underlying funds may cause it to underperform other funds with a similar investment objective. The Fund's performance and risks correspond directly to the performance and risks of the underlying funds in which it invests, proportionately in accordance with the weightings of such investments, and there is no assurance that the underlying funds will achieve their investment objectives. Management of the Fund entails potential conflicts of interest: the Fund invests in affiliated underlying funds; and the Advisor and its affiliates may earn different fees from different underlying funds and may have an incentive to allocate more Fund assets to underlying funds from which they receive higher fees.
Principal Risks due to the Fund's Investments in Underlying Funds
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.
•
Small and Medium Market Capitalization Companies Risk. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.
•
Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.
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 Currency Risk.  Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.
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; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).
Industry Concentration Risk. A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries.
•
Real Estate. A fund concentrating in the real estate industry is subject to the risks associated with direct ownership of real estate, securities of companies in the real estate industry, and/or real estate investment trusts.
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.
Preferred Securities Risk. Because preferred securities have a lower priority claim on assets or earnings than senior bonds and other debt instruments in a company's capital structure, they are subject to greater credit and liquidation risk than more senior debt instruments. In addition, preferred securities are subject to other risks, such as limited or no voting rights, deferring or skipping distributions, interest rate risk, and redeeming the security prior to any stated maturity date.
Real Estate Investment Trusts (“REITs”) Risk. In addition to risks associated with investing in real estate securities, REITs are dependent upon management skills, are not diversified, and are subject to heavy cash flow dependency, risks of default by borrowers, and self-liquidation. Investment in REITs also involves risks similar to risks of investing in small market capitalization companies, such as limited financial resources, less frequent and limited volume trading, and may be subject to more abrupt or erratic price movements than larger company securities. A REIT could fail to qualify for tax-free pass-through of income under the Internal Revenue Code. Fund shareholders will indirectly bear their proportionate share of the expenses of REITs in which the fund invests.
Real Estate Securities Risk. Investing in real estate securities subjects the fund to the risks associated with the real estate market (which are similar to the risks associated with direct ownership in real estate), including declines in real estate values, loss due to casualty or condemnation, property taxes, interest rate changes, increased expenses, cash flow of underlying real estate assets, regulatory changes (including zoning, land use and rents), and environmental problems, as well as to the risks related to the management skill and creditworthiness of the issuer.
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
Securitized Products Risk. Investments in securitized products are subject to risks similar to traditional fixed income securities, such as credit, interest rate, liquidity, prepayment, extension, and default risk, as well as additional risks associated with the nature of the assets and the servicing of those assets. Unscheduled prepayments on securitized products 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).
Risk Lose Money [Text] rr_RiskLoseMoney If you sell your shares when their value is less than the price you paid, you will lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Class A - www.principalfunds.com.
•
For Institutional Class - www.principal.com.
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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (December 31, 2014).
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Class A - www.principalfunds.com.•For Institutional Class - www.principal.com.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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex Performance of a blended index shows how the Fund's performance compares to a blend of indices with similar investment objectives. Performance of the components of the blended index are also shown. The weightings for the Real Estate Allocation Blended Index are as follows: 50% Bloomberg Barclays CMBS ERISA Eligible Index and 50% FTSE EPRA/NAREIT Developed Index.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [35]
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q2 '16
2.73%
Lowest return for a quarter during the period of the bar chart above:
Q4 '16
(4.72)%

(1) The year-to-date return as of September 30, 2017 was 6.31% for Class A shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class A shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 the other share classes.
Performance of a blended index shows how the Fund's performance compares to a blend of indices with similar investment objectives. Performance of the components of the blended index are also shown. The weightings for the Real Estate Allocation Blended Index are as follows: 50% Bloomberg Barclays CMBS ERISA Eligible Index and 50% FTSE EPRA/NAREIT Developed Index. The custom or blended index returns reflect the allocation in effect for the time period(s) for which fund returns are disclosed. Previous weightings or allocations of the custom or blended index are not restated.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Real Estate Allocation Fund | Bloomberg Barclays CMBS ERISA Eligible Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays CMBS ERISA Eligible Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 3.32%
Since Inception rr_AverageAnnualReturnSinceInception 2.14%
Principal Funds Inc | Real Estate Allocation Fund | FTSE EPRA/NAREIT Developed Markets Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel FTSE EPRA/NAREIT Developed Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 4.06%
Since Inception rr_AverageAnnualReturnSinceInception 1.61%
Principal Funds Inc | Real Estate Allocation Fund | Real Estate Allocation Blended Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Real Estate Allocation Blended Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 3.90%
Since Inception rr_AverageAnnualReturnSinceInception 2.04%
Principal Funds Inc | Real Estate Allocation Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PAEDX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets none
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 5.34%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.75%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 6.34%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (5.09%) [36]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.25%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 670
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,897
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 3,091
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 5,939
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Annual Return 2015 rr_AnnualReturn2015 (0.19%)
Annual Return 2016 rr_AnnualReturn2016 1.52%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 6.31%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 2.73%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (4.72%)
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (4.09%)
Since Inception rr_AverageAnnualReturnSinceInception (2.14%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2014
Principal Funds Inc | Real Estate Allocation Fund | Class A | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (5.19%)
Since Inception rr_AverageAnnualReturnSinceInception (3.20%)
Principal Funds Inc | Real Estate Allocation Fund | Class A | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 (2.10%)
Since Inception rr_AverageAnnualReturnSinceInception (2.03%)
Principal Funds Inc | Real Estate Allocation Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PADDX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets none
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 9.24%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.75%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 9.99%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (9.09%) [36]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.90%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination 12/30/2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 92
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 2,069
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 3,854
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 7,593
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.92%
Since Inception rr_AverageAnnualReturnSinceInception 1.01%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2014
Principal Funds Inc | Real Estate Debt Income Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading REAL ESTATE DEBT INCOME FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks to provide current income.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 13.1% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 13.10%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts 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 Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 100,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in debt securities of U.S. companies principally engaged in the real estate industry at the time of purchase. A real estate company has at least 50% of its assets, income or profits derived from products or services related to the real estate industry. Real estate companies include real estate investment trusts ("REITs") and companies with substantial real estate holdings such as paper, lumber, hotel and entertainment companies as well as those whose products and services relate to the real estate industry include building supply manufacturers, mortgage lenders and mortgage servicing companies. Of those real estate industry investments, the Fund will invest primarily in securitized products, including commercial mortgage-backed securities (“CMBS”), which are bonds that are secured by first mortgages on commercial real estate. The Fund will also invest in debt and preferred securities issued by REITs. REITs are pooled investment vehicles that invest in income producing real estate, real estate related loans, or other types of real estate interests. REITs are corporations or business trusts that are permitted to eliminate corporate level federal income taxes by meeting certain requirements of the Internal Revenue Code. The Fund is not managed to a particular maturity or duration.
The Fund concentrates its investments (invest more than 25% of its net assets) in securities in the real estate industry.
The Fund is considered non-diversified, which means it can invest a higher percentage of assets in securities of individual issuers than a diversified fund. As a result, changes in the value of a single investment could cause greater fluctuations in the Fund's share price than would occur in a more diversified fund.
During the fiscal year ended August 31, 2017, 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):
35.06% in securities rated Aaa
12.23% in securities rated Baa
1.31% in securities rated Caa
0.00% in securities rated D
10.62% in securities rated Aa
0.75% in securities rated Ba
0.00% in securities rated Ca
21.01% in securities not rated
12.48% in securities rated A
6.54% in securities rated B
0.00% in securities rated C
 
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration The Fund concentrates its investments (invest more than 25% of its net assets) in securities in the real estate industry.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
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.
Industry Concentration Risk. A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries.
•
Real Estate. A fund concentrating in the real estate industry is subject to the risks associated with direct ownership of real estate, securities of companies in the real estate industry, and/or real estate investment trusts.
Non-Diversification Risk. A non-diversified fund may invest a high percentage of its assets in the securities of a small number of issuers and is more likely than diversified funds to be significantly affected by a specific security’s poor performance.
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.
Preferred Securities Risk. Because preferred securities have a lower priority claim on assets or earnings than senior bonds and other debt instruments in a company's capital structure, they are subject to greater credit and liquidation risk than more senior debt instruments. In addition, preferred securities are subject to other risks, such as limited or no voting rights, deferring or skipping distributions, interest rate risk, and redeeming the security prior to any stated maturity date.
Real Estate Investment Trusts (“REITs”) Risk. In addition to risks associated with investing in real estate securities, REITs are dependent upon management skills, are not diversified, and are subject to heavy cash flow dependency, risks of default by borrowers, and self-liquidation. Investment in REITs also involves risks similar to risks of investing in small market capitalization companies, such as limited financial resources, less frequent and limited volume trading, and may be subject to more abrupt or erratic price movements than larger company securities. A REIT could fail to qualify for tax-free pass-through of income under the Internal Revenue Code. Fund shareholders will indirectly bear their proportionate share of the expenses of REITs in which the fund invests.
Real Estate Securities Risk. Investing in real estate securities subjects the fund to the risks associated with the real estate market (which are similar to the risks associated with direct ownership in real estate), including declines in real estate values, loss due to casualty or condemnation, property taxes, interest rate changes, increased expenses, cash flow of underlying real estate assets, regulatory changes (including zoning, land use and rents), and environmental problems, as well as to the risks related to the management skill and creditworthiness of the issuer.
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
Securitized Products Risk. Investments in securitized products are subject to risks similar to traditional fixed income securities, such as credit, interest rate, liquidity, prepayment, extension, and default risk, as well as additional risks associated with the nature of the assets and the servicing of those assets. Unscheduled prepayments on securitized products 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).
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus Non-Diversification Risk. A non-diversified fund may invest a high percentage of its assets in the securities of a small number of issuers and is more likely than diversified funds to be significantly affected by a specific security’s poor performance.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Class A - www.principalfunds.com.
•
For Institutional Class and Class R-6 - www.principal.com.
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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (December 31, 2014).
For periods prior to the inception date of Class R-6 shares (January 3, 2017), the performance shown in the table for R-6 shares is that of the Fund's Institutional Class shares, adjusted to reflect the fees and expenses of Class R-6 shares. However, where this adjustment for fees and expenses results in performance for Class R-6 shares that is higher than the historical performance of the Institutional Class shares, the historical performance of the Institutional Class shares is used. These adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares, which were first sold December 31, 2014.
During 2016, Class A experienced a significant withdrawal of monies by an affiliate. As the remaining shareholders held relatively small positions, the total return amounts expressed herein are greater than those that would have been experienced without the withdrawal.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Class A - www.principalfunds.com.•For Institutional Class and Class R-6 - www.principal.com.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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [37]
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q2 '16
4.05%
Lowest return for a quarter during the period of the bar chart above:
Q4 '16
(2.78)%

(1) The year-to-date return as of September 30, 2017 was 3.92% for Class A shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class A shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Real Estate Debt Income Fund | Bloomberg Barclays CMBS ERISA Eligible Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Bloomberg Barclays CMBS ERISA Eligible Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 3.32%
Since Inception rr_AverageAnnualReturnSinceInception 2.14%
Principal Funds Inc | Real Estate Debt Income Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PRDYX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 3.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.55%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 3.27%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 4.07%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (3.07%) [38]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.00%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 473
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,296
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 2,133
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 4,297
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Annual Return 2015 rr_AnnualReturn2015 (1.08%)
Annual Return 2016 rr_AnnualReturn2016 2.90%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 3.92%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.05%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (2.78%)
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (0.93%) [39]
Since Inception rr_AverageAnnualReturnSinceInception (1.02%) [39]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2014
Principal Funds Inc | Real Estate Debt Income Fund | Class A | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (2.11%) [39]
Since Inception rr_AverageAnnualReturnSinceInception (2.31%) [39]
Principal Funds Inc | Real Estate Debt Income Fund | Class A | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 (0.53%) [39]
Since Inception rr_AverageAnnualReturnSinceInception (1.36%) [39]
Principal Funds Inc | Real Estate Debt Income Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PRDIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.55%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.04%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.59%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [38]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.59%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 60
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 189
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 329
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 738
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.23%
Since Inception rr_AverageAnnualReturnSinceInception 0.70%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2014
Principal Funds Inc | Real Estate Debt Income Fund | R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PRDHX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.55%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.09%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.64%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.07%) [38]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.57%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 58
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 198
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 350
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 792
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-6 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 2.20%
Since Inception rr_AverageAnnualReturnSinceInception 0.63%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2014
Principal Funds Inc | Small-MidCap Dividend Income Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading SMALL-MIDCAP DIVIDEND INCOME FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks to provide current income and long-term growth of income and capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
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 $50,000 in Class A shares of 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 page 139 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 4 of the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 25.5% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 25.50%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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 also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption With respect to Class C shares, you would pay the following expenses if you did not redeem your shares (all other classes would be the same as in the above example):
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in dividend-paying equity securities of companies with small to medium market capitalizations at the time of purchase. For this Fund, companies with small to medium market capitalizations are those with market capitalizations similar to companies in the Russell 2500 Value Index (as of November 30, 2017, the range of the index was between approximately $21.4 million and $13.2 billion). The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund invests in the securities of foreign issuers, real estate investment trusts, preferred securities, convertible securities, master limited partnerships, and royalty trusts.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Convertible Securities Risk. Convertible securities are bonds, notes, debentures, preferred stock or other securities which are convertible into common stock. Convertible securities are subject to both the credit and interest rate risks associated with fixed income securities and to the stock market risk associated with equity securities.
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Small and Medium Market Capitalization Companies. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.
•
Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.
Foreign Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.
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; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).
Master Limited Partnership ("MLP") Risk. MLPs are publicly-traded limited partnership interests or units. An MLP that invests in a particular industry (e.g., oil and gas) will be harmed by detrimental economic events within that industry. As partnerships, MLPs may be subject to less regulation (and less protection for investors) under state laws than corporations. In addition, MLPs may be subject to state taxation in certain jurisdictions, which may reduce the amount of income an MLP pays to its investors.
Preferred Securities Risk. Because preferred securities have a lower priority claim on assets or earnings than senior bonds and other debt instruments in a company's capital structure, they are subject to greater credit and liquidation risk than more senior debt instruments. In addition, preferred securities are subject to other risks, such as limited or no voting rights, deferring or skipping distributions, interest rate risk, and redeeming the security prior to any stated maturity date.
Real Estate Investment Trusts (“REITs”) Risk. In addition to risks associated with investing in real estate securities, REITs are dependent upon management skills, are not diversified, and are subject to heavy cash flow dependency, risks of default by borrowers, and self-liquidation. Investment in REITs also involves risks similar to risks of investing in small market capitalization companies, such as limited financial resources, less frequent and limited volume trading, and may be subject to more abrupt or erratic price movements than larger company securities. A REIT could fail to qualify for tax-free pass-through of income under the Internal Revenue Code. Fund shareholders will indirectly bear their proportionate share of the expenses of REITs in which the fund invests.
Real Estate Securities Risk. Investing in real estate securities subjects the fund to the risks associated with the real estate market (which are similar to the risks associated with direct ownership in real estate), including declines in real estate values, loss due to casualty or condemnation, property taxes, interest rate changes, increased expenses, cash flow of underlying real estate assets, regulatory changes (including zoning, land use and rents), and environmental problems, as well as to the risks related to the management skill and creditworthiness of the issuer.
Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. 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, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. Moreover, a fund of fund’s redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.
Royalty Trust Risk. Royalty trust revenues and cash flows could be adversely affected by a sustained decline in demand for natural resource and related products resulting from a recession or other adverse economic conditions, an increase in the market price of the underlying commodity, higher taxes or other regulatory actions that increase costs, a shift in consumer demand, or other conditions. Rising interest rates could adversely affect the performance, and limit the capital appreciation, of royalty trusts because of the increased availability of alternative investments at more competitive yields. Fund shareholders will indirectly bear their proportionate share of the royalty trusts' expenses.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Classes A and C - www.principalfunds.com.
•
For Institutional Class and Class R-6 - www.principal.com.
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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (June 6, 2011).
For periods prior to the inception date of Class C shares (June 14, 2012) and Class R-6 shares (January 3, 2017), the performance shown in the table for these newer classes is that of the Fund's Institutional Class shares, adjusted to reflect the respective fees and expenses of each class. However, where this adjustment for fees and expenses results in performance for a newer class that is higher than the historical performance of the Institutional Class shares, the historical performance of the Institutional Class shares is used. These adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares, which were first sold on June 6, 2011.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Classes A and C - www.principalfunds.com.•For Institutional Class and Class R-6 - www.principal.com.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 on Class A shares; if they did, results would be lower. The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [40]
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q1 '13
12.32%
Lowest return for a quarter during the period of the bar chart above:
Q3 '15
(8.49)%

(1) The year-to-date return as of September 30, 2017 was 9.04% for Class A shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class A shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | Small-MidCap Dividend Income Fund | Russell 2500 Value Index [Member]  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Russell 2500 Value Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 25.20%
5 Years rr_AverageAnnualReturnYear05 15.04%
Since Inception rr_AverageAnnualReturnSinceInception 12.12%
Principal Funds Inc | Small-MidCap Dividend Income Fund | Class A  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PMDAX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.50%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.76%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.16%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.23%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.40%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [41]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.36%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 681
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 965
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,270
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,134
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Annual Return 2012 rr_AnnualReturn2012 15.54%
Annual Return 2013 rr_AnnualReturn2013 29.45%
Annual Return 2014 rr_AnnualReturn2014 7.21%
Annual Return 2015 rr_AnnualReturn2015 (3.60%)
Annual Return 2016 rr_AnnualReturn2016 29.68%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 9.04%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2013
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 12.32%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2015
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (8.49%)
Label rr_AverageAnnualReturnLabel Class A Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 22.53%
5 Years rr_AverageAnnualReturnYear05 13.64%
Since Inception rr_AverageAnnualReturnSinceInception 11.94%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 06, 2011
Principal Funds Inc | Small-MidCap Dividend Income Fund | Class A | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 21.47%
5 Years rr_AverageAnnualReturnYear05 12.49%
Since Inception rr_AverageAnnualReturnSinceInception 10.83%
Principal Funds Inc | Small-MidCap Dividend Income Fund | Class A | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class A Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 13.07%
5 Years rr_AverageAnnualReturnYear05 10.61%
Since Inception rr_AverageAnnualReturnSinceInception 9.26%
Principal Funds Inc | Small-MidCap Dividend Income Fund | Class C  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PMDDX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.76%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.16%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.23%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.15%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [41]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 2.11%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 314
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 669
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,151
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,480
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 214
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 669
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,151
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,480
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principalfunds.com
Label rr_AverageAnnualReturnLabel Class C Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 27.65%
5 Years rr_AverageAnnualReturnYear05 14.02%
Since Inception rr_AverageAnnualReturnSinceInception 12.15%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 06, 2011
Principal Funds Inc | Small-MidCap Dividend Income Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PMDIX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.76%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.13%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.23%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.12%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [41]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.09%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 111
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 353
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 614
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,360
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 30.05%
5 Years rr_AverageAnnualReturnYear05 15.39%
Since Inception rr_AverageAnnualReturnSinceInception 13.54%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 06, 2011
Principal Funds Inc | Small-MidCap Dividend Income Fund | R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PMDHX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.76%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.02%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.23%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.01%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [41]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.01%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 103
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 322
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 558
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,236
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Label rr_AverageAnnualReturnLabel Class R-6 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 29.99%
5 Years rr_AverageAnnualReturnYear05 15.33%
Since Inception rr_AverageAnnualReturnSinceInception 13.45%
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 06, 2011
Principal Funds Inc | SystematEx International Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading SYSTEMATEX INTERNATIONAL FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks long-term growth of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment):
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 44.3% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 44.30%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund invests primarily in foreign equity securities. The Fund has no limitation on the percentage of assets invested in any one country or denominated in any one currency, but the Fund typically invests in foreign securities of at least 3 countries and at least 40% of its net assets in foreign securities. The Fund invests in equity securities of small, medium, and large market capitalization companies and in growth and value stocks. In an attempt to match or exceed the performance of the Fund's benchmark index (the MSCI EAFE NR Index), the Fund uses a systematic approach to purchase certain equity securities in the index and to exclude or adjust the weight of certain equity securities relative to the index.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.
•
Small and Medium Market Capitalization Companies Risk. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.
•
Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.
Foreign Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.
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; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Institutional Class and Class R-6 - www.principal.com.
The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (September 22, 2015).
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Institutional Class and Class R-6 - www.principal.com.The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [42]
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q3 '16
6.71%
Lowest return for a quarter during the period of the bar chart above:
Q1 '16
(2.08)%
(1) The year-to-date return as of September 30, 2017 was 20.02% for Institutional Class shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Institutional Class shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 Institutional Class shares only and would be different for the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | SystematEx International Fund | MSCI EAFE NR Index [Member]  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel MSCI EAFE NR Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 1.00%
Since Inception rr_AverageAnnualReturnSinceInception 3.93%
Principal Funds Inc | SystematEx International Fund | Institutional Class  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PSOMX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.60%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.27%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.87%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (1.12%) [43]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.75%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 77
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 479
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 907
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,099
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www,principal.com
Annual Return 2016 rr_AnnualReturn2016 1.19%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 20.02%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 6.71%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (2.08%)
Label rr_AverageAnnualReturnLabel Institutional Class Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.19%
Since Inception rr_AverageAnnualReturnSinceInception 4.11%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 22, 2015
Principal Funds Inc | SystematEx International Fund | Institutional Class | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Institutional Class Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 0.77%
Since Inception rr_AverageAnnualReturnSinceInception 3.67%
Principal Funds Inc | SystematEx International Fund | Institutional Class | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Institutional Class Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 1.19%
Since Inception rr_AverageAnnualReturnSinceInception 3.22%
Principal Funds Inc | SystematEx International Fund | R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PSTMX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.60%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.18%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.78%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.16%) [43]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.62%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 63
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 233
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 418
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 951
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www,principal.com
Label rr_AverageAnnualReturnLabel Class R-6 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 1.39%
Since Inception rr_AverageAnnualReturnSinceInception 4.26%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 22, 2015
Principal Funds Inc | SystematEx Large Value Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading SYSTEMATEX LARGE VALUE FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks long-term growth of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment):
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
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 annualized portfolio turnover rate was 46.6% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 46.60%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies with large market capitalizations at the time of purchase. For this Fund, companies with large market capitalizations are those with market capitalizations within the range of companies comprising the Russell 1000® Value Index (which as of November 30, 2017 ranged between approximately $632.6 million and $476.1 billion). The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. In an attempt to match or exceed the performance of the Fund's benchmark index, the Fund uses a systematic approach to purchase certain equity securities in the index and to exclude or adjust the weight of certain equity securities relative to the index.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
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:
Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.
•
Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.
Risk Lose Money [Text] rr_RiskLoseMoney 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.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:
•
For Class R-6 - www.principal.com.
The bar chart shows the investment returns of the Fund’s Class R-6 shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows 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 with those of one or more broad measures of market performance.
Life of Fund returns are measured from the date the Fund's shares were first sold (September 22, 2015).
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following information provides some indication of the risks of investing in the Fund. 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 by calling 1-800-222-5852 or online at:•For Class R-6 - www.principal.com.The bar chart shows the investment returns of the Fund’s Class R-6 shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows 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 with those of one or more broad measures of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-222-5852
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Total Returns as of December 31 [44]
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest return for a quarter during the period of the bar chart above:
Q4 '16
6.78%
Lowest return for a quarter during the period of the bar chart above:
Q1 '16
1.63%
(1) The year-to-date return as of September 30, 2017 was 8.60% for Class R-6 shares.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Class R-6 shares only and would be different for the other share classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
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 R-6 shares only and would be different for the other share classes.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns For the periods ended December 31, 2016
Principal Funds Inc | SystematEx Large Value Fund | Russell 1000 Value Index [Member]  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for fees, expenses, or taxes)
Label rr_AverageAnnualReturnLabel Russell 1000 Value Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 17.34%
Since Inception rr_AverageAnnualReturnSinceInception 17.85%
Principal Funds Inc | SystematEx Large Value Fund | R-6  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol PSLVX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.40%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.72%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.12%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.70%) [45]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.42%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination December 30, 2018
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 43
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 286
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 549
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,300
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
Annual Return 2016 rr_AnnualReturn2016 14.87%
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2017
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 8.60%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest return for a quarter during the period of the bar chart above:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 6.78%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest return for a quarter during the period of the bar chart above:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 1.63%
Label rr_AverageAnnualReturnLabel Class R-6 Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 14.87%
Since Inception rr_AverageAnnualReturnSinceInception 16.04%
Inception Date rr_AverageAnnualReturnInceptionDate Sep. 22, 2015
Principal Funds Inc | SystematEx Large Value Fund | R-6 | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class R-6 Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 13.87%
Since Inception rr_AverageAnnualReturnSinceInception 14.90%
Principal Funds Inc | SystematEx Large Value Fund | R-6 | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Class R-6 Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 8.42%
Since Inception rr_AverageAnnualReturnSinceInception 11.75%
[1] The year-to-date return as of September 30, 2017 was 20.21% for Class A shares.
[2] Based on estimated amounts for the current fiscal year (Class J).
[3] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.81% for Institutional Class shares. In addition, for Class R-6, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.01%, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses). It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[4] The year-to-date return as of September 30, 2017 was 2.95% for Institutional Class shares.
[5] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund's Management Fees through the period ending December 30, 2018. The fee waiver will reduce the Fund's Management Fees by 0.10% (expressed as a percent of average net assets on an annualized basis). It is expected that the fee waiver will continue through the period disclosed; however, Principal Funds, Inc. and PGI, the parties to the agreement may mutually agree to terminate the fee waiver prior to the end of the period.
[6] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.71% for Class J, 0.16% for Institutional, 1.04% for Class R-1, 0.91% for Class R-2, 0.73% for Class R-3, 0.54% for Class R-4, and 0.42% for Class R-5 shares. It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[7] During 2014, the Institutional Class experienced a significant withdrawal of monies by an affiliate. As the remaining shareholders held relatively small positions, the total return amounts expressed herein are greater than those that would have been experienced without the withdrawal.
[8] The year-to-date return as of September 30, 2017 was 10.20% for Class S shares.
[9] Principal Global Investors, LLC ("PGI"), the investment advisor, has agreed contractually to limit the Fund's expenses attributable to Class S shares by paying, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.00%. It is expected that the expense limit will continue permanently (and in any event, through December 30, 2018); however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limit.
[10] The table reflects that Principal Global Investors, LLC ("PGI"), the investment advisor, is absorbing all expenses of the Fund. You should be aware, however, that the Fund is an integral part of "wrap-fee" programs, including those sponsored by registered investment advisors and broker-dealers unaffiliated with the Fund. Participants in these programs pay a "wrap" fee to the sponsor of the program. You should read carefully the wrap-fee brochure provided to you by your sponsor or your registered investment advisor. The brochure is required to include information about the fees charged to you by the sponsor and the fees paid to the registered investment advisor.
[11] The year-to-date return as of September 30, 2017 was 7.13% for Class A shares.
[12] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s Management Fees through the period ending December 30, 2018. The fee waiver will reduce the Fund's Management Fees by 0.03% (expressed as a percent of average net assets on an annualized basis). It is expected that the fee waiver will continue through the period disclosed; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the fee waiver prior to the end of the period.
[13] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 1.22% for Class A, 1.97% for Class C, 0.85% and for Institutional Class shares. In addition, for Class R-6, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.02%, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses). It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[14] The year-to-date return as of September 30, 2017 was 2.55% for Class A shares.
[15] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 1.10% for Class A and 0.75% for Institutional Class shares. It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[16] The year-to-date return as of September 30, 2017 was 8.86% for Institutional Class shares.
[17] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.90% for Institutional Class shares. In addition, for Class R-6, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.02%, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses). It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[18] The year-to-date return as of September 30, 2017 was 4.71% for Class A shares.
[19] Based on estimated amounts for the current fiscal year (R-6).
[20] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s Management Fees through the period ending December 30, 2018. The fee waiver will reduce the Fund's Management Fees by 0.04% (expressed as a percent of average net assets on an annualized basis). It is expected that the fee waiver will continue through the period disclosed; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the fee waiver prior to the end of the period.
[21] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 2.75% for Class C and 1.63% for Institutional Class shares. In addition, for Class R-6, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.02%, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses). It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[22] The year-to-date return as of September 30, 2017 was 16.08% for Class A shares.
[23] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 1.50% for Class A, 2.25% for Class C and 0.85% for Institutional Class shares. It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[24] The year-to-date return as of September 30, 2017 was 20.42% for Institutional Class shares.
[25] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.31% for Institutional Class shares. In addition, for Class R-6, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.02%, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses). It is expected that the expense limit will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limit prior to the end of the period.
[26] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 1.60% for Class A and 1.20% for Institutional Class shares. In addition, for Class R-6, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.02% (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses). It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[27] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 2.02% for Class A and 1.67% for Institutional Class shares. In addition, for Class R-6, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.02%, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses). It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[28] The year-to-date return as of September 30, 2017 was 7.80% for Class A shares.
[29] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.90% for Class A,1.65% for Class C, and 0.62% for Institutional Class shares. It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[30] The year-to-date return as of September 30, 2017 was 41.30% for Class A shares.
[31] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 1.75% for Class A and 1.25% for Institutional Class shares. In addition, for Class R-6, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.02%, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses). It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[32] During 2015, the Class experienced a significant withdrawal of monies by an affiliate. As the remaining shareholders held relatively small positions, the total return amounts expressed herein are greater than those that would have been experienced without the withdrawal.
[33] The year-to-date return as of September 30, 2017 was 9.36% for Class A shares.
[34] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.81% for Institutional Class shares. In addition, for Class R-6, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.02%, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses). It is expected that the expense limit will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limit prior to the end of the period.
[35] The year-to-date return as of September 30, 2017 was 6.31% for Class A shares.
[36] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.50% for Class A and 0.15% for Institutional Class shares. It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[37] The year-to-date return as of September 30, 2017 was 3.92% for Class A shares.
[38] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 1.00% for Class A and 0.70% for Institutional Class shares. In addition, for Class R-6, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.02%, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses). It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[39] During 2016, the Class experienced a significant withdrawal of monies by an affiliate. As the remaining shareholders held relatively small positions, the total return amounts expressed herein are greater than those that would have been experienced without the withdrawal.
[40] The year-to-date return as of September 30, 2017 was 9.04% for Class A shares.
[41] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 1.13% for Class A, 1.88% for Class C and 0.86% for Institutional Class shares. In addition, for Class R-6, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.02%, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses). It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[42] The year-to-date return as of September 30, 2017 was 20.02% for Institutional Class shares.
[43] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.75% for Institutional Class shares. In addition, for Class R-6, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.02%, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses). It is expected that the expense limits will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limits prior to the end of the period.
[44] The year-to-date return as of September 30, 2017 was 8.60% for Class R-6 shares.
[45] Principal Global Investors, LLC ("PGI"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.42% for R-6 shares. It is expected that the expense limit will continue through the period ending December 30, 2018; however, Principal Funds, Inc. and PGI, the parties to the agreement, may mutually agree to terminate the expense limit prior to the end of the period.