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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType Other
Document Period End Date dei_DocumentPeriodEndDate Oct. 31, 2013
Registrant Name dei_EntityRegistrantName PRINCIPAL FUNDS INC
Central Index Key dei_EntityCentralIndexKey 0000898745
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Sep. 30, 2014
Document Effective Date dei_DocumentEffectiveDate Sep. 30, 2014
Prospectus Date rr_ProspectusDate Sep. 03, 2014
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid Income Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading PRINCIPAL LIFETIME HYBRID INCOME FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks current income,
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock
and as a secondary objective, capital appreciation.
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):    None
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
As a fund of funds, the Fund does not pay transaction costs, such as commissions, when it buys and sells shares of underlying funds (or “turns over” its portfolio). An underlying fund does pay transaction costs when it buys and sells portfolio securities, and a higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the examples, affect the performance of the underlying fund and the Fund. This is a new fund and does not yet have a portfolio turnover rate to disclose.
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. 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 in underlying Principal Funds, Inc. (“PFI”) domestic and foreign equity, real asset and alternative investments, and fixed-income Funds according to an asset allocation strategy designed for investors primarily seeking current income and secondarily capital appreciation. Alternative investments aim to offer diversification beyond traditional equity and fixed-income securities and include investments in such assets as infrastructure, commodities, currencies and public timber companies. The Fund's asset allocation is designed for investors who are approximately 15 years beyond the normal retirement age of 65. The Fund invests in PFI Institutional Class shares of underlying funds, and a majority of its assets will be invested in index funds. It is managed by Principal Management Corporation (“Principal”).

Principal develops, implements and monitors the Fund's strategic or long-term asset class targets and target ranges, is responsible for an active rebalancing strategy designed to identify asset classes that appear attractive over the short term, and sets the percentage of Fund assets to be allocated to a particular asset class. Principal selects the underlying funds for each asset class and the target weights for each underlying fund and may shift asset class targets in response to normal evaluative processes, the shortening time horizon of the Fund or changes in market forces or Fund circumstances. Principal may add, remove, or substitute underlying funds at any time.
In selecting underlying funds and target weights, Principal considers both quantitative measures (e.g., past performance, expected levels of risk and returns, expense levels, diversification and style consistency) and qualitative factors (e.g., organizational stability, investment experience, investment and risk management processes, and information, trading, and compliance systems). There are no minimum or maximum percentages of assets that the Fund must invest in a specific asset class or underlying fund.
The underlying funds invest in growth and value stocks of large market capitalization companies, fixed-income securities (including high yield or “junk” bonds), domestic and foreign securities, securities denominated in foreign currencies, investment companies (including index funds), real estate securities, derivatives, mortgage-backed securities, and U.S. government and U.S. government-sponsored securities. The underlying funds engage in derivative transactions to gain exposure to a variety of securities or asset classes or attempt to reduce risk. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The underlying funds principally use futures, options, swaps (including, for example, credit default, interest rate, and currency swaps) and forwards.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The broad diversification of the Fund is designed to cushion severe losses in any one investment sector and 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 in 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 that are inherent in the fund of funds, in alphabetical order, are:

Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.
Conflict of Interest Risk. The Advisor and its affiliates earn different fees from different underlying funds and may have an incentive to allocate more fund-of-fund assets to underlying funds from which they receive higher fees.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Target Date Fund Risk. A target date fund should not be selected based solely on age or retirement date because there is no guarantee that this fund will provide adequate income at or through retirement.
The principal risks of investing in the Fund that are inherent in the underlying funds, in alphabetical order, are:
Counterparty Risk. Counterparty risk is the risk that the counterparty to a derivatives contract or repurchase agreement, the borrower of a portfolio’s securities, or other obligation, will be unable or unwilling to make timely principal, interest, or settlement payments, or otherwise to honor its obligations.
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.
Derivatives Risk. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.
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 large cap, mid cap or small cap stocks, or growth or value stocks, may underperform other market segments or the equity markets as a whole. Investments in smaller companies and mid-size companies may involve greater risk and price volatility than investments in larger, more mature companies.
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).
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.
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.
Index Fund Investment Risk. More likely than not, an index fund will underperform the index due to cashflows and the fees and expenses of the fund.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.
Prepayment Risk. Unscheduled prepayments on mortgage-backed and asset-backed securities may have to be reinvested at lower rates. A reduction in prepayments may increase the effective maturities of these securities, exposing them to the risk of decline in market value over time (extension risk).
Real Estate Securities Risk. Real estate securities are subject to the risks associated with direct ownership of real estate, including declines in value, adverse economic conditions, increases in expenses, regulatory changes and environmental problems. Investing in securities of companies in the real estate industry, subjects a fund to the special risks associated with the real estate market including factors such as loss to casualty or condemnation, changes in real estate values, property taxes, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents, and the management skill and creditworthiness of the issuer.
Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.
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.
Value Stock Risk. The market may not recognize the intrinsic value of value stocks for a long time, or they may be appropriately priced at the time of purchase.
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 in 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 S&P Target Date Retirement Income 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 online at www.principal.com or by calling 1-800-222-5852.
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 Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
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.
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid Income Fund | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PHTFX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.01%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.24% [1]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.37% [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.62%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.19%) [2]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.43%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 28, 2016
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 44
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 156
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2015 Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading PRINCIPAL LIFETIME HYBRID 2015 FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks a total return consisting of long-term growth of capital and 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):    None
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
As a fund of funds, the Fund does not pay transaction costs, such as commissions, when it buys and sells shares of underlying funds (or “turns over” its portfolio). An underlying fund does pay transaction costs when it buys and sells portfolio securities, and a higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the examples, affect the performance of the underlying fund and the Fund. This is a new fund and does not yet have a portfolio turnover rate to disclose.
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. 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 operates as a “target date fund.” It invests in underlying Principal Funds, Inc. (“PFI”) domestic and foreign equity, real asset and alternative investments, and fixed-income Funds according to an asset allocation strategy designed for investors having a retirement investment goal close to the year in the Fund’s name. Alternative investments aim to offer diversification beyond traditional equity and fixed-income securities and include investments in such assets as infrastructure, commodities, currencies and public timber companies. The Fund's asset allocation will become more conservative over time as investment goals near (for example, retirement, which is assumed to begin at age 65) and investors become more risk-averse. The Fund invests in PFI Institutional Class shares of underlying funds, and a majority of its assets will be invested in index funds. It is managed by Principal Management Corporation (“Principal”).
Principal develops, implements and monitors the Fund's strategic or long-term asset class targets and target ranges, is responsible for an active rebalancing strategy designed to identify asset classes that appear attractive over the short term, and sets the percentage of Fund assets to be allocated to a particular asset class. Principal selects the underlying funds for each asset class and the target weights for each underlying fund and may shift asset class targets in response to normal evaluative processes, the shortening time horizon of the Fund or changes in market forces or Fund circumstances. Principal may add, remove, or substitute underlying funds at any time.
In selecting underlying funds and target weights, Principal considers both quantitative measures (e.g., past performance, expected levels of risk and returns, expense levels, diversification and style consistency) and qualitative factors (e.g., organizational stability, investment experience, investment and risk management processes, and information, trading, and compliance systems). There are no minimum or maximum percentages of assets that the Fund must invest in a specific asset class or underlying fund.
The underlying funds invest in growth and value stocks of large market capitalization companies, fixed-income securities (including high yield or “junk” bonds), domestic and foreign (including those in emerging markets) securities, securities denominated in foreign currencies, investment companies (including index funds), real estate securities, derivatives, mortgage-backed and asset-backed securities, and U.S. government and U.S. government-sponsored securities. The underlying funds engage in derivative transactions to gain exposure to a variety of securities or asset classes or attempt to reduce risk. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The underlying funds principally use futures, options, swaps (including, for example, credit default, interest rate, and currency swaps) and forwards.
Within 10 to 15 years after its target year, the Fund's underlying fund allocation is expected to match that of the Principal LifeTime Hybrid Income Fund. At that time, the Fund may be combined with the Principal LifeTime Hybrid Income Fund if the Board of Directors determines that the combination is in the best interests of Fund shareholders. It is expected that at the target date in the Fund’s name, the shareholder will begin gradually withdrawing the account's value.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The broad diversification of the Fund is designed to cushion severe losses in any one investment sector and 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. The principal risks of investing in the Fund that are inherent in the fund of funds, in alphabetical order, are:
Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.
Conflict of Interest Risk. The Advisor and its affiliates earn different fees from different underlying funds and may have an incentive to allocate more fund-of-fund assets to underlying funds from which they receive higher fees.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Target Date Fund Risk. A target date fund should not be selected based solely on age or retirement date because there is no guarantee that this fund will provide adequate income at or through retirement.
The principal risks of investing in the Fund that are inherent in the underlying funds, in alphabetical order, are:
Counterparty Risk. Counterparty risk is the risk that the counterparty to a derivatives contract or repurchase agreement, the borrower of a portfolio’s securities, or other obligation, will be unable or unwilling to make timely principal, interest, or settlement payments, or otherwise to honor its obligations.
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.
Derivatives Risk. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.
Emerging Market 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 large cap, mid cap or small cap stocks, or growth or value stocks, may underperform other market segments or the equity markets as a whole. Investments in smaller companies and mid-size companies may involve greater risk and price volatility than investments in larger, more mature companies.
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).
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.
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.
Index Fund Investment Risk. More likely than not, an index fund will underperform the index due to cashflows and the fees and expenses of the fund.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.
Prepayment Risk. Unscheduled prepayments on mortgage-backed and asset-backed securities may have to be reinvested at lower rates. A reduction in prepayments may increase the effective maturities of these securities, exposing them to the risk of decline in market value over time (extension risk).
Real Estate Securities Risk. Real estate securities are subject to the risks associated with direct ownership of real estate, including declines in value, adverse economic conditions, increases in expenses, regulatory changes and environmental problems. Investing in securities of companies in the real estate industry, subjects a fund to the special risks associated with the real estate market including factors such as loss to casualty or condemnation, changes in real estate values, property taxes, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents, and the management skill and creditworthiness of the issuer.
Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.
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.
Value Stock Risk. The market may not recognize the intrinsic value of value stocks for a long time, or they may be appropriately priced at the time of purchase
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
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 S&P Target Date 2015 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 online at www.principal.com or by calling 1-800-222-5852.
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 Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
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.
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2015 Fund | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PHTMX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.01%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.12% [1]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.38% [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.51%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.07%) [2]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.44%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 28, 2016
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 45
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 148
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2020 Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading PRINCIPAL LIFETIME HYBRID 2020 FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks a total return consisting of long-term growth of capital and 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):    None
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
As a fund of funds, the Fund does not pay transaction costs, such as commissions, when it buys and sells shares of underlying funds (or “turns over” its portfolio). An underlying fund does pay transaction costs when it buys and sells portfolio securities, and a higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the examples, affect the performance of the underlying fund and the Fund. This is a new fund and does not yet have a portfolio turnover rate to disclose.
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. 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 operates as a “target date fund.” It invests in underlying Principal Funds, Inc. (“PFI”) domestic and foreign equity, real asset and alternative investments, and fixed-income Funds according to an asset allocation strategy designed for investors having a retirement investment goal close to the year in the Fund’s name. Alternative investments aim to offer diversification beyond traditional equity and fixed-income securities and include investments in such assets as infrastructure, commodities, currencies and public timber companies. The Fund's asset allocation will become more conservative over time as investment goals near (for example, retirement, which is assumed to begin at age 65) and investors become more risk-averse. The Fund invests in PFI Institutional Class shares of underlying funds, and a majority of its assets will be invested in index funds. It is managed by Principal Management Corporation (“Principal”).

Principal develops, implements and monitors the Fund's strategic or long-term asset class targets and target ranges, is responsible for an active rebalancing strategy designed to identify asset classes that appear attractive over the short term, and sets the percentage of Fund assets to be allocated to a particular asset class. Principal selects the underlying funds for each asset class and the target weights for each underlying fund and may shift asset class targets in response to normal evaluative processes, the shortening time horizon of the Fund or changes in market forces or Fund circumstances. Principal may add, remove, or substitute underlying funds at any time.
In selecting underlying funds and target weights, Principal considers both quantitative measures (e.g., past performance, expected levels of risk and returns, expense levels, diversification and style consistency) and qualitative factors (e.g., organizational stability, investment experience, investment and risk management processes, and information, trading, and compliance systems). There are no minimum or maximum percentages of assets that the Fund must invest in a specific asset class or underlying fund.
The underlying funds invest in growth and value stocks of large market capitalization companies, fixed-income securities (including high yield or “junk” bonds), domestic and foreign (including those in emerging markets) securities, securities denominated in foreign currencies, investment companies (including index funds), real estate securities, derivatives, mortgage-backed and asset-backed securities, and U.S. government and U.S. government-sponsored securities. The underlying funds engage in derivative transactions to gain exposure to a variety of securities or asset classes or attempt to reduce risk. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The underlying funds principally use futures, options, swaps (including, for example, credit default, interest rate, and currency swaps) and forwards.
Within 10 to 15 years after its target year, the Fund's underlying fund allocation is expected to match that of the Principal LifeTime Hybrid Income Fund. At that time, the Fund may be combined with the Principal LifeTime Hybrid Income Fund if the Board of Directors determines that the combination is in the best interests of Fund shareholders. It is expected that at the target date in the Fund’s name, the shareholder will begin gradually withdrawing the account's value.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The broad diversification of the Fund is designed to cushion severe losses in any one investment sector and 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. The principal risks of investing in the Fund that are inherent in the fund of funds, in alphabetical order, are:
Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.
Conflict of Interest Risk. The Advisor and its affiliates earn different fees from different underlying funds and may have an incentive to allocate more fund-of-fund assets to underlying funds from which they receive higher fees.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Target Date Fund Risk. A target date fund should not be selected based solely on age or retirement date because there is no guarantee that this fund will provide adequate income at or through retirement.
The principal risks of investing in the Fund that are inherent in the underlying funds, in alphabetical order, are:
Counterparty Risk. Counterparty risk is the risk that the counterparty to a derivatives contract or repurchase agreement, the borrower of a portfolio’s securities, or other obligation, will be unable or unwilling to make timely principal, interest, or settlement payments, or otherwise to honor its obligations.
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.
Derivatives Risk. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.
Emerging Market 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 large cap, mid cap or small cap stocks, or growth or value stocks, may underperform other market segments or the equity markets as a whole. Investments in smaller companies and mid-size companies may involve greater risk and price volatility than investments in larger, more mature companies.
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).
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.
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.
Index Fund Investment Risk. More likely than not, an index fund will underperform the index due to cashflows and the fees and expenses of the fund.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.
Prepayment Risk. Unscheduled prepayments on mortgage-backed and asset-backed securities may have to be reinvested at lower rates. A reduction in prepayments may increase the effective maturities of these securities, exposing them to the risk of decline in market value over time (extension risk).
Real Estate Securities Risk. Real estate securities are subject to the risks associated with direct ownership of real estate, including declines in value, adverse economic conditions, increases in expenses, regulatory changes and environmental problems. Investing in securities of companies in the real estate industry, subjects a fund to the special risks associated with the real estate market including factors such as loss to casualty or condemnation, changes in real estate values, property taxes, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents, and the management skill and creditworthiness of the issuer.
Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.
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.
Value Stock Risk. The market may not recognize the intrinsic value of value stocks for a long time, or they may be appropriately priced at the time of purchase.
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
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 S&P Target Date 2020 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 online at www.principal.com or by calling 1-800-222-5852.
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 Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
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.
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2020 Fund | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PHTTX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.01%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.12% [1]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.40% [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.53%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.07%) [2]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.46%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 28, 2016
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 47
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 154
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2025 Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading PRINCIPAL LIFETIME HYBRID 2025 FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks a total return consisting of long-term growth of capital and 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):    None
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
As a fund of funds, the Fund does not pay transaction costs, such as commissions, when it buys and sells shares of underlying funds (or “turns over” its portfolio). An underlying fund does pay transaction costs when it buys and sells portfolio securities, and a higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the examples, affect the performance of the underlying fund and the Fund. This is a new fund and does not yet have a portfolio turnover rate to disclose.
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. 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 operates as a “target date fund.” It invests in underlying Principal Funds, Inc. (“PFI”) domestic and foreign equity, real asset and alternative investments, and fixed-income Funds according to an asset allocation strategy designed for investors having a retirement investment goal close to the year in the Fund’s name. Alternative investments aim to offer diversification beyond traditional equity and fixed-income securities and include investments in such assets as infrastructure, commodities, currencies and public timber companies. The Fund's asset allocation will become more conservative over time as investment goals near (for example, retirement, which is assumed to begin at age 65) and investors become more risk-averse. The Fund invests in PFI Institutional Class shares of underlying funds, and a majority of its assets will be invested in index funds. It is managed by Principal Management Corporation (“Principal”).

Principal develops, implements and monitors the Fund's strategic or long-term asset class targets and target ranges, is responsible for an active rebalancing strategy designed to identify asset classes that appear attractive over the short term, and sets the percentage of Fund assets to be allocated to a particular asset class. Principal selects the underlying funds for each asset class and the target weights for each underlying fund and may shift asset class targets in response to normal evaluative processes, the shortening time horizon of the Fund or changes in market forces or Fund circumstances. Principal may add, remove, or substitute underlying funds at any time.
In selecting underlying funds and target weights, Principal considers both quantitative measures (e.g., past performance, expected levels of risk and returns, expense levels, diversification and style consistency) and qualitative factors (e.g., organizational stability, investment experience, investment and risk management processes, and information, trading, and compliance systems). There are no minimum or maximum percentages of assets that the Fund must invest in a specific asset class or underlying fund.
The underlying funds invest in growth and value stocks of small, medium, and large market capitalization companies, fixed-income securities (including high yield or “junk” bonds), domestic and foreign (including those in emerging markets) securities, securities denominated in foreign currencies, investment companies (including index funds), real estate securities, derivatives, and U.S. government and U.S. government-sponsored securities. The underlying funds engage in derivative transactions to gain exposure to a variety of securities or asset classes or attempt to reduce risk. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The underlying funds principally use futures, options, swaps (including, for example, credit default, interest rate, and currency swaps) and forwards.
Within 10 to 15 years after its target year, the Fund's underlying fund allocation is expected to match that of the Principal LifeTime Hybrid Income Fund. At that time, the Fund may be combined with the Principal LifeTime Hybrid Income Fund if the Board of Directors determines that the combination is in the best interests of Fund shareholders. It is expected that at the target date in the Fund’s name, the shareholder will begin gradually withdrawing the account's value.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The broad diversification of the Fund is designed to cushion severe losses in any one investment sector and 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. The principal risks of investing in the Fund that are inherent in the fund of funds, in alphabetical order, are:
Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.
Conflict of Interest Risk. The Advisor and its affiliates earn different fees from different underlying funds and may have an incentive to allocate more fund-of-fund assets to underlying funds from which they receive higher fees.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Target Date Fund Risk. A target date fund should not be selected based solely on age or retirement date because there is no guarantee that this fund will provide adequate income at or through retirement.
The principal risks of investing in the Fund that are inherent in the underlying funds, in alphabetical order, are:
Counterparty Risk. Counterparty risk is the risk that the counterparty to a derivatives contract or repurchase agreement, the borrower of a portfolio’s securities, or other obligation, will be unable or unwilling to make timely principal, interest, or settlement payments, or otherwise to honor its obligations.
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.
Derivatives Risk. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.
Emerging Market 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 large cap, mid cap or small cap stocks, or growth or value stocks, may underperform other market segments or the equity markets as a whole. Investments in smaller companies and mid-size companies may involve greater risk and price volatility than investments in larger, more mature companies.
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).
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.
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.
Index Fund Investment Risk. More likely than not, an index fund will underperform the index due to cashflows and the fees and expenses of the fund.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
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 Securities Risk. Real estate securities are subject to the risks associated with direct ownership of real estate, including declines in value, adverse economic conditions, increases in expenses, regulatory changes and environmental problems. Investing in securities of companies in the real estate industry, subjects a fund to the special risks associated with the real estate market including factors such as loss to casualty or condemnation, changes in real estate values, property taxes, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents, and the management skill and creditworthiness of the issuer.
Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.
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.
Value Stock Risk. The market may not recognize the intrinsic value of value stocks for a long time, or they may be appropriately priced at the time of purchase.
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
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 S&P Target Date 2025 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 online at www.principal.com or by calling 1-800-222-5852.
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 Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
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.
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2025 Fund | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PHTQX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.01%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.04% [1]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.42% [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.47%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [2]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.47%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 28, 2016
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 48
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 151
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2030 Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading PRINCIPAL LIFETIME HYBRID 2030 FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks a total return consisting of long-term growth of capital and 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):    None
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
As a fund of funds, the Fund does not pay transaction costs, such as commissions, when it buys and sells shares of underlying funds (or “turns over” its portfolio). An underlying fund does pay transaction costs when it buys and sells portfolio securities, and a higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the examples, affect the performance of the underlying fund and the Fund. This is a new fund and does not yet have a portfolio turnover rate to disclose.
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. 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 operates as a “target date fund.” It invests in underlying Principal Funds, Inc. (“PFI”) domestic and foreign equity, real asset and alternative investments, and fixed-income Funds according to an asset allocation strategy designed for investors having a retirement investment goal close to the year in the Fund’s name. Alternative investments aim to offer diversification beyond traditional equity and fixed-income securities and include investments in such assets as infrastructure, commodities, currencies and public timber companies. The Fund's asset allocation will become more conservative over time as investment goals near (for example, retirement, which is assumed to begin at age 65) and investors become more risk-averse. The Fund invests in PFI Institutional Class shares of underlying funds, and a majority of its assets will be invested in index funds. It is managed by Principal Management Corporation (“Principal”).
Principal develops, implements and monitors the Fund's strategic or long-term asset class targets and target ranges, is responsible for an active rebalancing strategy designed to identify asset classes that appear attractive over the short term, and sets the percentage of Fund assets to be allocated to a particular asset class. Principal selects the underlying funds for each asset class and the target weights for each underlying fund and may shift asset class targets in response to normal evaluative processes, the shortening time horizon of the Fund or changes in market forces or Fund circumstances. Principal may add, remove, or substitute underlying funds at any time.
In selecting underlying funds and target weights, Principal considers both quantitative measures (e.g., past performance, expected levels of risk and returns, expense levels, diversification and style consistency) and qualitative factors (e.g., organizational stability, investment experience, investment and risk management processes, and information, trading, and compliance systems). There are no minimum or maximum percentages of assets that the Fund must invest in a specific asset class or underlying fund.
The underlying funds invest in growth and value stocks of small, medium, and large market capitalization companies, fixed-income securities (including high yield or “junk” bonds), domestic and foreign (including those in emerging markets) securities, securities denominated in foreign currencies, investment companies (including index funds), real estate securities, derivatives, and U.S. government and U.S. government-sponsored securities. The underlying funds engage in derivative transactions to gain exposure to a variety of securities or asset classes or attempt to reduce risk. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The underlying funds principally use futures, options, swaps (including, for example, credit default, interest rate, and currency swaps) and forwards.
Within 10 to 15 years after its target year, the Fund's underlying fund allocation is expected to match that of the Principal LifeTime Hybrid Income Fund. At that time, the Fund may be combined with the Principal LifeTime Hybrid Income Fund if the Board of Directors determines that the combination is in the best interests of Fund shareholders. It is expected that at the target date in the Fund’s name, the shareholder will begin gradually withdrawing the account's value.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The broad diversification of the Fund is designed to cushion severe losses in any one investment sector and 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. The principal risks of investing in the Fund that are inherent in the fund of funds, in alphabetical order, are:
Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.
Conflict of Interest Risk. The Advisor and its affiliates earn different fees from different underlying funds and may have an incentive to allocate more fund-of-fund assets to underlying funds from which they receive higher fees.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Target Date Fund Risk. A target date fund should not be selected based solely on age or retirement date because there is no guarantee that this fund will provide adequate income at or through retirement.
The principal risks of investing in the Fund that are inherent in the underlying funds, in alphabetical order, are:
Counterparty Risk. Counterparty risk is the risk that the counterparty to a derivatives contract or repurchase agreement, the borrower of a portfolio’s securities, or other obligation, will be unable or unwilling to make timely principal, interest, or settlement payments, or otherwise to honor its obligations.
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.
Derivatives Risk. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.
Emerging Market 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 large cap, mid cap or small cap stocks, or growth or value stocks, may underperform other market segments or the equity markets as a whole. Investments in smaller companies and mid-size companies may involve greater risk and price volatility than investments in larger, more mature companies.
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).
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.
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.
Index Fund Investment Risk. More likely than not, an index fund will underperform the index due to cashflows and the fees and expenses of the fund.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
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 Securities Risk. Real estate securities are subject to the risks associated with direct ownership of real estate, including declines in value, adverse economic conditions, increases in expenses, regulatory changes and environmental problems. Investing in securities of companies in the real estate industry, subjects a fund to the special risks associated with the real estate market including factors such as loss to casualty or condemnation, changes in real estate values, property taxes, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents, and the management skill and creditworthiness of the issuer.
Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.
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.
Value Stock Risk. The market may not recognize the intrinsic value of value stocks for a long time, or they may be appropriately priced at the time of purchase.
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
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 S&P Target Date 2030 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 online at www.principal.com or by calling 1-800-222-5852.
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 Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
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.
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2030 Fund | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PHTNX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.01%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.04% [1]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.43% [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.48%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [2]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.48%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 28, 2016
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 49
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 154
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2035 Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading PRINCIPAL LIFETIME HYBRID 2035 FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks a total return consisting of long-term growth of capital and 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):    None
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
As a fund of funds, the Fund does not pay transaction costs, such as commissions, when it buys and sells shares of underlying funds (or “turns over” its portfolio). An underlying fund does pay transaction costs when it buys and sells portfolio securities, and a higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the examples, affect the performance of the underlying fund and the Fund. This is a new fund and does not yet have a portfolio turnover rate to disclose.
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. 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 operates as a “target date fund.” It invests in underlying Principal Funds, Inc. (“PFI”) domestic and foreign equity, real asset and alternative investments, and fixed-income Funds according to an asset allocation strategy designed for investors having a retirement investment goal close to the year in the Fund’s name. Alternative investments aim to offer diversification beyond traditional equity and fixed-income securities and include investments in such assets as infrastructure, commodities, currencies and public timber companies. The Fund's asset allocation will become more conservative over time as investment goals near (for example, retirement, which is assumed to begin at age 65) and investors become more risk-averse. The Fund invests in PFI Institutional Class shares of underlying funds, and a majority of its assets will be invested in index funds. It is managed by Principal Management Corporation (“Principal”).
Principal develops, implements and monitors the Fund's strategic or long-term asset class targets and target ranges, is responsible for an active rebalancing strategy designed to identify asset classes that appear attractive over the short term, and sets the percentage of Fund assets to be allocated to a particular asset class. Principal selects the underlying funds for each asset class and the target weights for each underlying fund and may shift asset class targets in response to normal evaluative processes, the shortening time horizon of the Fund or changes in market forces or Fund circumstances. Principal may add, remove, or substitute underlying funds at any time.
In selecting underlying funds and target weights, Principal considers both quantitative measures (e.g., past performance, expected levels of risk and returns, expense levels, diversification and style consistency) and qualitative factors (e.g., organizational stability, investment experience, investment and risk management processes, and information, trading, and compliance systems). There are no minimum or maximum percentages of assets that the Fund must invest in a specific asset class or underlying fund.
The underlying funds invest in growth and value stocks of small, medium, and large market capitalization companies, fixed-income securities, domestic and foreign (including those in emerging markets) securities, securities denominated in foreign currencies, investment companies (including index funds), real estate securities, derivatives, and U.S. government and U.S. government-sponsored securities. The underlying funds engage in derivative transactions to gain exposure to a variety of securities or asset classes or attempt to reduce risk. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The underlying funds principally use equity index futures and options to manage equity exposure.
Within 10 to 15 years after its target year, the Fund's underlying fund allocation is expected to match that of the Principal LifeTime Hybrid Income Fund. At that time, the Fund may be combined with the Principal LifeTime Hybrid Income Fund if the Board of Directors determines that the combination is in the best interests of Fund shareholders. It is expected that at the target date in the Fund’s name, the shareholder will begin gradually withdrawing the account's value.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The broad diversification of the Fund is designed to cushion severe losses in any one investment sector and 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. The principal risks of investing in the Fund that are inherent in the fund of funds, in alphabetical order, are:
Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.
Conflict of Interest Risk. The Advisor and its affiliates earn different fees from different underlying funds and may have an incentive to allocate more fund-of-fund assets to underlying funds from which they receive higher fees.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Target Date Fund Risk. A target date fund should not be selected based solely on age or retirement date because there is no guarantee that this fund will provide adequate income at or through retirement.
The principal risks of investing in the Fund that are inherent in the underlying funds, in alphabetical order, are:
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.
Derivatives Risk. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.
Emerging Market 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 large cap, mid cap or small cap stocks, or growth or value stocks, may underperform other market segments or the equity markets as a whole. Investments in smaller companies and mid-size companies may involve greater risk and price volatility than investments in larger, more mature companies.
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).
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.
Index Fund Investment Risk. More likely than not, an index fund will underperform the index due to cashflows and the fees and expenses of the fund.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
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 Securities Risk. Real estate securities are subject to the risks associated with direct ownership of real estate, including declines in value, adverse economic conditions, increases in expenses, regulatory changes and environmental problems. Investing in securities of companies in the real estate industry, subjects a fund to the special risks associated with the real estate market including factors such as loss to casualty or condemnation, changes in real estate values, property taxes, interest rates, cash flow of underlying real estate assets, occupancy rates, government regulations affecting zoning, land use and rents, and the management skill and creditworthiness of the issuer.
Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.
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.
Value Stock Risk. The market may not recognize the intrinsic value of value stocks for a long time, or they may be appropriately priced at the time of purchase.
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
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 S&P Target Date 2035 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 online at www.principal.com or by calling 1-800-222-5852.
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 Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
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.
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2035 Fund | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PHTJX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.01%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.05% [1]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.43% [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.49%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [2]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.49%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 28, 2016
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 50
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 157
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2040 Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading PRINCIPAL LIFETIME HYBRID 2040 FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks a total return consisting of long-term growth of capital and 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):    None
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
As a fund of funds, the Fund does not pay transaction costs, such as commissions, when it buys and sells shares of underlying funds (or “turns over” its portfolio). An underlying fund does pay transaction costs when it buys and sells portfolio securities, and a higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the examples, affect the performance of the underlying fund and the Fund. This is a new fund and does not yet have a portfolio turnover rate to disclose.
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. 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 operates as a “target date fund.” It invests in underlying Principal Funds, Inc. (“PFI”) domestic and foreign equity, real asset and alternative investments, and fixed-income Funds according to an asset allocation strategy designed for investors having a retirement investment goal close to the year in the Fund’s name. Alternative investments aim to offer diversification beyond traditional equity and fixed-income securities and include investments in such assets as infrastructure, commodities, currencies and public timber companies. The Fund's asset allocation will become more conservative over time as investment goals near (for example, retirement, which is assumed to begin at age 65) and investors become more risk-averse. The Fund invests in PFI Institutional Class shares of underlying funds, and a majority of its assets will be invested in index funds. It is managed by Principal Management Corporation (“Principal”).
Principal develops, implements and monitors the Fund's strategic or long-term asset class targets and target ranges, is responsible for an active rebalancing strategy designed to identify asset classes that appear attractive over the short term, and sets the percentage of Fund assets to be allocated to a particular asset class. Principal selects the underlying funds for each asset class and the target weights for each underlying fund and may shift asset class targets in response to normal evaluative processes, the shortening time horizon of the Fund or changes in market forces or Fund circumstances. Principal may add, remove, or substitute underlying funds at any time.
In selecting underlying funds and target weights, Principal considers both quantitative measures (e.g., past performance, expected levels of risk and returns, expense levels, diversification and style consistency) and qualitative factors (e.g., organizational stability, investment experience, investment and risk management processes, and information, trading, and compliance systems). There are no minimum or maximum percentages of assets that the Fund must invest in a specific asset class or underlying fund.
The underlying funds invest in growth and value stocks of small, medium, and large market capitalization companies, fixed-income securities, domestic and foreign (including those in emerging markets) securities, securities denominated in foreign currencies, investment companies (including index funds), and derivatives. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The underlying funds principally use equity index futures and options to manage equity exposure.
Within 10 to 15 years after its target year, the Fund's underlying fund allocation is expected to match that of the Principal LifeTime Hybrid Income Fund. At that time, the Fund may be combined with the Principal LifeTime Hybrid Income Fund if the Board of Directors determines that the combination is in the best interests of Fund shareholders. It is expected that at the target date in the Fund’s name, the shareholder will begin gradually withdrawing the account's value.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The broad diversification of the Fund is designed to cushion severe losses in any one investment sector and 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 the 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 that are inherent in the fund of funds, in alphabetical order, are:
Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.
Conflict of Interest Risk. The Advisor and its affiliates earn different fees from different underlying funds and may have an incentive to allocate more fund-of-fund assets to underlying funds from which they receive higher fees.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Target Date Fund Risk. A target date fund should not be selected based solely on age or retirement date because there is no guarantee that this fund will provide adequate income at or through retirement.
The principal risks of investing in the Fund that are inherent in the underlying funds, in alphabetical order, are:
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.
Derivatives Risk. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.
Emerging Market 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 large cap, mid cap or small cap stocks, or growth or value stocks, may underperform other market segments or the equity markets as a whole. Investments in smaller companies and mid-size companies may involve greater risk and price volatility than investments in larger, more mature companies.
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).
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.
Index Fund Investment Risk. More likely than not, an index fund will underperform the index due to cashflows and the fees and expenses of the fund.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
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.
Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.
Value Stock Risk. The market may not recognize the intrinsic value of value stocks for a long time, or they may be appropriately priced at the time of purchase.
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 the 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 S&P Target Date 2040 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 online at www.principal.com or by calling 1-800-222-5852.
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 Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
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.
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2040 Fund | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PLTQX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.01%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.05% [1]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.44% [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.50%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets none [2]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.50%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 28, 2016
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 51
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 160
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2045 Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading PRINCIPAL LIFETIME HYBRID 2045 FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks a total return consisting of long-term growth of capital and 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):    None
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
As a fund of funds, the Fund does not pay transaction costs, such as commissions, when it buys and sells shares of underlying funds (or “turns over” its portfolio). An underlying fund does pay transaction costs when it buys and sells portfolio securities, and a higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the examples, affect the performance of the underlying fund and the Fund. This is a new fund and does not yet have a portfolio turnover rate to disclose.
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. 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 operates as a “target date fund.” It invests in underlying Principal Funds, Inc. (“PFI”) domestic and foreign equity, real asset and alternative investments, and fixed-income Funds according to an asset allocation strategy designed for investors having a retirement investment goal close to the year in the Fund’s name. Alternative investments aim to offer diversification beyond traditional equity and fixed-income securities and include investments in such assets as infrastructure, commodities, currencies and public timber companies. The Fund's asset allocation will become more conservative over time as investment goals near (for example, retirement, which is assumed to begin at age 65) and investors become more risk-averse. The Fund invests in PFI Institutional Class shares of underlying funds, and a majority of its assets will be invested in index funds. It is managed by Principal Management Corporation (“Principal”).
Principal develops, implements and monitors the Fund's strategic or long-term asset class targets and target ranges, is responsible for an active rebalancing strategy designed to identify asset classes that appear attractive over the short term, and sets the percentage of Fund assets to be allocated to a particular asset class. Principal selects the underlying funds for each asset class and the target weights for each underlying fund and may shift asset class targets in response to normal evaluative processes, the shortening time horizon of the Fund or changes in market forces or Fund circumstances. Principal may add, remove, or substitute underlying funds at any time.
In selecting underlying funds and target weights, Principal considers both quantitative measures (e.g., past performance, expected levels of risk and returns, expense levels, diversification and style consistency) and qualitative factors (e.g., organizational stability, investment experience, investment and risk management processes, and information, trading, and compliance systems). There are no minimum or maximum percentages of assets that the Fund must invest in a specific asset class or underlying fund.
The underlying funds invest in growth and value stocks of small, medium, and large market capitalization companies, fixed-income securities, domestic and foreign (including those in emerging markets) securities, securities denominated in foreign currencies, investment companies (including index funds), and derivatives. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The underlying funds principally use equity index futures and options to manage equity exposure.
Within 10 to 15 years after its target year, the Fund's underlying fund allocation is expected to match that of the Principal LifeTime Hybrid Income Fund. At that time, the Fund may be combined with the Principal LifeTime Hybrid Income Fund if the Board of Directors determines that the combination is in the best interests of Fund shareholders. It is expected that at the target date in the Fund’s name, the shareholder will begin gradually withdrawing the account's value.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The broad diversification of the Fund is designed to cushion severe losses in any one investment sector and 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. The principal risks of investing in the Fund that are inherent in the fund of funds, in alphabetical order, are:
Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.
Conflict of Interest Risk. The Advisor and its affiliates earn different fees from different underlying funds and may have an incentive to allocate more fund-of-fund assets to underlying funds from which they receive higher fees.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Target Date Fund Risk. A target date fund should not be selected based solely on age or retirement date because there is no guarantee that this fund will provide adequate income at or through retirement.
The principal risks of investing in the Fund that are inherent in the underlying funds, in alphabetical order, are:
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.
Derivatives Risk. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.
Emerging Market 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 large cap, mid cap or small cap stocks, or growth or value stocks, may underperform other market segments or the equity markets as a whole. Investments in smaller companies and mid-size companies may involve greater risk and price volatility than investments in larger, more mature companies.
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).
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.
Index Fund Investment Risk. More likely than not, an index fund will underperform the index due to cashflows and the fees and expenses of the fund.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
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.
Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.
Value Stock Risk. The market may not recognize the intrinsic value of value stocks for a long time, or they may be appropriately priced at the time of purchase.
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
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 S&P Target Date 2045 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 online at www.principal.com or by calling 1-800-222-5852.
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 Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
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.
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2045 Fund | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PHTYX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.01%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.08% [1]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.44% [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.53%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [2]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.50%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 28, 2016
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 51
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 163
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2050 Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading PRINCIPAL LIFETIME HYBRID 2050 FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks a total return consisting of long-term growth of capital and 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):    None
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
As a fund of funds, the Fund does not pay transaction costs, such as commissions, when it buys and sells shares of underlying funds (or “turns over” its portfolio). An underlying fund does pay transaction costs when it buys and sells portfolio securities, and a higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the examples, affect the performance of the underlying fund and the Fund. This is a new fund and does not yet have a portfolio turnover rate to disclose.
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. 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 operates as a “target date fund.” It invests in underlying Principal Funds, Inc. (“PFI”) domestic and foreign equity, real asset and alternative investments, and fixed-income Funds according to an asset allocation strategy designed for investors having a retirement investment goal close to the year in the Fund’s name. Alternative investments aim to offer diversification beyond traditional equity and fixed-income securities and include investments in such assets as infrastructure, commodities, currencies and public timber companies. The Fund's asset allocation will become more conservative over time as investment goals near (for example, retirement, which is assumed to begin at age 65) and investors become more risk-averse. The Fund invests in PFI Institutional Class shares of underlying funds, and a majority of its assets will be invested in index funds. It is managed by Principal Management Corporation (“Principal”).
Principal develops, implements and monitors the Fund's strategic or long-term asset class targets and target ranges, is responsible for an active rebalancing strategy designed to identify asset classes that appear attractive over the short term, and sets the percentage of Fund assets to be allocated to a particular asset class. Principal selects the underlying funds for each asset class and the target weights for each underlying fund and may shift asset class targets in response to normal evaluative processes, the shortening time horizon of the Fund or changes in market forces or Fund circumstances. Principal may add, remove, or substitute underlying funds at any time.
In selecting underlying funds and target weights, Principal considers both quantitative measures (e.g., past performance, expected levels of risk and returns, expense levels, diversification and style consistency) and qualitative factors (e.g., organizational stability, investment experience, investment and risk management processes, and information, trading, and compliance systems). There are no minimum or maximum percentages of assets that the Fund must invest in a specific asset class or underlying fund.
The underlying funds invest in growth and value stocks of small, medium, and large market capitalization companies, fixed-income securities, domestic and foreign (including those in emerging markets) securities, securities denominated in foreign currencies, investment companies (including index funds), and derivatives. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The underlying funds principally use equity index futures and options to manage equity exposure.
Within 10 to 15 years after its target year, the Fund's underlying fund allocation is expected to match that of the Principal LifeTime Hybrid Income Fund. At that time, the Fund may be combined with the Principal LifeTime Hybrid Income Fund if the Board of Directors determines that the combination is in the best interests of Fund shareholders. It is expected that at the target date in the Fund’s name, the shareholder will begin gradually withdrawing the account's value.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The broad diversification of the Fund is designed to cushion severe losses in any one investment sector and 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. The principal risks of investing in the Fund that are inherent in the fund of funds, in alphabetical order, are:
Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.
Conflict of Interest Risk. The Advisor and its affiliates earn different fees from different underlying funds and may have an incentive to allocate more fund-of-fund assets to underlying funds from which they receive higher fees.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Target Date Fund Risk. A target date fund should not be selected based solely on age or retirement date because there is no guarantee that this fund will provide adequate income at or through retirement.
The principal risks of investing in the Fund that are inherent in the underlying funds, in alphabetical order, are:
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.
Derivatives Risk. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.
Emerging Market 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 large cap, mid cap or small cap stocks, or growth or value stocks, may underperform other market segments or the equity markets as a whole. Investments in smaller companies and mid-size companies may involve greater risk and price volatility than investments in larger, more mature companies.
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).
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.
Index Fund Investment Risk. More likely than not, an index fund will underperform the index due to cashflows and the fees and expenses of the fund.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
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.
Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.
Value Stock Risk. The market may not recognize the intrinsic value of value stocks for a long time, or they may be appropriately priced at the time of purchase
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
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 S&P Target Date 2050 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 online at www.principal.com or by calling 1-800-222-5852.
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 Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
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.
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2050 Fund | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PHTUX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.01%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.08% [1]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.45% [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.54%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.03%) [2]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.51%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 28, 2016
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 52
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 166
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2055 Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading PRINCIPAL LIFETIME HYBRID 2055 FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks a total return consisting of long-term growth of capital and 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):    None
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
As a fund of funds, the Fund does not pay transaction costs, such as commissions, when it buys and sells shares of underlying funds (or “turns over” its portfolio). An underlying fund does pay transaction costs when it buys and sells portfolio securities, and a higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the examples, affect the performance of the underlying fund and the Fund. This is a new fund and does not yet have a portfolio turnover rate to disclose.
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. 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 operates as a “target date fund.” It invests in underlying Principal Funds, Inc. (“PFI”) domestic and foreign equity, real asset and alternative investments, and fixed-income Funds according to an asset allocation strategy designed for investors having a retirement investment goal close to the year in the Fund’s name. Alternative investments aim to offer diversification beyond traditional equity and fixed-income securities and include investments in such assets as infrastructure, commodities, currencies and public timber companies. The Fund's asset allocation will become more conservative over time as investment goals near (for example, retirement, which is assumed to begin at age 65) and investors become more risk-averse. The Fund invests in PFI Institutional Class shares of underlying funds, and a majority of its assets will be invested in index funds. It is managed by Principal Management Corporation (“Principal”).
Principal develops, implements and monitors the Fund's strategic or long-term asset class targets and target ranges, is responsible for an active rebalancing strategy designed to identify asset classes that appear attractive over the short term, and sets the percentage of Fund assets to be allocated to a particular asset class. Principal selects the underlying funds for each asset class and the target weights for each underlying fund and may shift asset class targets in response to normal evaluative processes, the shortening time horizon of the Fund or changes in market forces or Fund circumstances. Principal may add, remove, or substitute underlying funds at any time.
In selecting underlying funds and target weights, Principal considers both quantitative measures (e.g., past performance, expected levels of risk and returns, expense levels, diversification and style consistency) and qualitative factors (e.g., organizational stability, investment experience, investment and risk management processes, and information, trading, and compliance systems). There are no minimum or maximum percentages of assets that the Fund must invest in a specific asset class or underlying fund.
The underlying funds invest in growth and value stocks of small, medium, and large market capitalization companies, fixed-income securities, domestic and foreign (including those in emerging markets) securities, securities denominated in foreign currencies, investment companies (including index funds), and derivatives. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The underlying funds principally use equity index futures and options to manage equity exposure.
Within 10 to 15 years after its target year, the Fund's underlying fund allocation is expected to match that of the Principal LifeTime Hybrid Income Fund. At that time, the Fund may be combined with the Principal LifeTime Hybrid Income Fund if the Board of Directors determines that the combination is in the best interests of Fund shareholders. It is expected that at the target date in the Fund’s name, the shareholder will begin gradually withdrawing the account's value.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The broad diversification of the Fund is designed to cushion severe losses in any one investment sector and 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. The principal risks of investing in the Fund that are inherent in the fund of funds, in alphabetical order, are:
Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.
Conflict of Interest Risk. The Advisor and its affiliates earn different fees from different underlying funds and may have an incentive to allocate more fund-of-fund assets to underlying funds from which they receive higher fees.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Target Date Fund Risk. A target date fund should not be selected based solely on age or retirement date because there is no guarantee that this fund will provide adequate income at or through retirement.
The principal risks of investing in the Fund that are inherent in the underlying funds, in alphabetical order, are:
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.
Derivatives Risk. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.
Emerging Market 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 large cap, mid cap or small cap stocks, or growth or value stocks, may underperform other market segments or the equity markets as a whole. Investments in smaller companies and mid-size companies may involve greater risk and price volatility than investments in larger, more mature companies.
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).
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.
Index Fund Investment Risk. More likely than not, an index fund will underperform the index due to cashflows and the fees and expenses of the fund.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
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.
Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.
Value Stock Risk. The market may not recognize the intrinsic value of value stocks for a long time, or they may be appropriately priced at the time of purchase.
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
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 S&P Target Date 2055+ 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 online at www.principal.com or by calling 1-800-222-5852.
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 Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
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.
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2055 Fund | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PLTNX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.01%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.12% [1]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.45% [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.58%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.07%) [2]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.51%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 28, 2016
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 52
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 170
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2060 Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading PRINCIPAL LIFETIME HYBRID 2060 FUND
Objective [Heading] rr_ObjectiveHeading Objective:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Fund seeks a total return consisting of long-term growth of capital and 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):    None
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
As a fund of funds, the Fund does not pay transaction costs, such as commissions, when it buys and sells shares of underlying funds (or “turns over” its portfolio). An underlying fund does pay transaction costs when it buys and sells portfolio securities, and a higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual account operating expenses or in the examples, affect the performance of the underlying fund and the Fund. This is a new fund and does not yet have a portfolio turnover rate to disclose.
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. If separate account expenses and contract level expenses were included, expenses would be higher. 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 operates as a “target date fund.” It invests in underlying Principal Funds, Inc. (“PFI”) domestic and foreign equity, real asset and alternative investments, and fixed-income Funds according to an asset allocation strategy designed for investors having a retirement investment goal close to the year in the Fund’s name. Alternative investments aim to offer diversification beyond traditional equity and fixed-income securities and include investments in such assets as infrastructure, commodities, currencies and public timber companies. The Fund's asset allocation will become more conservative over time as investment goals near (for example, retirement, which is assumed to begin at age 65) and investors become more risk-averse. The Fund invests in PFI Institutional Class shares of underlying funds, and a majority of its assets will be invested in index funds. It is managed by Principal Management Corporation (“Principal”).
Principal develops, implements and monitors the Fund's strategic or long-term asset class targets and target ranges, is responsible for an active rebalancing strategy designed to identify asset classes that appear attractive over the short term, and sets the percentage of Fund assets to be allocated to a particular asset class. Principal selects the underlying funds for each asset class and the target weights for each underlying fund and may shift asset class targets in response to normal evaluative processes, the shortening time horizon of the Fund or changes in market forces or Fund circumstances. Principal may add, remove, or substitute underlying funds at any time.
In selecting underlying funds and target weights, Principal considers both quantitative measures (e.g., past performance, expected levels of risk and returns, expense levels, diversification and style consistency) and qualitative factors (e.g., organizational stability, investment experience, investment and risk management processes, and information, trading, and compliance systems). There are no minimum or maximum percentages of assets that the Fund must invest in a specific asset class or underlying fund.
The underlying funds invest in growth and value stocks of small, medium, and large market capitalization companies, fixed-income securities, domestic and foreign (including those in emerging markets) securities, securities denominated in foreign currencies, investment companies (including index funds), and derivatives. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. The underlying funds principally use equity index futures and options to manage equity exposure.
Within 10 to 15 years after its target year, the Fund's underlying fund allocation is expected to match that of the Principal LifeTime Hybrid Income Fund. At that time, the Fund may be combined with the Principal LifeTime Hybrid Income Fund if the Board of Directors determines that the combination is in the best interests of Fund shareholders. It is expected that at the target date in the Fund’s name, the shareholder will begin gradually withdrawing the account's value.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
The broad diversification of the Fund is designed to cushion severe losses in any one investment sector and 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. The principal risks of investing in the Fund that are inherent in the fund of funds, in alphabetical order, are:
Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.
Conflict of Interest Risk. The Advisor and its affiliates earn different fees from different underlying funds and may have an incentive to allocate more fund-of-fund assets to underlying funds from which they receive higher fees.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
Target Date Fund Risk. A target date fund should not be selected based solely on age or retirement date because there is no guarantee that this fund will provide adequate income at or through retirement.
The principal risks of investing in the Fund that are inherent in the underlying funds, in alphabetical order, are:
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.
Derivatives Risk. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.
Emerging Market 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 large cap, mid cap or small cap stocks, or growth or value stocks, may underperform other market segments or the equity markets as a whole. Investments in smaller companies and mid-size companies may involve greater risk and price volatility than investments in larger, more mature companies.
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).
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.
Index Fund Investment Risk. More likely than not, an index fund will underperform the index due to cashflows and the fees and expenses of the fund.
Investment Company Securities Risk. Fund shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the fund invests.
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.
Risk of Being an Underlying Fund. A fund is subject to the risk of being an underlying fund to the extent that a fund of funds invests in the fund. An underlying fund of a fund of funds may experience relatively large redemptions or investments as the fund of funds periodically reallocates or rebalances its assets. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance.
Value Stock Risk. The market may not recognize the intrinsic value of value stocks for a long time, or they may be appropriately priced at the time of purchase.
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
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 S&P Target Date 2055+ 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 online at www.principal.com or by calling 1-800-222-5852.
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 Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.principal.com
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.
PFI Prospectus - Institutional Class Shares [Member] | Principal LifeTime Hybrid 2060 Fund | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol PLTHX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.01%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.12% [1]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.45% [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.58%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.07%) [2]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.51%
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination February 28, 2016
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 52
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 $ 170
[1] Based on estimated amounts for the current fiscal year.
[2] Principal Management Corporation ("Principal"), 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 0.06% for Institutional class shares. It is expected that the expense limit will continue through the period ending February 28, 2016; however, Principal Funds, Inc. and Principal, the parties to the agreement, may agree to terminate the expense limit prior to the end of the period.