Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Dec. 30, 2011
Diversified Real Asset Fund (First Prospectus Summary) | Diversified Real Asset Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return, Heading	rr_RiskReturnHeading	Diversified Real Asset Fund
Investment Objective, Heading	rr_ObjectiveHeading	Objective:
investment Objective, Primary	rr_ObjectivePrimaryTextBlock	The Fund seeks a long-term total return in excess of inflation.
Expense, Heading	rr_ExpenseHeading	Fees and Expenses of the Fund
Expense, Narrative	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in Principal Funds, Inc. More information about these and other discounts is available from your financial professional and in "Choosing a Share Class and The Costs of Investing" beginning on page 47 of the Fund's prospectus and "Multiple Class Structure" beginning on page 58 of the Fund's Statement of Additional Information.
Shareholder Fees, Caption	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses, Caption	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	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's annualized portfolio turnover rate was 59.7% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	59.70%
Expense Breakpoint, Discounts	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in Principal Funds, Inc.
Expense Breakpoint, Minimum Investment Required Amount	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	100,000
Expense Example, Heading	rr_ExpenseExampleHeading	Example
Expense Example, Narrative	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. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption, By Year, Caption	rr_ExpenseExampleNoRedemptionByYearCaption	You would pay the following expenses if you did not redeem your shares:
Investment Strategy, Heading	rr_StrategyHeading	Principal Investment Strategies
Investment Strategy, Narrative	rr_StrategyNarrativeTextBlock	The Fund seeks to achieve its investment objective by allocating its assets among the following general investment categories: inflation-indexed bonds, real estate investment trusts (REITs), commodity index-linked notes, fixed-income securities, securities of natural resource companies and master limited partnerships (MLPs). Under normal circumstances, the Fund invests at least 80% of its assets in securities that fall into these categories at the time of purchase. The Fund may concentrate its investments (invest more than 25% of its net assets) in securities in the real estate and energy/natural resources industries. In managing the Fund, Principal Management Corporation ("Principal"), the Fund's investment advisor, determines the Fund's strategic asset allocation among the general investment categories described below, which are executed by multiple sub-advisors. The allocations will vary from time to time, and the Fund may add additional investment categories. A portion of the Fund's assets currently will be invested primarily in inflation-indexed bonds issued by the U.S. and non-U.S. governments, their agencies or instrumentalities and U.S. and non-U.S. corporations. Inflation-indexed bonds are fixed-income securities that are structured to provide protection against inflation. The value of the bond's principal or the interest income paid on the bond is adjusted to track changes in an official inflation measure. A portion of the Fund's assets currently will be invested in a combination of commodity index-linked notes and fixed-income securities. Commodities are assets that have tangible properties, such as oil, coal, natural gas, agricultural products, industrial metals, livestock and precious metals. In order to gain exposure to the commodities markets without investing directly in physical commodities, the Fund invests in commodity index-linked notes. Commodity index-linked notes are derivative debt instruments with principal and/or coupon payments linked to the performance of commodity indices. These notes are sometimes referred to as "structured notes" because the terms of these notes may be structured by the issuer and the purchaser of the note. The value of these notes will rise or fall in response to changes in the underlying commodity index and will be subject to credit and interest rate risks that typically affect debt securities. The fixed income securities will primarily be short-term U.S. Treasury and Agency notes and bonds. A portion of the Fund's assets currently will be invested in REITs. REITs are corporations or business trusts that are permitted to eliminate corporate level federal income taxes by meeting certain requirements of the Internal Revenue Code. A portion of the Fund's assets currently will be invested in securities of all companies that primarily own, explore, mine, process or otherwise develop natural resources, or supply goods and services to such companies. Natural resources generally include precious metals, such as gold, silver and platinum, ferrous and nonferrous metals, such as iron, aluminum and copper, strategic metals such as uranium and titanium, hydrocarbons such as coal and oil, timberland, undeveloped real property and agricultural commodities. A portion of the Fund's assets currently will be invested in MLPs. MLPs are engaged in the transportation, storage, processing, refining, marketing, production, or mining of natural resources. The Fund will invest primarily in the mid-stream category, which is generally comprised of pipelines used to gather, transport, and distribute natural gas, crude oil, and refined petroleum products.
Risk, Heading	rr_RiskHeading	Principal Risks
Risk, Narrative	rr_RiskNarrativeTextBlock	The Fund may be an appropriate investment for investors seeking to maintain their purchasing power, who are willing to accept the risks associated with investing in commodity index-linked notes, fixed-income securities, inflation-indexed bonds, equity securities and real estate. The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are: Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective. Commodity Index-Linked Notes Risk. The value of commodities may be affected by overall market movements and other factors affecting the value of a particular industry or commodity. These notes expose the fund to movements in commodity prices. They are also subject to credit, counterparty, and interest rate risk. Commodity index-linked notes are often leveraged. At the maturity of the note, the fund may receive more or less principal than it originally invested. The fund may also receive interest payments on the note that are less than the stated coupon interest payments. Counterparty Risk. Counterparty risk is the risk that the counterparty to a derivatives contract or repurchase agreement, the borrower of a portfolio's securities, or other obligation, will be unable or unwilling to make timely principal, interest, or settlement payments, or otherwise to honor its obligations. Derivatives Risk. Transactions in derivatives (such as options, futures, currency contracts, and swaps) may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses. Equity Securities Risk. Equity securities (common, convertible preferred stocks and other securities whose values are tied to the price of stocks, such as rights, warrants and convertible debt securities) could decline in value 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. Industry Concentration (Sector) Risk. A fund that concentrates investments in a particular industry or group of industries (e.g., energy, real estate, technology, financial services) has greater exposure than other funds to market, economic and other factors affecting that industry or sector. Leverage Risk. Leverage created by borrowing or certain types of transactions or investments, such as reverse repurchase agreements, loans of portfolio securities, and the use of when-issued, delayed delivery or forward commitment transactions, or derivative instruments, may impair the fund's liquidity, cause it to liquidate positions at an unfavorable time, increase volatility of the fund's net asset value, or diminish the fund's performance. Master Limited Partnership ("MLP") Risk. MLPs are publicly-traded limited partnership interests or units. An MLP that invests in a particular industry (e.g., oil and gas) will be harmed by detrimental economic events within that industry. As partnerships, MLPs may be subject to less regulation (and less protection for investors) under state laws than corporations. In addition, MLPs may be subject to state taxation in certain jurisdictions, which may reduce the amount of income an MLP pays to its investors. Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates. Real Estate Investment Trusts ("REITs") Risk. A REIT could fail to qualify for tax-free pass-through of income under the Internal Revenue Code, and fund shareholders will indirectly bear their proportionate share of the expenses of REITs in which the fund invests. 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. Risk of Being an Underlying 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.
Risk, Lose Money	rr_RiskLoseMoney	Many factors affect that value, and it is possible to lose money by investing in the Fund.
Risk, Not Insured Depository Institution	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	rr_PerformanceNarrativeTextBlock	No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund's performance will be benchmarked against the Barclays Capital U.S. Treasury Inflation Protected Securities (TIPS) Index.
Performance, One Year or Less	rr_PerformanceOneYearOrLess	No performance information is shown because the Fund has not yet had a calendar year of performance.
Diversified Real Asset Fund (First Prospectus Summary) | Diversified Real Asset Fund | Class A Shares
Risk Return [Abstract]	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.75%
Maximum Deferred Sales Charge (Load) (as a percentage of dollars subject to charge)	rr_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Management Fees	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.22%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.32%
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.07%)	[1]
Total Annual Fund Operating Expenses after Expense Reimbursement	rr_NetExpensesOverAssets	1.25%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2012-12-31
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	498
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	770
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	1,064
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	1,900
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	498
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	770
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,064
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	1,900
Diversified Real Asset Fund (First Prospectus Summary) | Diversified Real Asset Fund | Class C Shares
Risk Return [Abstract]	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of dollars subject to charge)	rr_MaximumDeferredSalesChargeOverOfferingPrice	1.00%
Management Fees	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.33%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.18%
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.18%)	[1]
Total Annual Fund Operating Expenses after Expense Reimbursement	rr_NetExpensesOverAssets	2.00%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2012-12-31
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	303
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	662
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	1,152
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	2,500
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	203
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	662
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,152
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,500
Diversified Real Asset Fund (First Prospectus Summary) | Diversified Real Asset Fund | Class P Shares
Risk Return [Abstract]	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of dollars subject to charge)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none
Management Fees	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets
Other Expenses	rr_OtherExpensesOverAssets	1.04%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.89%
Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.84%)	[1]
Total Annual Fund Operating Expenses after Expense Reimbursement	rr_NetExpensesOverAssets	1.05%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2012-12-31
Expense Example, With Redemption, 1 Year	rr_ExpenseExampleYear01	107
Expense Example, With Redemption, 3 Years	rr_ExpenseExampleYear03	500
Expense Example, With Redemption, 5 Years	rr_ExpenseExampleYear05	935
Expense Example, With Redemption, 10 Years	rr_ExpenseExampleYear10	2,145
Expense Example, No Redemption, 1 Year	rr_ExpenseExampleNoRedemptionYear01	107
Expense Example, No Redemption, 3 Years	rr_ExpenseExampleNoRedemptionYear03	500
Expense Example, No Redemption, 5 Years	rr_ExpenseExampleNoRedemptionYear05	935
Expense Example, No Redemption, 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,145

[1] Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund's expenses attributable to Class A and Class C shares, and expenses identified as "Other Expenses" for Class P and, if necessary, pay expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2012. The expense limit will maintain a total level of operating expenses, (expressed as a percent of average net assets on an annualized basis) not to exceed 1.25% for Class A and 2.00% for Class C. In addition, for Class P, the expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.20%. It is expected that the expense limit will continue through the period disclosed; 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.