485BPOS

Registration No. 33-59474

U.S. SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D. C. 20549

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POST-EFFECTIVE AMENDMENT NO. 121 TO

FORM N-1A

REGISTRATION STATEMENT

under

THE SECURITIES ACT OF 1933

and

REGISTRATION STATEMENT

under

THE INVESTMENT COMPANY ACT OF 1940

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PRINCIPAL FUNDS, INC.

(Exact name of Registrant as specified in Charter)

The Principal Financial Group

Des Moines, Iowa 50392

(Address of principal executive offices)

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Telephone Number (515) 235-9154

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	Copy to:
Jennifer A. Mills		JOHN W. BLOUCH, Esq.
The Principal Financial Group		Drinker Biddle & Reath, LLP
Des Moines, Iowa 50392		1500 K Street, N.W.
		Washington, DC 20005-1209

(Name and address of agent for service)

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It is proposed that this filing will become effective (check appropriate box)

__XX_    immediately upon filing pursuant to paragraph (b) of Rule 485

_____    on (date) pursuant to paragraph (b) of Rule 485

_____    60 days after filing pursuant to paragraph (a)(1) of Rule 485

____     on (date) pursuant to paragraph (a)(1) of Rule 485

_____    75 days after filing pursuant to paragraph (a)(2) of Rule 485

_____    on (date) pursuant to paragraph (a)(2) of Rule 485

If appropriate, check the following box:)

_____ This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

EXPLANATORY NOTE

This filing relates only to the Series in the Registrant’s Class A, Class C, and Class P; Class J; and Classes Institutional, R-1, R-2, R-3, R-4, and R-5 shares prospectuses dated December 28, 2012, and is filed for the purpose of submitting interactive data files.

SIGNATURES
Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant has duly caused this Amendment to the Registration Statement to be signed on its behalf by the undersigned, duly authorized in the City of Des Moines and State of Iowa, on the 17th day of January, 2013.
	Principal Funds, Inc.    (Registrant) /s/ N. M. Everett _____________________________________ N. M. Everett Chair, President and Chief Executive Officer
Attest: /s/ Beth Wilson ______________________________________ Beth Wilson Vice President and Secretary

Pursuant to the requirements of the Securities Act of 1933, this Amendment to the Registration Statement has been signed below by the following persons in the capacities and on the dates indicated.
Signature	Title	Date
/s/ N. M. Everett __________________________ N. M. Everett	Chairman, President and Chief Executive Officer (Principal Executive Officer)	January 17, 2013
/s/ L. A. Rasmussen __________________________ L. A. Rasmussen
	Vice President, Controller and Chief Financial Office (Principal Financial Officer and Controller)	January 17, 2013
/s/ M. J. Beer __________________________ M. J. Beer	Executive Vice President and Director	January 17, 2013
(E. Ballantine)* __________________________ E. Ballantine	Director	January 17, 2013
(L. T. Barnes)* __________________________ L. T. Barnes	Director	January 17, 2013
(K. Blake)* __________________________ K. Blake	Director	January 17, 2013
(C. Damos)* __________________________ C. Damos	Director	January 17, 2013
(M. A. Grimmett)* __________________________ M. A. Grimmett	Director	January 17, 2013
(F. S. Hirsch)* __________________________ F. S. Hirsch	Director	January 17, 2013
(T. Huang)* __________________________ T. Huang	Director	January 17, 2013
(W. C. Kimball)* __________________________ W. C. Kimball	Director	January 17, 2013

Signature	Title		Date
(D. Pavelich)* __________________________ D. Pavelich	Director		January 17, 2013
		/s/ M. J. Beer _______________________________ M. J. Beer Executive Vice President and Director * Pursuant to Power of Attorney    Previously Filed

Exhibit No.    Exhibits

Ex-101.INS    XBRL Instance Document

Ex-101.SCH    XBRL Taxonomy Extension Schema Document

Ex-101.CAL    XBRL Taxonomy Extension Calculations Linkbase Document

Ex-101.DEF    XBRL Taxonomy Extension Definition Linkbase Document

Ex-101.LAB    XBRL Taxonomy Extension Labels Linkbase Document

Ex-101.PRE    XBRL Taxonomy Extension Presentation Linkbase Document

XML

Bond Market Index Fund

BOND MARKET INDEX FUND

Objective:

The Fund seeks to provide current income.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees - Class J
Maximum Deferred Sales Charge (as a percentage) PFI Prospectus - Class J Bond Market Index Fund Bond Market Index Fund, Class J	1.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Class J		PFI Prospectus - Class J Bond Market Index Fund Bond Market Index Fund, Class J
Management Fees (as a percentage of Assets)		0.25%
Distribution and Service (12b-1) Fees		0.45%
Other Expenses (as a percentage of Assets):		0.37%
Expenses (as a percentage of Assets)		1.07%
Fee Waiver or Reimbursement	[1]	0.20%
Net Expenses (as a percentage of Assets)		0.87%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 - Class J (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
PFI Prospectus - Class J Bond Market Index Fund Bond Market Index Fund, Class J	189	320	571	1,288

You would pay the following expenses if you did not redeem your shares:

Expense Example, No Redemption - Class J (USD $)	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
PFI Prospectus - Class J Bond Market Index Fund Bond Market Index Fund, Class J	89	320	571	1,288

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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 144.0% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in debt securities held by the Barclays U.S. Aggregate Bond Index (the "Index") at the time of purchase. The Index is composed of investment grade, fixed rate debt issues, including government, corporate, asset-backed, and mortgage-backed securities, with maturities of one year or more. The Fund employs a passive investment approach designed to attempt to track the performance of the Index. Under normal circumstances, the Fund maintains an average portfolio duration that is in line with the duration of the Barclays U.S. Aggregate Bond Index, which as of August 31, 2012 was 4.99 years. The Fund actively trades portfolio securities.

Principal Risks

The Fund may be an appropriate investment for investors interested in investing in a fixed-income mutual fund and preferring a passive, rather than active, management style.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Fixed-Income Securities Risk. Fixed-income securities are subject to interest rate risk and credit quality risk. The market value of fixed-income securities generally declines when interest rates rise, and an issuer of fixed-income securities could default on its payment obligations.

Index Fund Investment Risk. More likely than not, an index fund will not provide investment performance that matches the index performance due to cashflows and the fees and expenses of the fund.

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.

Performance

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Class J shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). These annual returns do not reflect sales charges; if they did, returns would be lower. The table shows, for Class J shares of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principalfunds.com or by calling 1-800-222-5852.

Life of Fund returns are measured from December 30, 2009, the date the Class J shares were first sold.

Total Returns as of December 31 each year (Class J shares)

^[1]

The year-to-date return as of September 30, 2012 was 3.33% for Class J shares.

Highest return for a quarter during the period of the bar chart above:	Q3 ‘11	3.60	%
Lowest return for a quarter during the period of the bar chart above:	Q4 ‘10	-1.49	%

Average Annual Total Returns - Class J PFI Prospectus - Class J Bond Market Index Fund	Label	1 Year	Since Inception	Inception Date
Bond Market Index Fund, Class J	Class J Return Before Taxes	5.77%	5.72%	Dec. 30, 2009
Bond Market Index Fund, Class J After Taxes on Distributions	Class J Return After Taxes on Distributions	5.06%	5.08%	Dec. 30, 2009
Bond Market Index Fund, Class J After Taxes on Distributions and Sales	Class J Return After Taxes on Distribution and Sale of Fund Shares	3.75%	4.51%	Dec. 30, 2009
Barclays Aggregate Bond Index	Barclays Aggregate Bond Index (reflects no deduction for fees, expenses, or taxes)	7.84%	7.09%	Dec. 30, 2009

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Preferred Securities Fund

PREFERRED SECURITIES FUND

Objective:

The Fund seeks to provide current income.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees - Class J
Maximum Deferred Sales Charge (as a percentage) PFI Prospectus - Class J Preferred Securities Fund Preferred Securities Fund, Class J	1.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Class J		PFI Prospectus - Class J Preferred Securities Fund Preferred Securities Fund, Class J
Management Fees (as a percentage of Assets)		0.71%
Distribution and Service (12b-1) Fees		0.45%
Other Expenses (as a percentage of Assets):		0.30%
Expenses (as a percentage of Assets)		1.46%
Fee Waiver or Reimbursement	[1]	0.20%
Net Expenses (as a percentage of Assets)		1.26%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 - Class J (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
PFI Prospectus - Class J Preferred Securities Fund Preferred Securities Fund, Class J	228	442	778	1,729

You would pay the following expenses if you did not redeem your shares:

Expense Example, No Redemption - Class J (USD $)	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
PFI Prospectus - Class J Preferred Securities Fund Preferred Securities Fund, Class J	128	442	778	1,729

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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 22.9% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in preferred securities at the time of purchase. Preferred securities generally pay fixed rate dividends (though some are adjustable rate) and typically have "preference" over common stock in the payment of dividends and the liquidation of a company's assets, but are junior to all forms of the company's debt. Most of the securities purchased by the Fund are preferred securities of companies rated at the time of purchase BBB- or higher by Standard & Poor's Rating Service ("S&P") or Baa3 or higher by Moody's Investor Service, Inc. ("Moody's") or, if unrated, of comparable quality in the opinion of the Sub-Advisor. The Fund also invests up to 15% of its assets in below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, the Sub-Advisor will determine whether the bond is of a quality comparable to those rated below investment grade).

The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the U.S. and non-U.S financial services (i.e., banking, insurance and commercial finance,) industry. The Fund also regularly invests in the real estate investment trust (i.e. REIT) and utility industries.

Principal Risks

The Fund may be an appropriate investment for investors who are seeking dividends to generate income or to reinvest for growth and are willing to accept fluctuations in the value of the investment.

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:

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.

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).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Industry Concentration Risk (Financial Services). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in financial services companies may be more susceptible to adverse economic or regulatory occurrences affecting financial services companies. Financial companies may be adversely affected in certain market cycles, including periods of rising interest rates, which may restrict the availability and increase the cost of capital, and declining economic conditions, which may cause credit losses due to financial difficulties of borrowers. Because many types of financial companies are especially vulnerable to these economic cycles, the Fund’s investments in these companies may lose significant value during such periods.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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. 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.

Performance

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Class J shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). These annual returns do not reflect sales charges; if they did, returns would be lower. The table shows, for Class J shares of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principalfunds.com or by calling 1-800-222-5852.

Class J shares were first sold on December 29, 2003. The returns for the periods prior to that date are based on the performance of the Institutional Class shares adjusted to reflect the fees and expenses of Class J shares. The adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares. The Institutional Class shares were first sold on May 1, 2002.

Performance of a blended index shows how the Fund's performance compares to an index with similar investment objectives. Performance of the components of the blended index are also shown. The weightings for the Preferreds Blended Index are 50% BofA Merrill Lynch Fixed Rate Preferred Securities and 50% Barclays U.S. Tier I Capital Securities Index. The custom or blended index returns reflect the allocation in effect for the time period(s) for which fund returns are disclosed. Previous weightings or allocations of the custom or blended index are not restated.

Total Returns as of December 31 each year (Class J shares)

^[2]

The year-to-date return as of September 30, 2012 was 15.24% for Class J shares.

Highest return for a quarter during the period of the bar chart above:	Q2 '09	38.56	%
Lowest return for a quarter during the period of the bar chart above:	Q3 '08	-21.11	%

Average Annual Total Returns - Class J PFI Prospectus - Class J Preferred Securities Fund	Label	1 Year	5 Years	Since Inception	Inception Date
Preferred Securities Fund, Class J	Class J Return Before Taxes	0.04%	3.67%	4.41%	May 01, 2002
Preferred Securities Fund, Class J After Taxes on Distributions	Class J Return After Taxes on Distributions	(1.80%)	1.66%	2.68%	May 01, 2002
Preferred Securities Fund, Class J After Taxes on Distributions and Sales	Class J Return After Taxes on Distribution and Sale of Fund Shares	0.35%	2.00%	2.80%	May 01, 2002
BofA Merrill Lynch Fixed Rate Preferred Securities Index	BofA Merrill Lynch Fixed Rate Preferred Securities Index (reflects no deduction for fees, expenses, or taxes)	4.11%	(1.19%)	2.42%	May 01, 2002
Barclays U.S. Tier I Capital Securities Index	Barclays U.S. Tier I Capital Securities Index (reflects no deduction for fees, expenses, or taxes)	(0.53%)	1.71%	4.87%	May 01, 2002
Preferreds Blended Index	Preferreds Blended Index (reflects no deduction for fees, expenses, or taxes)	1.81%	0.01%	3.38%	May 01, 2002

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

[1] Principal Funds Distributor, Inc. ("the Distributor") has contractually agreed to limit the Distribution Fees attributable to Class J through December 31, 2013. The limit will maintain the level of Distribution Fees not to exceed 0.25%. It is expected that the expense limit will continue through the period disclosed; however, Principal Funds, Inc. and the Distributor, the parties to the agreement, may agree to terminate the expense limit prior to the end of the period.

[1] Principal Funds Distributor, Inc. ("the Distributor") has contractually agreed to limit the Distribution Fees attributable to Class J through December 31, 2013. The limit will maintain the level of Distribution Fees not to exceed 0.25%. It is expected that the expense limit will continue through the period disclosed; however, Principal Funds, Inc. and the Distributor, the parties to the agreement, may agree to terminate the expense limit prior to the end of the period.

[1] The year-to-date return as of September 30, 2012 was 3.33% for Class J shares.

[2] The year-to-date return as of September 30, 2012 was 15.24% for Class J shares.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Document Type

dei_DocumentType

485BPOS

Document Period End Date

dei_DocumentPeriodEndDate

Aug. 31, 2012

Registrant Name

dei_EntityRegistrantName

PRINCIPAL FUNDS INC

Central Index Key

dei_EntityCentralIndexKey

0000898745

Amendment Flag

dei_AmendmentFlag

false

Document Creation Date

dei_DocumentCreationDate

Dec. 27, 2012

Document Effective Date

dei_DocumentEffectiveDate

Dec. 28, 2012

PFI Prospectus - Institutional Class Shares

Risk/Return:

rr_RiskReturnAbstract

Prospectus Date

rr_ProspectusDate

Dec. 28, 2012

PFI Prospectus - Institutional Class Shares | Blue Chip Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

BLUE CHIP FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term growth of capital.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

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

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. From June 13, 2012, date operations commenced, through August 31, 2012, the Fund’s annualized portfolio turnover rate was 7.3% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

7.30%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated 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:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies with large market capitalizations (those with market capitalizations similar to companies in the Russell 1000 Growth^® Index (as of September 30, 2012, this range was between approximately $743.1 million and $610.3 billion) at the time of purchase. The Fund invests in foreign securities.

The Fund invests in growth equity securities; growth orientation emphasizes buying equity securities of companies whose potential for growth of capital and earnings is expected to be above average.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The Fund may be an appropriate investment for investors seeking long-term growth of capital and willing to accept the potential for short-term fluctuations in the value of investments.

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:

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.

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.

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.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance will be benchmarked against the Russell 1000 Growth Index.

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

No performance information is shown because the Fund has not yet had a calendar year of performance.

PFI Prospectus - Institutional Class Shares | Blue Chip Fund | Blue Chip Fund, Institutional Class

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PBCKX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.70%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.51%

^[1]

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

1.21%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.46%)

^[2]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.75%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

77

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

339

PFI Prospectus - Institutional Class Shares | Bond Market Index Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

BOND MARKET INDEX FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide current income.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment):    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

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 144.0% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

144.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in debt securities held by the Barclays U.S. Aggregate Bond Index (the "Index") at the time of purchase. The Index is composed of investment grade, fixed rate debt issues, including government, corporate, asset-backed, and mortgage-backed securities, with maturities of one year or more. The Fund employs a passive investment approach designed to attempt to track the performance of the Index. Under normal circumstances, the Fund maintains an average portfolio duration that is in line with the duration of the Barclays U.S. Aggregate Bond Index, which as of August 31, 2012 was 4.99 years. The Fund actively trades portfolio securities.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The Fund may be an appropriate investment for investors interested in investing in a fixed-income mutual fund and preferring a passive, rather than active, management style.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Fixed-Income Securities Risk. Fixed-income securities are subject to interest rate risk and credit quality risk. The market value of fixed-income securities generally declines when interest rates rise, and an issuer of fixed-income securities could default on its payment obligations.

Index Fund Investment Risk. More likely than not, an index fund will not provide investment performance that matches the index performance due to cashflows and the fees and expenses of the fund.

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.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principal.com or by calling 1-800-222-5852.

Life of Fund returns are measured from December 30, 2009, the date the Institutional, R-1, R-2, R-3, R-4, and R-5 Class shares were first sold.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides an indication of the risks of investing in the Fund.

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.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns as of December 31 each year (Institutional Class shares)

^[3]

Bar Chart Footnotes [Text Block]

rr_BarChartFootnotesTextBlock

The year-to-date return as of September 30, 2012 was 3.77% for Institutional shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest return for a quarter during the period of the bar chart above:	Q3 '11	3.76	%
Lowest return for a quarter during the period of the bar chart above:	Q4 ‘10	-1.31	%

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

reflects no deduction for fees, expenses, or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Institutional Class shares only and would be different for Class R-1, R-2, R-3, R-4 and R-5 shares.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Institutional Class shares only and would be different for Class R-1, R-2, R-3, R-4 and R-5 shares.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns For the periods ended December 31, 2011

PFI Prospectus - Institutional Class Shares | Bond Market Index Fund | Barclays Aggregate Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Barclays Aggregate Bond Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

7.84%

Since Inception

rr_AverageAnnualReturnSinceInception

7.09%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | Bond Market Index Fund | Bond Market Index Fund, Institutional Class

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PNIIX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.01%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.26%

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.26%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

27

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

84

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

146

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

331

Annual Return 2010

rr_AnnualReturn2010

5.90%

Annual Return 2011

rr_AnnualReturn2011

7.45%

Year to Date Return, Label

rr_YearToDateReturnLabel

year-to-date return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

3.77%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest return for a quarter during the period of the bar chart above:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2011

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

3.76%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest return for a quarter during the period of the bar chart above:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(1.31%)

Label

rr_AverageAnnualReturnLabel

Institutional Class Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

7.45%

Since Inception

rr_AverageAnnualReturnSinceInception

6.61%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | Bond Market Index Fund | Bond Market Index Fund, Institutional Class | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Institutional Class Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

6.53%

Since Inception

rr_AverageAnnualReturnSinceInception

5.79%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | Bond Market Index Fund | Bond Market Index Fund, Institutional Class | After Taxes on Distributions and Sales

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Institutional Class Return After Taxes on Distribution and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

4.84%

Since Inception

rr_AverageAnnualReturnSinceInception

5.16%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | Bond Market Index Fund | Bond Market Index Fund, Class R-1

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PBIMX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.35%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.54%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

1.14%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[4]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.14%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

116

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

362

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

628

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,386

Label

rr_AverageAnnualReturnLabel

Class R-1 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

6.48%

Since Inception

rr_AverageAnnualReturnSinceInception

5.66%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | Bond Market Index Fund | Bond Market Index Fund, Class R-2

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PBINX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.30%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.46%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

1.01%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[4]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.01%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

103

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

322

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

558

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,236

Label

rr_AverageAnnualReturnLabel

Class R-2 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

6.69%

Since Inception

rr_AverageAnnualReturnSinceInception

5.81%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | Bond Market Index Fund | Bond Market Index Fund, Class R-3

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PBOIX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.33%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.83%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[4]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.83%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

85

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

265

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

460

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,025

Label

rr_AverageAnnualReturnLabel

Class R-3 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

6.79%

Since Inception

rr_AverageAnnualReturnSinceInception

5.99%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | Bond Market Index Fund | Bond Market Index Fund, Class R-4

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PBIPX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.10%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.29%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.64%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[4]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.64%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

65

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

205

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

357

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

798

Label

rr_AverageAnnualReturnLabel

Class R-4 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

7.10%

Since Inception

rr_AverageAnnualReturnSinceInception

6.22%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | Bond Market Index Fund | Bond Market Index Fund, Class R-5

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PBIQX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.27%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.52%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[4]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.52%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

53

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

167

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

291

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

653

Label

rr_AverageAnnualReturnLabel

Class R-5 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

7.18%

Since Inception

rr_AverageAnnualReturnSinceInception

6.34%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

DIVERSIFIED REAL ASSET FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks a long-term total return in excess of inflation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

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

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 107.3% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

107.30%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated 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:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund seeks to achieve its investment objective by allocating its assets among the following general investment categories: inflation-indexed bonds, securities of real estate companies, commodity index-linked notes, fixed-income securities, securities of natural resource companies, master limited partnerships (MLPs), publicly-listed infrastructure companies, and floating rate debt. The Fund actively trades portfolio securities.

The Fund concentrates its investments (invests 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. Except for its policy to concentrate in the real estate and energy/natural resources industries, the Fund retains considerable latitude in allocating its assets.

A portion of the Fund's assets is 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 is 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 are primarily short-term U.S. Treasury and Agency notes and bonds.

A portion of the Fund's assets is invested in the real estate industry. The Fund invests in equity securities of global companies principally engaged in the real estate industry ("real estate companies"). A real estate company has at least 50% of its assets, income or profits derived from products or services related to the real estate industry. Real estate companies include real estate investment trusts ("REITs"), REIT-like entities, and companies with substantial real estate holdings such as paper, lumber, hotel and entertainment companies as well as building supply manufacturers, mortgage lenders, and mortgage servicing companies.

A portion of the Fund's assets is invested in securities of 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, oil and natural gas, timberland, undeveloped real property and agricultural commodities.

A portion of the Fund's assets is invested in MLPs. Generally, MLPs are engaged in the transportation, storage, processing, refining, marketing, production, or mining of natural resources. The Fund invests primarily in the mid-stream category of MLPs, which is generally comprised of pipelines used to gather, process, transport, and distribute natural gas, crude oil, and refined petroleum products.

A portion of the Fund’s assets is invested in domestic and foreign publicly-listed infrastructure companies. Publicly-listed infrastructure equity securities trade on an exchange and include, but are not limited to, companies involved in the ownership and/or operations of infrastructure assets within the transportation, communications, water, electricity transmission and distribution, and oil and gas storage, processing and transportation industries.

A portion of the Fund’s assets is invested in below-investment-grade (sometimes called “junk”) or comparable unrated floating rate debt (also known as bank loans, syndicated loans, leveraged loans or senior floating rate interests). Floating rate debt has a variable coupon that resets periodically, with interest payments determined by a representative interest rate index (e.g. LIBOR or the federal funds rate) plus a fixed spread. As a result, the coupon payments vary, or “float” with prevailing market interest rates.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the real estate and energy/natural resources industries.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The 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:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.

Bank Loans Risk. Changes in economic conditions are likely to cause issuers of bank loans (also known as senior floating rate interests) to be unable to meet their obligations. In addition, the value of the collateral securing the loan may decline, causing a loan to be substantially unsecured. Underlying credit agreements governing the bank loans, reliance on market makers, priority of repayment and overall market volatility may harm the liquidity of loans.

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.

Commodity-Related Investment Risk. The value of commodities investments will generally be affected by overall market movements and factors specific to a particular industry or commodity, which may include weather, embargoes, tariffs, and economic health, political, international regulatory and other developments. Exposure to the commodities markets may subject the fund to greater volatility than investments in traditional securities.

Counterparty Risk. Counterparty risk is the risk that the counterparty to a 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).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Industry Concentration Risk (Energy/Natural Resources). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in energy/natural resource companiesmay be affected by numerous factors, including events occurring in nature, inflationary pressures, international politics, the success of exploration projects, commodity prices, energy conservation, taxes and other government regulations. In addition, interest rates and general economic conditions may affect the demand for energy/natural resources. For example, events occurring in nature (such as earthquakes or fires in prime energy/natural resource areas) and political events (such as coups, military confrontations or acts of terrorism) can affect overall supply of energy/natural resources and the value of companies involved in energy/natural resources.

Industry Concentration Risk (Real Estate). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in the real estate industry can be subject to the risks associated with direct ownership of real estate, securities of companies in the real estate industry, and/or real estate investment trusts.

Leverage Risk. Leverage created by borrowing or certain types of transactions or investments, 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. 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.

Risk Lose Money [Text]

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Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

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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]

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Performance

Performance Narrative [Text Block]

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The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principal.com or by calling 1-800-222-5852.

Life of Fund returns are measured from March 16, 2010, the date the Institutional Class shares were first sold.

Performance of a blended index shows how the Fund’s performance compares to an index with similar investment objectives. Performance of the components of the blended index are also shown. The Diversified Real Asset Custom Index was composed of 30% Barclays U.S. Treasury TIPS Index, 20% MSCI U.S. REIT Index, 25% Dow Jones UBS Commodity Index, 15% S&P N.A. Natural Resources Index, and 10% Tortoise MLP Index. Effective January 31, 2012, the weightings for the Diversified Real Asset Custom Index changed to 30% Barclays U.S. Treasury TIPS Index, 20% Dow Jones UBS Commodity Index, 10% S&P N.A. Natural Resources Index, 10% Tortoise MLP Index, 10% Dow Jones Brookfield Global Infrastructure Index, 10% Credit Suisse Leveraged Loan Index, and 10% FTSE EPRA/NAREIT Developed Index. The custom or blended index returns reflect the allocation in effect for the time period(s) for which fund returns are disclosed. Previous weightings or allocations of the custom or blended index are not restated.

Performance Information Illustrates Variability of Returns [Text]

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The following information provides an indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

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1-800-222-5852

Performance Availability Website Address [Text]

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www.principal.com

Performance Past Does Not Indicate Future [Text]

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Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.

Bar Chart [Heading]

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Total Returns as of December 31 each year (Institutional Class shares)

^[5]

Bar Chart Footnotes [Text Block]

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The year-to-date return as of September 30, 2012 was 8.17% for Institutional shares.

Bar Chart Closing [Text Block]

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Highest return for a quarter during the period of the bar chart above:	Q4 '11	7.18	%
Lowest return for a quarter during the period of the bar chart above:	Q3 '11	-9.16	%

Index No Deduction for Fees, Expenses, Taxes [Text]

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reflects no deduction for fees, expenses, or taxes

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Closing [Text Block]

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Caption

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Average Annual Total Returns For the periods ended December 31, 2011

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund | Barclays US Treasury TIPS Index

Risk/Return:

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Label

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Barclays US Treasury TIPS Index (reflects no deduction for fees, expenses, or taxes)

1 Year

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13.56%

Since Inception

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10.42%

Inception Date

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Mar. 16, 2010

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund | MSCI US REIT Index

Risk/Return:

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Label

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MSCI US REIT Index (reflects no deduction for fees, expenses, or taxes)

1 Year

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8.69%

Since Inception

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14.22%

Inception Date

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Mar. 16, 2010

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund | Dow Jones UBS Commodity Index

Risk/Return:

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Label

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Dow Jones UBS Commodity Index (reflects no deduction for fees, expenses, or taxes)

1 Year

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(13.32%)

Since Inception

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3.32%

Inception Date

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Mar. 16, 2010

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund | S&P North American Natural Resources Index

Risk/Return:

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Label

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S&P North American Natural Resources Index (reflects no deduction for fees, expenses, or taxes)

1 Year

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(7.35%)

Since Inception

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6.85%

Inception Date

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Mar. 16, 2010

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund | Tortoise MLP Index

Risk/Return:

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Label

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Tortoise MLP Index (reflects no deduction for fees, expenses, or taxes)

1 Year

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13.73%

Since Inception

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22.36%

Inception Date

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Mar. 16, 2010

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund | Dow Jones Brookfield Global Infrastructure Index

Risk/Return:

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Label

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Dow Jones Brookfield Global Infrastructure Index (reflects no deduction for fees, expenses, or taxes)

1 Year

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13.75%

Since Inception

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14.07%

Inception Date

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Mar. 16, 2010

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund | Credit Suisse Leveraged Loan Index

Risk/Return:

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Label

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Credit Suisse Leveraged Loan Index (reflects no deduction for fees, expenses, or taxes)

1 Year

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1.82%

Since Inception

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5.26%

Inception Date

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Mar. 16, 2010

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund | FTSE EPRA/NAREIT Developed Index

Risk/Return:

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Label

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FTSE EPRA/NAREIT Developed Index (reflects no deduction for fees, expenses, or taxes)

1 Year

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(5.82%)

Since Inception

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5.28%

Inception Date

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Mar. 16, 2010

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund | Diversified Real Asset Custom Index

Risk/Return:

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Label

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Diversified Real Asset Custom Index (reflects no deduction for fees, expenses, or taxes)

1 Year

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2.80%

Since Inception

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10.63%

Inception Date

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Mar. 16, 2010

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund | Diversified Real Asset Fund, Institutional Class

Risk/Return:

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Trading Symbol

dei_TradingSymbol

PDRDX

Management Fees (as a percentage of Assets)

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0.84%

Other Expenses (as a percentage of Assets):

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0.03%

Net Expenses (as a percentage of Assets)

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0.87%

Expense Example, with Redemption, 1 Year

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89

Expense Example, with Redemption, 3 Years

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278

Expense Example, with Redemption, 5 Years

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482

Expense Example, with Redemption, 10 Years

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1,073

Annual Return 2011

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0.83%

Year to Date Return, Label

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year-to-date return

Bar Chart, Year to Date Return, Date

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Sep. 30, 2012

Bar Chart, Year to Date Return

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8.17%

Highest Quarterly Return, Label

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Highest return for a quarter during the period of the bar chart above:

Highest Quarterly Return, Date

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Dec. 31, 2011

Highest Quarterly Return

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7.18%

Lowest Quarterly Return, Label

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Lowest return for a quarter during the period of the bar chart above:

Lowest Quarterly Return, Date

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Sep. 30, 2011

Lowest Quarterly Return

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(9.16%)

Label

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Institutional Class Return Before Taxes

1 Year

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0.83%

Since Inception

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9.00%

Inception Date

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Mar. 16, 2010

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund | Diversified Real Asset Fund, Institutional Class | After Taxes on Distributions

Risk/Return:

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Label

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Institutional Class Return After Taxes on Distributions

1 Year

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0.20%

Since Inception

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8.47%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Institutional Class Shares | Diversified Real Asset Fund | Diversified Real Asset Fund, Institutional Class | After Taxes on Distributions and Sales

Risk/Return:

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Label

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Institutional Class Return After Taxes on Distribution and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

0.89%

Since Inception

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7.47%

Inception Date

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Mar. 16, 2010

PFI Prospectus - Institutional Class Shares | Global Multi-Strategy Fund

Risk/Return:

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Risk/Return [Heading]

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GLOBAL MULTI-STRATEGY FUND

Objective [Heading]

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Objective:

Objective, Primary [Text Block]

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The Fund seeks to achieve long-term capital appreciation with an emphasis on positive total returns and relatively low volatility.

Expense [Heading]

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Fees and Expenses of the Fund

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees Caption [Text]

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Shareholder Fees (fees paid directly from your investment):    None

Operating Expenses Caption [Text]

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Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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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. From October 14, 2011, date operations commenced, through August 31, 2012, the Fund’s annualized portfolio turnover rate was 196.0% of the average value of its portfolio.

Portfolio Turnover, Rate

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196.00%

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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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]

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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:

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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Principal Management Corporation ("Principal"), the Fund's investment adviser, allocates the Fund's assets among one or more of the investment strategies described below, which are executed by one or more of the Fund's sub-advisors. In making these allocations, Principal seeks to combine the strategies of the sub-advisors efficiently and systematically so that the Fund generates, through a diversified set of investment strategies, a positive total return with relatively low volatility and low sensitivity or correlation to market indices. By allocating the Fund’s assets among a variety of investment strategies, which will vary from time-to-time, the Fund seeks to lessen risk and reduce volatility. Principal may also direct a sub-advisor to reduce or omit its investment in certain assets or asset classes in an effort to achieve its desired combination of the Fund's strategies.

In pursuing its strategies, the Fund invests in a broad range of instruments including, but not limited to, equities, bonds, currencies, convertible securities and derivatives such as futures, options, swaps (including, for example, credit default, interest rate, and currency swaps) and forwards. The Fund intends to engage in derivative transactions to gain exposure to a variety of securities or attempt to reduce risk. The Fund intends to invest in securities that are tied economically to a number of countries throughout the world, including the U.S.; however, the Fund has no requirements as to the amount of its net assets that it invests in foreign securities. The Fund is considered non-diversified, which means it can invest a higher percentage of assets in securities of individual issuers than a diversified fund. The Fund actively trades securities.

Some of the strategies take long and/or short positions. When taking a short position, the Fund may sell an instrument that it does not own and then borrow to meet its settlement obligations. The Fund may take short positions in futures, forwards or swaps. A short position will benefit from a decrease in price of the underlying instrument and will lose value if the price of the underlying instrument increases. Long positions will profit if the value of the instrument increases. Simultaneously engaging in long investing and short selling reduces the net exposure of the overall portfolio to general market movements. Relative value positions may be taken as well in the various strategies. Relative value strategies capitalize on price differences between similar securities or relative value among securities of the same company.

The Fund may use all or some of the following strategies to varying degrees, depending on market conditions, and may add additional strategies. Principal may allocate 0 to 100% of the Fund’s assets to any of these strategies at any time.

Credit Long/Short and Distressed Credit. This strategy utilizes a flexible investment approach that allocates investments across a global range of investment opportunities related to credit, currencies and interest rates, while employing risk management strategies. This strategy invests in fixed income securities and instruments and may invest in both investment-grade securities and below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, the Sub-Advisor will determine whether the bond is of a quality comparable to those rated below investment grade). This strategy may also invest in the following securities: securities denominated in foreign currencies and in U.S. dollar denominated securities of foreign issuers, preferred securities, convertible securities, Rule 144A securities, mortgage or asset-backed securities, floating rate debt (including bank loans), distressed investments, emerging markets, equities and derivative instruments, such as options, futures contracts, forwards or swap agreements. This strategy may utilize derivative instruments in an effort to minimize volatility. Also, at times, this strategy expects to gain its investment exposure substantially through the use of derivatives. The notional value of this strategy’s long and short investment exposures may at times each reach 100% of the assets invested in this strategy (excluding instruments used primarily for duration, yield curve, and interest rate management and short-term investments), although these exposures may be higher or lower at any given time. This strategy may purchase or sell securities on a when-issued, delayed delivery or forward commitment basis and may engage in short sales. The strategy may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as buy backs or dollar rolls).

Equity Long/Short. This strategy provides long and short exposure to a diversified portfolio of equities which involves simultaneously investing in equities (i.e., investing long) the sub-advisor expects to increase in value (securities the sub-advisor believes are undervalued) and either selling equities (i.e., short sales or short selling) the sub-advisor expects to decrease in value (securities the sub-advisor believes are overvalued) or hedging equity market exposure in another way (i.e., by using derivatives such as futures or options). Long/short equity expresses industry views by emphasizing certain industries and it also seeks to exploit pricing inefficiencies between related equity securities. An example of exploiting pricing inefficiencies between related equity securities is building a portfolio containing long positions in the strongest companies of several industries and taking short positions in companies showing signs of weakness in the corresponding industries. This strategy has available two methods of analysis: fundamental analysis, a method of security analysis that involves examining a company's financial statements and operations, especially sales, earnings, products, management and competition and quantitative analysis, a method of security analysis that involves use of mathematical models to examine a company's measurable characteristics such as revenue, earnings, margins and market share.

Equity Market Neutral. This strategy seeks to profit by exploiting pricing inefficiencies between related equity securities and neutralizing exposure to market risk by maintaining long and short positions. Equity market neutral is not expected to have industry overweights.

Dedicated Short Bias. The dedicated short bias strategy seeks to profit by shorting stocks that have negative market sentiment and neutralizing exposure to market risk by maintaining long and short positions.

Global Macro. Global macro strategies seek to profit from movement in the prices of securities that are highly sensitive to macroeconomic conditions, across a broad spectrum of assets. This strategy provides long and short exposure to developed country equities, currencies and bonds markets.

Emerging Markets. This strategy seeks to profit from investing in equities, bonds, and currencies of issuers in emerging markets. This strategy provides long and short exposure to emerging country equity, debt, and currency markets, and long and short exposure to a basket of liquid equity securities traded on emerging and developed market exchanges.

Convertible Arbitrage. Convertible arbitrage strategies seek to profit from the complexity of the pricing of convertible bonds (which contain elements of both a fixed income security and an equity option) by structuring trades using multiple securities within the capital structure of a convertible bond issuer. The Fund may purchase the convertible bond of a given issuer and simultaneously sell short the common stock of that same issuer to take advantage of a mispricing of either security. This strategy takes positions in various global convertible debt and preferred securities and an offsetting position in various global equities directly linked to the convertible securities. In implementing this strategy, the Fund may use derivatives to hedge against a decline in interest rates or credit exposure.

Currency Instruments, Futures Contracts, Futures-Related Instruments and Equity Swaps. These strategies seek to profit from the design and implementation of quantitative selection models to help predict upcoming movements in any combination of fixed income, currency, or equity markets. This strategy provides long and short exposure to developed country equities, bonds and currency markets and long and short exposure to emerging country equity and currency markets.

Event Driven. Event driven strategies seek to profit from investing in the securities of companies based not on a value or growth investment style but rather on the basis that a specific event or catalyst will affect future prices. This strategy attempts to capitalize on price discrepancies and returns generated by corporate activity, such as merger arbitrage. In merger arbitrage, the Fund will employ a diversified, disciplined strategy to attempt to capture the returns from holding a long/short portfolio of stocks of companies involved in mergers.

Fixed Income Arbitrage. Fixed income arbitrage seeks to profit from exploiting mispricing of various, liquid fixed income or interest rate sensitive securities. This strategy provides long and short exposure to developed country bond and currency markets, long and short exposure to investment grade credit markets and long and short exposure to forward mortgage-backed securities trading in the to be announced (“TBA”) market.

Risk [Heading]

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Principal Risks

Risk Narrative [Text Block]

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The Fund may be an appropriate investment for investors who seek long-term capital appreciation and who can accept the risks of investing in a variety of global markets and a variety of instruments.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Arbitrage Trading Risk. The underlying relationships between securities in which the fund takes arbitrage investment positions may change in an adverse manner, in which case the fund may realize losses.

Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.

Bank Loans Risk. Changes in economic conditions are likely to cause issuers of bank loans (also known as senior floating rate interests) to be unable to meet their obligations. In addition, the value of the collateral securing the loan may decline, causing a loan to be substantially unsecured. Underlying credit agreements governing the bank loans, reliance on market makers, priority of repayment and overall market volatility may harm the liquidity of loans.

Basis Risk. A hedge using derivatives and/or securities could expose the fund to basis risk. Basis risk could arise when the change in price of the hedge may not match the change in price of the asset it hedges. In other words, the hedge moves in a direction that does not match the asset it is trying to hedge.

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.

Convertible Securities Risk. Convertible securities can be bonds, notes, debentures, preferred stock or other securities which are convertible into common stock. Convertible securities are subject to both the credit and interest rate risks associated with fixed income securities and to the stock market risk associated with equity securities.

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.

Distressed Investments Risk. A fund’s investment in instruments involving loans, loan participations, bonds, notes, non-performing and sub-performing mortgage loans, many of which are not publicly traded, may involve a substantial degree of risk for the following reasons. These instruments may become illiquid and the prices of such instruments may be extremely volatile. Valuing such instruments may be difficult and a fund may lose all of its investment, or it may be required to accept cash or securities with a value less than the fund’s original investment. Issuers of distressed securities are typically in a weak financial condition and may default, in which case the fund may lose its entire investment.

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.

Event-Driven Trading Risk. Event-driven trading involves the risk that the special situation may not occur as anticipated, if at all, and that the market price of a stock declines.

Fixed-Income Securities Risk. Fixed-income securities are subject to interest rate risk and credit quality risk. The market value of fixed-income securities generally declines when interest rates rise, and an issuer of fixed-income securities could default on its payment obligations.

Foreign Securities Risk. The risks of foreign securities include loss of value as a result of: political or economic instability; nationalization, expropriation or confiscatory taxation; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

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.

Non-Diversification Risk. A non-diversified fund may invest a high percentage of its assets in the securities of a small number of issuers and is more likely than diversified funds to be significantly affected by a specific security’s poor performance.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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).

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.

Short Sale Risk. A short sale involves the sale by the fund of a security that it does not own with the hope of purchasing the same security at a later date at a lower price. A fund may also enter into a short derivative position through a futures contract or swap agreement. If the price of the security or derivative has increased during this time, then the fund will incur a loss equal to the increase in price from the time that the short sale was entered into plus any premiums and interest paid to the third party. Therefore, short sales involve the risk that losses may be exaggerated, potentially losing more money than the actual cost of the investment. Also, there is the risk that the third party to the short sale may fail to honor its contract terms, causing a loss to the fund.

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

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

A non-diversified fund may invest a high percentage of its assets in the securities of a small number of issuers and is more likely than diversified funds to be significantly affected by a specific security’s poor performance.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

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 HRFI (Hedge Fund Research Inc.) Funds-of-Funds Composite Index.

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

No performance information is shown because the Fund has not yet had a calendar year of performance.

PFI Prospectus - Institutional Class Shares | Global Multi-Strategy Fund | Global Multi-Strategy Fund, Institutional Class

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PSMIX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

1.60%

Component1 Other Expenses

rr_Component1OtherExpensesOverAssets

0.70%

Component2 Other Expenses

rr_Component2OtherExpensesOverAssets

0.08%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

2.38%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[6]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

2.35%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

238

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

740

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,268

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,714

PFI Prospectus - Institutional Class Shares | Global Opportunities Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GLOBAL OPPORTUNITIES FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term growth of capital.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

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

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. 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 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:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund invests primarily in equity securities. The Fund intends to invest in securities that are tied economically to a number of countries throughout the world, including the U.S. and emerging markets; however, the Fund has no requirements as to the amount of its net assets that invests in foreign securities. The Fund has a flexible investment strategy and may invest in equity securities regardless of market capitalization (small, medium, or large) and style (growth or value). The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund also invests in growth equity securities; growth orientation emphasizes buying equity securities of companies whose potential for growth of capital and earnings is expected to be above average. The Fund actively trades portfolio securities. The Fund uses derivative instruments. Specifically, the Fund engages in certain options or swaps transactions and enter into futures contracts for portfolio and cash management purposes.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The Fund may be an appropriate investment for investors seeking long-term growth of capital in global markets, including emerging markets, who are able to assume the increased risks of higher price volatility and currency fluctuations associated with investments in international equity securities which trade in non-U.S. currencies.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Counterparty Risk. Counterparty risk is the risk that the counterparty to a derivatives contract or repurchase agreement, the borrower of a portfolio’s securities, or other obligation, will be unable or unwilling to make timely principal, interest, or settlement payments, or otherwise to honor its obligations.

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.

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.

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

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance will be benchmarked against the MSCI All Country World Index (ACWI).

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

No performance information is shown because the Fund has not yet had a calendar year of performance.

PFI Prospectus - Institutional Class Shares | Global Opportunities Fund | Global Opportunities Fund, Institutional Class

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PGOIX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.85%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

3.14%

^[1]

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

3.99%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(3.04%)

^[7]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.95%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2014

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

97

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

632

PFI Prospectus - Institutional Class Shares | International Equity Index Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

INTERNATIONAL EQUITY INDEX FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term growth of capital.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment):    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

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 53.5% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

53.50%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in securities held by MSCI EAFE NDTR D Index (the "Index") at the time of purchase. The Index is a weighted equity index designed to measure the equity performance of developed markets (Europe, Australia, New Zealand, and Far East), excluding the United States and Canada. The Fund employs a passive investment approach designed to attempt to track the performance of the Index. The Fund invests in index futures and options and exchange-traded funds ("ETFs") on a daily basis to gain exposure to the Index in an effort to minimize tracking error relative to the benchmark.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The Fund may be an appropriate investment for investors seeking long-term growth of capital, willing to accept the potential for volatile fluctuations in the value of investments and preferring a passive, rather than active, management style.

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:

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.

Exchange-Traded Funds ("ETFs") Risk. An ETF is subject to the risks associated with direct ownership of the securities comprising the index on which the ETF is based. Fund shareholders indirectly bear their proportionate share of the expenses of the ETFs in which the fund invests.

Foreign Securities Risk. The risks of foreign securities include loss of value as a result of: political or economic instability; nationalization, expropriation or confiscatory taxation; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).

Index Fund Investment Risk. More likely than not, an index fund will not provide investment performance that matches the index performance due to cashflows and the fees and expenses of the fund.

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.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Institutional shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principal.com or by calling 1-800-222-5852.

Life of Fund returns are measured from December 30, 2009, the date the Institutional, R-1, R-2, R-3, R-4, and R-5 Class shares were first sold.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides an indication of the risks of investing in the Fund.

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.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns as of December 31 each year (Institutional Class shares)

^[8]

Bar Chart Footnotes [Text Block]

rr_BarChartFootnotesTextBlock

The year-to-date return as of September 30, 2012 was 9.89% for Institutional shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest return for a quarter during the period of the bar chart above:	Q3 ‘10	17.39	%
Lowest return for a quarter during the period of the bar chart above:	Q3 ‘11	-20.25	%

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

reflects no deduction for fees, expenses, or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Institutional Class shares only and would be different for Class R-1, R-2, R-3, R-4 and R-5 shares.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Institutional Class shares only and would be different for Class R-1, R-2, R-3, R-4 and R-5 shares.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns For the periods ended December 31, 2011

PFI Prospectus - Institutional Class Shares | International Equity Index Fund | MSCI - EAFE NDTR D Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

MSCI - EAFE NDTR D Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

(12.14%)

Since Inception

rr_AverageAnnualReturnSinceInception

(2.47%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | International Equity Index Fund | International Equity Index Fund, Institutional Class

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PIDIX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.07%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.33%

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.33%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

34

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

106

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

185

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

418

Annual Return 2010

rr_AnnualReturn2010

6.24%

Annual Return 2011

rr_AnnualReturn2011

(12.39%)

Year to Date Return, Label

rr_YearToDateReturnLabel

year-to-date return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

9.89%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest return for a quarter during the period of the bar chart above:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2010

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

17.39%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest return for a quarter during the period of the bar chart above:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(20.25%)

Label

rr_AverageAnnualReturnLabel

Institutional Class Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

(12.39%)

Since Inception

rr_AverageAnnualReturnSinceInception

(3.52%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | International Equity Index Fund | International Equity Index Fund, Institutional Class | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Institutional Class Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

(12.60%)

Since Inception

rr_AverageAnnualReturnSinceInception

(3.76%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | International Equity Index Fund | International Equity Index Fund, Institutional Class | After Taxes on Distributions and Sales

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Institutional Class Return After Taxes on Distribution and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

(7.44%)

Since Inception

rr_AverageAnnualReturnSinceInception

(2.87%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | International Equity Index Fund | International Equity Index Fund, Class R-1

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PILIX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.35%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.59%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

1.20%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[9]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.20%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

122

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

381

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

660

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,455

Label

rr_AverageAnnualReturnLabel

Class R-1 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

(13.22%)

Since Inception

rr_AverageAnnualReturnSinceInception

(4.38%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | International Equity Index Fund | International Equity Index Fund, Class R-2

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PINEX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.30%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.51%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

1.07%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[9]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.07%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

109

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

340

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

590

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,306

Label

rr_AverageAnnualReturnLabel

Class R-2 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

(13.20%)

Since Inception

rr_AverageAnnualReturnSinceInception

(4.32%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | International Equity Index Fund | International Equity Index Fund, Class R-3

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PIIOX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.38%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.89%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[9]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.89%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

91

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

284

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

493

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,096

Label

rr_AverageAnnualReturnLabel

Class R-3 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

(12.93%)

Since Inception

rr_AverageAnnualReturnSinceInception

(4.12%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | International Equity Index Fund | International Equity Index Fund, Class R-4

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PIIPX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.10%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.34%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.70%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[9]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.70%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

72

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

224

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

390

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

871

Label

rr_AverageAnnualReturnLabel

Class R-4 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

(12.79%)

Since Inception

rr_AverageAnnualReturnSinceInception

(3.89%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | International Equity Index Fund | International Equity Index Fund, Class R-5

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PIIQX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.32%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.58%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[9]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.58%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

59

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

186

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

324

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

726

Label

rr_AverageAnnualReturnLabel

Class R-5 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

(12.68%)

Since Inception

rr_AverageAnnualReturnSinceInception

(3.79%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Institutional Class Shares | Preferred Securities Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

PREFERRED SECURITIES FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide current income.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

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

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 22.9% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

22.90%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated 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:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in preferred securities at the time of purchase. Preferred securities generally pay fixed rate dividends (though some are adjustable rate) and typically have "preference" over common stock in the payment of dividends and the liquidation of a company's assets, but are junior to all forms of the company's debt. Most of the securities purchased by the Fund are preferred securities of companies rated at the time of purchase BBB- or higher by Standard & Poor's Rating Service ("S&P") or Baa3 or higher by Moody's Investor Service, Inc. ("Moody's") or, if unrated, of comparable quality in the opinion of the Sub-Advisor. The Fund also invests up to 15% of its assets in below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, the Sub-Advisor will determine whether the bond is of a quality comparable to those rated below investment grade).

The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the U.S. and non-U.S financial services (i.e., banking, insurance and commercial finance,) industry. The Fund also regularly invests in the real estate investment trust (i.e. REIT) and utility industries.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the U.S. and non-U.S financial services (i.e., banking, insurance and commercial finance,) industry.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The Fund may be an appropriate investment for investors who are seeking dividends to generate income or to reinvest for growth and are willing to accept fluctuations in the value of the investment.

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:

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.

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).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Industry Concentration Risk (Financial Services). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in financial services companies may be more susceptible to adverse economic or regulatory occurrences affecting financial services companies. Financial companies may be adversely affected in certain market cycles, including periods of rising interest rates, which may restrict the availability and increase the cost of capital, and declining economic conditions, which may cause credit losses due to financial difficulties of borrowers. Because many types of financial companies are especially vulnerable to these economic cycles, the Fund’s investments in these companies may lose significant value during such periods.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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. 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.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principal.com or by calling 1-800-222-5852.

The Institutional Class shares were first sold May 1, 2002. The R-1 Class shares were first sold on November 1, 2004. The R-2, R-3, R-4, and R-5 share classes were first sold on June 1, 2004. For periods prior to the date on which the R-1, R-2, R-3, R-4 and R-5 class shares began operations, their returns are based on the performance of the Fund’s Institutional Class shares adjusted to reflect the fees and expenses of these classes. The adjustments result in performance (for the periods prior to the date these classes began operations) that is no higher than the historical performance of the Institutional Class shares.

Performance of a blended index shows how the Fund's performance compares to an index with similar investment objectives. Performance of the components of the blended index are also shown. The weightings for the Preferreds Blended Index are 50% BofA Merrill Lynch Fixed Rate Preferred Securities and 50% Barclays U.S. Tier I Capital Securities Index. The custom or blended index returns reflect the allocation in effect for the time period(s) for which fund returns are disclosed. Previous weightings or allocations of the custom or blended index are not restated.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides an indication of the risks of investing in the Fund.

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.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns as of December 31 each year (Institutional Class shares)

^[10]

Bar Chart Footnotes [Text Block]

rr_BarChartFootnotesTextBlock

The year-to-date return as of September 30, 2012 was 15.67% for Institutional shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest return for a quarter during the period of the bar chart above:	Q2 ‘09	38.94	%
Lowest return for a quarter during the period of the bar chart above:	Q3 ‘08	-20.90	%

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

reflects no deduction for fees, expenses, or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Institutional Class shares only and would be different for Class R-1, R-2, R-3, R-4 and R-5 shares.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Institutional Class shares only and would be different for Class R-1, R-2, R-3, R-4 and R-5 shares.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns For the periods ended December 31, 2011

PFI Prospectus - Institutional Class Shares | Preferred Securities Fund | BofA Merrill Lynch Fixed Rate Preferred Securities Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

BofA Merrill Lynch Fixed Rate Preferred Securities Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

4.11%

5 Years

rr_AverageAnnualReturnYear05

(1.19%)

Since Inception

rr_AverageAnnualReturnSinceInception

2.42%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Institutional Class Shares | Preferred Securities Fund | Barclays U.S. Tier I Capital Securities Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Barclays U.S. Tier I Capital Securities Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

(0.53%)

5 Years

rr_AverageAnnualReturnYear05

1.71%

Since Inception

rr_AverageAnnualReturnSinceInception

4.87%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Institutional Class Shares | Preferred Securities Fund | Preferreds Blended Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Preferreds Blended Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

1.81%

5 Years

rr_AverageAnnualReturnYear05

0.01%

Since Inception

rr_AverageAnnualReturnSinceInception

3.38%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Institutional Class Shares | Preferred Securities Fund | Preferred Securities Fund, Institutional Class

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PPSIX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.71%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.04%

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.75%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

77

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

240

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

417

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

930

Annual Return 2003

rr_AnnualReturn2003

10.72%

Annual Return 2004

rr_AnnualReturn2004

4.36%

Annual Return 2005

rr_AnnualReturn2005

1.62%

Annual Return 2006

rr_AnnualReturn2006

6.94%

Annual Return 2007

rr_AnnualReturn2007

(7.99%)

Annual Return 2008

rr_AnnualReturn2008

(22.30%)

Annual Return 2009

rr_AnnualReturn2009

46.57%

Annual Return 2010

rr_AnnualReturn2010

16.49%

Annual Return 2011

rr_AnnualReturn2011

1.53%

Year to Date Return, Label

rr_YearToDateReturnLabel

year-to-date return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

15.67%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest return for a quarter during the period of the bar chart above:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

38.94%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest return for a quarter during the period of the bar chart above:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(20.90%)

Label

rr_AverageAnnualReturnLabel

Institutional Class Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

1.53%

5 Years

rr_AverageAnnualReturnYear05

4.38%

Since Inception

rr_AverageAnnualReturnSinceInception

5.21%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Institutional Class Shares | Preferred Securities Fund | Preferred Securities Fund, Institutional Class | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Institutional Class Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

(0.46%)

5 Years

rr_AverageAnnualReturnYear05

2.16%

Since Inception

rr_AverageAnnualReturnSinceInception

3.31%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Institutional Class Shares | Preferred Securities Fund | Preferred Securities Fund, Institutional Class | After Taxes on Distributions and Sales

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Institutional Class Return After Taxes on Distribution and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

1.34%

5 Years

rr_AverageAnnualReturnYear05

2.48%

Since Inception

rr_AverageAnnualReturnSinceInception

3.39%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Institutional Class Shares | Preferred Securities Fund | Preferred Securities Fund, Class R-1

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PUSAX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.71%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.35%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.53%

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.59%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

162

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

502

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

866

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,889

Label

rr_AverageAnnualReturnLabel

Class R-1 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

0.71%

5 Years

rr_AverageAnnualReturnYear05

3.49%

Since Inception

rr_AverageAnnualReturnSinceInception

4.29%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Institutional Class Shares | Preferred Securities Fund | Preferred Securities Fund, Class R-2

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PPRSX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.71%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.30%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.45%

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.46%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

149

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

462

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

797

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,746

Label

rr_AverageAnnualReturnLabel

Class R-2 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

0.94%

5 Years

rr_AverageAnnualReturnYear05

3.62%

Since Inception

rr_AverageAnnualReturnSinceInception

4.44%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Institutional Class Shares | Preferred Securities Fund | Preferred Securities Fund, Class R-3

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PNARX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.71%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.32%

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.28%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

130

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

406

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

702

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,545

Label

rr_AverageAnnualReturnLabel

Class R-3 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

1.03%

5 Years

rr_AverageAnnualReturnYear05

3.81%

Since Inception

rr_AverageAnnualReturnSinceInception

4.63%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Institutional Class Shares | Preferred Securities Fund | Preferred Securities Fund, Class R-4

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PQARX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.71%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.10%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.28%

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.09%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

111

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

347

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

601

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,329

Label

rr_AverageAnnualReturnLabel

Class R-4 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

1.20%

5 Years

rr_AverageAnnualReturnYear05

3.99%

Since Inception

rr_AverageAnnualReturnSinceInception

4.80%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Institutional Class Shares | Preferred Securities Fund | Preferred Securities Fund, Class R-5

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PPARX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.71%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.26%

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.97%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

99

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

309

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

536

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,190

Label

rr_AverageAnnualReturnLabel

Class R-5 Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

1.33%

5 Years

rr_AverageAnnualReturnYear05

4.10%

Since Inception

rr_AverageAnnualReturnSinceInception

4.93%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Institutional Class Shares | Small-MidCap Dividend Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

SMALL-MIDCAP DIVIDEND INCOME FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund primarily seeks to provide a relatively high level of current income and long-term growth of income, and

Objective, Secondary [Text Block]

rr_ObjectiveSecondaryTextBlock

secondarily long-term growth of capital, while investing primarily in small- to mid-capitalization companies.

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

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 19.1% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

19.10%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in dividend-paying equity securities of companies with small to medium market capitalizations (those with market capitalizations ranging from between $200 million and $7 billion) at the time of purchase. The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund invests in the securities of foreign issuers, real estate investment trusts, preferred securities, convertible securities, fixed-income securities, master limited partnerships, and royalty trusts.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The Fund may be an appropriate investment for investors who seek dividends to generate income or to reinvest for growth and who can accept fluctuations in the value of investments and the risks of investing in equity securities, the securities of foreign issuers, real estate investment trusts, preferred securities, convertible securities, fixed-income securities, master limited partnerships, and royalty trusts.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Convertible Securities Risk. Convertible securities can be bonds, notes, debentures, preferred stock or other securities which are convertible into common stock. Convertible securities are subject to both the credit and interest rate risks associated with fixed income securities and to the stock market risk associated with equity securities.

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.

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).

Master Limited Partnership ("MLP") Risk. MLPs are publicly-traded limited partnership interests or units. An MLP that invests in a particular industry (e.g., oil and gas) will be harmed by detrimental economic events within that industry. As partnerships, MLPs may be subject to less regulation (and less protection for investors) under state laws than corporations. In addition, MLPs may be subject to state taxation in certain jurisdictions, which may reduce the amount of income an MLP pays to its investors.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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. 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.

Royalty Trust Risk. A royalty trust generally acquires an interest in natural resource or chemical companies and distributes the income it receives to its investors. A sustained decline in demand for natural resource and related products could adversely affect royalty trust revenues and cash flows. Such a decline could result from a recession or other adverse economic conditions, an increase in the market price of the underlying commodity, higher taxes or other regulatory actions that increase costs, or a shift in consumer demand. Rising interest rates could adversely affect the performance, and limit the capital appreciation, of royalty trusts because of the increased availability of alternative investments at more competitive yields. Fund shareholders will indirectly bear their proportionate share of the royalty trusts' expenses.

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

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance will be benchmarked against the Russell 2500 Value Index.

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

No performance information is shown because the Fund has not yet had a calendar year of performance.

PFI Prospectus - Institutional Class Shares | Small-MidCap Dividend Income Fund | Small-MidCap Dividend Income Fund, Institutional Class

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PMDIX

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.80%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.04%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.10%

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.94%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

96

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

300

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

520

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,155

[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 attributable to Institutional class shares by paying, if necessary, expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2013. The expense limit will maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.75% for Institutional class shares, excluding interest expense. 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.

[3] The year-to-date return as of September 30, 2012 was 3.77% for Institutional shares.

[4] Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund’s expenses attributable to Class R-1, R-2, R-3, R-4, and R-5 shares by paying, if necessary, expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2013. 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 1.18% for Class R-1, 1.05% for Class R-2, 0.87% for Class R-3, 0.68% for Class R-4, and 0.56% for Class R-5, excluding interest expense. 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.

[5] The year-to-date return as of September 30, 2012 was 8.17% for Institutional shares.

[6] Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund's expenses attributable to Institutional class shares by paying, if necessary, expenses normally payable by the Fund, excluding I think expense and short sale dividends and interest, through the period ending December 31, 2013. 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 1.65% for Institutional class shares, excluding interest expense and short sale dividends and interest. 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.

[7] Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund’s expenses attributable to Institutional class shares by paying, if necessary, expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2014. The expense limit will maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.95% for Institutional class shares, excluding interest expense. 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.

[8] The year-to-date return as of September 30, 2012 was 9.89% for Institutional shares.

[9] Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund’s expenses attributable to Class R-1, R-2, R-3, R-4, and R-5 shares by paying, if necessary,expenses normally payable by the Fund, excluding interest expense and Acquired Fund Fees and Expenses, through the period ending December 31, 2013. 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 1.28% for Class R-1, 1.15% for Class R-2, 0.97% for Class R-3, 0.78% for Class R-4, and 0.66% for Class R-5, excluding interest expense and Acquired Fund Fees and Expenses. 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.

[10] The year-to-date return as of September 30, 2012 was 15.67% for Institutional shares.

XML

Blue Chip Fund

BLUE CHIP FUND

Objective:

The Fund seeks long-term growth of capital.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees (fees paid directly from your investment):    None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Institutional Plan		PFI Prospectus - Institutional Class Shares Blue Chip Fund Blue Chip Fund, Institutional Class
Management Fees (as a percentage of Assets)		0.70%
Other Expenses (as a percentage of Assets):	[1]	0.51%
Expenses (as a percentage of Assets)		1.21%
Fee Waiver or Reimbursement	[2]	0.46%
Net Expenses (as a percentage of Assets)		0.75%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 - Institutional Plan (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years
PFI Prospectus - Institutional Class Shares Blue Chip Fund Blue Chip Fund, Institutional Class	77	339

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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. From June 13, 2012, date operations commenced, through August 31, 2012, the Fund’s annualized portfolio turnover rate was 7.3% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies with large market capitalizations (those with market capitalizations similar to companies in the Russell 1000 Growth^® Index (as of September 30, 2012, this range was between approximately $743.1 million and $610.3 billion) at the time of purchase. The Fund invests in foreign securities.

The Fund invests in growth equity securities; growth orientation emphasizes buying equity securities of companies whose potential for growth of capital and earnings is expected to be above average.

Principal Risks

The Fund may be an appropriate investment for investors seeking long-term growth of capital and willing to accept the potential for short-term fluctuations in the value of investments.

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:

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.

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.

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.

Performance

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 Russell 1000 Growth Index.

Bond Market Index Fund

BOND MARKET INDEX FUND

Objective:

The Fund seeks to provide current income.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees (fees paid directly from your investment):    None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Institutional Plan PFI Prospectus - Institutional Class Shares Bond Market Index Fund		Bond Market Index Fund, Institutional Class	Bond Market Index Fund, Class R-1	Bond Market Index Fund, Class R-2	Bond Market Index Fund, Class R-3	Bond Market Index Fund, Class R-4	Bond Market Index Fund, Class R-5
Management Fees (as a percentage of Assets)		0.25%	0.25%	0.25%	0.25%	0.25%	0.25%
Distribution and Service (12b-1) Fees			0.35%	0.30%	0.25%	0.10%
Other Expenses (as a percentage of Assets):		0.01%	0.54%	0.46%	0.33%	0.29%	0.27%
Expenses (as a percentage of Assets)		0.26%	1.14%	1.01%	0.83%	0.64%	0.52%
Fee Waiver or Reimbursement	[1]		none	none	none	none	none
Net Expenses (as a percentage of Assets)		0.26%	1.14%	1.01%	0.83%	0.64%	0.52%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 - Institutional Plan PFI Prospectus - Institutional Class Shares Bond Market Index Fund (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Bond Market Index Fund, Institutional Class	27	84	146	331
Bond Market Index Fund, Class R-1	116	362	628	1,386
Bond Market Index Fund, Class R-2	103	322	558	1,236
Bond Market Index Fund, Class R-3	85	265	460	1,025
Bond Market Index Fund, Class R-4	65	205	357	798
Bond Market Index Fund, Class R-5	53	167	291	653

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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 144.0% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in debt securities held by the Barclays U.S. Aggregate Bond Index (the "Index") at the time of purchase. The Index is composed of investment grade, fixed rate debt issues, including government, corporate, asset-backed, and mortgage-backed securities, with maturities of one year or more. The Fund employs a passive investment approach designed to attempt to track the performance of the Index. Under normal circumstances, the Fund maintains an average portfolio duration that is in line with the duration of the Barclays U.S. Aggregate Bond Index, which as of August 31, 2012 was 4.99 years. The Fund actively trades portfolio securities.

Principal Risks

The Fund may be an appropriate investment for investors interested in investing in a fixed-income mutual fund and preferring a passive, rather than active, management style.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Fixed-Income Securities Risk. Fixed-income securities are subject to interest rate risk and credit quality risk. The market value of fixed-income securities generally declines when interest rates rise, and an issuer of fixed-income securities could default on its payment obligations.

Index Fund Investment Risk. More likely than not, an index fund will not provide investment performance that matches the index performance due to cashflows and the fees and expenses of the fund.

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.

Performance

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principal.com or by calling 1-800-222-5852.

Life of Fund returns are measured from December 30, 2009, the date the Institutional, R-1, R-2, R-3, R-4, and R-5 Class shares were first sold.

Total Returns as of December 31 each year (Institutional Class shares)

^[1]

The year-to-date return as of September 30, 2012 was 3.77% for Institutional shares.

Highest return for a quarter during the period of the bar chart above:	Q3 '11	3.76	%
Lowest return for a quarter during the period of the bar chart above:	Q4 ‘10	-1.31	%

Average Annual Total Returns - Institutional Plan PFI Prospectus - Institutional Class Shares Bond Market Index Fund	Label	1 Year	Since Inception	Inception Date
Bond Market Index Fund, Institutional Class	Institutional Class Return Before Taxes	7.45%	6.61%	Dec. 30, 2009
Bond Market Index Fund, Institutional Class After Taxes on Distributions	Institutional Class Return After Taxes on Distributions	6.53%	5.79%	Dec. 30, 2009
Bond Market Index Fund, Institutional Class After Taxes on Distributions and Sales	Institutional Class Return After Taxes on Distribution and Sale of Fund Shares	4.84%	5.16%	Dec. 30, 2009
Bond Market Index Fund, Class R-1	Class R-1 Return Before Taxes	6.48%	5.66%	Dec. 30, 2009
Bond Market Index Fund, Class R-2	Class R-2 Return Before Taxes	6.69%	5.81%	Dec. 30, 2009
Bond Market Index Fund, Class R-3	Class R-3 Return Before Taxes	6.79%	5.99%	Dec. 30, 2009
Bond Market Index Fund, Class R-4	Class R-4 Return Before Taxes	7.10%	6.22%	Dec. 30, 2009
Bond Market Index Fund, Class R-5	Class R-5 Return Before Taxes	7.18%	6.34%	Dec. 30, 2009
Barclays Aggregate Bond Index	Barclays Aggregate Bond Index (reflects no deduction for fees, expenses, or taxes)	7.84%	7.09%	Dec. 30, 2009

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Institutional Class shares only and would be different for Class R-1, R-2, R-3, R-4 and R-5 shares.

Diversified Real Asset Fund

DIVERSIFIED REAL ASSET FUND

Objective:

The Fund seeks a long-term total return in excess of inflation.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees (fees paid directly from your investment): None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Institutional Plan	PFI Prospectus - Institutional Class Shares Diversified Real Asset Fund Diversified Real Asset Fund, Institutional Class
Management Fees (as a percentage of Assets)	0.84%
Other Expenses (as a percentage of Assets):	0.03%
Net Expenses (as a percentage of Assets)	0.87%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 - Institutional Plan (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
PFI Prospectus - Institutional Class Shares Diversified Real Asset Fund Diversified Real Asset Fund, Institutional Class	89	278	482	1,073

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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 107.3% of the average value of its portfolio.

Principal Investment Strategies

The Fund seeks to achieve its investment objective by allocating its assets among the following general investment categories: inflation-indexed bonds, securities of real estate companies, commodity index-linked notes, fixed-income securities, securities of natural resource companies, master limited partnerships (MLPs), publicly-listed infrastructure companies, and floating rate debt. The Fund actively trades portfolio securities.

The Fund concentrates its investments (invests 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. Except for its policy to concentrate in the real estate and energy/natural resources industries, the Fund retains considerable latitude in allocating its assets.

A portion of the Fund's assets is 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 is 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 are primarily short-term U.S. Treasury and Agency notes and bonds.

A portion of the Fund's assets is invested in the real estate industry. The Fund invests in equity securities of global companies principally engaged in the real estate industry ("real estate companies"). A real estate company has at least 50% of its assets, income or profits derived from products or services related to the real estate industry. Real estate companies include real estate investment trusts ("REITs"), REIT-like entities, and companies with substantial real estate holdings such as paper, lumber, hotel and entertainment companies as well as building supply manufacturers, mortgage lenders, and mortgage servicing companies.

A portion of the Fund's assets is invested in securities of 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, oil and natural gas, timberland, undeveloped real property and agricultural commodities.

A portion of the Fund's assets is invested in MLPs. Generally, MLPs are engaged in the transportation, storage, processing, refining, marketing, production, or mining of natural resources. The Fund invests primarily in the mid-stream category of MLPs, which is generally comprised of pipelines used to gather, process, transport, and distribute natural gas, crude oil, and refined petroleum products.

A portion of the Fund’s assets is invested in domestic and foreign publicly-listed infrastructure companies. Publicly-listed infrastructure equity securities trade on an exchange and include, but are not limited to, companies involved in the ownership and/or operations of infrastructure assets within the transportation, communications, water, electricity transmission and distribution, and oil and gas storage, processing and transportation industries.

A portion of the Fund’s assets is invested in below-investment-grade (sometimes called “junk”) or comparable unrated floating rate debt (also known as bank loans, syndicated loans, leveraged loans or senior floating rate interests). Floating rate debt has a variable coupon that resets periodically, with interest payments determined by a representative interest rate index (e.g. LIBOR or the federal funds rate) plus a fixed spread. As a result, the coupon payments vary, or “float” with prevailing market interest rates.

Principal Risks

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:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.

Bank Loans Risk. Changes in economic conditions are likely to cause issuers of bank loans (also known as senior floating rate interests) to be unable to meet their obligations. In addition, the value of the collateral securing the loan may decline, causing a loan to be substantially unsecured. Underlying credit agreements governing the bank loans, reliance on market makers, priority of repayment and overall market volatility may harm the liquidity of loans.

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.

Commodity-Related Investment Risk. The value of commodities investments will generally be affected by overall market movements and factors specific to a particular industry or commodity, which may include weather, embargoes, tariffs, and economic health, political, international regulatory and other developments. Exposure to the commodities markets may subject the fund to greater volatility than investments in traditional securities.

Counterparty Risk. Counterparty risk is the risk that the counterparty to a 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).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Industry Concentration Risk (Energy/Natural Resources). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in energy/natural resource companiesmay be affected by numerous factors, including events occurring in nature, inflationary pressures, international politics, the success of exploration projects, commodity prices, energy conservation, taxes and other government regulations. In addition, interest rates and general economic conditions may affect the demand for energy/natural resources. For example, events occurring in nature (such as earthquakes or fires in prime energy/natural resource areas) and political events (such as coups, military confrontations or acts of terrorism) can affect overall supply of energy/natural resources and the value of companies involved in energy/natural resources.

Industry Concentration Risk (Real Estate). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in the real estate industry can be subject to the risks associated with direct ownership of real estate, securities of companies in the real estate industry, and/or real estate investment trusts.

Leverage Risk. Leverage created by borrowing or certain types of transactions or investments, 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. 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.

Performance

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principal.com or by calling 1-800-222-5852.

Life of Fund returns are measured from March 16, 2010, the date the Institutional Class shares were first sold.

Performance of a blended index shows how the Fund’s performance compares to an index with similar investment objectives. Performance of the components of the blended index are also shown. The Diversified Real Asset Custom Index was composed of 30% Barclays U.S. Treasury TIPS Index, 20% MSCI U.S. REIT Index, 25% Dow Jones UBS Commodity Index, 15% S&P N.A. Natural Resources Index, and 10% Tortoise MLP Index. Effective January 31, 2012, the weightings for the Diversified Real Asset Custom Index changed to 30% Barclays U.S. Treasury TIPS Index, 20% Dow Jones UBS Commodity Index, 10% S&P N.A. Natural Resources Index, 10% Tortoise MLP Index, 10% Dow Jones Brookfield Global Infrastructure Index, 10% Credit Suisse Leveraged Loan Index, and 10% FTSE EPRA/NAREIT Developed Index. The custom or blended index returns reflect the allocation in effect for the time period(s) for which fund returns are disclosed. Previous weightings or allocations of the custom or blended index are not restated.

Total Returns as of December 31 each year (Institutional Class shares)

^[2]

The year-to-date return as of September 30, 2012 was 8.17% for Institutional shares.

Highest return for a quarter during the period of the bar chart above:	Q4 '11	7.18	%
Lowest return for a quarter during the period of the bar chart above:	Q3 '11	-9.16	%

Average Annual Total Returns - Institutional Plan PFI Prospectus - Institutional Class Shares Diversified Real Asset Fund	Label	1 Year	Since Inception	Inception Date
Diversified Real Asset Fund, Institutional Class	Institutional Class Return Before Taxes	0.83%	9.00%	Mar. 16, 2010
Diversified Real Asset Fund, Institutional Class After Taxes on Distributions	Institutional Class Return After Taxes on Distributions	0.20%	8.47%	Mar. 16, 2010
Diversified Real Asset Fund, Institutional Class After Taxes on Distributions and Sales	Institutional Class Return After Taxes on Distribution and Sale of Fund Shares	0.89%	7.47%	Mar. 16, 2010
Barclays US Treasury TIPS Index	Barclays US Treasury TIPS Index (reflects no deduction for fees, expenses, or taxes)	13.56%	10.42%	Mar. 16, 2010
MSCI US REIT Index	MSCI US REIT Index (reflects no deduction for fees, expenses, or taxes)	8.69%	14.22%	Mar. 16, 2010
Dow Jones UBS Commodity Index	Dow Jones UBS Commodity Index (reflects no deduction for fees, expenses, or taxes)	(13.32%)	3.32%	Mar. 16, 2010
S&P North American Natural Resources Index	S&P North American Natural Resources Index (reflects no deduction for fees, expenses, or taxes)	(7.35%)	6.85%	Mar. 16, 2010
Tortoise MLP Index	Tortoise MLP Index (reflects no deduction for fees, expenses, or taxes)	13.73%	22.36%	Mar. 16, 2010
Dow Jones Brookfield Global Infrastructure Index	Dow Jones Brookfield Global Infrastructure Index (reflects no deduction for fees, expenses, or taxes)	13.75%	14.07%	Mar. 16, 2010
Credit Suisse Leveraged Loan Index	Credit Suisse Leveraged Loan Index (reflects no deduction for fees, expenses, or taxes)	1.82%	5.26%	Mar. 16, 2010
FTSE EPRA/NAREIT Developed Index	FTSE EPRA/NAREIT Developed Index (reflects no deduction for fees, expenses, or taxes)	(5.82%)	5.28%	Mar. 16, 2010
Diversified Real Asset Custom Index	Diversified Real Asset Custom Index (reflects no deduction for fees, expenses, or taxes)	2.80%	10.63%	Mar. 16, 2010

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Global Multi-Strategy Fund

GLOBAL MULTI-STRATEGY FUND

Objective:

The Fund seeks to achieve long-term capital appreciation with an emphasis on positive total returns and relatively low volatility.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees (fees paid directly from your investment):    None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Institutional Plan		PFI Prospectus - Institutional Class Shares Global Multi-Strategy Fund Global Multi-Strategy Fund, Institutional Class
Management Fees (as a percentage of Assets)		1.60%
Component1 Other Expenses		0.70%
Component2 Other Expenses		0.08%
Expenses (as a percentage of Assets)		2.38%
Fee Waiver or Reimbursement	[1]	0.03%
Net Expenses (as a percentage of Assets)		2.35%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 - Institutional Plan (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
PFI Prospectus - Institutional Class Shares Global Multi-Strategy Fund Global Multi-Strategy Fund, Institutional Class	238	740	1,268	2,714

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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. From October 14, 2011, date operations commenced, through August 31, 2012, the Fund’s annualized portfolio turnover rate was 196.0% of the average value of its portfolio.

Principal Investment Strategies

Principal Management Corporation ("Principal"), the Fund's investment adviser, allocates the Fund's assets among one or more of the investment strategies described below, which are executed by one or more of the Fund's sub-advisors. In making these allocations, Principal seeks to combine the strategies of the sub-advisors efficiently and systematically so that the Fund generates, through a diversified set of investment strategies, a positive total return with relatively low volatility and low sensitivity or correlation to market indices. By allocating the Fund’s assets among a variety of investment strategies, which will vary from time-to-time, the Fund seeks to lessen risk and reduce volatility. Principal may also direct a sub-advisor to reduce or omit its investment in certain assets or asset classes in an effort to achieve its desired combination of the Fund's strategies.

In pursuing its strategies, the Fund invests in a broad range of instruments including, but not limited to, equities, bonds, currencies, convertible securities and derivatives such as futures, options, swaps (including, for example, credit default, interest rate, and currency swaps) and forwards. The Fund intends to engage in derivative transactions to gain exposure to a variety of securities or attempt to reduce risk. The Fund intends to invest in securities that are tied economically to a number of countries throughout the world, including the U.S.; however, the Fund has no requirements as to the amount of its net assets that it invests in foreign securities. The Fund is considered non-diversified, which means it can invest a higher percentage of assets in securities of individual issuers than a diversified fund. The Fund actively trades securities.

Some of the strategies take long and/or short positions. When taking a short position, the Fund may sell an instrument that it does not own and then borrow to meet its settlement obligations. The Fund may take short positions in futures, forwards or swaps. A short position will benefit from a decrease in price of the underlying instrument and will lose value if the price of the underlying instrument increases. Long positions will profit if the value of the instrument increases. Simultaneously engaging in long investing and short selling reduces the net exposure of the overall portfolio to general market movements. Relative value positions may be taken as well in the various strategies. Relative value strategies capitalize on price differences between similar securities or relative value among securities of the same company.

The Fund may use all or some of the following strategies to varying degrees, depending on market conditions, and may add additional strategies. Principal may allocate 0 to 100% of the Fund’s assets to any of these strategies at any time.

Credit Long/Short and Distressed Credit. This strategy utilizes a flexible investment approach that allocates investments across a global range of investment opportunities related to credit, currencies and interest rates, while employing risk management strategies. This strategy invests in fixed income securities and instruments and may invest in both investment-grade securities and below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, the Sub-Advisor will determine whether the bond is of a quality comparable to those rated below investment grade). This strategy may also invest in the following securities: securities denominated in foreign currencies and in U.S. dollar denominated securities of foreign issuers, preferred securities, convertible securities, Rule 144A securities, mortgage or asset-backed securities, floating rate debt (including bank loans), distressed investments, emerging markets, equities and derivative instruments, such as options, futures contracts, forwards or swap agreements. This strategy may utilize derivative instruments in an effort to minimize volatility. Also, at times, this strategy expects to gain its investment exposure substantially through the use of derivatives. The notional value of this strategy’s long and short investment exposures may at times each reach 100% of the assets invested in this strategy (excluding instruments used primarily for duration, yield curve, and interest rate management and short-term investments), although these exposures may be higher or lower at any given time. This strategy may purchase or sell securities on a when-issued, delayed delivery or forward commitment basis and may engage in short sales. The strategy may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as buy backs or dollar rolls).

Equity Long/Short. This strategy provides long and short exposure to a diversified portfolio of equities which involves simultaneously investing in equities (i.e., investing long) the sub-advisor expects to increase in value (securities the sub-advisor believes are undervalued) and either selling equities (i.e., short sales or short selling) the sub-advisor expects to decrease in value (securities the sub-advisor believes are overvalued) or hedging equity market exposure in another way (i.e., by using derivatives such as futures or options). Long/short equity expresses industry views by emphasizing certain industries and it also seeks to exploit pricing inefficiencies between related equity securities. An example of exploiting pricing inefficiencies between related equity securities is building a portfolio containing long positions in the strongest companies of several industries and taking short positions in companies showing signs of weakness in the corresponding industries. This strategy has available two methods of analysis: fundamental analysis, a method of security analysis that involves examining a company's financial statements and operations, especially sales, earnings, products, management and competition and quantitative analysis, a method of security analysis that involves use of mathematical models to examine a company's measurable characteristics such as revenue, earnings, margins and market share.

Equity Market Neutral. This strategy seeks to profit by exploiting pricing inefficiencies between related equity securities and neutralizing exposure to market risk by maintaining long and short positions. Equity market neutral is not expected to have industry overweights.

Dedicated Short Bias. The dedicated short bias strategy seeks to profit by shorting stocks that have negative market sentiment and neutralizing exposure to market risk by maintaining long and short positions.

Global Macro. Global macro strategies seek to profit from movement in the prices of securities that are highly sensitive to macroeconomic conditions, across a broad spectrum of assets. This strategy provides long and short exposure to developed country equities, currencies and bonds markets.

Emerging Markets. This strategy seeks to profit from investing in equities, bonds, and currencies of issuers in emerging markets. This strategy provides long and short exposure to emerging country equity, debt, and currency markets, and long and short exposure to a basket of liquid equity securities traded on emerging and developed market exchanges.

Convertible Arbitrage. Convertible arbitrage strategies seek to profit from the complexity of the pricing of convertible bonds (which contain elements of both a fixed income security and an equity option) by structuring trades using multiple securities within the capital structure of a convertible bond issuer. The Fund may purchase the convertible bond of a given issuer and simultaneously sell short the common stock of that same issuer to take advantage of a mispricing of either security. This strategy takes positions in various global convertible debt and preferred securities and an offsetting position in various global equities directly linked to the convertible securities. In implementing this strategy, the Fund may use derivatives to hedge against a decline in interest rates or credit exposure.

Currency Instruments, Futures Contracts, Futures-Related Instruments and Equity Swaps. These strategies seek to profit from the design and implementation of quantitative selection models to help predict upcoming movements in any combination of fixed income, currency, or equity markets. This strategy provides long and short exposure to developed country equities, bonds and currency markets and long and short exposure to emerging country equity and currency markets.

Event Driven. Event driven strategies seek to profit from investing in the securities of companies based not on a value or growth investment style but rather on the basis that a specific event or catalyst will affect future prices. This strategy attempts to capitalize on price discrepancies and returns generated by corporate activity, such as merger arbitrage. In merger arbitrage, the Fund will employ a diversified, disciplined strategy to attempt to capture the returns from holding a long/short portfolio of stocks of companies involved in mergers.

Fixed Income Arbitrage. Fixed income arbitrage seeks to profit from exploiting mispricing of various, liquid fixed income or interest rate sensitive securities. This strategy provides long and short exposure to developed country bond and currency markets, long and short exposure to investment grade credit markets and long and short exposure to forward mortgage-backed securities trading in the to be announced (“TBA”) market.

Principal Risks

The Fund may be an appropriate investment for investors who seek long-term capital appreciation and who can accept the risks of investing in a variety of global markets and a variety of instruments.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Arbitrage Trading Risk. The underlying relationships between securities in which the fund takes arbitrage investment positions may change in an adverse manner, in which case the fund may realize losses.

Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.

Bank Loans Risk. Changes in economic conditions are likely to cause issuers of bank loans (also known as senior floating rate interests) to be unable to meet their obligations. In addition, the value of the collateral securing the loan may decline, causing a loan to be substantially unsecured. Underlying credit agreements governing the bank loans, reliance on market makers, priority of repayment and overall market volatility may harm the liquidity of loans.

Basis Risk. A hedge using derivatives and/or securities could expose the fund to basis risk. Basis risk could arise when the change in price of the hedge may not match the change in price of the asset it hedges. In other words, the hedge moves in a direction that does not match the asset it is trying to hedge.

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.

Convertible Securities Risk. Convertible securities can be bonds, notes, debentures, preferred stock or other securities which are convertible into common stock. Convertible securities are subject to both the credit and interest rate risks associated with fixed income securities and to the stock market risk associated with equity securities.

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.

Distressed Investments Risk. A fund’s investment in instruments involving loans, loan participations, bonds, notes, non-performing and sub-performing mortgage loans, many of which are not publicly traded, may involve a substantial degree of risk for the following reasons. These instruments may become illiquid and the prices of such instruments may be extremely volatile. Valuing such instruments may be difficult and a fund may lose all of its investment, or it may be required to accept cash or securities with a value less than the fund’s original investment. Issuers of distressed securities are typically in a weak financial condition and may default, in which case the fund may lose its entire investment.

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.

Event-Driven Trading Risk. Event-driven trading involves the risk that the special situation may not occur as anticipated, if at all, and that the market price of a stock declines.

Fixed-Income Securities Risk. Fixed-income securities are subject to interest rate risk and credit quality risk. The market value of fixed-income securities generally declines when interest rates rise, and an issuer of fixed-income securities could default on its payment obligations.

Foreign Securities Risk. The risks of foreign securities include loss of value as a result of: political or economic instability; nationalization, expropriation or confiscatory taxation; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

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.

Non-Diversification Risk. A non-diversified fund may invest a high percentage of its assets in the securities of a small number of issuers and is more likely than diversified funds to be significantly affected by a specific security’s poor performance.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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).

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.

Short Sale Risk. A short sale involves the sale by the fund of a security that it does not own with the hope of purchasing the same security at a later date at a lower price. A fund may also enter into a short derivative position through a futures contract or swap agreement. If the price of the security or derivative has increased during this time, then the fund will incur a loss equal to the increase in price from the time that the short sale was entered into plus any premiums and interest paid to the third party. Therefore, short sales involve the risk that losses may be exaggerated, potentially losing more money than the actual cost of the investment. Also, there is the risk that the third party to the short sale may fail to honor its contract terms, causing a loss to the fund.

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.

Performance

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 HRFI (Hedge Fund Research Inc.) Funds-of-Funds Composite Index.

Global Opportunities Fund

GLOBAL OPPORTUNITIES FUND

Objective:

The Fund seeks long-term growth of capital.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees (fees paid directly from your investment): None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Institutional Plan		PFI Prospectus - Institutional Class Shares Global Opportunities Fund Global Opportunities Fund, Institutional Class
Management Fees (as a percentage of Assets)		0.85%
Other Expenses (as a percentage of Assets):	[1]	3.14%
Expenses (as a percentage of Assets)		3.99%
Fee Waiver or Reimbursement	[2]	3.04%
Net Expenses (as a percentage of Assets)		0.95%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 - Institutional Plan (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years
PFI Prospectus - Institutional Class Shares Global Opportunities Fund Global Opportunities Fund, Institutional Class	97	632

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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. This is a new Fund and does not yet have a portfolio turnover rate to disclose.

Principal Investment Strategies

The Fund invests primarily in equity securities. The Fund intends to invest in securities that are tied economically to a number of countries throughout the world, including the U.S. and emerging markets; however, the Fund has no requirements as to the amount of its net assets that invests in foreign securities. The Fund has a flexible investment strategy and may invest in equity securities regardless of market capitalization (small, medium, or large) and style (growth or value). The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund also invests in growth equity securities; growth orientation emphasizes buying equity securities of companies whose potential for growth of capital and earnings is expected to be above average. The Fund actively trades portfolio securities. The Fund uses derivative instruments. Specifically, the Fund engages in certain options or swaps transactions and enter into futures contracts for portfolio and cash management purposes.

Principal Risks

The Fund may be an appropriate investment for investors seeking long-term growth of capital in global markets, including emerging markets, who are able to assume the increased risks of higher price volatility and currency fluctuations associated with investments in international equity securities which trade in non-U.S. currencies.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Counterparty Risk. Counterparty risk is the risk that the counterparty to a derivatives contract or repurchase agreement, the borrower of a portfolio’s securities, or other obligation, will be unable or unwilling to make timely principal, interest, or settlement payments, or otherwise to honor its obligations.

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.

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.

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.

Performance

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 MSCI All Country World Index (ACWI).

International Equity Index Fund

INTERNATIONAL EQUITY INDEX FUND

Objective:

The Fund seeks long-term growth of capital.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees (fees paid directly from your investment):    None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Institutional Plan PFI Prospectus - Institutional Class Shares International Equity Index Fund		International Equity Index Fund, Institutional Class	International Equity Index Fund, Class R-1	International Equity Index Fund, Class R-2	International Equity Index Fund, Class R-3	International Equity Index Fund, Class R-4	International Equity Index Fund, Class R-5
Management Fees (as a percentage of Assets)		0.25%	0.25%	0.25%	0.25%	0.25%	0.25%
Distribution and Service (12b-1) Fees			0.35%	0.30%	0.25%	0.10%
Other Expenses (as a percentage of Assets):		0.07%	0.59%	0.51%	0.38%	0.34%	0.32%
Acquired Fund Fees and Expenses		0.01%	0.01%	0.01%	0.01%	0.01%	0.01%
Expenses (as a percentage of Assets)		0.33%	1.20%	1.07%	0.89%	0.70%	0.58%
Fee Waiver or Reimbursement	[1]		none	none	none	none	none
Net Expenses (as a percentage of Assets)		0.33%	1.20%	1.07%	0.89%	0.70%	0.58%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 - Institutional Plan PFI Prospectus - Institutional Class Shares International Equity Index Fund (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
International Equity Index Fund, Institutional Class	34	106	185	418
International Equity Index Fund, Class R-1	122	381	660	1,455
International Equity Index Fund, Class R-2	109	340	590	1,306
International Equity Index Fund, Class R-3	91	284	493	1,096
International Equity Index Fund, Class R-4	72	224	390	871
International Equity Index Fund, Class R-5	59	186	324	726

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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 53.5% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in securities held by MSCI EAFE NDTR D Index (the "Index") at the time of purchase. The Index is a weighted equity index designed to measure the equity performance of developed markets (Europe, Australia, New Zealand, and Far East), excluding the United States and Canada. The Fund employs a passive investment approach designed to attempt to track the performance of the Index. The Fund invests in index futures and options and exchange-traded funds ("ETFs") on a daily basis to gain exposure to the Index in an effort to minimize tracking error relative to the benchmark.

Principal Risks

The Fund may be an appropriate investment for investors seeking long-term growth of capital, willing to accept the potential for volatile fluctuations in the value of investments and preferring a passive, rather than active, management style.

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:

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.

Exchange-Traded Funds ("ETFs") Risk. An ETF is subject to the risks associated with direct ownership of the securities comprising the index on which the ETF is based. Fund shareholders indirectly bear their proportionate share of the expenses of the ETFs in which the fund invests.

Foreign Securities Risk. The risks of foreign securities include loss of value as a result of: political or economic instability; nationalization, expropriation or confiscatory taxation; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).

Index Fund Investment Risk. More likely than not, an index fund will not provide investment performance that matches the index performance due to cashflows and the fees and expenses of the fund.

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.

Performance

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Institutional shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principal.com or by calling 1-800-222-5852.

Life of Fund returns are measured from December 30, 2009, the date the Institutional, R-1, R-2, R-3, R-4, and R-5 Class shares were first sold.

Total Returns as of December 31 each year (Institutional Class shares)

^[3]

The year-to-date return as of September 30, 2012 was 9.89% for Institutional shares.

Highest return for a quarter during the period of the bar chart above:	Q3 ‘10	17.39	%
Lowest return for a quarter during the period of the bar chart above:	Q3 ‘11	-20.25	%

Average Annual Total Returns - Institutional Plan PFI Prospectus - Institutional Class Shares International Equity Index Fund	Label	1 Year	Since Inception	Inception Date
International Equity Index Fund, Institutional Class	Institutional Class Return Before Taxes	(12.39%)	(3.52%)	Dec. 30, 2009
International Equity Index Fund, Institutional Class After Taxes on Distributions	Institutional Class Return After Taxes on Distributions	(12.60%)	(3.76%)	Dec. 30, 2009
International Equity Index Fund, Institutional Class After Taxes on Distributions and Sales	Institutional Class Return After Taxes on Distribution and Sale of Fund Shares	(7.44%)	(2.87%)	Dec. 30, 2009
International Equity Index Fund, Class R-1	Class R-1 Return Before Taxes	(13.22%)	(4.38%)	Dec. 30, 2009
International Equity Index Fund, Class R-2	Class R-2 Return Before Taxes	(13.20%)	(4.32%)	Dec. 30, 2009
International Equity Index Fund, Class R-3	Class R-3 Return Before Taxes	(12.93%)	(4.12%)	Dec. 30, 2009
International Equity Index Fund, Class R-4	Class R-4 Return Before Taxes	(12.79%)	(3.89%)	Dec. 30, 2009
International Equity Index Fund, Class R-5	Class R-5 Return Before Taxes	(12.68%)	(3.79%)	Dec. 30, 2009
MSCI - EAFE NDTR D Index	MSCI - EAFE NDTR D Index (reflects no deduction for fees, expenses, or taxes)	(12.14%)	(2.47%)	Dec. 30, 2009

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Institutional Class shares only and would be different for Class R-1, R-2, R-3, R-4 and R-5 shares.

Preferred Securities Fund

PREFERRED SECURITIES FUND

Objective:

The Fund seeks to provide current income.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees (fees paid directly from your investment):    None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Institutional Plan PFI Prospectus - Institutional Class Shares Preferred Securities Fund	Preferred Securities Fund, Institutional Class	Preferred Securities Fund, Class R-1	Preferred Securities Fund, Class R-2	Preferred Securities Fund, Class R-3	Preferred Securities Fund, Class R-4	Preferred Securities Fund, Class R-5
Management Fees (as a percentage of Assets)	0.71%	0.71%	0.71%	0.71%	0.71%	0.71%
Distribution and Service (12b-1) Fees		0.35%	0.30%	0.25%	0.10%
Other Expenses (as a percentage of Assets):	0.04%	0.53%	0.45%	0.32%	0.28%	0.26%
Net Expenses (as a percentage of Assets)	0.75%	1.59%	1.46%	1.28%	1.09%	0.97%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 - Institutional Plan PFI Prospectus - Institutional Class Shares Preferred Securities Fund (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Preferred Securities Fund, Institutional Class	77	240	417	930
Preferred Securities Fund, Class R-1	162	502	866	1,889
Preferred Securities Fund, Class R-2	149	462	797	1,746
Preferred Securities Fund, Class R-3	130	406	702	1,545
Preferred Securities Fund, Class R-4	111	347	601	1,329
Preferred Securities Fund, Class R-5	99	309	536	1,190

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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 22.9% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in preferred securities at the time of purchase. Preferred securities generally pay fixed rate dividends (though some are adjustable rate) and typically have "preference" over common stock in the payment of dividends and the liquidation of a company's assets, but are junior to all forms of the company's debt. Most of the securities purchased by the Fund are preferred securities of companies rated at the time of purchase BBB- or higher by Standard & Poor's Rating Service ("S&P") or Baa3 or higher by Moody's Investor Service, Inc. ("Moody's") or, if unrated, of comparable quality in the opinion of the Sub-Advisor. The Fund also invests up to 15% of its assets in below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, the Sub-Advisor will determine whether the bond is of a quality comparable to those rated below investment grade).

The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the U.S. and non-U.S financial services (i.e., banking, insurance and commercial finance,) industry. The Fund also regularly invests in the real estate investment trust (i.e. REIT) and utility industries.

Principal Risks

The Fund may be an appropriate investment for investors who are seeking dividends to generate income or to reinvest for growth and are willing to accept fluctuations in the value of the investment.

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:

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.

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).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Industry Concentration Risk (Financial Services). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in financial services companies may be more susceptible to adverse economic or regulatory occurrences affecting financial services companies. Financial companies may be adversely affected in certain market cycles, including periods of rising interest rates, which may restrict the availability and increase the cost of capital, and declining economic conditions, which may cause credit losses due to financial difficulties of borrowers. Because many types of financial companies are especially vulnerable to these economic cycles, the Fund’s investments in these companies may lose significant value during such periods.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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. 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.

Performance

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Institutional Class shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principal.com or by calling 1-800-222-5852.

The Institutional Class shares were first sold May 1, 2002. The R-1 Class shares were first sold on November 1, 2004. The R-2, R-3, R-4, and R-5 share classes were first sold on June 1, 2004. For periods prior to the date on which the R-1, R-2, R-3, R-4 and R-5 class shares began operations, their returns are based on the performance of the Fund’s Institutional Class shares adjusted to reflect the fees and expenses of these classes. The adjustments result in performance (for the periods prior to the date these classes began operations) that is no higher than the historical performance of the Institutional Class shares.

Performance of a blended index shows how the Fund's performance compares to an index with similar investment objectives. Performance of the components of the blended index are also shown. The weightings for the Preferreds Blended Index are 50% BofA Merrill Lynch Fixed Rate Preferred Securities and 50% Barclays U.S. Tier I Capital Securities Index. The custom or blended index returns reflect the allocation in effect for the time period(s) for which fund returns are disclosed. Previous weightings or allocations of the custom or blended index are not restated.

Total Returns as of December 31 each year (Institutional Class shares)

^[4]

The year-to-date return as of September 30, 2012 was 15.67% for Institutional shares.

Highest return for a quarter during the period of the bar chart above:	Q2 ‘09	38.94	%
Lowest return for a quarter during the period of the bar chart above:	Q3 ‘08	-20.90	%

Average Annual Total Returns - Institutional Plan PFI Prospectus - Institutional Class Shares Preferred Securities Fund	Label	1 Year	5 Years	Since Inception	Inception Date
Preferred Securities Fund, Institutional Class	Institutional Class Return Before Taxes	1.53%	4.38%	5.21%	May 01, 2002
Preferred Securities Fund, Institutional Class After Taxes on Distributions	Institutional Class Return After Taxes on Distributions	(0.46%)	2.16%	3.31%	May 01, 2002
Preferred Securities Fund, Institutional Class After Taxes on Distributions and Sales	Institutional Class Return After Taxes on Distribution and Sale of Fund Shares	1.34%	2.48%	3.39%	May 01, 2002
Preferred Securities Fund, Class R-1	Class R-1 Return Before Taxes	0.71%	3.49%	4.29%	May 01, 2002
Preferred Securities Fund, Class R-2	Class R-2 Return Before Taxes	0.94%	3.62%	4.44%	May 01, 2002
Preferred Securities Fund, Class R-3	Class R-3 Return Before Taxes	1.03%	3.81%	4.63%	May 01, 2002
Preferred Securities Fund, Class R-4	Class R-4 Return Before Taxes	1.20%	3.99%	4.80%	May 01, 2002
Preferred Securities Fund, Class R-5	Class R-5 Return Before Taxes	1.33%	4.10%	4.93%	May 01, 2002
BofA Merrill Lynch Fixed Rate Preferred Securities Index	BofA Merrill Lynch Fixed Rate Preferred Securities Index (reflects no deduction for fees, expenses, or taxes)	4.11%	(1.19%)	2.42%	May 01, 2002
Barclays U.S. Tier I Capital Securities Index	Barclays U.S. Tier I Capital Securities Index (reflects no deduction for fees, expenses, or taxes)	(0.53%)	1.71%	4.87%	May 01, 2002
Preferreds Blended Index	Preferreds Blended Index (reflects no deduction for fees, expenses, or taxes)	1.81%	0.01%	3.38%	May 01, 2002

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Institutional Class shares only and would be different for Class R-1, R-2, R-3, R-4 and R-5 shares.

Small-MidCap Dividend Income Fund

SMALL-MIDCAP DIVIDEND INCOME FUND

Objective:

The Fund primarily seeks to provide a relatively high level of current income and long-term growth of income, and

secondarily long-term growth of capital, while investing primarily in small- to mid-capitalization companies.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees (fees paid directly from your investment):    None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Institutional Plan	PFI Prospectus - Institutional Class Shares Small-MidCap Dividend Income Fund Small-MidCap Dividend Income Fund, Institutional Class
Management Fees (as a percentage of Assets)	0.80%
Other Expenses (as a percentage of Assets):	0.04%
Acquired Fund Fees and Expenses	0.10%
Net Expenses (as a percentage of Assets)	0.94%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 - Institutional Plan (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
PFI Prospectus - Institutional Class Shares Small-MidCap Dividend Income Fund Small-MidCap Dividend Income Fund, Institutional Class	96	300	520	1,155

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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 19.1% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in dividend-paying equity securities of companies with small to medium market capitalizations (those with market capitalizations ranging from between $200 million and $7 billion) at the time of purchase. The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund invests in the securities of foreign issuers, real estate investment trusts, preferred securities, convertible securities, fixed-income securities, master limited partnerships, and royalty trusts.

Principal Risks

The Fund may be an appropriate investment for investors who seek dividends to generate income or to reinvest for growth and who can accept fluctuations in the value of investments and the risks of investing in equity securities, the securities of foreign issuers, real estate investment trusts, preferred securities, convertible securities, fixed-income securities, master limited partnerships, and royalty trusts.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Convertible Securities Risk. Convertible securities can be bonds, notes, debentures, preferred stock or other securities which are convertible into common stock. Convertible securities are subject to both the credit and interest rate risks associated with fixed income securities and to the stock market risk associated with equity securities.

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.

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).

Master Limited Partnership ("MLP") Risk. MLPs are publicly-traded limited partnership interests or units. An MLP that invests in a particular industry (e.g., oil and gas) will be harmed by detrimental economic events within that industry. As partnerships, MLPs may be subject to less regulation (and less protection for investors) under state laws than corporations. In addition, MLPs may be subject to state taxation in certain jurisdictions, which may reduce the amount of income an MLP pays to its investors.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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. 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.

Royalty Trust Risk. A royalty trust generally acquires an interest in natural resource or chemical companies and distributes the income it receives to its investors. A sustained decline in demand for natural resource and related products could adversely affect royalty trust revenues and cash flows. Such a decline could result from a recession or other adverse economic conditions, an increase in the market price of the underlying commodity, higher taxes or other regulatory actions that increase costs, or a shift in consumer demand. Rising interest rates could adversely affect the performance, and limit the capital appreciation, of royalty trusts because of the increased availability of alternative investments at more competitive yields. Fund shareholders will indirectly bear their proportionate share of the royalty trusts' expenses.

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.

Performance

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 Russell 2500 Value Index.

[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 attributable to Institutional class shares by paying, if necessary, expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2013. The expense limit will maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.75% for Institutional class shares, excluding interest expense. 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.

[1] Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund’s expenses attributable to Class R-1, R-2, R-3, R-4, and R-5 shares by paying, if necessary, expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2013. 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 1.18% for Class R-1, 1.05% for Class R-2, 0.87% for Class R-3, 0.68% for Class R-4, and 0.56% for Class R-5, excluding interest expense. 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.

[1] Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund's expenses attributable to Institutional class shares by paying, if necessary, expenses normally payable by the Fund, excluding I think expense and short sale dividends and interest, through the period ending December 31, 2013. 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 1.65% for Institutional class shares, excluding interest expense and short sale dividends and interest. 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.

[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 attributable to Institutional class shares by paying, if necessary, expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2014. The expense limit will maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.95% for Institutional class shares, excluding interest expense. 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.

[1] Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund’s expenses attributable to Class R-1, R-2, R-3, R-4, and R-5 shares by paying, if necessary,expenses normally payable by the Fund, excluding interest expense and Acquired Fund Fees and Expenses, through the period ending December 31, 2013. 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 1.28% for Class R-1, 1.15% for Class R-2, 0.97% for Class R-3, 0.78% for Class R-4, and 0.66% for Class R-5, excluding interest expense and Acquired Fund Fees and Expenses. 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.

[1] The year-to-date return as of September 30, 2012 was 3.77% for Institutional shares.

[2] The year-to-date return as of September 30, 2012 was 8.17% for Institutional shares.

[3] The year-to-date return as of September 30, 2012 was 9.89% for Institutional shares.

[4] The year-to-date return as of September 30, 2012 was 15.67% for Institutional shares.

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Diversified Real Asset Fund

DIVERSIFIED REAL ASSET FUND

Objective:

The Fund seeks a long-term total return in excess of inflation.

Fees and Expenses of the Fund

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 56 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 48 of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees PFI Prospectus - Class A, C, P Diversified Real Asset Fund	Diversified Real Asset Fund, Class A	Diversified Real Asset Fund, Class C	Diversified Real Asset Fund, Class P
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)	3.75%	none	none
Maximum Deferred Sales Charge (as a percentage)	1.00%	1.00%	none

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses PFI Prospectus - Class A, C, P Diversified Real Asset Fund		Diversified Real Asset Fund, Class A	Diversified Real Asset Fund, Class C	Diversified Real Asset Fund, Class P
Management Fees (as a percentage of Assets)		0.84%	0.84%	0.84%
Distribution and Service (12b-1) Fees		0.25%	1.00%	none
Other Expenses (as a percentage of Assets):		0.35%	0.29%	0.29%
Expenses (as a percentage of Assets)		1.44%	2.13%	1.13%
Fee Waiver or Reimbursement	[1]	0.19%	0.13%	0.09%
Net Expenses (as a percentage of Assets)		1.25%	2.00%	1.04%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 PFI Prospectus - Class A, C, P Diversified Real Asset Fund (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Diversified Real Asset Fund, Class A	498	795	1,115	2,019
Diversified Real Asset Fund, Class C	303	654	1,132	2,452
Diversified Real Asset Fund, Class P	106	350	614	1,367

You would pay the following expenses if you did not redeem your shares:

Expense Example, No Redemption PFI Prospectus - Class A, C, P Diversified Real Asset Fund (USD $)	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
Diversified Real Asset Fund, Class A	498	795	1,115	2,019
Diversified Real Asset Fund, Class C	203	654	1,132	2,452
Diversified Real Asset Fund, Class P	106	350	614	1,367

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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 107.3% of the average value of its portfolio.

Principal Investment Strategies

The Fund seeks to achieve its investment objective by allocating its assets among the following general investment categories: inflation-indexed bonds, securities of real estate companies, commodity index-linked notes, fixed-income securities, securities of natural resource companies, master limited partnerships (MLPs), publicly-listed infrastructure companies, and floating rate debt. The Fund actively trades portfolio securities.

The Fund concentrates its investments (invests 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. Except for its policy to concentrate in the real estate and energy/natural resources industries, the Fund retains considerable latitude in allocating its assets.

A portion of the Fund's assets is 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 is 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 are primarily short-term U.S. Treasury and Agency notes and bonds.

A portion of the Fund's assets is invested in the real estate industry. The Fund invests in equity securities of global companies principally engaged in the real estate industry ("real estate companies"). A real estate company has at least 50% of its assets, income or profits derived from products or services related to the real estate industry. Real estate companies include real estate investment trusts ("REITs"), REIT-like entities, and companies with substantial real estate holdings such as paper, lumber, hotel and entertainment companies as well as building supply manufacturers, mortgage lenders, and mortgage servicing companies.

A portion of the Fund's assets is invested in securities of 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, oil and natural gas, timberland, undeveloped real property and agricultural commodities.

A portion of the Fund's assets is invested in MLPs. Generally, MLPs are engaged in the transportation, storage, processing, refining, marketing, production, or mining of natural resources. The Fund invests primarily in the mid-stream category of MLPs, which is generally comprised of pipelines used to gather, process, transport, and distribute natural gas, crude oil, and refined petroleum products.

A portion of the Fund’s assets is invested in domestic and foreign publicly-listed infrastructure companies. Publicly-listed infrastructure equity securities trade on an exchange and include, but are not limited to, companies involved in the ownership and/or operations of infrastructure assets within the transportation, communications, water, electricity transmission and distribution, and oil and gas storage, processing and transportation industries.

A portion of the Fund’s assets is invested in below-investment-grade (sometimes called “junk”) or comparable unrated floating rate debt (also known as bank loans, syndicated loans, leveraged loans or senior floating rate interests). Floating rate debt has a variable coupon that resets periodically, with interest payments determined by a representative interest rate index (e.g. LIBOR or the federal funds rate) plus a fixed spread. As a result, the coupon payments vary, or “float” with prevailing market interest rates.

Principal Risks

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:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.

Bank Loans Risk. Changes in economic conditions are likely to cause issuers of bank loans (also known as senior floating rate interests) to be unable to meet their obligations. In addition, the value of the collateral securing the loan may decline, causing a loan to be substantially unsecured. Underlying credit agreements governing the bank loans, reliance on market makers, priority of repayment and overall market volatility may harm the liquidity of loans.

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.

Commodity-Related Investment Risk. The value of commodities investments will generally be affected by overall market movements and factors specific to a particular industry or commodity, which may include weather, embargoes, tariffs, and economic health, political, international regulatory and other developments. Exposure to the commodities markets may subject the fund to greater volatility than investments in traditional securities.

Counterparty Risk. Counterparty risk is the risk that the counterparty to a 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).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Industry Concentration Risk (Energy/Natural Resources). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in energy/natural resource companiesmay be affected by numerous factors, including events occurring in nature, inflationary pressures, international politics, the success of exploration projects, commodity prices, energy conservation, taxes and other government regulations. In addition, interest rates and general economic conditions may affect the demand for energy/natural resources. For example, events occurring in nature (such as earthquakes or fires in prime energy/natural resource areas) and political events (such as coups, military confrontations or acts of terrorism) can affect overall supply of energy/natural resources and the value of companies involved in energy/natural resources.

Industry Concentration Risk (Real Estate). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in the real estate industry can be subject to the risks associated with direct ownership of real estate, securities of companies in the real estate industry, and/or real estate investment trusts.

Leverage Risk. Leverage created by borrowing or certain types of transactions or investments, 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. 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.

Performance

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Class A shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principal.com or by calling 1-800-222-5852.

Class A and Class C shares commenced operations on March 16, 2010, Class P shares were first sold on September 27, 2010. The returns for Class P shares, for the periods prior to that date, are based on the performance of the Institutional Class shares adjusted to reflect the fees and expenses of Class P shares. The adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares. Institutional Class shares were first sold on March 16, 2010.

Performance of a blended index shows how the Fund’s performance compares to an index with similar investment objectives. Performance of the components of the blended index are also shown. The Diversified Real Asset Custom Index was composed of 30% Barclays U.S. Treasury TIPS Index, 20% MSCI U.S. REIT Index, 25% Dow Jones UBS Commodity Index, 15% S&P N.A. Natural Resources Index, and 10% Tortoise MLP Index. Effective January 31, 2012, the weightings for the Diversified Real Asset Custom Index changed to 30% Barclays U.S. Treasury TIPS Index, 20% Dow Jones UBS Commodity Index, 10% S&P N.A. Natural Resources Index, 10% Tortoise MLP Index, 10% Dow Jones Brookfield Global Infrastructure Index, 10% Credit Suisse Leveraged Loan Index, and 10% FTSE EPRA/NAREIT Developed Index. The custom or blended index returns reflect the allocation in effect for the time period(s) for which fund returns are disclosed. Previous weightings or allocations of the custom or blended index are not restated.

Total Returns as of December 31 each year (Class A shares)

^[1]

The year-to-date return as of September 30, 2012 was 7.85% for Class A shares.

Highest return for a quarter during the period of the bar chart above:	Q4 '11	7.04	%
Lowest return for a quarter during the period of the bar chart above:	Q3 '11	-9.20	%

Average Annual Total Returns PFI Prospectus - Class A, C, P Diversified Real Asset Fund	Label	1 Year	Since Inception	Inception Date
Diversified Real Asset Fund, Class A	Class A Return Before Taxes	(3.38%)	6.24%	Mar. 16, 2010
Diversified Real Asset Fund, Class A After Taxes on Distributions	Class A Return After Taxes on Distributions	(3.93%)	5.79%	Mar. 16, 2010
Diversified Real Asset Fund, Class A After Taxes on Distributions and Sales	Class A Return After Taxes on Distribution and Sale of Fund Shares	(1.86%)	5.15%	Mar. 16, 2010
Diversified Real Asset Fund, Class C	Class C Return Before Taxes	(1.22%)	7.82%	Mar. 16, 2010
Diversified Real Asset Fund, Class P	Class P Return Before Taxes	0.58%	8.81%	Mar. 16, 2010
Barclays US Treasury TIPS Index	Barclays US Treasury TIPS Index (reflects no deduction for fees, expenses, or taxes)	13.56%	10.42%	Mar. 16, 2010
MSCI US REIT Index	MSCI US REIT Index (reflects no deduction for fees, expenses, or taxes)	8.69%	14.22%	Mar. 16, 2010
Dow Jones UBS Commodity Index	Dow Jones UBS Commodity Index (reflects no deduction for fees, expenses, or taxes)	(13.32%)	3.32%	Mar. 16, 2010
S&P North American Natural Resources Index	S&P North American Natural Resources Index (reflects no deduction for fees, expenses, or taxes)	(7.35%)	6.85%	Mar. 16, 2010
Tortoise MLP Index	Tortoise MLP Index (reflects no deduction for fees, expenses, or taxes)	13.73%	22.36%	Mar. 16, 2010
Dow Jones Brookfield Global Infrastructure Index	Dow Jones Brookfield Global Infrastructure Index (reflects no deduction for fees, expenses, or taxes)	13.75%	14.07%	Mar. 16, 2010
Credit Suisse Leveraged Loan Index	Credit Suisse Leveraged Loan Index (reflects no deduction for fees, expenses, or taxes)	1.82%	5.26%	Mar. 16, 2010
FTSE EPRA/NAREIT Developed Index	FTSE EPRA/NAREIT Developed Index (reflects no deduction for fees, expenses, or taxes)	(5.82%)	5.28%	Mar. 16, 2010
Diversified Real Asset Custom Index	Diversified Real Asset Custom Index (reflects no deduction for fees, expenses, or taxes)	2.80%	10.63%	Mar. 16, 2010

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Class A shares only and would be different for Class C and Class P shares.

Global Multi-Strategy Fund

GLOBAL MULTI-STRATEGY FUND

Objective:

The Fund seeks to achieve long-term capital appreciation with an emphasis on positive total returns and relatively low volatility.

Fees and Expenses of the Fund

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 56 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 48 of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees PFI Prospectus - Class A, C, P Global Multi-Strategy Fund	Global Multi-Strategy Fund, Class A	Global Multi-Strategy Fund, Class C	Global Multi-Strategy Fund, Class P
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)	3.75%	none	none
Maximum Deferred Sales Charge (as a percentage)	1.00%	1.00%	none

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses PFI Prospectus - Class A, C, P Global Multi-Strategy Fund		Global Multi-Strategy Fund, Class A	Global Multi-Strategy Fund, Class C		Global Multi-Strategy Fund, Class P
Management Fees (as a percentage of Assets)		1.60%	1.60%		1.60%
Distribution and Service (12b-1) Fees		0.25%	1.00%		none
Component1 Other Expenses		0.70%	0.70%		0.70%
Component2 Other Expenses		1.07%	0.45%	[1]	10.50%
Expenses (as a percentage of Assets)		3.62%	3.75%		12.80%
Fee Waiver or Reimbursement	[2]	0.92%	0.30%		10.30%
Net Expenses (as a percentage of Assets)		2.70%	3.45%		2.50%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 PFI Prospectus - Class A, C, P Global Multi-Strategy Fund (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Global Multi-Strategy Fund, Class A	638	1,361	2,103	4,052
Global Multi-Strategy Fund, Class C	448	1,119
Global Multi-Strategy Fund, Class P	253	2,676	4,736	8,635

You would pay the following expenses if you did not redeem your shares:

Expense Example, No Redemption PFI Prospectus - Class A, C, P Global Multi-Strategy Fund (USD $)	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
Global Multi-Strategy Fund, Class A	638	1,361	2,103	4,052
Global Multi-Strategy Fund, Class C	348	1,119
Global Multi-Strategy Fund, Class P	253	2,676	4,736	8,635

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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. From October 14, 2011, date operations commenced, through August 31, 2012, the Fund’s annualized portfolio turnover rate was 196.0% of the average value of its portfolio.

Principal Investment Strategies

Principal Management Corporation ("Principal"), the Fund's investment adviser, allocates the Fund's assets among one or more of the investment strategies described below, which are executed by one or more of the Fund's sub-advisors. In making these allocations, Principal seeks to combine the strategies of the sub-advisors efficiently and systematically so that the Fund generates, through a diversified set of investment strategies, a positive total return with relatively low volatility and low sensitivity or correlation to market indices. By allocating the Fund’s assets among a variety of investment strategies, which will vary from time-to-time, the Fund seeks to lessen risk and reduce volatility. Principal may also direct a sub-advisor to reduce or omit its investment in certain assets or asset classes in an effort to achieve its desired combination of the Fund's strategies.

In pursuing its strategies, the Fund invests in a broad range of instruments including, but not limited to, equities, bonds, currencies, convertible securities and derivatives such as futures, options, swaps (including, for example, credit default, interest rate, and currency swaps) and forwards. The Fund intends to engage in derivative transactions to gain exposure to a variety of securities or attempt to reduce risk. The Fund intends to invest in securities that are tied economically to a number of countries throughout the world, including the U.S.; however, the Fund has no requirements as to the amount of its net assets that it invests in foreign securities. The Fund is considered non-diversified, which means it can invest a higher percentage of assets in securities of individual issuers than a diversified fund. The Fund actively trades securities.

Some of the strategies take long and/or short positions. When taking a short position, the Fund may sell an instrument that it does not own and then borrow to meet its settlement obligations. The Fund may take short positions in futures, forwards or swaps. A short position will benefit from a decrease in price of the underlying instrument and will lose value if the price of the underlying instrument increases. Long positions will profit if the value of the instrument increases. Simultaneously engaging in long investing and short selling reduces the net exposure of the overall portfolio to general market movements. Relative value positions may be taken as well in the various strategies. Relative value strategies capitalize on price differences between similar securities or relative value among securities of the same company.

The Fund may use all or some of the following strategies to varying degrees, depending on market conditions, and may add additional strategies. Principal may allocate 0 to 100% of the Fund’s assets to any of these strategies at any time.

Credit Long/Short and Distressed Credit. This strategy utilizes a flexible investment approach that allocates investments across a global range of investment opportunities related to credit, currencies and interest rates, while employing risk management strategies. This strategy invests in fixed income securities and instruments and may invest in both investment-grade securities and below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, the Sub-Advisor will determine whether the bond is of a quality comparable to those rated below investment grade). This strategy may also invest in the following securities: securities denominated in foreign currencies and in U.S. dollar denominated securities of foreign issuers, preferred securities, convertible securities, Rule 144A securities, mortgage or asset-backed securities, floating rate debt (including bank loans), distressed investments, emerging markets, equities and derivative instruments, such as options, futures contracts, forwards or swap agreements. This strategy may utilize derivative instruments in an effort to minimize volatility. Also, at times, this strategy expects to gain its investment exposure substantially through the use of derivatives. The notional value of this strategy’s long and short investment exposures may at times each reach 100% of the assets invested in this strategy (excluding instruments used primarily for duration, yield curve, and interest rate management and short-term investments), although these exposures may be higher or lower at any given time. This strategy may purchase or sell securities on a when-issued, delayed delivery or forward commitment basis and may engage in short sales. The strategy may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as buy backs or dollar rolls).

Equity Long/Short. This strategy provides long and short exposure to a diversified portfolio of equities which involves simultaneously investing in equities (i.e., investing long) the sub-advisor expects to increase in value (securities the sub-advisor believes are undervalued) and either selling equities (i.e., short sales or short selling) the sub-advisor expects to decrease in value (securities the sub-advisor believes are overvalued) or hedging equity market exposure in another way (i.e., by using derivatives such as futures or options). Long/short equity expresses industry views by emphasizing certain industries and it also seeks to exploit pricing inefficiencies between related equity securities. An example of exploiting pricing inefficiencies between related equity securities is building a portfolio containing long positions in the strongest companies of several industries and taking short positions in companies showing signs of weakness in the corresponding industries. This strategy has available two methods of analysis: fundamental analysis, a method of security analysis that involves examining a company's financial statements and operations, especially sales, earnings, products, management and competition and quantitative analysis, a method of security analysis that involves use of mathematical models to examine a company's measurable characteristics such as revenue, earnings, margins and market share.

Equity Market Neutral. This strategy seeks to profit by exploiting pricing inefficiencies between related equity securities and neutralizing exposure to market risk by maintaining long and short positions. Equity market neutral is not expected to have industry overweights.

Dedicated Short Bias. The dedicated short bias strategy seeks to profit by shorting stocks that have negative market sentiment and neutralizing exposure to market risk by maintaining long and short positions.

Global Macro. Global macro strategies seek to profit from movement in the prices of securities that are highly sensitive to macroeconomic conditions, across a broad spectrum of assets. This strategy provides long and short exposure to developed country equities, currencies, and bonds markets.

Emerging Markets. This strategy seeks to profit from investing in equities, bonds, and currencies of issuers in emerging markets. This strategy provides long and short exposure to emerging country equity, debt, and currency markets, and long and short exposure to a basket of liquid equity securities traded on emerging and developed market exchanges.

Convertible Arbitrage. Convertible arbitrage strategies seek to profit from the complexity of the pricing of convertible bonds (which contain elements of both a fixed income security and an equity option) by structuring trades using multiple securities within the capital structure of a convertible bond issuer. The Fund may purchase the convertible bond of a given issuer and simultaneously sell short the common stock of that same issuer to take advantage of a mispricing of either security. This strategy takes positions in various global convertible debt and preferred securities and an offsetting position in various global equities directly linked to the convertible securities. In implementing this strategy, the Fund may use derivatives to hedge against a decline in interest rates or credit exposure.

Currency Instruments, Futures Contracts, Futures-Related Instruments and Equity Swaps. These strategies seek to profit from the design and implementation of quantitative selection models to help predict upcoming movements in any combination of fixed income, currency, or equity markets. This strategy provides long and short exposure to developed country equities, bonds and currency markets and long and short exposure to emerging country equity and currency markets.

Event Driven. Event driven strategies seek to profit from investing in the securities of companies based not on a value or growth investment style but rather on the basis that a specific event or catalyst will affect future prices. This strategy attempts to capitalize on price discrepancies and returns generated by corporate activity, such as merger arbitrage. In merger arbitrage, the Fund will employ a diversified, disciplined strategy to attempt to capture the returns from holding a long/short portfolio of stocks of companies involved in mergers.

Fixed Income Arbitrage. Fixed income arbitrage seeks to profit from exploiting mispricing of various, liquid fixed income or interest rate sensitive securities. This strategy provides long and short exposure to developed country bond and currency markets, long and short exposure to investment grade credit markets and long and short exposure to forward mortgage-backed securities trading in the to be announced (“TBA”) market.

Principal Risks

The Fund may be an appropriate investment for investors who seek long-term capital appreciation and who can accept the risks of investing in a variety of global markets and a variety of instruments.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Arbitrage Trading Risk. The underlying relationships between securities in which the fund takes arbitrage investment positions may change in an adverse manner, in which case the fund may realize losses.

Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.

Bank Loans Risk. Changes in economic conditions are likely to cause issuers of bank loans (also known as senior floating rate interests) to be unable to meet their obligations. In addition, the value of the collateral securing the loan may decline, causing a loan to be substantially unsecured. Underlying credit agreements governing the bank loans, reliance on market makers, priority of repayment and overall market volatility may harm the liquidity of loans.

Basis Risk. A hedge using derivatives and/or securities could expose the fund to basis risk. Basis risk could arise when the change in price of the hedge may not match the change in price of the asset it hedges. In other words, the hedge moves in a direction that does not match the asset it is trying to hedge.

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.

Convertible Securities Risk. Convertible securities can be bonds, notes, debentures, preferred stock or other securities which are convertible into common stock. Convertible securities are subject to both the credit and interest rate risks associated with fixed income securities and to the stock market risk associated with equity securities.

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.

Distressed Investments Risk. A fund’s investment in instruments involving loans, loan participations, bonds, notes, non-performing and sub-performing mortgage loans, many of which are not publicly traded, may involve a substantial degree of risk for the following reasons. These instruments may become illiquid and the prices of such instruments may be extremely volatile. Valuing such instruments may be difficult and a fund may lose all of its investment, or it may be required to accept cash or securities with a value less than the fund’s original investment. Issuers of distressed securities are typically in a weak financial condition and may default, in which case the fund may lose its entire investment.

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.

Event-Driven Trading Risk. Event-driven trading involves the risk that the special situation may not occur as anticipated, if at all, and that the market price of a stock declines.

Fixed-Income Securities Risk. Fixed-income securities are subject to interest rate risk and credit quality risk. The market value of fixed-income securities generally declines when interest rates rise, and an issuer of fixed-income securities could default on its payment obligations.

Foreign Securities Risk. The risks of foreign securities include loss of value as a result of: political or economic instability; nationalization, expropriation or confiscatory taxation; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

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.

Non-Diversification Risk. A non-diversified fund may invest a high percentage of its assets in the securities of a small number of issuers and is more likely than diversified funds to be significantly affected by a specific security’s poor performance.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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).

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.

Short Sale Risk. A short sale involves the sale by the fund of a security that it does not own with the hope of purchasing the same security at a later date at a lower price. A fund may also enter into a short derivative position through a futures contract or swap agreement. If the price of the security or derivative has increased during this time, then the fund will incur a loss equal to the increase in price from the time that the short sale was entered into plus any premiums and interest paid to the third party. Therefore, short sales involve the risk that losses may be exaggerated, potentially losing more money than the actual cost of the investment. Also, there is the risk that the third party to the short sale may fail to honor its contract terms, causing a loss to the fund.

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.

Performance

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 HRFI (Hedge Fund Research Inc.) Funds-of-Funds Composite Index.

Opportunistic Municipal Fund

OPPORTUNISTIC MUNICIPAL FUND

Objective:

The Fund seeks to provide a high level of income that is exempt from federal income tax while protecting investors’ capital.

Fees and Expenses of the Fund

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 56 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 48 of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees PFI Prospectus - Class A, C, P Opportunistic Municipal Fund	Opportunistic Municipal Fund, Class A	Opportunistic Municipal Fund, Class C
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)	3.75%	none
Maximum Deferred Sales Charge (as a percentage)	1.00%	1.00%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses PFI Prospectus - Class A, C, P Opportunistic Municipal Fund		Opportunistic Municipal Fund, Class A	Opportunistic Municipal Fund, Class C
Management Fees (as a percentage of Assets)		0.50%	0.50%
Distribution and Service (12b-1) Fees		0.25%	1.00%
Component1 Other Expenses		0.23%	0.23%
Component2 Other Expenses	[1]	0.44%	0.47%
Expenses (as a percentage of Assets)		1.42%	2.20%
Fee Waiver or Reimbursement	[2]	0.29%	0.32%
Net Expenses (as a percentage of Assets)		1.13%	1.88%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 PFI Prospectus - Class A, C, P Opportunistic Municipal Fund (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years
Opportunistic Municipal Fund, Class A	486	780
Opportunistic Municipal Fund, Class C	291	657

You would pay the following expenses if you did not redeem your shares:

Expense Example, No Redemption PFI Prospectus - Class A, C, P Opportunistic Municipal Fund (USD $)	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years
Opportunistic Municipal Fund, Class A	486	780
Opportunistic Municipal Fund, Class C	191	657

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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. From June 13, 2012, date operations commenced, through August 31, 2012, the Fund’s annualized portfolio turnover rate was 93.8% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in municipal obligations (securities issued by or on behalf of state or local governments and other public authorities). Many of these are from California. Municipal obligations pay interest that is exempt from federal income tax. The Fund has a flexible investment strategy and invests in obligations of any duration and credit quality, including below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, the Sub-Advisor will determine whether the bond is of a quality comparable to those rated below investment grade).

The Fund invests in other debt obligations, including (but not limited to) taxable municipal obligations, U.S. Treasury securities, obligations of the U.S. Government, its agencies and instrumentalities (“Agency Securities”) and inverse floating rate obligations, which are generally more volatile than other types of municipal obligations. The Fund invests in exchange-traded funds (ETFs) to gain exposure to the municipal market.

The Fund purchases derivative instruments, which derive their value from another instrument, security or index. The Fund purchases or sells various kinds of financial futures contracts to hedge against changes in interest rates or as a substitute for the purchase of portfolio securities. The Fund also enters into interest rate swaps and credit derivatives, which includes credit default swaps.

Principal Risks

The Fund may be an appropriate investment for investors who are seeking monthly, federally tax-exempt dividends to produce income or to reinvest for modest growth and are willing to accept fluctuations in the value of their investment.

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:

Basis Risk. A hedge using derivatives and/or securities could expose the fund to basis risk. Basis risk could arise when the change in price of the hedge may not match the change in price of the asset it hedges. In other words, the hedge moves in a direction that does not match the asset it is trying to hedge.

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 may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.

Exchange-Traded Funds ("ETFs") Risk. An ETF is subject to the risks associated with direct ownership of the securities comprising the index on which the ETF is based. Fund shareholders indirectly bear their proportionate share of the expenses of the ETFs in which the fund invests.

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.

Geographic Concentration Risk. A fund that invests significant portions of its assets in particular geographic areas (such as California or Illinois) has greater exposure than other funds to economic conditions and developments in those areas.

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Inverse Floating Rate Investments. Inverse floating rate investments are extremely sensitive to changes in interest rates and in some cases their market value may be extremely volatile.

Leverage Risk. Leverage created by borrowing or certain types of transactions or investments, such as reverse repurchase agreements, loans of portfolio securities, and the use of when-issued, delayed delivery or forward commitment transactions, or derivative instruments, may impair the fund’s liquidity, cause it to liquidate positions at an unfavorable time, increase volatility of the fund’s net asset value, or diminish the fund’s performance.

Municipal Securities Risk. Principal and interest payments on municipal securities may not be guaranteed by the issuing body and may be payable only from a particular source. That source may not perform as expected and payment obligations may not be made or made on time.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

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.

Performance

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 Municipal Bond Index.

Preferred Securities Fund

PREFERRED SECURITIES FUND

Objective:

The Fund seeks to provide current income.

Fees and Expenses of the Fund

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 56 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 48 of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees PFI Prospectus - Class A, C, P Preferred Securities Fund	Preferred Securities Fund, Class A	Preferred Securities Fund, Class C	Preferred Securities Fund, Class P
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)	3.75%	none	none
Maximum Deferred Sales Charge (as a percentage)	1.00%	1.00%	none

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses PFI Prospectus - Class A, C, P Preferred Securities Fund		Preferred Securities Fund, Class A	Preferred Securities Fund, Class C	Preferred Securities Fund, Class P
Management Fees (as a percentage of Assets)		0.71%	0.71%	0.71%
Distribution and Service (12b-1) Fees		0.25%	1.00%	none
Other Expenses (as a percentage of Assets):		0.10%	0.11%	0.14%
Expenses (as a percentage of Assets)		1.06%	1.82%	0.85%
Fee Waiver or Reimbursement	[1]			none
Net Expenses (as a percentage of Assets)		1.06%	1.82%	0.85%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 PFI Prospectus - Class A, C, P Preferred Securities Fund (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Preferred Securities Fund, Class A	479	700	938	1,621
Preferred Securities Fund, Class C	285	573	985	2,137
Preferred Securities Fund, Class P	87	271	471	1,049

You would pay the following expenses if you did not redeem your shares:

Expense Example, No Redemption PFI Prospectus - Class A, C, P Preferred Securities Fund (USD $)	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
Preferred Securities Fund, Class A	479	700	938	1,621
Preferred Securities Fund, Class C	185	573	985	2,137
Preferred Securities Fund, Class P	87	271	471	1,049

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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 22.9% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in preferred securities at the time of purchase. Preferred securities generally pay fixed rate dividends (though some are adjustable rate) and typically have "preference" over common stock in the payment of dividends and the liquidation of a company's assets, but are junior to all forms of the company's debt. Most of the securities purchased by the Fund are preferred securities of companies rated at the time of purchase BBB- or higher by Standard & Poor's Rating Service ("S&P") or Baa3 or higher by Moody's Investor Service, Inc. ("Moody's") or, if unrated, of comparable quality in the opinion of the Sub-Advisor. The Fund also invests up to 15% of its assets in high yield, below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, the Sub-Advisor will determine whether the bond is of a quality comparable to those rated below investment grade).

The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the U.S. and non-U.S financial services (i.e., banking, insurance and commercial finance,) industry. The Fund also regularly invests in the real estate investment trust (i.e. REIT) and utility industries.

Principal Risks

The Fund may be an appropriate investment for investors who are seeking dividends to generate income or to reinvest for growth and are willing to accept fluctuations in the value of the investment.

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:

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.

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).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Industry Concentration Risk (Financial Services). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in financial services companies may be more susceptible to adverse economic or regulatory occurrences affecting financial services companies. Financial companies may be adversely affected in certain market cycles, including periods of rising interest rates, which may restrict the availability and increase the cost of capital, and declining economic conditions, which may cause credit losses due to financial difficulties of borrowers. Because many types of financial companies are especially vulnerable to these economic cycles, the Fund’s investments in these companies may lose significant value during such periods.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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. 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.

Performance

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Class A shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). These annual returns do not reflect sales charges; if they did, returns would be lower. The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principalfunds.com or by calling 1-800-222-5852.

Class A shares commenced operations on June 28, 2005, Class C shares were first sold on January 16, 2007, and Class P shares were first sold on September 27, 2010. The returns for Class A, C, and P shares, for the periods prior to those dates, are based on the performance of the Institutional Class shares adjusted to reflect the fees and expenses of Class A, C, and P shares. The adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares. Institutional Class shares were first sold on May 1, 2002.

Performance of a blended index shows how the Fund's performance compares to an index with similar investment objectives. Performance of the components of the blended index are also shown. The weightings for the Preferreds Blended Index are 50% BofA Merrill Lynch Fixed Rate Preferred Securities and 50% Barclays U.S. Tier I Capital Securities Index. The custom or blended index returns reflect the allocation in effect for the time period(s) for which fund returns are disclosed. Previous weightings or allocations of the custom or blended index are not restated.

Total Returns as of December 31 each year (Class A shares)

^[2]

The year-to-date return as of September 30, 2012 was 15.47% for Class A shares.

Highest return for a quarter during the period of the bar chart above:	Q2 ‘09	38.89	%
Lowest return for a quarter during the period of the bar chart above:	Q3 ‘08	-20.97	%

Average Annual Total Returns PFI Prospectus - Class A, C, P Preferred Securities Fund	1 Year	5 Years	Since Inception	Inception Date
Preferred Securities Fund, Class A	(2.67%)	3.27%	4.37%	May 01, 2002
Preferred Securities Fund, Class A After Taxes on Distributions	(4.47%)	1.18%	2.57%	May 01, 2002
Preferred Securities Fund, Class A After Taxes on Distributions and Sales	(1.42%)	1.60%	2.71%	May 01, 2002
Preferred Securities Fund, Class C	(0.39%)	3.31%	4.14%	May 01, 2002
Preferred Securities Fund, Class P	1.51%	4.20%	5.02%	May 01, 2002
BofA Merrill Lynch Fixed Rate Preferred Securities Index	4.11%	(1.19%)	2.42%	May 01, 2002
Barclays U.S. Tier I Capital Securities Index	(0.53%)	1.71%	4.87%	May 01, 2002
Preferreds Blended Index	1.81%	0.01%	3.38%	May 01, 2002

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Class A shares only and would be different for Class C and Class P shares.

Small-MidCap Dividend Income Fund

SMALL-MIDCAP DIVIDEND INCOME FUND

Objective:

The Fund primarily seeks to provide a relatively high level of current income and long-term growth of income

secondarily long-term growth of capital, while investing primarily in small- to mid-capitalization companies

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in 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 56 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 48 of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees PFI Prospectus - Class A, C, P Small-MidCap Dividend Income Fund	Small-MidCap Dividend Income Fund, Class A	Small-MidCap Dividend Income Fund, Class C	Small-MidCap Dividend Income Fund, Class P
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)	5.50%	none	none
Maximum Deferred Sales Charge (as a percentage)	1.00%	1.00%	none

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses PFI Prospectus - Class A, C, P Small-MidCap Dividend Income Fund		Small-MidCap Dividend Income Fund, Class A	Small-MidCap Dividend Income Fund, Class C		Small-MidCap Dividend Income Fund, Class P
Management Fees (as a percentage of Assets)		0.80%	0.80%		0.80%
Distribution and Service (12b-1) Fees		0.25%	1.00%		none
Other Expenses (as a percentage of Assets):		0.55%	0.39%	[1]	1.17%
Acquired Fund Fees and Expenses		0.10%	0.10%		0.10%
Expenses (as a percentage of Assets)		1.70%	2.29%		2.07%
Fee Waiver or Reimbursement	[2]	0.20%	0.04%		0.97%
Net Expenses (as a percentage of Assets)		1.50%	2.25%		1.10%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then 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 PFI Prospectus - Class A, C, P Small-MidCap Dividend Income Fund (USD $)	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Small-MidCap Dividend Income Fund, Class A	694	1,038	1,405	2,432
Small-MidCap Dividend Income Fund, Class C	328	712
Small-MidCap Dividend Income Fund, Class P	112	555	1,024	2,323

You would pay the following expenses if you did not redeem your shares:

Expense Example, No Redemption PFI Prospectus - Class A, C, P Small-MidCap Dividend Income Fund (USD $)	Expense Example, No Redemption, 1 Year	Expense Example, No Redemption, 3 Years	Expense Example, No Redemption, 5 Years	Expense Example, No Redemption, 10 Years
Small-MidCap Dividend Income Fund, Class A	694	1,038	1,405	2,432
Small-MidCap Dividend Income Fund, Class C	228	712
Small-MidCap Dividend Income Fund, Class P	112	555	1,024	2,323

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover 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 19.1% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in dividend-paying equity securities of companies with small to medium market capitalizations (those with market capitalizations ranging from between $200 million and $7 billion) at the time of purchase. The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund invests in the securities of foreign issuers, real estate investment trusts, preferred securities, convertible securities, fixed-income securities, master limited partnerships, and royalty trusts.

Principal Risks

The Fund may be an appropriate investment for investors who seek dividends to generate income or to reinvest for growth and who can accept fluctuations in the value of investments and the risks of investing in equity securities, the securities of foreign issuers, real estate investment trusts, preferred securities, convertible securities, fixed-income securities, master limited partnerships, and royalty trusts.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Convertible Securities Risk. Convertible securities can be bonds, notes, debentures, preferred stock or other securities which are convertible into common stock. Convertible securities are subject to both the credit and interest rate risks associated with fixed income securities and to the stock market risk associated with equity securities.

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.

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).

Master Limited Partnership ("MLP") Risk. MLPs are publicly-traded limited partnership interests or units. An MLP that invests in a particular industry (e.g., oil and gas) will be harmed by detrimental economic events within that industry. As partnerships, MLPs may be subject to less regulation (and less protection for investors) under state laws than corporations. In addition, MLPs may be subject to state taxation in certain jurisdictions, which may reduce the amount of income an MLP pays to its investors.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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. 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.

Royalty Trust Risk. A royalty trust generally acquires an interest in natural resource or chemical companies and distributes the income it receives to its investors. A sustained decline in demand for natural resource and related products could adversely affect royalty trust revenues and cash flows. Such a decline could result from a recession or other adverse economic conditions, an increase in the market price of the underlying commodity, higher taxes or other regulatory actions that increase costs, or a shift in consumer demand. Rising interest rates could adversely affect the performance, and limit the capital appreciation, of royalty trusts because of the increased availability of alternative investments at more competitive yields. Fund shareholders will indirectly bear their proportionate share of the royalty trusts' expenses.

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.

Performance

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 Russell 2500 Value Index.

[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 by paying, if necessary, expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2013. 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 shares, excluding interest expense. 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%, excluding interest expense. 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.

[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 attributable to Class A and Class C shares, and expenses identified as "Other Expenses" for Class P by paying, if necessary, expenses normally payable by the Fund, excluding interest expense and dividend and interest expense on short sales, through the period ending December 31, 2013. 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 2.00% for Class A and 2.75% for Class C shares, excluding interest expense and dividend and interest expense on short sales. 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%, excluding interest expense. 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.

[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 attributable to Class A and Class C shares by paying, if necessary, expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2013. The expense limit will maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.90% for Class A and 1.65% for Class C shares, excluding interest expense. 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.

[1] Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund’s expenses identified as "Other Expenses" for Class P by paying, if necessary, expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2013. The expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.20%, excluding interest expense. 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.

[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 attributable to Class A and Class C shares, and expenses identified as "Other Expenses" for Class P by paying, if necessary, expenses normally payable by the Fund, excluding interest expense and Acquired Fund Fees and Expenses, through the period ending December 31, 2013. 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 1.40% for Class A and 2.15% for Class C shares, excluding interest expense and Acquired Fund Fees and Expenses. 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%, excluding interest expense. 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.

[1] The year-to-date return as of September 30, 2012 was 7.85% for Class A shares.

[2] The year-to-date return as of September 30, 2012 was 15.47% for Class A shares.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Document Type

dei_DocumentType

485BPOS

Document Period End Date

dei_DocumentPeriodEndDate

Aug. 31, 2012

Registrant Name

dei_EntityRegistrantName

PRINCIPAL FUNDS INC

Central Index Key

dei_EntityCentralIndexKey

0000898745

Amendment Flag

dei_AmendmentFlag

false

Document Creation Date

dei_DocumentCreationDate

Dec. 27, 2012

Document Effective Date

dei_DocumentEffectiveDate

Dec. 28, 2012

PFI Prospectus - Class J

Risk/Return:

rr_RiskReturnAbstract

Prospectus Date

rr_ProspectusDate

Dec. 28, 2012

PFI Prospectus - Class J | Bond Market Index Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

BOND MARKET INDEX FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide current income.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s annualized portfolio turnover rate was 144.0% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

144.00%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

You would pay the following expenses if you did not redeem your shares:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in debt securities held by the Barclays U.S. Aggregate Bond Index (the "Index") at the time of purchase. The Index is composed of investment grade, fixed rate debt issues, including government, corporate, asset-backed, and mortgage-backed securities, with maturities of one year or more. The Fund employs a passive investment approach designed to attempt to track the performance of the Index. Under normal circumstances, the Fund maintains an average portfolio duration that is in line with the duration of the Barclays U.S. Aggregate Bond Index, which as of August 31, 2012 was 4.99 years. The Fund actively trades portfolio securities.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The Fund may be an appropriate investment for investors interested in investing in a fixed-income mutual fund and preferring a passive, rather than active, management style.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Fixed-Income Securities Risk. Fixed-income securities are subject to interest rate risk and credit quality risk. The market value of fixed-income securities generally declines when interest rates rise, and an issuer of fixed-income securities could default on its payment obligations.

Index Fund Investment Risk. More likely than not, an index fund will not provide investment performance that matches the index performance due to cashflows and the fees and expenses of the fund.

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.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Class J shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). These annual returns do not reflect sales charges; if they did, returns would be lower. The table shows, for Class J shares of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principalfunds.com or by calling 1-800-222-5852.

Life of Fund returns are measured from December 30, 2009, the date the Class J shares were first sold.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides an indication of the risks of investing in the Fund

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-222-5852

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.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.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns as of December 31 each year (Class J shares)

^[1]

Bar Chart Footnotes [Text Block]

rr_BarChartFootnotesTextBlock

The year-to-date return as of September 30, 2012 was 3.33% for Class J shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest return for a quarter during the period of the bar chart above:	Q3 ‘11	3.60	%
Lowest return for a quarter during the period of the bar chart above:	Q4 ‘10	-1.49	%

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

reflects no deduction for fees, expenses, or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns for the period ended December 31, 2011

PFI Prospectus - Class J | Bond Market Index Fund | Barclays Aggregate Bond Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Barclays Aggregate Bond Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

7.84%

Since Inception

rr_AverageAnnualReturnSinceInception

7.09%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Class J | Bond Market Index Fund | Bond Market Index Fund, Class J

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PBIJX

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.25%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.45%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.37%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

1.07%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.20%)

^[2]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.87%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

189

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

320

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

571

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,288

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

89

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

320

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

571

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

1,288

Annual Return 2010

rr_AnnualReturn2010

4.80%

Annual Return 2011

rr_AnnualReturn2011

6.77%

Year to Date Return, Label

rr_YearToDateReturnLabel

The year-to-date return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

3.33%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest return for a quarter during the period of the bar chart above:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2011

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

3.60%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest return for a quarter during the period of the bar chart above:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(1.49%)

Label

rr_AverageAnnualReturnLabel

Class J Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

5.77%

Since Inception

rr_AverageAnnualReturnSinceInception

5.72%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Class J | Bond Market Index Fund | Bond Market Index Fund, Class J | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class J Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

5.06%

Since Inception

rr_AverageAnnualReturnSinceInception

5.08%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Class J | Bond Market Index Fund | Bond Market Index Fund, Class J | After Taxes on Distributions and Sales

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class J Return After Taxes on Distribution and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

3.75%

Since Inception

rr_AverageAnnualReturnSinceInception

4.51%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 2009

PFI Prospectus - Class J | Preferred Securities Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

PREFERRED SECURITIES FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide current income.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s annualized portfolio turnover rate was 22.9% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

22.90%

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated 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 [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

You would pay the following expenses if you did not redeem your shares:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in preferred securities at the time of purchase. Preferred securities generally pay fixed rate dividends (though some are adjustable rate) and typically have "preference" over common stock in the payment of dividends and the liquidation of a company's assets, but are junior to all forms of the company's debt. Most of the securities purchased by the Fund are preferred securities of companies rated at the time of purchase BBB- or higher by Standard & Poor's Rating Service ("S&P") or Baa3 or higher by Moody's Investor Service, Inc. ("Moody's") or, if unrated, of comparable quality in the opinion of the Sub-Advisor. The Fund also invests up to 15% of its assets in below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, the Sub-Advisor will determine whether the bond is of a quality comparable to those rated below investment grade).

The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the U.S. and non-U.S financial services (i.e., banking, insurance and commercial finance,) industry. The Fund also regularly invests in the real estate investment trust (i.e. REIT) and utility industries.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the U.S. and non-U.S financial services (i.e., banking, insurance and commercial finance,) industry.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The Fund may be an appropriate investment for investors who are seeking dividends to generate income or to reinvest for growth and are willing to accept fluctuations in the value of the investment.

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:

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.

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).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Industry Concentration Risk (Financial Services). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in financial services companies may be more susceptible to adverse economic or regulatory occurrences affecting financial services companies. Financial companies may be adversely affected in certain market cycles, including periods of rising interest rates, which may restrict the availability and increase the cost of capital, and declining economic conditions, which may cause credit losses due to financial difficulties of borrowers. Because many types of financial companies are especially vulnerable to these economic cycles, the Fund’s investments in these companies may lose significant value during such periods.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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. 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.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Class J shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). These annual returns do not reflect sales charges; if they did, returns would be lower. The table shows, for Class J shares of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principalfunds.com or by calling 1-800-222-5852.

Class J shares were first sold on December 29, 2003. The returns for the periods prior to that date are based on the performance of the Institutional Class shares adjusted to reflect the fees and expenses of Class J shares. The adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares. The Institutional Class shares were first sold on May 1, 2002.

Performance of a blended index shows how the Fund's performance compares to an index with similar investment objectives. Performance of the components of the blended index are also shown. The weightings for the Preferreds Blended Index are 50% BofA Merrill Lynch Fixed Rate Preferred Securities and 50% Barclays U.S. Tier I Capital Securities Index. The custom or blended index returns reflect the allocation in effect for the time period(s) for which fund returns are disclosed. Previous weightings or allocations of the custom or blended index are not restated.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides an indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-222-5852

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.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.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns as of December 31 each year (Class J shares)

^[3]

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

These annual returns do not reflect sales charges; if they did, returns would be lower.

Bar Chart Footnotes [Text Block]

rr_BarChartFootnotesTextBlock

The year-to-date return as of September 30, 2012 was 15.24% for Class J shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest return for a quarter during the period of the bar chart above:	Q2 '09	38.56	%
Lowest return for a quarter during the period of the bar chart above:	Q3 '08	-21.11	%

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

reflects no deduction for fees, expenses, or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns for the period ended December 31, 2011

PFI Prospectus - Class J | Preferred Securities Fund | BofA Merrill Lynch Fixed Rate Preferred Securities Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

BofA Merrill Lynch Fixed Rate Preferred Securities Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

4.11%

5 Years

rr_AverageAnnualReturnYear05

(1.19%)

Since Inception

rr_AverageAnnualReturnSinceInception

2.42%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class J | Preferred Securities Fund | Barclays U.S. Tier I Capital Securities Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Barclays U.S. Tier I Capital Securities Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

(0.53%)

5 Years

rr_AverageAnnualReturnYear05

1.71%

Since Inception

rr_AverageAnnualReturnSinceInception

4.87%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class J | Preferred Securities Fund | Preferreds Blended Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Preferreds Blended Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

1.81%

5 Years

rr_AverageAnnualReturnYear05

0.01%

Since Inception

rr_AverageAnnualReturnSinceInception

3.38%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class J | Preferred Securities Fund | Preferred Securities Fund, Class J

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PPSJX

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.71%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.45%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.30%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

1.46%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.20%)

^[2]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.26%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

228

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

442

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

778

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,729

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

128

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

442

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

778

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

1,729

Annual Return 2003

rr_AnnualReturn2003

9.70%

Annual Return 2004

rr_AnnualReturn2004

3.57%

Annual Return 2005

rr_AnnualReturn2005

0.69%

Annual Return 2006

rr_AnnualReturn2006

6.11%

Annual Return 2007

rr_AnnualReturn2007

(8.69%)

Annual Return 2008

rr_AnnualReturn2008

(22.86%)

Annual Return 2009

rr_AnnualReturn2009

45.38%

Annual Return 2010

rr_AnnualReturn2010

15.81%

Annual Return 2011

rr_AnnualReturn2011

0.99%

Year to Date Return, Label

rr_YearToDateReturnLabel

year-to-date return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

15.24%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest return for a quarter during the period of the bar chart above:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

38.56%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest return for a quarter during the period of the bar chart above:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(21.11%)

Label

rr_AverageAnnualReturnLabel

Class J Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

0.04%

5 Years

rr_AverageAnnualReturnYear05

3.67%

Since Inception

rr_AverageAnnualReturnSinceInception

4.41%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class J | Preferred Securities Fund | Preferred Securities Fund, Class J | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class J Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

(1.80%)

5 Years

rr_AverageAnnualReturnYear05

1.66%

Since Inception

rr_AverageAnnualReturnSinceInception

2.68%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class J | Preferred Securities Fund | Preferred Securities Fund, Class J | After Taxes on Distributions and Sales

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class J Return After Taxes on Distribution and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

0.35%

5 Years

rr_AverageAnnualReturnYear05

2.00%

Since Inception

rr_AverageAnnualReturnSinceInception

2.80%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

[1] The year-to-date return as of September 30, 2012 was 3.33% for Class J shares.

[2] Principal Funds Distributor, Inc. ("the Distributor") has contractually agreed to limit the Distribution Fees attributable to Class J through December 31, 2013. The limit will maintain the level of Distribution Fees not to exceed 0.25%. It is expected that the expense limit will continue through the period disclosed; however, Principal Funds, Inc. and the Distributor, the parties to the agreement, may agree to terminate the expense limit prior to the end of the period.

[3] The year-to-date return as of September 30, 2012 was 15.24% for Class J shares.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Document Type

dei_DocumentType

485BPOS

Document Period End Date

dei_DocumentPeriodEndDate

Aug. 31, 2012

Registrant Name

dei_EntityRegistrantName

PRINCIPAL FUNDS INC

Central Index Key

dei_EntityCentralIndexKey

0000898745

Amendment Flag

dei_AmendmentFlag

false

Document Creation Date

dei_DocumentCreationDate

Dec. 27, 2012

Document Effective Date

dei_DocumentEffectiveDate

Dec. 28, 2012

PFI Prospectus - Class A, C, P

Risk/Return:

rr_RiskReturnAbstract

Prospectus Date

rr_ProspectusDate

Dec. 28, 2012

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

DIVERSIFIED REAL ASSET FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks a long-term total return in excess of inflation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in 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 56 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 48 of the Fund’s Statement of Additional Information.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund's annualized portfolio turnover rate was 107.3% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

107.30%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $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 [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

You would pay the following expenses if you did not redeem your shares:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund seeks to achieve its investment objective by allocating its assets among the following general investment categories: inflation-indexed bonds, securities of real estate companies, commodity index-linked notes, fixed-income securities, securities of natural resource companies, master limited partnerships (MLPs), publicly-listed infrastructure companies, and floating rate debt. The Fund actively trades portfolio securities.

The Fund concentrates its investments (invests 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. Except for its policy to concentrate in the real estate and energy/natural resources industries, the Fund retains considerable latitude in allocating its assets.

A portion of the Fund's assets is 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 is 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 are primarily short-term U.S. Treasury and Agency notes and bonds.

A portion of the Fund's assets is invested in the real estate industry. The Fund invests in equity securities of global companies principally engaged in the real estate industry ("real estate companies"). A real estate company has at least 50% of its assets, income or profits derived from products or services related to the real estate industry. Real estate companies include real estate investment trusts ("REITs"), REIT-like entities, and companies with substantial real estate holdings such as paper, lumber, hotel and entertainment companies as well as building supply manufacturers, mortgage lenders, and mortgage servicing companies.

A portion of the Fund's assets is invested in securities of 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, oil and natural gas, timberland, undeveloped real property and agricultural commodities.

A portion of the Fund's assets is invested in MLPs. Generally, MLPs are engaged in the transportation, storage, processing, refining, marketing, production, or mining of natural resources. The Fund invests primarily in the mid-stream category of MLPs, which is generally comprised of pipelines used to gather, process, transport, and distribute natural gas, crude oil, and refined petroleum products.

A portion of the Fund’s assets is invested in domestic and foreign publicly-listed infrastructure companies. Publicly-listed infrastructure equity securities trade on an exchange and include, but are not limited to, companies involved in the ownership and/or operations of infrastructure assets within the transportation, communications, water, electricity transmission and distribution, and oil and gas storage, processing and transportation industries.

A portion of the Fund’s assets is invested in below-investment-grade (sometimes called “junk”) or comparable unrated floating rate debt (also known as bank loans, syndicated loans, leveraged loans or senior floating rate interests). Floating rate debt has a variable coupon that resets periodically, with interest payments determined by a representative interest rate index (e.g. LIBOR or the federal funds rate) plus a fixed spread. As a result, the coupon payments vary, or “float” with prevailing market interest rates.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the real estate and energy/natural resources industries.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The 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:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.

Bank Loans Risk. Changes in economic conditions are likely to cause issuers of bank loans (also known as senior floating rate interests) to be unable to meet their obligations. In addition, the value of the collateral securing the loan may decline, causing a loan to be substantially unsecured. Underlying credit agreements governing the bank loans, reliance on market makers, priority of repayment and overall market volatility may harm the liquidity of loans.

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.

Commodity-Related Investment Risk. The value of commodities investments will generally be affected by overall market movements and factors specific to a particular industry or commodity, which may include weather, embargoes, tariffs, and economic health, political, international regulatory and other developments. Exposure to the commodities markets may subject the fund to greater volatility than investments in traditional securities.

Counterparty Risk. Counterparty risk is the risk that the counterparty to a 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).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Industry Concentration Risk (Energy/Natural Resources). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in energy/natural resource companiesmay be affected by numerous factors, including events occurring in nature, inflationary pressures, international politics, the success of exploration projects, commodity prices, energy conservation, taxes and other government regulations. In addition, interest rates and general economic conditions may affect the demand for energy/natural resources. For example, events occurring in nature (such as earthquakes or fires in prime energy/natural resource areas) and political events (such as coups, military confrontations or acts of terrorism) can affect overall supply of energy/natural resources and the value of companies involved in energy/natural resources.

Industry Concentration Risk (Real Estate). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in the real estate industry can be subject to the risks associated with direct ownership of real estate, securities of companies in the real estate industry, and/or real estate investment trusts.

Leverage Risk. Leverage created by borrowing or certain types of transactions or investments, 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. 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.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Class A shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principal.com or by calling 1-800-222-5852.

Class A and Class C shares commenced operations on March 16, 2010, Class P shares were first sold on September 27, 2010. The returns for Class P shares, for the periods prior to that date, are based on the performance of the Institutional Class shares adjusted to reflect the fees and expenses of Class P shares. The adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares. Institutional Class shares were first sold on March 16, 2010.

Performance of a blended index shows how the Fund’s performance compares to an index with similar investment objectives. Performance of the components of the blended index are also shown. The Diversified Real Asset Custom Index was composed of 30% Barclays U.S. Treasury TIPS Index, 20% MSCI U.S. REIT Index, 25% Dow Jones UBS Commodity Index, 15% S&P N.A. Natural Resources Index, and 10% Tortoise MLP Index. Effective January 31, 2012, the weightings for the Diversified Real Asset Custom Index changed to 30% Barclays U.S. Treasury TIPS Index, 20% Dow Jones UBS Commodity Index, 10% S&P N.A. Natural Resources Index, 10% Tortoise MLP Index, 10% Dow Jones Brookfield Global Infrastructure Index, 10% Credit Suisse Leveraged Loan Index, and 10% FTSE EPRA/NAREIT Developed Index. The custom or blended index returns reflect the allocation in effect for the time period(s) for which fund returns are disclosed. Previous weightings or allocations of the custom or blended index are not restated.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides an indication of the risks of investing in the Fund.

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.

Bar Chart [Heading]

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Total Returns as of December 31 each year (Class A shares)

^[1]

Bar Chart Footnotes [Text Block]

rr_BarChartFootnotesTextBlock

The year-to-date return as of September 30, 2012 was 7.85% for Class A shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest return for a quarter during the period of the bar chart above:	Q4 '11	7.04	%
Lowest return for a quarter during the period of the bar chart above:	Q3 '11	-9.20	%

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

reflects no deduction for fees, expenses, or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class A shares only and would be different for Class C and Class P shares.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Class A shares only and would be different for Class C and Class P shares.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns for the periods ended December 31, 2011

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | Barclays US Treasury TIPS Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Barclays US Treasury TIPS Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

13.56%

Since Inception

rr_AverageAnnualReturnSinceInception

10.42%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | MSCI US REIT Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

MSCI US REIT Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

8.69%

Since Inception

rr_AverageAnnualReturnSinceInception

14.22%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | Dow Jones UBS Commodity Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Dow Jones UBS Commodity Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

(13.32%)

Since Inception

rr_AverageAnnualReturnSinceInception

3.32%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | S&P North American Natural Resources Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

S&P North American Natural Resources Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

(7.35%)

Since Inception

rr_AverageAnnualReturnSinceInception

6.85%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | Tortoise MLP Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Tortoise MLP Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

13.73%

Since Inception

rr_AverageAnnualReturnSinceInception

22.36%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | Dow Jones Brookfield Global Infrastructure Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Dow Jones Brookfield Global Infrastructure Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

13.75%

Since Inception

rr_AverageAnnualReturnSinceInception

14.07%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | Credit Suisse Leveraged Loan Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Credit Suisse Leveraged Loan Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

1.82%

Since Inception

rr_AverageAnnualReturnSinceInception

5.26%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | FTSE EPRA/NAREIT Developed Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

FTSE EPRA/NAREIT Developed Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

(5.82%)

Since Inception

rr_AverageAnnualReturnSinceInception

5.28%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | Diversified Real Asset Custom Index

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Diversified Real Asset Custom Index (reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

2.80%

Since Inception

rr_AverageAnnualReturnSinceInception

10.63%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | Diversified Real Asset Fund, Class A

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PRDAX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

3.75%

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.84%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.35%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

1.44%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.19%)

^[2]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.25%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

498

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

795

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,115

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,019

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

498

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

795

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,115

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

2,019

Annual Return 2011

rr_AnnualReturn2011

0.41%

Year to Date Return, Label

rr_YearToDateReturnLabel

year-to-date return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

7.85%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest return for a quarter during the period of the bar chart above:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Dec. 31, 2011

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

7.04%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest return for a quarter during the period of the bar chart above:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(9.20%)

Label

rr_AverageAnnualReturnLabel

Class A Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

(3.38%)

Since Inception

rr_AverageAnnualReturnSinceInception

6.24%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | Diversified Real Asset Fund, Class A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class A Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

(3.93%)

Since Inception

rr_AverageAnnualReturnSinceInception

5.79%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | Diversified Real Asset Fund, Class A | After Taxes on Distributions and Sales

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class A Return After Taxes on Distribution and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

(1.86%)

Since Inception

rr_AverageAnnualReturnSinceInception

5.15%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | Diversified Real Asset Fund, Class C

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PRDCX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.84%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.29%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

2.13%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.13%)

^[2]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

2.00%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

12/31/2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

303

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

654

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,132

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,452

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

203

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

654

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,132

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

2,452

Label

rr_AverageAnnualReturnLabel

Class C Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

(1.22%)

Since Inception

rr_AverageAnnualReturnSinceInception

7.82%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Diversified Real Asset Fund | Diversified Real Asset Fund, Class P

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PRDPX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

none

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.84%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.29%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

1.13%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.09%)

^[2]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.04%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

106

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

350

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

614

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,367

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

106

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

350

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

614

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

1,367

Label

rr_AverageAnnualReturnLabel

Class P Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

0.58%

Since Inception

rr_AverageAnnualReturnSinceInception

8.81%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 16, 2010

PFI Prospectus - Class A, C, P | Global Multi-Strategy Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GLOBAL MULTI-STRATEGY FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to achieve long-term capital appreciation with an emphasis on positive total returns and relatively low volatility.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in 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 56 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 48 of the Fund’s Statement of Additional Information.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. From October 14, 2011, date operations commenced, through August 31, 2012, the Fund’s annualized portfolio turnover rate was 196.0% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

196.00%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in Principal Funds, Inc.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

100,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

You would pay the following expenses if you did not redeem your shares:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Principal Management Corporation ("Principal"), the Fund's investment adviser, allocates the Fund's assets among one or more of the investment strategies described below, which are executed by one or more of the Fund's sub-advisors. In making these allocations, Principal seeks to combine the strategies of the sub-advisors efficiently and systematically so that the Fund generates, through a diversified set of investment strategies, a positive total return with relatively low volatility and low sensitivity or correlation to market indices. By allocating the Fund’s assets among a variety of investment strategies, which will vary from time-to-time, the Fund seeks to lessen risk and reduce volatility. Principal may also direct a sub-advisor to reduce or omit its investment in certain assets or asset classes in an effort to achieve its desired combination of the Fund's strategies.

In pursuing its strategies, the Fund invests in a broad range of instruments including, but not limited to, equities, bonds, currencies, convertible securities and derivatives such as futures, options, swaps (including, for example, credit default, interest rate, and currency swaps) and forwards. The Fund intends to engage in derivative transactions to gain exposure to a variety of securities or attempt to reduce risk. The Fund intends to invest in securities that are tied economically to a number of countries throughout the world, including the U.S.; however, the Fund has no requirements as to the amount of its net assets that it invests in foreign securities. The Fund is considered non-diversified, which means it can invest a higher percentage of assets in securities of individual issuers than a diversified fund. The Fund actively trades securities.

Some of the strategies take long and/or short positions. When taking a short position, the Fund may sell an instrument that it does not own and then borrow to meet its settlement obligations. The Fund may take short positions in futures, forwards or swaps. A short position will benefit from a decrease in price of the underlying instrument and will lose value if the price of the underlying instrument increases. Long positions will profit if the value of the instrument increases. Simultaneously engaging in long investing and short selling reduces the net exposure of the overall portfolio to general market movements. Relative value positions may be taken as well in the various strategies. Relative value strategies capitalize on price differences between similar securities or relative value among securities of the same company.

The Fund may use all or some of the following strategies to varying degrees, depending on market conditions, and may add additional strategies. Principal may allocate 0 to 100% of the Fund’s assets to any of these strategies at any time.

Credit Long/Short and Distressed Credit. This strategy utilizes a flexible investment approach that allocates investments across a global range of investment opportunities related to credit, currencies and interest rates, while employing risk management strategies. This strategy invests in fixed income securities and instruments and may invest in both investment-grade securities and below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, the Sub-Advisor will determine whether the bond is of a quality comparable to those rated below investment grade). This strategy may also invest in the following securities: securities denominated in foreign currencies and in U.S. dollar denominated securities of foreign issuers, preferred securities, convertible securities, Rule 144A securities, mortgage or asset-backed securities, floating rate debt (including bank loans), distressed investments, emerging markets, equities and derivative instruments, such as options, futures contracts, forwards or swap agreements. This strategy may utilize derivative instruments in an effort to minimize volatility. Also, at times, this strategy expects to gain its investment exposure substantially through the use of derivatives. The notional value of this strategy’s long and short investment exposures may at times each reach 100% of the assets invested in this strategy (excluding instruments used primarily for duration, yield curve, and interest rate management and short-term investments), although these exposures may be higher or lower at any given time. This strategy may purchase or sell securities on a when-issued, delayed delivery or forward commitment basis and may engage in short sales. The strategy may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as buy backs or dollar rolls).

Equity Long/Short. This strategy provides long and short exposure to a diversified portfolio of equities which involves simultaneously investing in equities (i.e., investing long) the sub-advisor expects to increase in value (securities the sub-advisor believes are undervalued) and either selling equities (i.e., short sales or short selling) the sub-advisor expects to decrease in value (securities the sub-advisor believes are overvalued) or hedging equity market exposure in another way (i.e., by using derivatives such as futures or options). Long/short equity expresses industry views by emphasizing certain industries and it also seeks to exploit pricing inefficiencies between related equity securities. An example of exploiting pricing inefficiencies between related equity securities is building a portfolio containing long positions in the strongest companies of several industries and taking short positions in companies showing signs of weakness in the corresponding industries. This strategy has available two methods of analysis: fundamental analysis, a method of security analysis that involves examining a company's financial statements and operations, especially sales, earnings, products, management and competition and quantitative analysis, a method of security analysis that involves use of mathematical models to examine a company's measurable characteristics such as revenue, earnings, margins and market share.

Equity Market Neutral. This strategy seeks to profit by exploiting pricing inefficiencies between related equity securities and neutralizing exposure to market risk by maintaining long and short positions. Equity market neutral is not expected to have industry overweights.

Dedicated Short Bias. The dedicated short bias strategy seeks to profit by shorting stocks that have negative market sentiment and neutralizing exposure to market risk by maintaining long and short positions.

Global Macro. Global macro strategies seek to profit from movement in the prices of securities that are highly sensitive to macroeconomic conditions, across a broad spectrum of assets. This strategy provides long and short exposure to developed country equities, currencies, and bonds markets.

Emerging Markets. This strategy seeks to profit from investing in equities, bonds, and currencies of issuers in emerging markets. This strategy provides long and short exposure to emerging country equity, debt, and currency markets, and long and short exposure to a basket of liquid equity securities traded on emerging and developed market exchanges.

Convertible Arbitrage. Convertible arbitrage strategies seek to profit from the complexity of the pricing of convertible bonds (which contain elements of both a fixed income security and an equity option) by structuring trades using multiple securities within the capital structure of a convertible bond issuer. The Fund may purchase the convertible bond of a given issuer and simultaneously sell short the common stock of that same issuer to take advantage of a mispricing of either security. This strategy takes positions in various global convertible debt and preferred securities and an offsetting position in various global equities directly linked to the convertible securities. In implementing this strategy, the Fund may use derivatives to hedge against a decline in interest rates or credit exposure.

Currency Instruments, Futures Contracts, Futures-Related Instruments and Equity Swaps. These strategies seek to profit from the design and implementation of quantitative selection models to help predict upcoming movements in any combination of fixed income, currency, or equity markets. This strategy provides long and short exposure to developed country equities, bonds and currency markets and long and short exposure to emerging country equity and currency markets.

Event Driven. Event driven strategies seek to profit from investing in the securities of companies based not on a value or growth investment style but rather on the basis that a specific event or catalyst will affect future prices. This strategy attempts to capitalize on price discrepancies and returns generated by corporate activity, such as merger arbitrage. In merger arbitrage, the Fund will employ a diversified, disciplined strategy to attempt to capture the returns from holding a long/short portfolio of stocks of companies involved in mergers.

Fixed Income Arbitrage. Fixed income arbitrage seeks to profit from exploiting mispricing of various, liquid fixed income or interest rate sensitive securities. This strategy provides long and short exposure to developed country bond and currency markets, long and short exposure to investment grade credit markets and long and short exposure to forward mortgage-backed securities trading in the to be announced (“TBA”) market.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The Fund may be an appropriate investment for investors who seek long-term capital appreciation and who can accept the risks of investing in a variety of global markets and a variety of instruments.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Active Trading Risk. Actively trading portfolio securities may accelerate realization of taxable gains and losses, lower fund performance and may result in high portfolio turnover rates and increased brokerage costs.

Arbitrage Trading Risk. The underlying relationships between securities in which the fund takes arbitrage investment positions may change in an adverse manner, in which case the fund may realize losses.

Asset Allocation Risk. A fund's selection and weighting of asset classes may cause it to underperform other funds with a similar investment objective.

Bank Loans Risk. Changes in economic conditions are likely to cause issuers of bank loans (also known as senior floating rate interests) to be unable to meet their obligations. In addition, the value of the collateral securing the loan may decline, causing a loan to be substantially unsecured. Underlying credit agreements governing the bank loans, reliance on market makers, priority of repayment and overall market volatility may harm the liquidity of loans.

Basis Risk. A hedge using derivatives and/or securities could expose the fund to basis risk. Basis risk could arise when the change in price of the hedge may not match the change in price of the asset it hedges. In other words, the hedge moves in a direction that does not match the asset it is trying to hedge.

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.

Convertible Securities Risk. Convertible securities can be bonds, notes, debentures, preferred stock or other securities which are convertible into common stock. Convertible securities are subject to both the credit and interest rate risks associated with fixed income securities and to the stock market risk associated with equity securities.

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.

Distressed Investments Risk. A fund’s investment in instruments involving loans, loan participations, bonds, notes, non-performing and sub-performing mortgage loans, many of which are not publicly traded, may involve a substantial degree of risk for the following reasons. These instruments may become illiquid and the prices of such instruments may be extremely volatile. Valuing such instruments may be difficult and a fund may lose all of its investment, or it may be required to accept cash or securities with a value less than the fund’s original investment. Issuers of distressed securities are typically in a weak financial condition and may default, in which case the fund may lose its entire investment.

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.

Event-Driven Trading Risk. Event-driven trading involves the risk that the special situation may not occur as anticipated, if at all, and that the market price of a stock declines.

Fixed-Income Securities Risk. Fixed-income securities are subject to interest rate risk and credit quality risk. The market value of fixed-income securities generally declines when interest rates rise, and an issuer of fixed-income securities could default on its payment obligations.

Foreign Securities Risk. The risks of foreign securities include loss of value as a result of: political or economic instability; nationalization, expropriation or confiscatory taxation; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

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.

Non-Diversification Risk. A non-diversified fund may invest a high percentage of its assets in the securities of a small number of issuers and is more likely than diversified funds to be significantly affected by a specific security’s poor performance.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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).

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.

Short Sale Risk. A short sale involves the sale by the fund of a security that it does not own with the hope of purchasing the same security at a later date at a lower price. A fund may also enter into a short derivative position through a futures contract or swap agreement. If the price of the security or derivative has increased during this time, then the fund will incur a loss equal to the increase in price from the time that the short sale was entered into plus any premiums and interest paid to the third party. Therefore, short sales involve the risk that losses may be exaggerated, potentially losing more money than the actual cost of the investment. Also, there is the risk that the third party to the short sale may fail to honor its contract terms, causing a loss to the fund.

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

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

A non-diversified fund may invest a high percentage of its assets in the securities of a small number of issuers and is more likely than diversified funds to be significantly affected by a specific security’s poor performance.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

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 HRFI (Hedge Fund Research Inc.) Funds-of-Funds Composite Index.

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

No performance information is shown because the Fund has not yet had a calendar year of performance.

PFI Prospectus - Class A, C, P | Global Multi-Strategy Fund | Global Multi-Strategy Fund, Class A

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PMSAX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

3.75%

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

1.60%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Component1 Other Expenses

rr_Component1OtherExpensesOverAssets

0.70%

Component2 Other Expenses

rr_Component2OtherExpensesOverAssets

1.07%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

3.62%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.92%)

^[3]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

2.70%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

638

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

1,361

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

2,103

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

4,052

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

638

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

1,361

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

2,103

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

4,052

PFI Prospectus - Class A, C, P | Global Multi-Strategy Fund | Global Multi-Strategy Fund, Class C

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PMSCX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

1.60%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Component1 Other Expenses

rr_Component1OtherExpensesOverAssets

0.70%

Component2 Other Expenses

rr_Component2OtherExpensesOverAssets

0.45%

^[4]

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

3.75%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.30%)

^[3]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

3.45%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

448

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

1,119

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

348

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

1,119

PFI Prospectus - Class A, C, P | Global Multi-Strategy Fund | Global Multi-Strategy Fund, Class P

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PMSPX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

none

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

1.60%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Component1 Other Expenses

rr_Component1OtherExpensesOverAssets

0.70%

Component2 Other Expenses

rr_Component2OtherExpensesOverAssets

10.50%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

12.80%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(10.30%)

^[3]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

2.50%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

12/31/2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

253

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

2,676

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

4,736

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

8,635

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

253

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

2,676

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

4,736

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

8,635

PFI Prospectus - Class A, C, P | Opportunistic Municipal Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

OPPORTUNISTIC MUNICIPAL FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide a high level of income that is exempt from federal income tax while protecting investors’ capital.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in 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 56 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 48 of the Fund’s Statement of Additional Information.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. From June 13, 2012, date operations commenced, through August 31, 2012, the Fund’s annualized portfolio turnover rate was 93.8% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

93.80%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $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 [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

You would pay the following expenses if you did not redeem your shares:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in municipal obligations (securities issued by or on behalf of state or local governments and other public authorities). Many of these are from California. Municipal obligations pay interest that is exempt from federal income tax. The Fund has a flexible investment strategy and invests in obligations of any duration and credit quality, including below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, the Sub-Advisor will determine whether the bond is of a quality comparable to those rated below investment grade).

The Fund invests in other debt obligations, including (but not limited to) taxable municipal obligations, U.S. Treasury securities, obligations of the U.S. Government, its agencies and instrumentalities (“Agency Securities”) and inverse floating rate obligations, which are generally more volatile than other types of municipal obligations. The Fund invests in exchange-traded funds (ETFs) to gain exposure to the municipal market.

The Fund purchases derivative instruments, which derive their value from another instrument, security or index. The Fund purchases or sells various kinds of financial futures contracts to hedge against changes in interest rates or as a substitute for the purchase of portfolio securities. The Fund also enters into interest rate swaps and credit derivatives, which includes credit default swaps.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The Fund may be an appropriate investment for investors who are seeking monthly, federally tax-exempt dividends to produce income or to reinvest for modest growth and are willing to accept fluctuations in the value of their investment.

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:

Basis Risk. A hedge using derivatives and/or securities could expose the fund to basis risk. Basis risk could arise when the change in price of the hedge may not match the change in price of the asset it hedges. In other words, the hedge moves in a direction that does not match the asset it is trying to hedge.

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 may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and produce disproportionate losses.

Exchange-Traded Funds ("ETFs") Risk. An ETF is subject to the risks associated with direct ownership of the securities comprising the index on which the ETF is based. Fund shareholders indirectly bear their proportionate share of the expenses of the ETFs in which the fund invests.

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.

Geographic Concentration Risk. A fund that invests significant portions of its assets in particular geographic areas (such as California or Illinois) has greater exposure than other funds to economic conditions and developments in those areas.

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Inverse Floating Rate Investments. Inverse floating rate investments are extremely sensitive to changes in interest rates and in some cases their market value may be extremely volatile.

Leverage Risk. Leverage created by borrowing or certain types of transactions or investments, such as reverse repurchase agreements, loans of portfolio securities, and the use of when-issued, delayed delivery or forward commitment transactions, or derivative instruments, may impair the fund’s liquidity, cause it to liquidate positions at an unfavorable time, increase volatility of the fund’s net asset value, or diminish the fund’s performance.

Municipal Securities Risk. Principal and interest payments on municipal securities may not be guaranteed by the issuing body and may be payable only from a particular source. That source may not perform as expected and payment obligations may not be made or made on time.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

U.S. Government Securities Risk. Yields available from U.S. government securities are generally lower than yields from many other fixed-income securities.

U.S. Government Sponsored Securities Risk. Securities issued by U.S. government-sponsored or -chartered enterprises such as the Federal Home Loan Mortgage Corporation, the Federal National Mortgage Association, and the Federal Home Loan Banks are not issued or guaranteed by the U.S. Treasury.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance will be benchmarked against the Barclays Municipal Bond Index.

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

No performance information is shown because the Fund has not yet had a calendar year of performance.

PFI Prospectus - Class A, C, P | Opportunistic Municipal Fund | Opportunistic Municipal Fund, Class A

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PMOAX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

3.75%

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.50%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Component1 Other Expenses

rr_Component1OtherExpensesOverAssets

0.23%

Component2 Other Expenses

rr_Component2OtherExpensesOverAssets

0.44%

^[4]

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

1.42%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.29%)

^[5]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.13%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

486

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

780

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

486

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

780

PFI Prospectus - Class A, C, P | Opportunistic Municipal Fund | Opportunistic Municipal Fund, Class C

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PMODX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.50%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Component1 Other Expenses

rr_Component1OtherExpensesOverAssets

0.23%

Component2 Other Expenses

rr_Component2OtherExpensesOverAssets

0.47%

^[4]

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

2.20%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.32%)

^[5]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.88%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

291

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

657

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

191

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

657

PFI Prospectus - Class A, C, P | Preferred Securities Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

PREFERRED SECURITIES FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide current income.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in 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 56 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 48 of the Fund’s Statement of Additional Information.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund's annualized portfolio turnover rate was 22.9% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

22.90%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in Principal Funds, Inc.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

100,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

You would pay the following expenses if you did not redeem your shares:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in preferred securities at the time of purchase. Preferred securities generally pay fixed rate dividends (though some are adjustable rate) and typically have "preference" over common stock in the payment of dividends and the liquidation of a company's assets, but are junior to all forms of the company's debt. Most of the securities purchased by the Fund are preferred securities of companies rated at the time of purchase BBB- or higher by Standard & Poor's Rating Service ("S&P") or Baa3 or higher by Moody's Investor Service, Inc. ("Moody's") or, if unrated, of comparable quality in the opinion of the Sub-Advisor. The Fund also invests up to 15% of its assets in high yield, below investment grade bonds (sometimes called “high yield bonds” or "junk bonds") which are rated at the time of purchase Ba1 or lower by Moody's and BB+ or lower by S&P (if the bond has been rated by only one of those agencies, that rating will determine whether the bond is below investment grade; if the bond has not been rated by either of those agencies, the Sub-Advisor will determine whether the bond is of a quality comparable to those rated below investment grade).

The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the U.S. and non-U.S financial services (i.e., banking, insurance and commercial finance,) industry. The Fund also regularly invests in the real estate investment trust (i.e. REIT) and utility industries.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund concentrates its investments (invests more than 25% of its net assets) in securities in the U.S. and non-U.S financial services (i.e., banking, insurance and commercial finance,) industry.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The Fund may be an appropriate investment for investors who are seeking dividends to generate income or to reinvest for growth and are willing to accept fluctuations in the value of the investment.

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:

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.

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).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Industry Concentration Risk (Financial Services). A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries. A fund concentrating in financial services companies may be more susceptible to adverse economic or regulatory occurrences affecting financial services companies. Financial companies may be adversely affected in certain market cycles, including periods of rising interest rates, which may restrict the availability and increase the cost of capital, and declining economic conditions, which may cause credit losses due to financial difficulties of borrowers. Because many types of financial companies are especially vulnerable to these economic cycles, the Fund’s investments in these companies may lose significant value during such periods.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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. 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.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides an indication of the risks of investing in the Fund. The bar chart shows the investment returns of the Fund’s Class A shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). These annual returns do not reflect sales charges; if they did, returns would be lower. The table shows, for each share class of the Fund and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare to the returns of one or more broad-based market indices. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information online at www.principalfunds.com or by calling 1-800-222-5852.

Class A shares commenced operations on June 28, 2005, Class C shares were first sold on January 16, 2007, and Class P shares were first sold on September 27, 2010. The returns for Class A, C, and P shares, for the periods prior to those dates, are based on the performance of the Institutional Class shares adjusted to reflect the fees and expenses of Class A, C, and P shares. The adjustments result in performance for such periods that is no higher than the historical performance of the Institutional Class shares. Institutional Class shares were first sold on May 1, 2002.

Performance of a blended index shows how the Fund's performance compares to an index with similar investment objectives. Performance of the components of the blended index are also shown. The weightings for the Preferreds Blended Index are 50% BofA Merrill Lynch Fixed Rate Preferred Securities and 50% Barclays U.S. Tier I Capital Securities Index. The custom or blended index returns reflect the allocation in effect for the time period(s) for which fund returns are disclosed. Previous weightings or allocations of the custom or blended index are not restated.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides an indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-222-5852

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.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.

Bar Chart [Heading]

rr_BarChartHeading

Total Returns as of December 31 each year (Class A shares)

^[6]

Bar Chart Footnotes [Text Block]

rr_BarChartFootnotesTextBlock

The year-to-date return as of September 30, 2012 was 15.47% for Class A shares.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest return for a quarter during the period of the bar chart above:	Q2 ‘09	38.89	%
Lowest return for a quarter during the period of the bar chart above:	Q3 ‘08	-20.97	%

Index No Deduction for Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

reflects no deduction for fees, expenses, or taxes

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class A shares only and would be different for Class C and Class P shares.

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Class A shares only and would be different for Class C and Class P shares.

Caption

rr_AverageAnnualReturnCaption

Average Annual Total Returns for the periods ended December 31, 2011

PFI Prospectus - Class A, C, P | Preferred Securities Fund | BofA Merrill Lynch Fixed Rate Preferred Securities Index

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

4.11%

5 Years

rr_AverageAnnualReturnYear05

(1.19%)

Since Inception

rr_AverageAnnualReturnSinceInception

2.42%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class A, C, P | Preferred Securities Fund | Barclays U.S. Tier I Capital Securities Index

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

(0.53%)

5 Years

rr_AverageAnnualReturnYear05

1.71%

Since Inception

rr_AverageAnnualReturnSinceInception

4.87%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class A, C, P | Preferred Securities Fund | Preferreds Blended Index

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

1.81%

5 Years

rr_AverageAnnualReturnYear05

0.01%

Since Inception

rr_AverageAnnualReturnSinceInception

3.38%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class A, C, P | Preferred Securities Fund | Preferred Securities Fund, Class A

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PPSAX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

3.75%

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.71%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.10%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

1.06%

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.06%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

479

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

700

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

938

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,621

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

479

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

700

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

938

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

1,621

Annual Return 2003

rr_AnnualReturn2003

10.06%

Annual Return 2004

rr_AnnualReturn2004

3.74%

Annual Return 2005

rr_AnnualReturn2005

1.05%

Annual Return 2006

rr_AnnualReturn2006

6.67%

Annual Return 2007

rr_AnnualReturn2007

(8.29%)

Annual Return 2008

rr_AnnualReturn2008

(22.42%)

Annual Return 2009

rr_AnnualReturn2009

46.15%

Annual Return 2010

rr_AnnualReturn2010

16.04%

Annual Return 2011

rr_AnnualReturn2011

1.17%

Year to Date Return, Label

rr_YearToDateReturnLabel

year-to-date return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

15.47%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest return for a quarter during the period of the bar chart above:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

38.89%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest return for a quarter during the period of the bar chart above:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(20.97%)

1 Year

rr_AverageAnnualReturnYear01

(2.67%)

5 Years

rr_AverageAnnualReturnYear05

3.27%

Since Inception

rr_AverageAnnualReturnSinceInception

4.37%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class A, C, P | Preferred Securities Fund | Preferred Securities Fund, Class A | After Taxes on Distributions

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

(4.47%)

5 Years

rr_AverageAnnualReturnYear05

1.18%

Since Inception

rr_AverageAnnualReturnSinceInception

2.57%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class A, C, P | Preferred Securities Fund | Preferred Securities Fund, Class A | After Taxes on Distributions and Sales

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

(1.42%)

5 Years

rr_AverageAnnualReturnYear05

1.60%

Since Inception

rr_AverageAnnualReturnSinceInception

2.71%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class A, C, P | Preferred Securities Fund | Preferred Securities Fund, Class C

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PRFCX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.71%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.11%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

1.82%

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.82%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

285

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

573

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

985

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,137

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

185

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

573

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

985

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

2,137

1 Year

rr_AverageAnnualReturnYear01

(0.39%)

5 Years

rr_AverageAnnualReturnYear05

3.31%

Since Inception

rr_AverageAnnualReturnSinceInception

4.14%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class A, C, P | Preferred Securities Fund | Preferred Securities Fund, Class P

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PPSPX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

none

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.71%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.14%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.85%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[7]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.85%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

87

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

271

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

471

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,049

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

87

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

271

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

471

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

1,049

1 Year

rr_AverageAnnualReturnYear01

1.51%

5 Years

rr_AverageAnnualReturnYear05

4.20%

Since Inception

rr_AverageAnnualReturnSinceInception

5.02%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 01, 2002

PFI Prospectus - Class A, C, P | Small-MidCap Dividend Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

SMALL-MIDCAP DIVIDEND INCOME FUND

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund primarily seeks to provide a relatively high level of current income and long-term growth of income

Objective, Secondary [Text Block]

rr_ObjectiveSecondaryTextBlock

secondarily long-term growth of capital, while investing primarily in small- to mid-capitalization companies

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in 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 56 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 48 of the Fund’s Statement of Additional Information.

Shareholder Fees Caption [Text]

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Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

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Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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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 19.1% of the average value of its portfolio.

Portfolio Turnover, Rate

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19.10%

Expense Breakpoint Discounts [Text]

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You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Principal Funds, Inc.

Expense Breakpoint, Minimum Investment Required [Amount]

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50,000

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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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]

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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 [Text]

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You would pay the following expenses if you did not redeem your shares:

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in dividend-paying equity securities of companies with small to medium market capitalizations (those with market capitalizations ranging from between $200 million and $7 billion) at the time of purchase. The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund invests in the securities of foreign issuers, real estate investment trusts, preferred securities, convertible securities, fixed-income securities, master limited partnerships, and royalty trusts.

Risk [Heading]

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Principal Risks

Risk Narrative [Text Block]

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The Fund may be an appropriate investment for investors who seek dividends to generate income or to reinvest for growth and who can accept fluctuations in the value of investments and the risks of investing in equity securities, the securities of foreign issuers, real estate investment trusts, preferred securities, convertible securities, fixed-income securities, master limited partnerships, and royalty trusts.

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund. An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The principal risks of investing in the Fund, in alphabetical order, are:

Convertible Securities Risk. Convertible securities can be bonds, notes, debentures, preferred stock or other securities which are convertible into common stock. Convertible securities are subject to both the credit and interest rate risks associated with fixed income securities and to the stock market risk associated with equity securities.

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.

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).

Master Limited Partnership ("MLP") Risk. MLPs are publicly-traded limited partnership interests or units. An MLP that invests in a particular industry (e.g., oil and gas) will be harmed by detrimental economic events within that industry. As partnerships, MLPs may be subject to less regulation (and less protection for investors) under state laws than corporations. In addition, MLPs may be subject to state taxation in certain jurisdictions, which may reduce the amount of income an MLP pays to its investors.

Preferred Securities Risk. Preferred securities are junior subordinated securities in a company’s capital structure and therefore can be subject to greater credit and liquidation risk. An issuer of preferred securities could redeem the security prior to the stated maturity date and reduce the return of the security.

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. 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.

Royalty Trust Risk. A royalty trust generally acquires an interest in natural resource or chemical companies and distributes the income it receives to its investors. A sustained decline in demand for natural resource and related products could adversely affect royalty trust revenues and cash flows. Such a decline could result from a recession or other adverse economic conditions, an increase in the market price of the underlying commodity, higher taxes or other regulatory actions that increase costs, or a shift in consumer demand. Rising interest rates could adversely affect the performance, and limit the capital appreciation, of royalty trusts because of the increased availability of alternative investments at more competitive yields. Fund shareholders will indirectly bear their proportionate share of the royalty trusts' expenses.

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]

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Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

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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]

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Performance

Performance Narrative [Text Block]

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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 Russell 2500 Value Index.

Performance One Year or Less [Text]

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No performance information is shown because the Fund has not yet had a calendar year of performance.

PFI Prospectus - Class A, C, P | Small-MidCap Dividend Income Fund | Small-MidCap Dividend Income Fund, Class A

Risk/Return:

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Trading Symbol

dei_TradingSymbol

PMDAX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

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5.50%

Maximum Deferred Sales Charge (as a percentage)

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1.00%

Management Fees (as a percentage of Assets)

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0.80%

Distribution and Service (12b-1) Fees

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0.25%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.55%

Acquired Fund Fees and Expenses

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0.10%

Expenses (as a percentage of Assets)

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1.70%

Fee Waiver or Reimbursement

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(0.20%)

^[8]

Net Expenses (as a percentage of Assets)

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1.50%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

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694

Expense Example, with Redemption, 3 Years

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1,038

Expense Example, with Redemption, 5 Years

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1,405

Expense Example, with Redemption, 10 Years

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2,432

Expense Example, No Redemption, 1 Year

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694

Expense Example, No Redemption, 3 Years

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1,038

Expense Example, No Redemption, 5 Years

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1,405

Expense Example, No Redemption, 10 Years

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2,432

PFI Prospectus - Class A, C, P | Small-MidCap Dividend Income Fund | Small-MidCap Dividend Income Fund, Class C

Risk/Return:

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Trading Symbol

dei_TradingSymbol

PMDDX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

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none

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.80%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.39%

^[4]

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.10%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

2.29%

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.04%)

^[8]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

2.25%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

328

Expense Example, with Redemption, 3 Years

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712

Expense Example, No Redemption, 1 Year

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228

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

712

PFI Prospectus - Class A, C, P | Small-MidCap Dividend Income Fund | Small-MidCap Dividend Income Fund, Class P

Risk/Return:

rr_RiskReturnAbstract

Trading Symbol

dei_TradingSymbol

PMDPX

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

none

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.80%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

1.17%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.10%

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

2.07%

Fee Waiver or Reimbursement

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(0.97%)

^[8]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

1.10%

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

December 31, 2013

Expense Example, with Redemption, 1 Year

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112

Expense Example, with Redemption, 3 Years

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555

Expense Example, with Redemption, 5 Years

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1,024

Expense Example, with Redemption, 10 Years

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2,323

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

112

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

555

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,024

Expense Example, No Redemption, 10 Years

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2,323

[1] The year-to-date return as of September 30, 2012 was 7.85% for Class A shares.

[2] 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 by paying, if necessary, expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2013. 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 shares, excluding interest expense. 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%, excluding interest expense. 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.

[3] 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 by paying, if necessary, expenses normally payable by the Fund, excluding interest expense and dividend and interest expense on short sales, through the period ending December 31, 2013. 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 2.00% for Class A and 2.75% for Class C shares, excluding interest expense and dividend and interest expense on short sales. 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%, excluding interest expense. 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.

[4] Based on estimated amounts for the current fiscal year.

[5] Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund’s expenses attributable to Class A and Class C shares by paying, if necessary, expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2013. The expense limit will maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.90% for Class A and 1.65% for Class C shares, excluding interest expense. 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.

[6] The year-to-date return as of September 30, 2012 was 15.47% for Class A shares.

[7] Principal Management Corporation ("Principal"), the investment advisor, has contractually agreed to limit the Fund’s expenses identified as "Other Expenses" for Class P by paying, if necessary, expenses normally payable by the Fund, excluding interest expense, through the period ending December 31, 2013. The expense limit will maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.20%, excluding interest expense. 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.

[8] 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 by paying, if necessary, expenses normally payable by the Fund, excluding interest expense and Acquired Fund Fees and Expenses, through the period ending December 31, 2013. 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 1.40% for Class A and 2.15% for Class C shares, excluding interest expense and Acquired Fund Fees and Expenses. 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%, excluding interest expense. 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.