485BPOS

Registration No. 333-201935

Investment Company Act of 1940 File No. 811-23029

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

_________________

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933	X
Post-Effective Amendment No. 76	X

and/or

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940	X
Amendment No. 78	X
(Check Appropriate Box or Boxes)

_____________________

PRINCIPAL EXCHANGE-TRADED FUNDS

(Exact Name of Registrant as Specified in Charter)

_____________________

711 High Street

Des Moines, IA 50392

(Address of Principal Executive Offices)

(515) 235-1209

(Registrant’s Telephone Number, including Area Code)

_____________________

Name and Address of Agent for Service:

Britney L. Schnathorst

Principal Financial Group

Des Moines, IA 50392

_________________

Approximate Date of Proposed Public Offering: Immediately

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

_XX_    immediately upon filing pursuant to paragraph (b)

____    on (date) pursuant to paragraph (b)

____    60 days after filing pursuant to paragraph (a)

____    on (date) pursuant to paragraph (a)

____    75 days after filing pursuant to paragraph (a)(2)

____    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.

Title of Securities Being Registered: Shares of Principal Active Global Dividend Income, Principal Contrarian Value Index, Principal EDGE Active Income, Principal Healthcare Innovators Index, Principal International Multi-Factor Index, Principal Investment Grade Corporate Active, Principal Millennials Index, Principal Price Setters Index, Principal Shareholder Yield Index, Principal Spectrum Preferred Securities Active, Principal Sustainable Momentum Index, Principal U.S. Mega-Cap Multi-Factor Index and Principal U.S. Small-Cap Multi-Factor Index ETFs.

EXPLANATORY NOTE

This filing relates to the Registrant’s prospectus dated November 1, 2018 for shares of Principal Active Global Dividend Income, Principal Contrarian Value Index, Principal EDGE Active Income, Principal Healthcare Innovators Index, Principal International Multi-Factor Index, Principal Investment Grade Corporate Active, Principal Millennials Index, Principal Price Setters Index, Principal Shareholder Yield Index, Principal Spectrum Preferred Securities Active, Principal Sustainable Momentum Index, Principal U.S. Mega-Cap Multi-Factor Index and Principal U.S. Small-Cap Multi-Factor Index ETFs, which were included in 1933 Act Post-Effective Amendment No. 74 (as filed on October 26, 2018, SEC Accession No. 0001572661-18-000159), 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 Fund certifies that it meets all of the requirements for effectiveness of this registration statement under rule 485(b) under the Securities Act and has duly caused this 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 16th day of November, 2018.
	Principal Exchange-Traded Funds
	(Registrant)
	/s/ M. J. Beer _____________________________________ M. J. Beer Director, 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/ M. J. Beer __________________________ M. J. Beer	Director, President and Chief Executive Officer (Principal Executive Officer)	November 16, 2018
/s/ T. W. Bollin __________________________ T. W. Bollin	Chief Financial Officer (Principal Financial Officer)	November 16, 2018
/s/ S. L. Reece __________________________ S. L. Reece	Vice President and Controller (Controller)	November 16, 2018
(E. Ballantine)* __________________________ E. Ballantine	Trustee	November 16, 2018
(L. T. Barnes)* __________________________ L. T. Barnes	Trustee	November 16, 2018
(C. Damos)* __________________________ C. Damos	Trustee	November 16, 2018
(N. M. Everett)* __________________________ N. M. Everett	Chair	November 16, 2018
(M. A. Grimmett)* __________________________ M. A. Grimmett	Trustee	November 16, 2018
(P. G. Halter)* __________________________ P. G. Halter	Trustee	November 16, 2018
(F. S. Hirsch)* __________________________ F. S. Hirsch	Trustee	November 16, 2018
(T. Huang)* __________________________ T. Huang	Trustee	November 16, 2018
(K. McMillan)* __________________________ K. McMillan	Trustee	November 16, 2018
(E. A. Nickels)* __________________________ E. A. Nickels	Trustee	November 16, 2018
(M. M. VanDeWeghe)* __________________________ M. M. VanDeWeghe	Trustee	November 16, 2018
*Pursuant to Power of Attorney appointing M. J. Beer Previously Filed as Ex-99(j)(ii) on February 6, 2015 (Accession No. 0001572661-15-000008), for E. A. Nickels on October 27, 2015 (Accession No. 0001572661-15-000049), for. P. G. Halter on January 19, 2018 (Accession No. 0001572661-18-000005), and for M. M. VanDeWeghe on 08/31/2018 (Accession No. 0001572661-18-000128).

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 Label Linkbase Document

Ex-101.PRE    XBRL Taxonomy Extension Presentation Linkbase Document

XML

Principal Exchange-Traded Funds | Principal Active Global Dividend Income ETF

PRINCIPAL ACTIVE GLOBAL DIVIDEND INCOME ETF

Objective:

The Fund seeks current income and long-term growth of income and 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 ("Shares"). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal Active Global Dividend Income ETF Principal Active Global Dividend Income ETF Share Class
Management Fees (as a percentage of Assets)	0.58%
Other Expenses (as a percentage of Assets):	none
Net Expenses (as a percentage of Assets)	0.58%	[1]

Example

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

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

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Principal Exchange-Traded Funds | Principal Active Global Dividend Income ETF | Principal Active Global Dividend Income ETF Share Class | USD ($)	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 22.0% of the average value of its portfolio.

Principal Investment Strategies

The Fund is an actively managed exchange-traded fund (“ETF”) that seeks to achieve its investment objective by investing, under normal circumstances, at least 80% of its net assets, plus any borrowings for investment purposes, in dividend-paying equity securities at the time of purchase. The advisor uses quantitative screens (such as dividend yield, return on invested capital, free cash flow and revenue growth metrics) followed by qualitative research on an industry level (such as supply/demand characteristics, near term expectation and longer term outlook) and on a company level (such as competitive advantage, financial strength, and potential for profitability) to identify companies it believes have the commitment and capacity to pay dividends and whose potential for growth of capital is expected to be above average.

The Fund invests in equity securities of small, medium and large market capitalization companies and in growth and value stocks. The Fund invests in real estate investment trusts (“REITs”).

The Fund invests in securities of issuers located throughout the world, including U.S. and foreign companies. Under normal market conditions, the Fund will invest at least 40% of its net assets in foreign and emerging market securities. The Fund typically holds investments tied economically to at least three countries outside of the U.S.

Principal Risks

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:

Dividend-Oriented Stocks Risk. Companies that have paid regular dividends to shareholders may decrease or eliminate dividend payments in the future. For example, a sharp rise in interest rates or economic downturn could cause a company to unexpectedly reduce or eliminate its dividend. Additionally, the Fund’s performance during a broad market advance could suffer because dividend-paying stocks may not experience the same capital appreciation as non-dividend paying stocks.

Emerging Markets Risk.Investments in emerging market countries may have more risk than those in developed market countries because the emerging markets are less developed and more illiquid. Emerging market countries can also be subject to increased social, economic, regulatory, and political uncertainties and can be extremely volatile.

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk.If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Small and Medium Market Capitalization Companies Risk.Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Foreign Currency Risk.Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.

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

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Real Estate Investment Trusts (“REITs”) Risk.In addition to risks associated with investing in real estate securities, REITs are dependent upon management skills, are not diversified, and are subject to heavy cash flow dependency, risks of default by borrowers, and self-liquidation. Investment in REITs also involves risks similar to risks of investing in small market capitalization companies, such as limited financial resources, less frequent and limited volume trading, and may be subject to more abrupt or erratic price movements than larger company securities. A REIT could fail to qualify for tax-free pass-through of income under the Internal Revenue Code. Fund shareholders will indirectly bear their proportionate share of the expenses of REITs in which the fund invests.

Real Estate Securities Risk.Investing in real estate securities subjects the fund to the risks associated with the real estate market (which are similar to the risks associated with direct ownership in real estate), including declines in real estate values, loss due to casualty or condemnation, property taxes, interest rate changes, increased expenses, cash flow of underlying real estate assets, regulatory changes (including zoning, land use and rents), and environmental problems, as well as to the risks related to the management skill and creditworthiness of the issuer.

Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. When creation or redemption baskets involve a cash component, such transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. These transactions may accelerate the realization of taxable income if sales of portfolio securities result in gains and could increase transaction costs.

Performance

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance is benchmarked against the MSCI All Country World Index (ACWI) NR. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Principal Exchange-Traded Funds | Principal Contrarian Value Index ETF

PRINCIPAL CONTRARIAN VALUE INDEX ETF

Objective:

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq US Contrarian Value Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal Contrarian Value Index ETF Principal Contrarian Value Index ETF, Share Class
Management Fees (as a percentage of Assets)	0.29%
Other Expenses (as a percentage of Assets):	none
Expenses (as a percentage of Assets)	0.29%	[1]

Example

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

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

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Principal Exchange-Traded Funds | Principal Contrarian Value Index ETF | Principal Contrarian Value Index ETF, Share Class | USD ($)	30	93	163	368

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 18, 2017, the date operations commenced, through June 30, 2018, the Fund's annualized portfolio turnover rate was 61.6% 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 that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities of companies in the Nasdaq US Large Mid Cap Index (the "Parent Index") that appear to be undervalued by the market relative to their fundamental value.

To be eligible for the Index, a security must be a component of the Parent Index, which is composed of equity securities of U.S. issuers with medium and large market capitalizations. Securities are included in the Index based on their book yields. Based upon the most recent median book yield of securities in the Parent Index as compared to the average of the median book yields over the prior 28 quarters, the Index methodology determines a market condition of either "bear" (where the recent book yield exceeds the prior book yields by a threshold amount) or "normal" (where a bear market is not present). Securities in either the top 30% by book yield (in a bear market) or the top 30% by adjusted book yield rankings (in a normal market) are then selected for the Index.

After selection, the securities are weighted, with those in the higher ranking groups receiving relatively more weight. Because securities in the financial sector often perform differently than other securities with respect to book yields, securities are selected for the Index separately from Financials and non-Financials according to Industry Classification Benchmark ("ICB") so that each such ICB classification maintains its respective weight from the Parent Index.

The Index is rebalanced annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The market condition is monitored quarterly. If the market condition changes from bear to normal or vice versa, there is a special rebalance. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Index included 256 components, and the Parent Index included 930 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also purchase securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Principal Risks

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Medium Market Capitalization Companies.Investments in medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk.Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Performance

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance is benchmarked against the Nasdaq US Contrarian Value Index. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Principal Exchange-Traded Funds | Principal EDGE Active Income ETF

PRINCIPAL EDGE ACTIVE INCOME ETF

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 ("Shares"). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal EDGE Active Income ETF Principal EDGE Active Income ETF, Share Class
Management Fees (as a percentage of Assets)	0.65%
Other Expenses (as a percentage of Assets):	none
Expenses (as a percentage of Assets)	0.65%	[1]

Example

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

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

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Principal Exchange-Traded Funds | Principal EDGE Active Income ETF | Principal EDGE Active Income ETF, Share Class | USD ($)	66	208	362	810

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 11.0% of the average value of its portfolio.

Principal Investment Strategies

The Fund is an actively managed exchange-traded fund (“ETF”) that seeks to achieve its investment objective by investing, under normal circumstances, its assets in investment grade and non-investment grade (commonly known as "junk") fixed income securities and in equity securities. In pursuing its strategies, the Fund invests in a diversified portfolio of a broad range of instruments. The Advisor actively and tactically allocates the Fund’s assets among fixed income securities and equity securities in an effort to take advantage of changing economic conditions that the Advisor believes favors one asset class over another. Based on analysis of various economic and market forces (such as interest rates, inflation, the business cycle, fiscal policy, monetary policy, valuations, momentum, risk premiums, investor sentiment, credit spreads, and fundamentals), the Advisor increases the allocation to the asset class that it believes has a higher probability of achieving the Fund’s objective of providing current income.

Fixed Income. A portion of the Fund's net assets is invested in a diversified portfolio of investment grade and non-investment grade (commonly known as "junk") fixed income securities issued by U.S., supranational and non-U.S. issuers, including investments in convertible bonds, U.S. government and agency securities, asset-backed, mortgage-backed, and commercial mortgage-backed securities (securitized products), and sovereign debt. “Investment grade” securities are rated BBB- or higher by S&P Global Ratings ("S&P Global") or Baa3 or higher by Moody's Investors Service, Inc. ("Moody's") or, if unrated, of comparable quality in the opinion of those selecting such investments. “Non-investment grade” securities are rated Ba1 or lower by Moody’s and BB+ or lower by S&P Global. If securities are rated differently by the rating agencies, the highest rating is used. If the security has been rated by only one of those agencies, that rating will determine whether the security is below investment grade. If the security has not been rated by either of those agencies, those selecting such investments will determine whether the security is of a quality comparable to those rated below investment grade. The fixed income portfolio is not managed to a particular average duration or maturity.

During the fiscal year ended June 30, 2018, the average ratings of the Fund’s fixed-income assets, based on market value at each month-end, were as follows (all ratings are by Moody’s):

0.00% in securities rated Aaa	10.16% in securities rated Baa	12.29% in securities rated Caa	0.00% in securities rated D
0.15% in securities rated Aa	27.19% in securities rated Ba	0.00% in securities rated Ca	4.28% in securities not rated
6.29% in securities rated A	39.64% in securities rated B	0.00% in securities rated C

Equity Securities. A portion of the Fund's net assets is invested in a diversified portfolio of dividend paying equity securities issued by companies located in the U.S. and/or foreign countries that trade on a U.S. or foreign exchange. The equity securities include common stocks (including value stocks), preferred stocks, master limited partnerships ("MLPs") and real estate investment trusts (“REITs”). Although not a factor in the selection of the equity securities, such securities generally are of medium market capitalization companies, which for this Fund are those with market capitalizations similar to companies in the Russell Midcap^® Index (as of June 30, 2018, this range was between approximately $2.3 billion and $35.5 billion).

Principal Risks

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

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

Convertible Securities Risk.Convertible securities are securities that are convertible into common stock. Convertible securities are subject to credit and interest rate risks associated with fixed-income securities and to stock market risk associated with equity securities.

Dividend-Oriented Stocks Risk. Companies that have paid regular dividends to shareholders may decrease or eliminate dividend payments in the future. For example, a sharp rise in interest rates or economic downturn could cause a company to unexpectedly reduce or eliminate its dividend. Additionally, the Fund’s performance during a broad market advance could suffer because dividend-paying stocks may not experience the same capital appreciation as non-dividend paying stocks.

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Medium Market Capitalization Companies.Investments in medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Fixed-Income Securities Risk.Fixed-income securities are subject to interest rate, credit quality, and liquidity risks. The market value of fixed-income securities generally declines when interest rates rise, and increased interest rates may adversely affect the liquidity of certain fixed-income securities. Moreover, an issuer of fixed-income securities could default on its payment obligations due to increased interest rates or for other reasons.

Foreign Currency Risk.Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.

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

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

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

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, which means funds with longer average portfolio durations may be more volatile than those with shorter durations.

Preferred Securities Risk. Because preferred securities have a lower priority claim on assets or earnings than senior bonds and other debt instruments in a company's capital structure, they are subject to greater credit and liquidation risk than more senior debt instruments. In addition, preferred securities are subject to other risks, such as limited or no voting rights, deferring or skipping distributions, interest rate risk, and redeeming the security prior to any stated maturity date.

Real Estate Investment Trusts (“REITs”) Risk.In addition to risks associated with investing in real estate securities, REITs are dependent upon management skills, are not diversified, and are subject to heavy cash flow dependency, risks of default by borrowers, and self-liquidation. Investment in REITs also involves risks similar to risks of investing in small market capitalization companies, such as limited financial resources, less frequent and limited volume trading, and may be subject to more abrupt or erratic price movements than larger company securities. A REIT could fail to qualify for tax-free pass-through of income under the Internal Revenue Code. Fund shareholders will indirectly bear their proportionate share of the expenses of REITs in which the fund invests.

Real Estate Securities Risk.Investing in real estate securities subjects the fund to the risks associated with the real estate market (which are similar to the risks associated with direct ownership in real estate), including declines in real estate values, loss due to casualty or condemnation, property taxes, interest rate changes, increased expenses, cash flow of underlying real estate assets, regulatory changes (including zoning, land use and rents), and environmental problems, as well as to the risks related to the management skill and creditworthiness of the issuer.

Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. When creation or redemption baskets involve a cash component, such transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. These transactions may accelerate the realization of taxable income if sales of portfolio securities result in gains and could increase transaction costs.

Securitized Products Risk. Investments in securitized products are subject to risks similar to traditional fixed income securities, such as credit, interest rate, liquidity, prepayment, extension, and default risk, as well as additional risks associated with the nature of the assets and the servicing of those assets. Unscheduled prepayments on securitized products may have to be reinvested at lower rates. A reduction in prepayments may increase the effective maturities of these securities, exposing them to the risk of decline in market value over time (extension risk).

U.S. Government Securities Risk. Yields available from U.S. government securities are generally lower than yields from many other fixed-income securities.

U.S. Government-Sponsored Securities Risk.Securities issued by U.S. government-sponsored or -chartered enterprises such as the Federal Home Loan Mortgage Corporation, the Federal National Mortgage Association, and the Federal Home Loan Banks are not issued or guaranteed by the U.S. Treasury.

Performance

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Life of Fund returns are measured from the date the Fund's shares were first sold (July 8, 2015).

Total Returns as of December 31 (1)

Highest return for a quarter during the period of the bar chart above:	Q2 '16	6.07%
Lowest return for a quarter during the period of the bar chart above:	Q4 '17	1.07%

⁽¹⁾ The year-to-date return as of September 30, 2018 is 1.34%.

Average Annual Total Returns (Based on NAV) For the periods ended December 31, 2017

Average Annual Total Returns - Principal Exchange-Traded Funds - Principal EDGE Active Income ETF - Principal EDGE Active Income ETF, Share Class	Label	1 Year	Since Inception
Before Taxes	Return Before Taxes	8.33%	6.63%
After Taxes on Distributions	Return After Taxes on Distributions	5.88%	4.42%
After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	4.94%	4.12%
Bloomberg Barclays U.S. Corporate High Yield 2% Issuer Capped Index [Member]	Bloomberg Barclays U.S. Corporate High Yield 2% Issuer Capped Index	7.50%	6.79%

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.

Principal Exchange-Traded Funds | Principal Healthcare Innovators Index ETF

PRINCIPAL HEALTHCARE INNOVATORS INDEX ETF

Objective:

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq Healthcare Innovators Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal Healthcare Innovators Index ETF Principal Healthcare Innovators Index ETF Share Class
Management Fees (as a percentage of Assets)	0.42%
Other Expenses (as a percentage of Assets):	none
Net Expenses (as a percentage of Assets)	0.42%	[1]

Example

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

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

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Principal Exchange-Traded Funds | Principal Healthcare Innovators Index ETF | Principal Healthcare Innovators Index ETF Share Class | USD ($)	43	135	235	530

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 33.6% 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 that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities in the Nasdaq US Benchmark Index (the "Parent Index") (including growth and value stock) that are small and medium capitalization U.S. healthcare companies. Most of the companies in the Index are "early-stage companies" within the healthcare equipment and supplies, pharmaceuticals, biotechnology, and life sciences industries that are not yet consistently profitable. Examples include companies developing products and services and companies in the pre-marketing stage seeking regulatory approvals.

To be eligible for the Index, a security must be a component of the Parent Index, and each security must be classified as Health Care according to Industry Classification Benchmark (ICB). Securities are ranked based upon their market capitalization and liquidity. The Index employs a modified market capitalization weighting methodology; final eligible securities receive a maximum weight of 3%, and all excess weight is distributed proportionally across the remaining index securities. The Index is rebalanced semi-annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Index included 190 components, and the Parent Index included 2,839 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also invest in securities not included in the Index that the Advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated. Given the present composition of the Index, the Fund expects to concentrate its investments in the healthcare industry.

Principal Risks

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

Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk.If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Small and Medium Market Capitalization Companies.Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Industry Concentration Risk. A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries.

• Healthcare Industry Risk. Given the present composition of the Index, the Fund expects to have more than 25% of its assets invested in the healthcare industry. A fund that invests in securities of companies in the healthcare industry (which are companies involved in medical services or health care, including biotechnology research and production, drugs and pharmaceuticals and health care facilities and services) is subject to the direct risks of investing in such companies. These companies are subject to extensive competition (due to, among others, generic drug sales or the loss of patent protection), product liability litigation and increased government regulation. Research and development costs of bringing new drugs to market are substantial, and there is no guarantee that a proposed product will ever come to market. Such companies are heavily dependent on patent and intellectual property rights, the loss or impairment of which may adversely affect profitability. Healthcare facility operators may be affected by the demand for services, efforts by government or insurers to limit rates, restriction of government financial assistance and competition from other providers.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Performance

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Life of Fund returns are measured from the date the Fund's shares were first sold (August 19, 2016).

Total Returns as of December 31 (1)

Highest return for a quarter during the period of the bar chart above:	Q1 '17	16.66%
Lowest return for a quarter during the period of the bar chart above:	Q4 '17	2.24%

⁽¹⁾ The year-to-date return as of September 30, 2018 is 18.26%.

Average Annual Total Returns For the periods ended December 31, 2017

Average Annual Total Returns - Principal Exchange-Traded Funds - Principal Healthcare Innovators Index ETF	Label	1 Year	Since Inception
Nasdaq US Healthcare Innovators Index	Nasdaq US Healthcare Innovators Index	37.00%	18.50%
Principal Healthcare Innovators Index ETF Share Class	Return Before Taxes	36.31%	17.93%
Principal Healthcare Innovators Index ETF Share Class | After Taxes on Distributions	Return After Taxes on Distributions	36.22%	17.87%
Principal Healthcare Innovators Index ETF Share Class | After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	20.56%	13.73%

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.

Principal Exchange-Traded Funds | Principal International Multi-Factor Index ETF

PRINCIPAL INTERNATIONAL MULTI-FACTOR INDEX ETF

Objective:

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq Developed Select Leaders Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal International Multi-Factor Index ETF Principal International Multi-Factor Index ETF, Share Class
Management Fees (as a percentage of Assets)	0.39%
Other Expenses (as a percentage of Assets):	none
Expenses (as a percentage of Assets)	0.39%	[1]

Example

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

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

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Principal Exchange-Traded Funds | Principal International Multi-Factor Index ETF | Principal International Multi-Factor Index ETF, Share Class | USD ($)	40	125	219	493

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 November 8, 2017, the date operations commenced, through June 30, 2018, the Fund's annualized portfolio turnover rate was 54.1% 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 equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities of companies in the Nasdaq Developed Market Ex-US Ex-Korea Large Mid Cap Index (the "Parent Index") that exhibit a combination of value, growth and momentum characteristics, with higher weights given to securities that are more liquid and less volatile.

The Parent Index is composed of developed foreign market equity securities of issuers that have medium and large market capitalizations. Securities in the top 90% of the Parent Index based on three month average daily dollar trading volume are eligible for the Index. Each security is ranked according to three factors:

• The Shareholder Yield (value factor) ranks securities based on the collective financial impact on a company's shareholders from the return of free cash flow through cash dividends, stock repurchases, and debt reduction. This factor is designed to identify securities with low prices relative to their fundamental value.

• The Price Setters (growth factor) ranks securities based on pricing power, which is the extent to which a company can raise the prices of its products without reducing the demand for them.

• The Momentum Factor ranks securities based on recent performance relative to their peers.

Each security has a Shareholder Yield, Price Setters, and Momentum rank that is based on that security's country within the Index. The ranks are then averaged to determine a rank for each security within each country. Securities that rank in the top 20% are included in the Index, in addition to securities already in the Index that rank in the top 50%. Securities are weighted by their liquidity-volatility score, in an effort to give greater weight to securities that are more liquid and less volatile. Each security weight is capped at 1.5%, and any excess weight is distributed proportionally first by country then across the Index.

The Index is rebalanced semi-annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after the Index changes are made public. As of June 30, 2018, the Underlying Index included 316 components, and the Parent Index included 1,200 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also purchase securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Principal Risks

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk.If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Medium Market Capitalization Companies.Investments in medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk.Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Foreign Currency Risk.Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.

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

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Momentum Style Risk. Stocks that previously exhibited high momentum characteristics may not experience positive momentum or may experience more volatility than the market as a whole. In addition, there may be periods when momentum style is out of favor, during which the investment performance of a Fund that uses momentum-based strategies may suffer.

Performance

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance is benchmarked against the Nasdaq Developed Select Leaders Index. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Principal Exchange-Traded Funds | Principal Investment Grade Corporate Active ETF Series

PRINCIPAL INVESTMENT GRADE CORPORATE ACTIVE ETF

Objective:

The Fund seeks to provide current income

and, as a secondary objective, capital appreciation.

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 ("Shares"). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal Investment Grade Corporate Active ETF Series Principal Investment Grade Corporate Active ETF Class
Management Fees (as a percentage of Assets)	0.26%
Other Expenses (as a percentage of Assets):	none
Expenses (as a percentage of Assets)	0.26%	[1]

Example

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

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

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years
Principal Exchange-Traded Funds | Principal Investment Grade Corporate Active ETF Series | Principal Investment Grade Corporate Active ETF Class | USD ($)	27	84

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 April 16, 2018, the date operations commenced, through June 30, 2018, the Fund's annualized portfolio turnover rate was 47.8% of the average value of its portfolio.

Principal Investment Strategies

The Fund is an actively managed exchange-traded fund (“ETF”) that seeks to achieve its investment objective by investing, under normal circumstances, at least 80% of its net assets, plus any borrowings for investment purposes, in investment grade corporate bonds and other fixed income securities at the time of purchase. “Investment grade” securities are rated BBB- or higher by S&P Global Ratings ("S&P Global") or Baa3 or higher by Moody's Investors Service, Inc. ("Moody's") or, if unrated, of comparable quality in the opinion of those selecting such investments. If the security has been rated by only one of those agencies, that rating will determine whether the security is investment grade. If securities are rated differently by the rating agencies, the highest rating is used.

The fixed income securities in which the Fund invests include foreign securities, corporate securities, securities issued or guaranteed by the U.S. government or its agencies and instrumentalities, and securities issued or guaranteed by foreign governments payable in U.S. dollars. The Fund invests in other investment companies, including exchange-traded funds that invest in fixed income securities. The portfolio is not managed to a particular maturity. Under normal circumstances, the Fund maintains an average portfolio duration that is within +/- 10% of the duration of the Bloomberg Barclays U.S. Corporate Investment Grade Bond Index, which as of June 30, 2018 was 7.26 years. The Fund actively trades securities.

The Fund utilizes exchange-traded and over-the-counter derivative strategies. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. Specifically, the Fund invests in treasury futures for hedging or to otherwise manage fixed income exposure, as well as credit default swaps, including buying and selling on individual securities and/or baskets of securities, to efficiently manage exposures to certain sectors or individual issuers.

Principal Risks

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

Counterparty Risk. Counterparty risk is the risk that the counterparty to a contract or other obligation will be unable or unwilling to honor its obligations.

Derivatives Risk.Derivatives may not move in the direction anticipated by the portfolio manager. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and result in disproportionate losses that may be substantially greater than a fund's initial investment.

• Credit Default Swaps.Credit default swaps involve special risks in addition to those associated with swaps generally because they are difficult to value, are highly susceptible to liquidity and credit risk, and generally pay a return to the party that has paid the premium only in the event of an actual default by the issuer of the underlying obligation (as opposed to a credit downgrade or other indication of financial difficulty). The protection “buyer” in a credit default contract may be obligated to pay the protection “seller” an up-front payment or a periodic stream of payments over the term of the contract provided generally that no credit event on a reference obligation has occurred. If a credit event occurs, the seller generally must pay the buyer the “par value” (i.e., full notional value) of the swap in exchange for an equal face amount of deliverable obligations of the reference entity described in the swap, or the seller may be required to deliver the related net cash amount, if the swap is cash settled. The Fund may be either the buyer or seller in the transaction.

• Futures.These derivative instruments involve specific risks, including: the imperfect correlation between the change in market value of the instruments held by the fund and the price of the instruments; possible lack of a liquid secondary market for an instrument and the resulting inability to close it when desired; counterparty risk; and if the fund has insufficient cash, it may have to sell securities from its portfolio to meet any applicable daily variation margin requirements.

Fixed-Income Securities Risk.Fixed-income securities are subject to interest rate, credit quality, and liquidity risks. The market value of fixed-income securities generally declines when interest rates rise, and increased interest rates may adversely affect the liquidity of certain fixed-income securities. Moreover, an issuer of fixed-income securities could default on its payment obligations due to increased interest rates or for other reasons.

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

Hedging Risk.A fund that implements a hedging strategy using derivatives and/or securities could expose the fund to the risk that can arise when a change in the value of a hedge does not match a change in the value of the asset it hedges. In other words, the change in value of the hedge could move in a direction that does not match the change in value of the underlying asset, resulting in a risk of loss to the fund.

Investment Company Securities Risk.A fund that invests in another investment company (for example, another fund or ETF) is subject to the risks associated with direct ownership of the securities in which such investment company invests. Fund shareholders indirectly bear their proportionate share of the expenses of each such investment company.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

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, which means funds with longer average portfolio durations may be more volatile than those with shorter durations.

Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. When creation or redemption baskets involve a cash component, such transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. These transactions may accelerate the realization of taxable income if sales of portfolio securities result in gains and could increase transaction costs.

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 is benchmarked against the Bloomberg Barclays U.S. Corporate Investment Grade Bond Index. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Principal Exchange-Traded Funds | Principal Millennials Index ETF

PRINCIPAL MILLENNIALS INDEX ETF

Objective:

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq Global Millennial Opportunity Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal Millennials Index ETF Principal Millennials Index ETF Share Class
Management Fees (as a percentage of Assets)	0.45%
Other Expenses (as a percentage of Assets):	none
Net Expenses (as a percentage of Assets)	0.45%	[1]

Example

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

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

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Principal Exchange-Traded Funds | Principal Millennials Index ETF | Principal Millennials Index ETF Share Class | USD ($)	46	144	252	567

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 35.6% 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 that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities of companies in the Nasdaq Global Index (the "Parent Index") that are impacted by the spending and lifestyle activities of the Millennial generation, which refers to people born from 1980 to the mid-2000s. The Index may include equity securities of different market capitalizations (small, medium, or large) and styles (growth or value) and is weighted based upon capitalization and exposure to Millennials. Market segments with the greatest Millennial exposure are likely to include, without limitation, consumer goods (including fashion and apparel), social media and e-commerce, and digital media and technology.

To be eligible for the Index, a security must be a component of the Parent Index. However, an exchange-listed security that is not a component of the Parent Index may be eligible if it otherwise meets all of the eligibility criteria. Each security's exposure to Millennials is determined using a proprietary, multi-step research process. Each company is identified as having low, medium, or high exposure to Millennials based on the materiality of the company's exposure to Millennial-related themes and the potential role of Millennials in driving long-term growth. To be eligible for the Index, a security must have high or medium exposure to Millennials. "Medium exposure" means that Millennials-related products, technologies, services and solutions are an important factor of the company's business model, strategy and research and development, and are material to sales and/or growth. "High exposure" means that Millennials-related products, technologies, services and solutions are core to the company's business model, strategy and research and development, and are material to sales and/or growth. Securities of companies having high exposure to Millennials receive 70% of the weight of the index, and securities of companies having medium exposure to Millennials receive 30% of the weight of the index.

The Index is rebalanced annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Index included 103 components, and the Parent Index included 8,945 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also invest in securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Principal Risks

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:

Consumer Goods and Consumer Services Sectors Risk. The Fund expects to invest in securities of companies in the consumer services and consumers goods sectors to the extent the Index is composed of such securities. Such companies are particularly subject to risks related to performance of the overall global economy, interest rates, competition, government regulation, and consumer confidence. Success depends heavily on disposable income and consumer spending, and is also impacted by consumer interest and marketing campaigns. Companies in these sectors may be subject to severe competition, which may have an adverse impact on their profitability. Changes in demographics and consumer tastes can affect the demand for, and success of, consumer goods and
services in the marketplace.

Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk.If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Small and Medium Market Capitalization Companies. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Foreign Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.

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

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Information Technology Sector Risk.The Fund expects to invest in securities of companies in the information technology sector to the extent the Index is composed of such securities. Such companies may face dramatic and often unpredictable changes in growth rates and are particularly vulnerable to changes in technology product cycles, product obsolescence, government regulation, and competition, both domestically and internationally. Such companies are heavily dependent on patent and intellectual property rights, the loss or impairment of which may adversely affect profitability.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Performance

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Life of Fund returns are measured from the date the Fund's shares were first sold (August 19, 2016).

Total Returns as of December 31 (1)

Highest return for a quarter during the period of the bar chart above:	Q4 '17	10.26%
Lowest return for a quarter during the period of the bar chart above:	Q1 '17	8.24%

⁽¹⁾ The year-to-date return as of September 30, 2018 is 12.69%.

Average Annual Total Returns For the periods ended December 31, 2017

Average Annual Total Returns - Principal Exchange-Traded Funds - Principal Millennials Index ETF	Label	1 Year	Since Inception
Nasdaq Global Millennial Opportunity Index	Nasdaq Global Millennial Opportunity Index	41.97%	28.11%
Principal Millennials Index ETF Share Class	Return Before Taxes	41.08%	27.33%
Principal Millennials Index ETF Share Class | After Taxes on Distributions	Return After Taxes on Distributions	40.76%	27.04%
Principal Millennials Index ETF Share Class | After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	23.47%	20.98%

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.

Principal Exchange-Traded Funds | Principal Price Setters Index ETF

PRINCIPAL PRICE SETTERS INDEX ETF

Objective:

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq US Price Setters Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal Price Setters Index ETF Principal Price Setters Index ETF Share Class
Management Fees (as a percentage of Assets)	0.40%
Other Expenses (as a percentage of Assets):	none
Expenses (as a percentage of Assets)	0.40%	[1]
Fee Waiver or Reimbursement	(0.11%)	[2]
Net Expenses (as a percentage of Assets)	0.29%

Example

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

The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Principal Exchange-Traded Funds | Principal Price Setters Index ETF | Principal Price Setters Index ETF Share Class | USD ($)	30	117	213	494

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 63.5% 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 equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities of mid- to large-capitalization companies in the Nasdaq US Large Mid Cap Index (the "Parent Index") that exhibit high degrees of pricing power. "Pricing power" refers to the extent to which a company can raise the prices of its products without reducing the demand for them.

To be eligible for the Index, a security must be a component of the Parent Index and must be a top 550 name by market capitalization. Securities are ranked based upon eleven factors that include calculations based on earnings per share ("EPS") growth, operating margin, operating margin growth, return volatility, sales growth, return on equity, and earning quality. The average of the 11 factor scores is taken to create one score used to rank the securities. The top 150 securities by final rank are selected. The Index employs a modified equal dollar weighting methodology with those in the higher ranking groups receiving relatively more weight.

The Index is rebalanced annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Index included 146 components, and the Parent Index included 930 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also purchase securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Principal Risks

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Medium Market Capitalization Companies.Investments in medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Performance

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Life of Fund returns are measured from the date the Fund's shares were first sold (March 21, 2016).

Total Returns as of December 31 (1)

Highest return for a quarter during the period of the bar chart above:	Q4 '17	7.05%
Lowest return for a quarter during the period of the bar chart above:	Q3 '17	3.90%

⁽¹⁾ The year-to-date return as of September 30, 2018 is 10.15%.

Average Annual Total Returns For the periods ended December 31, 2017

Average Annual Total Returns - Principal Exchange-Traded Funds - Principal Price Setters Index ETF	Label	1 Year	Since Inception
Nasdaq US Price Setters Index	Nasdaq US Price Setters Index	24.97%	17.05%
Principal Price Setters Index ETF Share Class	Return Before Taxes	24.46%	16.56%
Principal Price Setters Index ETF Share Class | After Taxes on Distributions	Return After Taxes on Distributions	24.08%	16.17%
Principal Price Setters Index ETF Share Class | After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	14.03%	12.71%

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.

Principal Exchange-Traded Funds | Principal Shareholder Yield Index ETF

PRINCIPAL SHAREHOLDER YIELD INDEX ETF

Objective:

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq US Shareholder Yield Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal Shareholder Yield Index ETF Principal Shareholder Yield Index ETF Share Class
Management Fees (as a percentage of Assets)	0.40%
Other Expenses (as a percentage of Assets):	none
Expenses (as a percentage of Assets)	0.40%	[1]
Fee Waiver or Reimbursement	(0.11%)	[2]
Net Expenses (as a percentage of Assets)	0.29%

Example

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

The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Principal Exchange-Traded Funds | Principal Shareholder Yield Index ETF | Principal Shareholder Yield Index ETF Share Class | USD ($)	30	117	213	494

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 55.5% 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 equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities (including value stock) of mid- to large-capitalization companies in the Nasdaq US Large Mid Cap Index (the "Parent Index") that exhibit high degrees of sustainable, shareholder yield. "Shareholder yield" refers to the collective financial impact on a company's shareholders from the return of free cash flow through cash dividends, stock repurchases, and debt reduction.

To be eligible for the Index, a security must be a component of the Parent Index and the security must have paid a regular dividend in the prior year. Securities are ranked based upon nine factors that include calculations based on dividend yield, buyback yield, dividend payout per share, free cash flow, price, Sharpe ratio, EBITDA, debt, dividend yield historical valuation, and dividend growth. Securities that rank in the top 20% are included in the Index. The Index employs a modified equal dollar weighting methodology with those in the higher ranking groups receiving relatively more weight.

The Index is rebalanced annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Index included 138 components, and the Parent Index included 930 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also purchase securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Principal Risks

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Medium Market Capitalization Companies.Investments in medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Performance

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Life of Fund returns are measured from the date the Fund's shares were first sold (March 21, 2016).

Total Returns as of December 31 (1)

Highest return for a quarter during the period of the bar chart above:	Q4 '17	7.88%
Lowest return for a quarter during the period of the bar chart above:	Q2 '17	1.96%

⁽¹⁾ The year-to-date return as of September 30, 2018 is 4.76%.

Average Annual Total Returns For the periods ended December 31, 2017

Average Annual Total Returns - Principal Exchange-Traded Funds - Principal Shareholder Yield Index ETF	Label	1 Year	Since Inception
Nasdaq US Shareholder Yield Index	Nasdaq US Shareholder Yield Index	19.54%	18.77%
Principal Shareholder Yield Index ETF Share Class	Return Before Taxes	19.07%	18.25%
Principal Shareholder Yield Index ETF Share Class | After Taxes on Distributions	Return After Taxes on Distributions	18.55%	17.65%
Principal Shareholder Yield Index ETF Share Class | After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	11.16%	14.03%

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.

Principal Exchange-Traded Funds | Principal Spectrum Preferred Securities Active ETF

PRINCIPAL SPECTRUM PREFERRED SECURITIES ACTIVE ETF

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 ("Shares"). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal Spectrum Preferred Securities Active ETF Principal Spectrum Preferred Securities Active ETF, Share Class
Management Fees (as a percentage of Assets)	0.55%
Other Expenses (as a percentage of Assets):	none
Net Expenses (as a percentage of Assets)	0.55%	[1]

Example

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

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

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Principal Exchange-Traded Funds | Principal Spectrum Preferred Securities Active ETF | Principal Spectrum Preferred Securities Active ETF, Share Class | USD ($)	56	176	307	689

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 July 7, 2017, the date operations commenced, through June 30, 2018, the Fund's annualized portfolio turnover rate was 41.0% 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 preferred securities at the time of purchase. Examples of preferred securities include preferred stock, certain depositary receipts, and various types of junior subordinated debt (such debt generally includes the contractual ability to defer payment of interest without accelerating an immediate default event). In particular, the Fund focuses on preferred securities known as “$1,000 par preferred securities” which are issued in large, institutional lot sizes, typically by U.S. and non-U.S. financial services companies (i.e., banking, insurance and commercial finance companies) and other corporations. Preferred securities generally pay fixed and floating rate distributions and are junior to all forms of the company's senior debt, but may have "preference" over common stock in the payment of distributions and the liquidation of a company's assets. The Fund may invest its assets in below investment grade preferred securities (sometimes called “high yield” or "junk") which are rated at the time of purchase Ba1 or lower by Moody's Investors Service, Inc. (“Moody’s”) and BB+ or lower by Standard & Poor’s Rating Service (“S&P”) (if a security is rated differently by the rating agencies, the highest rating is used; if the security has been rated by only one of those agencies, that rating will determine whether the security is below investment grade; If the security has not been rated by either of those agencies, the Sub-Advisor will determine whether the security is of a quality comparable to those rated below investment grade).

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

During the fiscal year ended June 30, 2018, the average ratings of the Fund’s fixed-income assets, based on market value at each month-end, were as follows (all ratings are by Moody’s):

0.00% in securities rated Aaa	44.70% in securities rated Baa	0.00% in securities rated Caa	0.00% in securities rated D
0.00% in securities rated Aa	48.10% in securities rated Ba	0.00% in securities rated Ca	0.00% in securities not rated
7.20% in securities rated A	0.00% in securities rated B	0.00% in securities rated C

Principal Risks

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

Fixed-Income Securities Risk.Fixed-income securities are subject to interest rate, credit quality, and liquidity risks. The market value of fixed-income securities generally declines when interest rates rise, and increased interest rates may adversely affect the liquidity of certain fixed-income securities. Moreover, an issuer of fixed-income securities could default on its payment obligations due to increased interest rates or for other reasons.

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

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

Industry Concentration Risk.A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries.

• Financial Services. A fund concentrating in financial services companies may be more susceptible to adverse economic or regulatory occurrences affecting financial services companies. Financial companies may be adversely affected in certain market cycles, including periods of rising interest rates, which may restrict the availability and increase the cost of capital, and declining economic conditions, which may cause credit losses due to financial difficulties of borrowers. Because many types of financial companies are especially vulnerable to these economic cycles, the Fund’s investments in these companies may lose significant value during such periods.

Liquidity Risk. A Fund is exposed to liquidity risk when trading volume, lack of a market maker, or legal restrictions impair the Fund's ability to sell particular securities or close derivative positions at an advantageous price. Funds with principal investment strategies that involve certain fixed-income securities, securities of companies with smaller market capitalizations, foreign securities, derivatives, high yield bonds and bank loans or securities with substantial market and/or credit risk tend to have the greatest exposure to liquidity risk.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

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, which means funds with longer average portfolio durations may be more volatile than those with shorter durations.

Preferred Securities Risk. Because preferred securities have a lower priority claim on assets or earnings than senior bonds and other debt instruments in a company's capital structure, they are subject to greater credit and liquidation risk than more senior debt instruments. In addition, preferred securities are subject to other risks, such as limited or no voting rights, deferring or skipping distributions, interest rate risk, and redeeming the security prior to any stated maturity date.

Performance

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance is benchmarked against the BofA Merrill Lynch US Investment Grade Institutional Capital Securities Index. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Principal Exchange-Traded Funds | Principal Sustainable Momentum Index ETF

PRINCIPAL SUSTAINABLE MOMENTUM INDEX ETF

Objective:

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq US Sustainable Momentum Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal Sustainable Momentum Index ETF Principal Sustainable Momentum Index ETF, Share Class
Management Fees (as a percentage of Assets)	0.29%
Other Expenses (as a percentage of Assets):	none
Expenses (as a percentage of Assets)	0.29%	[1]

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other 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	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Principal Exchange-Traded Funds | Principal Sustainable Momentum Index ETF | Principal Sustainable Momentum Index ETF, Share Class | USD ($)	30	93	163	368

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 18, 2017, the date operations commenced, through June 30, 2018, the Fund's annualized portfolio turnover rate was 158.1% 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 equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities (including growth and value stocks) of companies in the Nasdaq US Large Mid Cap Index (the “Parent Index”) that exhibit sustainable price momentum, based on historical stock prices over multiple periods and taking multiple market environments into consideration. The Fund actively trades portfolio securities.

To be eligible for the Index, a security must be a component of the Parent Index, which is composed of equity securities of U.S. issuers with medium and large market capitalizations. Each security is assigned Sustainable Momentum (SUMO) Score based on intermediate factors (3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 month risk-adjusted returns) and long-term factors (36, 48, and 60 month risk-adjusted returns), with volatility adjustments used to determine a composite score. Securities with SUMO scores that rank in the top 15% are included in the Index, in addition to securities already in the Index that rank in the top 35%. Once selected, the securities are weighted, generally giving those in the higher ranking groups relatively more weight. Weighting is also determined in part on whether the Index is in a "high volatility regime" (where the ratio of the 1 month to 12 month standard deviation of the daily returns of the Parent Index exceeds the trailing seven year average of this ratio by a threshold amount).

The Index is rebalanced annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. Market volatility is monitored monthly; if the Index is determined to be in a high volatility regime, there is a special rebalance. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Underlying Index included 137 components, and the Parent Index included 930 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also purchase securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Principal Risks

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk.If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Medium Market Capitalization Companies.Investments in medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk.Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Momentum Style Risk. Stocks that previously exhibited high momentum characteristics may not experience positive momentum or may experience more volatility than the market as a whole. In addition, there may be periods when momentum style is out of favor, during which the investment performance of a Fund that uses momentum-based strategies may suffer.

Portfolio Turnover (Active Trading) Risk. High portfolio turnover (more than 100%) caused by actively trading portfolio securities may result in accelerating the realization of taxable gains and losses, lower fund performance and increased brokerage costs.

Performance

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance is benchmarked against the Nasdaq US Sustainable Momentum Index. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Principal Exchange-Traded Funds | Principal U.S. Mega-Cap Multi-Factor Index ETF

PRINCIPAL U.S. MEGA-CAP MULTI-FACTOR INDEX ETF

Objective:

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq US Mega Cap Select Leaders Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal U.S. Mega-Cap Multi-Factor Index ETF Principal U.S. Mega-Cap Multi-Factor Index ETF, Share Class
Management Fees (as a percentage of Assets)	0.15%
Other Expenses (as a percentage of Assets):	none
Expenses (as a percentage of Assets)	0.15%	[1]
Fee Waiver or Reimbursement	(0.03%)	[2]
Net Expenses (as a percentage of Assets)	0.12%

Example

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

The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Principal Exchange-Traded Funds | Principal U.S. Mega-Cap Multi-Factor Index ETF | Principal U.S. Mega-Cap Multi-Factor Index ETF, Share Class | USD ($)	12	45	82	189

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 11, 2017, the date operations commenced, through June 30, 2018, the Fund's annualized portfolio turnover rate was 39.8% 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 equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities of companies in the Nasdaq US 500 Large Cap Index (the "Parent Index") that have the largest market capitalizations, with higher weights given to less volatile securities.

The Parent Index is composed of equity securities of U.S. issuers with large market capitalizations. To be eligible for the Index, a security must be in the top 50th percentile of the Parent Index by aggregate company market capitalization. As of June 30, 2018, the market capitalization range of the companies in the Parent Index was between approximately $8.2 billion and $909.8 billion.

The Index employs a modified equal-dollar weighting methodology. With respect to securities of companies in the top 10% of aggregate market capitalization, companies with the largest market capitalizations receive relatively more weight. Securities of the remaining companies are equally weighted and volatility adjusted, which gives higher weight to securities that are more liquid and less volatile.

The Index is rebalanced semi-annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after the Index changes are made public. As of June 30, 2018, the Index included 52 components, and the Parent Index included 500 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also purchase securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Principal Risks

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Redemption Risk.A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. When creation or redemption baskets involve a cash component, such transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. These transactions may accelerate the realization of taxable income if sales of portfolio securities result in gains and could increase transaction costs.

Performance

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance is benchmarked against the Nasdaq US Mega Cap Select Leaders Index. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Principal Exchange-Traded Funds | Principal U.S. Small Cap Index ETF

PRINCIPAL U.S. SMALL-CAP MULTI-FACTOR INDEX ETF

Objective:

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq US Small Cap Select Leaders Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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

Annual Fund Operating Expenses	Principal Exchange-Traded Funds Principal U.S. Small Cap Index ETF Principal U.S. Small Cap Index ETF, Share Class
Management Fees (as a percentage of Assets)	0.38%
Other Expenses (as a percentage of Assets):	none
Net Expenses (as a percentage of Assets)	0.38%	[1]

Example

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

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

Expense Example	Expense Example, with Redemption, 1 Year	Expense Example, with Redemption, 3 Years	Expense Example, with Redemption, 5 Years	Expense Example, with Redemption, 10 Years
Principal Exchange-Traded Funds | Principal U.S. Small Cap Index ETF | Principal U.S. Small Cap Index ETF, Share Class | USD ($)	39	122	213	480

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 76.3% 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 that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities (including growth and value stock) of small-capitalization companies in the Nasdaq US Small Cap Index (the "Parent Index") that exhibit potential for high degrees of sustainable shareholder yield, pricing power and strong momentum, while adjusting for liquidity and quality. As of June 30, 2018, the market capitalization range of the companies comprising the Parent Index was between approximately $8.0 million and $6.8 billion.

To be eligible for the Index, a security must: be a component of the Parent Index; be in the top 90th percentile of the Nasdaq US Benchmark Index in terms of 3-month Average Daily Dollar Volume and have a minimum 3-month trading history, among other factors. One security per issuer is permitted.

Each security is ranked according to three factors:

• The Shareholder Yield (value factor) ranks securities based on the collective financial impact on a company's shareholders from the return of free cash flow through cash dividends, stock repurchases, and debt reduction. This factor is designed to identify securities with low prices relative to their fundamental value.

• The Price Setters (growth factor) ranks securities based on pricing power, which is the extent to which a company can raise the prices of its products without reducing the demand for them.

• The Momentum Factor ranks securities based on recent performance relative to their peers.

Each security has a Shareholder Yield, Price Setters, and Momentum rank that is based on that security's Industry Classification Benchmark ("ICB") within the Index. The ranks are then averaged to determine a rank for each security within each ICB. The ranks are then averaged to determine eligibility for inclusion in the Index. Securities that rank in the top 20% are included in the Index, in addition to securities already in the Index that rank in the top 50%. Securities are weighted by their liquidity-volatility score, in an effort to give greater weight to securities that are more liquid and less volatile. Once an initial weight is determined, a final weight initially caps each security's weight at 0.7%.

The Index is rebalanced semi-annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Index included 462 components, and the Parent Index included 1,909 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also invest in securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate (invest more than 25% of its assets) its investments in a particular industry except to the extent the Index is so concentrated.

Principal Risks

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Small Market Capitalization Companies. Investments in smaller companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Momentum Style Risk. Stocks that previously exhibited high momentum characteristics may not experience positive momentum or may experience more volatility than the market as a whole. In addition, there may be periods when momentum style is out of favor, during which the investment performance of a Fund that uses momentum-based strategies may suffer.

Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. When creation or redemption baskets involve a cash component, such transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. These transactions may accelerate the realization of taxable income if sales of portfolio securities result in gains and could increase transaction costs.

Performance

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Life of Fund returns are measured from the date the Fund's shares were first sold (September 21, 2016).

Total Returns as of December 31 (1)

Highest return for a quarter during the period of the bar chart above:	Q3 '17	4.73%
Lowest return for a quarter during the period of the bar chart above:	Q2 '17	1.99%

⁽¹⁾ The year-to-date return as of September 30, 2018 is 13.86%.

Average Annual Total Returns For the periods ended December 31, 2017

Average Annual Total Returns - Principal Exchange-Traded Funds - Principal U.S. Small Cap Index ETF	Label	1 Year	Since Inception
Nasdaq US Small Cap Select Leaders Index	Nasdaq US Small Cap Select Leaders Index	13.91%	20.10%
Principal U.S. Small Cap Index ETF, Share Class	Return Before Taxes	13.41%	19.53%
Principal U.S. Small Cap Index ETF, Share Class | After Taxes on Distributions	Return After Taxes on Distributions	13.13%	19.23%
Principal U.S. Small Cap Index ETF, Share Class | After Taxes on Distributions and Sales	Return After Taxes on Distributions and Sale of Fund Shares	7.80%	14.94%

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] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[2] PGI has contractually agreed to reduce total annual fund operating expenses for the Fund by waiving a portion of its management fee, to the extent that total expenses exceed 0.29% (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) expressed as a percent of average net assets on an annualized basis. It is expected that the expense limit will continue through the period ending October 31, 2019; however, Principal Exchange-Traded Funds and PGI, the parties to the agreement, may mutually agree to terminate the expense limit prior to the end of the period.

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[2] PGI has contractually agreed to reduce total annual fund operating expenses for the Fund by waiving a portion of its management fee, to the extent that total expenses exceed 0.29% (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) expressed as a percent of average net assets on an annualized basis. It is expected that the expense limit will continue through the period ending October 31, 2019; however, Principal Exchange-Traded Funds and PGI, the parties to the agreement, may mutually agree to terminate the expense limit prior to the end of the period.

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[2] Principal Global Investors, LLC ("PGI") has contractually agreed to reduce total annual fund operating expenses for the Fund by waiving a portion of its management fee, or reimbursing the Fund, to the extent that total expenses exceed 0.12% (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) expressed as a percent of average net assets on an annualized basis. It is expected that the expense limit will continue through the period ending October 31, 2019; however, Principal Exchange-Traded Funds and PGI, the parties to the agreement, may mutually agree to terminate the expense limit prior to the end of the period.

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

XML

Label

Element

Value

Prospectus:

rr_ProspectusTable

Document Type

dei_DocumentType

485BPOS

Document Period End Date

dei_DocumentPeriodEndDate

Jun. 30, 2018

Entity Registrant Name

dei_EntityRegistrantName

Principal Exchange-Traded Funds

Central Index Key

dei_EntityCentralIndexKey

0001572661

Amendment Flag

dei_AmendmentFlag

false

Document Creation Date

dei_DocumentCreationDate

Nov. 01, 2018

Document Effective Date

dei_DocumentEffectiveDate

Nov. 01, 2018

Prospectus Date

rr_ProspectusDate

Nov. 01, 2018

Principal Exchange-Traded Funds | Principal Active Global Dividend Income ETF

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

PRINCIPAL ACTIVE GLOBAL DIVIDEND INCOME ETF

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks current income and long-term growth of income and capital.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund ("Shares"). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 22.0% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

22.00%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

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

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is an actively managed exchange-traded fund (“ETF”) that seeks to achieve its investment objective by investing, under normal circumstances, at least 80% of its net assets, plus any borrowings for investment purposes, in dividend-paying equity securities at the time of purchase. The advisor uses quantitative screens (such as dividend yield, return on invested capital, free cash flow and revenue growth metrics) followed by qualitative research on an industry level (such as supply/demand characteristics, near term expectation and longer term outlook) and on a company level (such as competitive advantage, financial strength, and potential for profitability) to identify companies it believes have the commitment and capacity to pay dividends and whose potential for growth of capital is expected to be above average.

The Fund invests in equity securities of small, medium and large market capitalization companies and in growth and value stocks. The Fund invests in real estate investment trusts (“REITs”).

The Fund invests in securities of issuers located throughout the world, including U.S. and foreign companies. Under normal market conditions, the Fund will invest at least 40% of its net assets in foreign and emerging market securities. The Fund typically holds investments tied economically to at least three countries outside of the U.S.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

Dividend-Oriented Stocks Risk. Companies that have paid regular dividends to shareholders may decrease or eliminate dividend payments in the future. For example, a sharp rise in interest rates or economic downturn could cause a company to unexpectedly reduce or eliminate its dividend. Additionally, the Fund’s performance during a broad market advance could suffer because dividend-paying stocks may not experience the same capital appreciation as non-dividend paying stocks.

Emerging Markets Risk.Investments in emerging market countries may have more risk than those in developed market countries because the emerging markets are less developed and more illiquid. Emerging market countries can also be subject to increased social, economic, regulatory, and political uncertainties and can be extremely volatile.

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk.If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Small and Medium Market Capitalization Companies Risk.Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Foreign Currency Risk.Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.

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

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Real Estate Investment Trusts (“REITs”) Risk.In addition to risks associated with investing in real estate securities, REITs are dependent upon management skills, are not diversified, and are subject to heavy cash flow dependency, risks of default by borrowers, and self-liquidation. Investment in REITs also involves risks similar to risks of investing in small market capitalization companies, such as limited financial resources, less frequent and limited volume trading, and may be subject to more abrupt or erratic price movements than larger company securities. A REIT could fail to qualify for tax-free pass-through of income under the Internal Revenue Code. Fund shareholders will indirectly bear their proportionate share of the expenses of REITs in which the fund invests.

Real Estate Securities Risk.Investing in real estate securities subjects the fund to the risks associated with the real estate market (which are similar to the risks associated with direct ownership in real estate), including declines in real estate values, loss due to casualty or condemnation, property taxes, interest rate changes, increased expenses, cash flow of underlying real estate assets, regulatory changes (including zoning, land use and rents), and environmental problems, as well as to the risks related to the management skill and creditworthiness of the issuer.

Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. When creation or redemption baskets involve a cash component, such transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. These transactions may accelerate the realization of taxable income if sales of portfolio securities result in gains and could increase transaction costs.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance is benchmarked against the MSCI All Country World Index (ACWI) NR. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The Fund’s performance is benchmarked against the MSCI All Country World Index (ACWI) NR. Performance information provides an indication of the risks of investing in the Fund.

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.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

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

Principal Exchange-Traded Funds | Principal Active Global Dividend Income ETF | Principal Active Global Dividend Income ETF Share Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

GDVD

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.58%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.58%

^[1]

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

Principal Exchange-Traded Funds | Principal Contrarian Value Index ETF

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

PRINCIPAL CONTRARIAN VALUE INDEX ETF

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq US Contrarian Value Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 18, 2017, the date operations commenced, through June 30, 2018, the Fund's annualized portfolio turnover rate was 61.6% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

61.60%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

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

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities of companies in the Nasdaq US Large Mid Cap Index (the "Parent Index") that appear to be undervalued by the market relative to their fundamental value.

To be eligible for the Index, a security must be a component of the Parent Index, which is composed of equity securities of U.S. issuers with medium and large market capitalizations. Securities are included in the Index based on their book yields. Based upon the most recent median book yield of securities in the Parent Index as compared to the average of the median book yields over the prior 28 quarters, the Index methodology determines a market condition of either "bear" (where the recent book yield exceeds the prior book yields by a threshold amount) or "normal" (where a bear market is not present). Securities in either the top 30% by book yield (in a bear market) or the top 30% by adjusted book yield rankings (in a normal market) are then selected for the Index.

After selection, the securities are weighted, with those in the higher ranking groups receiving relatively more weight. Because securities in the financial sector often perform differently than other securities with respect to book yields, securities are selected for the Index separately from Financials and non-Financials according to Industry Classification Benchmark ("ICB") so that each such ICB classification maintains its respective weight from the Parent Index.

The Index is rebalanced annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The market condition is monitored quarterly. If the market condition changes from bear to normal or vice versa, there is a special rebalance. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Index included 256 components, and the Parent Index included 930 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also purchase securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Medium Market Capitalization Companies.Investments in medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk.Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance is benchmarked against the Nasdaq US Contrarian Value Index. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The Fund’s performance is benchmarked against the Nasdaq US Contrarian Value Index. Performance information provides an indication of the risks of investing in the Fund.

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.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

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

Principal Exchange-Traded Funds | Principal Contrarian Value Index ETF | Principal Contrarian Value Index ETF, Share Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

PVAL

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.29%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.29%

^[2]

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 30

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

93

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

163

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 368

Principal Exchange-Traded Funds | Principal EDGE Active Income ETF

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

PRINCIPAL EDGE ACTIVE INCOME ETF

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 ("Shares"). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

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

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund's annualized portfolio turnover rate was 11.0% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

11.00%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

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

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is an actively managed exchange-traded fund (“ETF”) that seeks to achieve its investment objective by investing, under normal circumstances, its assets in investment grade and non-investment grade (commonly known as "junk") fixed income securities and in equity securities. In pursuing its strategies, the Fund invests in a diversified portfolio of a broad range of instruments. The Advisor actively and tactically allocates the Fund’s assets among fixed income securities and equity securities in an effort to take advantage of changing economic conditions that the Advisor believes favors one asset class over another. Based on analysis of various economic and market forces (such as interest rates, inflation, the business cycle, fiscal policy, monetary policy, valuations, momentum, risk premiums, investor sentiment, credit spreads, and fundamentals), the Advisor increases the allocation to the asset class that it believes has a higher probability of achieving the Fund’s objective of providing current income.

Fixed Income. A portion of the Fund's net assets is invested in a diversified portfolio of investment grade and non-investment grade (commonly known as "junk") fixed income securities issued by U.S., supranational and non-U.S. issuers, including investments in convertible bonds, U.S. government and agency securities, asset-backed, mortgage-backed, and commercial mortgage-backed securities (securitized products), and sovereign debt. “Investment grade” securities are rated BBB- or higher by S&P Global Ratings ("S&P Global") or Baa3 or higher by Moody's Investors Service, Inc. ("Moody's") or, if unrated, of comparable quality in the opinion of those selecting such investments. “Non-investment grade” securities are rated Ba1 or lower by Moody’s and BB+ or lower by S&P Global. If securities are rated differently by the rating agencies, the highest rating is used. If the security has been rated by only one of those agencies, that rating will determine whether the security is below investment grade. If the security has not been rated by either of those agencies, those selecting such investments will determine whether the security is of a quality comparable to those rated below investment grade. The fixed income portfolio is not managed to a particular average duration or maturity.

During the fiscal year ended June 30, 2018, the average ratings of the Fund’s fixed-income assets, based on market value at each month-end, were as follows (all ratings are by Moody’s):

0.00% in securities rated Aaa	10.16% in securities rated Baa	12.29% in securities rated Caa	0.00% in securities rated D
0.15% in securities rated Aa	27.19% in securities rated Ba	0.00% in securities rated Ca	4.28% in securities not rated
6.29% in securities rated A	39.64% in securities rated B	0.00% in securities rated C

Equity Securities. A portion of the Fund's net assets is invested in a diversified portfolio of dividend paying equity securities issued by companies located in the U.S. and/or foreign countries that trade on a U.S. or foreign exchange. The equity securities include common stocks (including value stocks), preferred stocks, master limited partnerships ("MLPs") and real estate investment trusts (“REITs”). Although not a factor in the selection of the equity securities, such securities generally are of medium market capitalization companies, which for this Fund are those with market capitalizations similar to companies in the Russell Midcap^® Index (as of June 30, 2018, this range was between approximately $2.3 billion and $35.5 billion).

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

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

Convertible Securities Risk.Convertible securities are securities that are convertible into common stock. Convertible securities are subject to credit and interest rate risks associated with fixed-income securities and to stock market risk associated with equity securities.

Dividend-Oriented Stocks Risk. Companies that have paid regular dividends to shareholders may decrease or eliminate dividend payments in the future. For example, a sharp rise in interest rates or economic downturn could cause a company to unexpectedly reduce or eliminate its dividend. Additionally, the Fund’s performance during a broad market advance could suffer because dividend-paying stocks may not experience the same capital appreciation as non-dividend paying stocks.

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Medium Market Capitalization Companies.Investments in medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Fixed-Income Securities Risk.Fixed-income securities are subject to interest rate, credit quality, and liquidity risks. The market value of fixed-income securities generally declines when interest rates rise, and increased interest rates may adversely affect the liquidity of certain fixed-income securities. Moreover, an issuer of fixed-income securities could default on its payment obligations due to increased interest rates or for other reasons.

Foreign Currency Risk.Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.

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

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

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

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, which means funds with longer average portfolio durations may be more volatile than those with shorter durations.

Preferred Securities Risk. Because preferred securities have a lower priority claim on assets or earnings than senior bonds and other debt instruments in a company's capital structure, they are subject to greater credit and liquidation risk than more senior debt instruments. In addition, preferred securities are subject to other risks, such as limited or no voting rights, deferring or skipping distributions, interest rate risk, and redeeming the security prior to any stated maturity date.

Real Estate Investment Trusts (“REITs”) Risk.In addition to risks associated with investing in real estate securities, REITs are dependent upon management skills, are not diversified, and are subject to heavy cash flow dependency, risks of default by borrowers, and self-liquidation. Investment in REITs also involves risks similar to risks of investing in small market capitalization companies, such as limited financial resources, less frequent and limited volume trading, and may be subject to more abrupt or erratic price movements than larger company securities. A REIT could fail to qualify for tax-free pass-through of income under the Internal Revenue Code. Fund shareholders will indirectly bear their proportionate share of the expenses of REITs in which the fund invests.

Real Estate Securities Risk.Investing in real estate securities subjects the fund to the risks associated with the real estate market (which are similar to the risks associated with direct ownership in real estate), including declines in real estate values, loss due to casualty or condemnation, property taxes, interest rate changes, increased expenses, cash flow of underlying real estate assets, regulatory changes (including zoning, land use and rents), and environmental problems, as well as to the risks related to the management skill and creditworthiness of the issuer.

Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. When creation or redemption baskets involve a cash component, such transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. These transactions may accelerate the realization of taxable income if sales of portfolio securities result in gains and could increase transaction costs.

Securitized Products Risk. Investments in securitized products are subject to risks similar to traditional fixed income securities, such as credit, interest rate, liquidity, prepayment, extension, and default risk, as well as additional risks associated with the nature of the assets and the servicing of those assets. Unscheduled prepayments on securitized products may have to be reinvested at lower rates. A reduction in prepayments may increase the effective maturities of these securities, exposing them to the risk of decline in market value over time (extension risk).

U.S. Government Securities Risk. Yields available from U.S. government securities are generally lower than yields from many other fixed-income securities.

U.S. Government-Sponsored Securities Risk.Securities issued by U.S. government-sponsored or -chartered enterprises such as the Federal Home Loan Mortgage Corporation, the Federal National Mortgage Association, and the Federal Home Loan Banks are not issued or guaranteed by the U.S. Treasury.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Life of Fund returns are measured from the date the Fund's shares were first sold (July 8, 2015).

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

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

Bar Chart [Heading]

rr_BarChartHeading

Total Returns as of December 31 (1)

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest return for a quarter during the period of the bar chart above:	Q2 '16	6.07%
Lowest return for a quarter during the period of the bar chart above:	Q4 '17	1.07%

⁽¹⁾ The year-to-date return as of September 30, 2018 is 1.34%.

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns (Based on NAV) For the periods ended December 31, 2017

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.

Principal Exchange-Traded Funds | Principal EDGE Active Income ETF | Principal EDGE Active Income ETF, Share Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

YLD

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.65%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.65%

^[3]

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 66

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

208

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

362

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 810

Annual Return 2016

rr_AnnualReturn2016

16.19%

Annual Return 2017

rr_AnnualReturn2017

8.33%

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.34%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

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

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2016

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.07%

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, 2017

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

1.07%

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

8.33%

Since Inception

rr_AverageAnnualReturnSinceInception

6.63%

Principal Exchange-Traded Funds | Principal EDGE Active Income ETF | Principal EDGE Active Income ETF, Share Class | After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

5.88%

Since Inception

rr_AverageAnnualReturnSinceInception

4.42%

Principal Exchange-Traded Funds | Principal EDGE Active Income ETF | Principal EDGE Active Income ETF, Share Class | After Taxes on Distributions and Sales

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

4.94%

Since Inception

rr_AverageAnnualReturnSinceInception

4.12%

Principal Exchange-Traded Funds | Principal EDGE Active Income ETF | Principal EDGE Active Income ETF, Share Class | Bloomberg Barclays U.S. Corporate High Yield 2% Issuer Capped Index [Member]

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Bloomberg Barclays U.S. Corporate High Yield 2% Issuer Capped Index

1 Year

rr_AverageAnnualReturnYear01

7.50%

Since Inception

rr_AverageAnnualReturnSinceInception

6.79%

Principal Exchange-Traded Funds | Principal Healthcare Innovators Index ETF

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

PRINCIPAL HEALTHCARE INNOVATORS INDEX ETF

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq Healthcare Innovators Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 33.6% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

33.60%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

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

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities in the Nasdaq US Benchmark Index (the "Parent Index") (including growth and value stock) that are small and medium capitalization U.S. healthcare companies. Most of the companies in the Index are "early-stage companies" within the healthcare equipment and supplies, pharmaceuticals, biotechnology, and life sciences industries that are not yet consistently profitable. Examples include companies developing products and services and companies in the pre-marketing stage seeking regulatory approvals.

To be eligible for the Index, a security must be a component of the Parent Index, and each security must be classified as Health Care according to Industry Classification Benchmark (ICB). Securities are ranked based upon their market capitalization and liquidity. The Index employs a modified market capitalization weighting methodology; final eligible securities receive a maximum weight of 3%, and all excess weight is distributed proportionally across the remaining index securities. The Index is rebalanced semi-annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Index included 190 components, and the Parent Index included 2,839 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also invest in securities not included in the Index that the Advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated. Given the present composition of the Index, the Fund expects to concentrate its investments in the healthcare industry.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated. Given the present composition of the Index, the Fund expects to concentrate its investments in the healthcare industry.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk.If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Small and Medium Market Capitalization Companies.Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Industry Concentration Risk. A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries.

• Healthcare Industry Risk. Given the present composition of the Index, the Fund expects to have more than 25% of its assets invested in the healthcare industry. A fund that invests in securities of companies in the healthcare industry (which are companies involved in medical services or health care, including biotechnology research and production, drugs and pharmaceuticals and health care facilities and services) is subject to the direct risks of investing in such companies. These companies are subject to extensive competition (due to, among others, generic drug sales or the loss of patent protection), product liability litigation and increased government regulation. Research and development costs of bringing new drugs to market are substantial, and there is no guarantee that a proposed product will ever come to market. Such companies are heavily dependent on patent and intellectual property rights, the loss or impairment of which may adversely affect profitability. Healthcare facility operators may be affected by the demand for services, efforts by government or insurers to limit rates, restriction of government financial assistance and competition from other providers.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Life of Fund returns are measured from the date the Fund's shares were first sold (August 19, 2016).

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

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

Bar Chart [Heading]

rr_BarChartHeading

Total Returns as of December 31 (1)

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest return for a quarter during the period of the bar chart above:	Q1 '17	16.66%
Lowest return for a quarter during the period of the bar chart above:	Q4 '17	2.24%

⁽¹⁾ The year-to-date return as of September 30, 2018 is 18.26%.

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns For the periods ended December 31, 2017

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.

Principal Exchange-Traded Funds | Principal Healthcare Innovators Index ETF | Nasdaq US Healthcare Innovators Index

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Nasdaq US Healthcare Innovators Index

1 Year

rr_AverageAnnualReturnYear01

37.00%

Since Inception

rr_AverageAnnualReturnSinceInception

18.50%

Principal Exchange-Traded Funds | Principal Healthcare Innovators Index ETF | Principal Healthcare Innovators Index ETF Share Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

BTEC

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.42%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.42%

^[4]

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 43

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

135

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

235

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 530

Annual Return 2017

rr_AnnualReturn2017

36.31%

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

18.26%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

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

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2017

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

16.66%

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, 2017

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

2.24%

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

36.31%

Since Inception

rr_AverageAnnualReturnSinceInception

17.93%

Principal Exchange-Traded Funds | Principal Healthcare Innovators Index ETF | Principal Healthcare Innovators Index ETF Share Class | After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

36.22%

Since Inception

rr_AverageAnnualReturnSinceInception

17.87%

Principal Exchange-Traded Funds | Principal Healthcare Innovators Index ETF | Principal Healthcare Innovators Index ETF Share Class | After Taxes on Distributions and Sales

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

20.56%

Since Inception

rr_AverageAnnualReturnSinceInception

13.73%

Principal Exchange-Traded Funds | Principal International Multi-Factor Index ETF

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

PRINCIPAL INTERNATIONAL MULTI-FACTOR INDEX ETF

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq Developed Select Leaders Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 November 8, 2017, the date operations commenced, through June 30, 2018, the Fund's annualized portfolio turnover rate was 54.1% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

54.10%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

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

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities of companies in the Nasdaq Developed Market Ex-US Ex-Korea Large Mid Cap Index (the "Parent Index") that exhibit a combination of value, growth and momentum characteristics, with higher weights given to securities that are more liquid and less volatile.

The Parent Index is composed of developed foreign market equity securities of issuers that have medium and large market capitalizations. Securities in the top 90% of the Parent Index based on three month average daily dollar trading volume are eligible for the Index. Each security is ranked according to three factors:

• The Shareholder Yield (value factor) ranks securities based on the collective financial impact on a company's shareholders from the return of free cash flow through cash dividends, stock repurchases, and debt reduction. This factor is designed to identify securities with low prices relative to their fundamental value.

• The Price Setters (growth factor) ranks securities based on pricing power, which is the extent to which a company can raise the prices of its products without reducing the demand for them.

• The Momentum Factor ranks securities based on recent performance relative to their peers.

Each security has a Shareholder Yield, Price Setters, and Momentum rank that is based on that security's country within the Index. The ranks are then averaged to determine a rank for each security within each country. Securities that rank in the top 20% are included in the Index, in addition to securities already in the Index that rank in the top 50%. Securities are weighted by their liquidity-volatility score, in an effort to give greater weight to securities that are more liquid and less volatile. Each security weight is capped at 1.5%, and any excess weight is distributed proportionally first by country then across the Index.

The Index is rebalanced semi-annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after the Index changes are made public. As of June 30, 2018, the Underlying Index included 316 components, and the Parent Index included 1,200 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also purchase securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk.If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Medium Market Capitalization Companies.Investments in medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk.Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Foreign Currency Risk.Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.

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

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Momentum Style Risk. Stocks that previously exhibited high momentum characteristics may not experience positive momentum or may experience more volatility than the market as a whole. In addition, there may be periods when momentum style is out of favor, during which the investment performance of a Fund that uses momentum-based strategies may suffer.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

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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 is benchmarked against the Nasdaq Developed Select Leaders Index. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The Fund’s performance is benchmarked against the Nasdaq Developed Select Leaders Index. Performance information provides an indication of the risks of investing in the Fund.

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.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

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

Principal Exchange-Traded Funds | Principal International Multi-Factor Index ETF | Principal International Multi-Factor Index ETF, Share Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

PXUS

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.39%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.39%

^[5]

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 40

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

125

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

219

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 493

Principal Exchange-Traded Funds | Principal Investment Grade Corporate Active ETF Series

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

PRINCIPAL INVESTMENT GRADE CORPORATE ACTIVE ETF

Objective [Heading]

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Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide current income

Objective, Secondary [Text Block]

rr_ObjectiveSecondaryTextBlock

and, as a secondary objective, capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund ("Shares"). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 April 16, 2018, the date operations commenced, through June 30, 2018, the Fund's annualized portfolio turnover rate was 47.8% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

47.80%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

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

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is an actively managed exchange-traded fund (“ETF”) that seeks to achieve its investment objective by investing, under normal circumstances, at least 80% of its net assets, plus any borrowings for investment purposes, in investment grade corporate bonds and other fixed income securities at the time of purchase. “Investment grade” securities are rated BBB- or higher by S&P Global Ratings ("S&P Global") or Baa3 or higher by Moody's Investors Service, Inc. ("Moody's") or, if unrated, of comparable quality in the opinion of those selecting such investments. If the security has been rated by only one of those agencies, that rating will determine whether the security is investment grade. If securities are rated differently by the rating agencies, the highest rating is used.

The fixed income securities in which the Fund invests include foreign securities, corporate securities, securities issued or guaranteed by the U.S. government or its agencies and instrumentalities, and securities issued or guaranteed by foreign governments payable in U.S. dollars. The Fund invests in other investment companies, including exchange-traded funds that invest in fixed income securities. The portfolio is not managed to a particular maturity. Under normal circumstances, the Fund maintains an average portfolio duration that is within +/- 10% of the duration of the Bloomberg Barclays U.S. Corporate Investment Grade Bond Index, which as of June 30, 2018 was 7.26 years. The Fund actively trades securities.

The Fund utilizes exchange-traded and over-the-counter derivative strategies. A derivative is a financial arrangement, the value of which is derived from, or based on, a traditional security, asset, or market index. Specifically, the Fund invests in treasury futures for hedging or to otherwise manage fixed income exposure, as well as credit default swaps, including buying and selling on individual securities and/or baskets of securities, to efficiently manage exposures to certain sectors or individual issuers.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

Counterparty Risk. Counterparty risk is the risk that the counterparty to a contract or other obligation will be unable or unwilling to honor its obligations.

Derivatives Risk.Derivatives may not move in the direction anticipated by the portfolio manager. Transactions in derivatives may increase volatility, cause the liquidation of portfolio positions when not advantageous to do so and result in disproportionate losses that may be substantially greater than a fund's initial investment.

• Credit Default Swaps.Credit default swaps involve special risks in addition to those associated with swaps generally because they are difficult to value, are highly susceptible to liquidity and credit risk, and generally pay a return to the party that has paid the premium only in the event of an actual default by the issuer of the underlying obligation (as opposed to a credit downgrade or other indication of financial difficulty). The protection “buyer” in a credit default contract may be obligated to pay the protection “seller” an up-front payment or a periodic stream of payments over the term of the contract provided generally that no credit event on a reference obligation has occurred. If a credit event occurs, the seller generally must pay the buyer the “par value” (i.e., full notional value) of the swap in exchange for an equal face amount of deliverable obligations of the reference entity described in the swap, or the seller may be required to deliver the related net cash amount, if the swap is cash settled. The Fund may be either the buyer or seller in the transaction.

• Futures.These derivative instruments involve specific risks, including: the imperfect correlation between the change in market value of the instruments held by the fund and the price of the instruments; possible lack of a liquid secondary market for an instrument and the resulting inability to close it when desired; counterparty risk; and if the fund has insufficient cash, it may have to sell securities from its portfolio to meet any applicable daily variation margin requirements.

Fixed-Income Securities Risk.Fixed-income securities are subject to interest rate, credit quality, and liquidity risks. The market value of fixed-income securities generally declines when interest rates rise, and increased interest rates may adversely affect the liquidity of certain fixed-income securities. Moreover, an issuer of fixed-income securities could default on its payment obligations due to increased interest rates or for other reasons.

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

Hedging Risk.A fund that implements a hedging strategy using derivatives and/or securities could expose the fund to the risk that can arise when a change in the value of a hedge does not match a change in the value of the asset it hedges. In other words, the change in value of the hedge could move in a direction that does not match the change in value of the underlying asset, resulting in a risk of loss to the fund.

Investment Company Securities Risk.A fund that invests in another investment company (for example, another fund or ETF) is subject to the risks associated with direct ownership of the securities in which such investment company invests. Fund shareholders indirectly bear their proportionate share of the expenses of each such investment company.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

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, which means funds with longer average portfolio durations may be more volatile than those with shorter durations.

Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. When creation or redemption baskets involve a cash component, such transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. These transactions may accelerate the realization of taxable income if sales of portfolio securities result in gains and could increase transaction costs.

U.S. Government Securities Risk. Yields available from U.S. government securities are generally lower than yields from many other fixed-income securities.

U.S. Government-Sponsored Securities Risk.Securities issued by U.S. government-sponsored or -chartered enterprises such as the Federal Home Loan Mortgage Corporation, the Federal National Mortgage Association, and the Federal Home Loan Banks are not issued or guaranteed by the U.S. Treasury.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

No performance information is shown because the Fund has not yet had a calendar year of performance. The Fund’s performance is benchmarked against the Bloomberg Barclays U.S. Corporate Investment Grade Bond Index. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The Fund’s performance is benchmarked against the Bloomberg Barclays U.S. Corporate Investment Grade Bond Index. Performance information provides an indication of the risks of investing in the Fund.

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.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

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

Principal Exchange-Traded Funds | Principal Investment Grade Corporate Active ETF Series | Principal Investment Grade Corporate Active ETF Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

IG

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.26%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.26%

^[6]

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 27

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

$ 84

Principal Exchange-Traded Funds | Principal Millennials Index ETF

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

PRINCIPAL MILLENNIALS INDEX ETF

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq Global Millennial Opportunity Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 35.6% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

35.60%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

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

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities of companies in the Nasdaq Global Index (the "Parent Index") that are impacted by the spending and lifestyle activities of the Millennial generation, which refers to people born from 1980 to the mid-2000s. The Index may include equity securities of different market capitalizations (small, medium, or large) and styles (growth or value) and is weighted based upon capitalization and exposure to Millennials. Market segments with the greatest Millennial exposure are likely to include, without limitation, consumer goods (including fashion and apparel), social media and e-commerce, and digital media and technology.

To be eligible for the Index, a security must be a component of the Parent Index. However, an exchange-listed security that is not a component of the Parent Index may be eligible if it otherwise meets all of the eligibility criteria. Each security's exposure to Millennials is determined using a proprietary, multi-step research process. Each company is identified as having low, medium, or high exposure to Millennials based on the materiality of the company's exposure to Millennial-related themes and the potential role of Millennials in driving long-term growth. To be eligible for the Index, a security must have high or medium exposure to Millennials. "Medium exposure" means that Millennials-related products, technologies, services and solutions are an important factor of the company's business model, strategy and research and development, and are material to sales and/or growth. "High exposure" means that Millennials-related products, technologies, services and solutions are core to the company's business model, strategy and research and development, and are material to sales and/or growth. Securities of companies having high exposure to Millennials receive 70% of the weight of the index, and securities of companies having medium exposure to Millennials receive 30% of the weight of the index.

The Index is rebalanced annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Index included 103 components, and the Parent Index included 8,945 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also invest in securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

Consumer Goods and Consumer Services Sectors Risk. The Fund expects to invest in securities of companies in the consumer services and consumers goods sectors to the extent the Index is composed of such securities. Such companies are particularly subject to risks related to performance of the overall global economy, interest rates, competition, government regulation, and consumer confidence. Success depends heavily on disposable income and consumer spending, and is also impacted by consumer interest and marketing campaigns. Companies in these sectors may be subject to severe competition, which may have an adverse impact on their profitability. Changes in demographics and consumer tastes can affect the demand for, and success of, consumer goods and
services in the marketplace.

Equity Securities Risk. The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk.If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Small and Medium Market Capitalization Companies. Investments in small and medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Foreign Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.

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

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Information Technology Sector Risk.The Fund expects to invest in securities of companies in the information technology sector to the extent the Index is composed of such securities. Such companies may face dramatic and often unpredictable changes in growth rates and are particularly vulnerable to changes in technology product cycles, product obsolescence, government regulation, and competition, both domestically and internationally. Such companies are heavily dependent on patent and intellectual property rights, the loss or impairment of which may adversely affect profitability.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Life of Fund returns are measured from the date the Fund's shares were first sold (August 19, 2016).

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

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

Bar Chart [Heading]

rr_BarChartHeading

Total Returns as of December 31 (1)

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest return for a quarter during the period of the bar chart above:	Q4 '17	10.26%
Lowest return for a quarter during the period of the bar chart above:	Q1 '17	8.24%

⁽¹⁾ The year-to-date return as of September 30, 2018 is 12.69%.

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns For the periods ended December 31, 2017

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.

Principal Exchange-Traded Funds | Principal Millennials Index ETF | Nasdaq Global Millennial Opportunity Index

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Nasdaq Global Millennial Opportunity Index

1 Year

rr_AverageAnnualReturnYear01

41.97%

Since Inception

rr_AverageAnnualReturnSinceInception

28.11%

Principal Exchange-Traded Funds | Principal Millennials Index ETF | Principal Millennials Index ETF Share Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

GENY

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.45%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.45%

^[7]

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 46

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

144

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

252

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 567

Annual Return 2017

rr_AnnualReturn2017

41.08%

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

12.69%

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, 2017

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

10.26%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

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

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Mar. 31, 2017

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

8.24%

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

41.08%

Since Inception

rr_AverageAnnualReturnSinceInception

27.33%

Principal Exchange-Traded Funds | Principal Millennials Index ETF | Principal Millennials Index ETF Share Class | After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

40.76%

Since Inception

rr_AverageAnnualReturnSinceInception

27.04%

Principal Exchange-Traded Funds | Principal Millennials Index ETF | Principal Millennials Index ETF Share Class | After Taxes on Distributions and Sales

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

23.47%

Since Inception

rr_AverageAnnualReturnSinceInception

20.98%

Principal Exchange-Traded Funds | Principal Price Setters Index ETF

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

PRINCIPAL PRICE SETTERS INDEX ETF

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq US Price Setters Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

October 31, 2019

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 63.5% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

63.50%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities of mid- to large-capitalization companies in the Nasdaq US Large Mid Cap Index (the "Parent Index") that exhibit high degrees of pricing power. "Pricing power" refers to the extent to which a company can raise the prices of its products without reducing the demand for them.

To be eligible for the Index, a security must be a component of the Parent Index and must be a top 550 name by market capitalization. Securities are ranked based upon eleven factors that include calculations based on earnings per share ("EPS") growth, operating margin, operating margin growth, return volatility, sales growth, return on equity, and earning quality. The average of the 11 factor scores is taken to create one score used to rank the securities. The top 150 securities by final rank are selected. The Index employs a modified equal dollar weighting methodology with those in the higher ranking groups receiving relatively more weight.

The Index is rebalanced annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Index included 146 components, and the Parent Index included 930 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also purchase securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Medium Market Capitalization Companies.Investments in medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Life of Fund returns are measured from the date the Fund's shares were first sold (March 21, 2016).

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

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

Bar Chart [Heading]

rr_BarChartHeading

Total Returns as of December 31 (1)

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest return for a quarter during the period of the bar chart above:	Q4 '17	7.05%
Lowest return for a quarter during the period of the bar chart above:	Q3 '17	3.90%

⁽¹⁾ The year-to-date return as of September 30, 2018 is 10.15%.

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns For the periods ended December 31, 2017

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.

Principal Exchange-Traded Funds | Principal Price Setters Index ETF | Nasdaq US Price Setters Index

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Nasdaq US Price Setters Index

1 Year

rr_AverageAnnualReturnYear01

24.97%

Since Inception

rr_AverageAnnualReturnSinceInception

17.05%

Principal Exchange-Traded Funds | Principal Price Setters Index ETF | Principal Price Setters Index ETF Share Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

PSET

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.40%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.40%

^[8]

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.11%)

^[9]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.29%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 30

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

117

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

213

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 494

Annual Return 2017

rr_AnnualReturn2017

24.46%

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

10.15%

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, 2017

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

7.05%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

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

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2017

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

3.90%

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

24.46%

Since Inception

rr_AverageAnnualReturnSinceInception

16.56%

Principal Exchange-Traded Funds | Principal Price Setters Index ETF | Principal Price Setters Index ETF Share Class | After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

24.08%

Since Inception

rr_AverageAnnualReturnSinceInception

16.17%

Principal Exchange-Traded Funds | Principal Price Setters Index ETF | Principal Price Setters Index ETF Share Class | After Taxes on Distributions and Sales

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

14.03%

Since Inception

rr_AverageAnnualReturnSinceInception

12.71%

Principal Exchange-Traded Funds | Principal Shareholder Yield Index ETF

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

PRINCIPAL SHAREHOLDER YIELD INDEX ETF

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq US Shareholder Yield Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

October 31, 2019

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 55.5% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

55.50%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities (including value stock) of mid- to large-capitalization companies in the Nasdaq US Large Mid Cap Index (the "Parent Index") that exhibit high degrees of sustainable, shareholder yield. "Shareholder yield" refers to the collective financial impact on a company's shareholders from the return of free cash flow through cash dividends, stock repurchases, and debt reduction.

To be eligible for the Index, a security must be a component of the Parent Index and the security must have paid a regular dividend in the prior year. Securities are ranked based upon nine factors that include calculations based on dividend yield, buyback yield, dividend payout per share, free cash flow, price, Sharpe ratio, EBITDA, debt, dividend yield historical valuation, and dividend growth. Securities that rank in the top 20% are included in the Index. The Index employs a modified equal dollar weighting methodology with those in the higher ranking groups receiving relatively more weight.

The Index is rebalanced annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Index included 138 components, and the Parent Index included 930 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also purchase securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Medium Market Capitalization Companies.Investments in medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Life of Fund returns are measured from the date the Fund's shares were first sold (March 21, 2016).

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

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

Bar Chart [Heading]

rr_BarChartHeading

Total Returns as of December 31 (1)

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest return for a quarter during the period of the bar chart above:	Q4 '17	7.88%
Lowest return for a quarter during the period of the bar chart above:	Q2 '17	1.96%

⁽¹⁾ The year-to-date return as of September 30, 2018 is 4.76%.

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns For the periods ended December 31, 2017

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.

Principal Exchange-Traded Funds | Principal Shareholder Yield Index ETF | Nasdaq US Shareholder Yield Index

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Nasdaq US Shareholder Yield Index

1 Year

rr_AverageAnnualReturnYear01

19.54%

Since Inception

rr_AverageAnnualReturnSinceInception

18.77%

Principal Exchange-Traded Funds | Principal Shareholder Yield Index ETF | Principal Shareholder Yield Index ETF Share Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

PY

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.40%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.40%

^[10]

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.11%)

^[11]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.29%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 30

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

117

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

213

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 494

Annual Return 2017

rr_AnnualReturn2017

19.07%

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

4.76%

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, 2017

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

7.88%

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

Jun. 30, 2017

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

1.96%

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

19.07%

Since Inception

rr_AverageAnnualReturnSinceInception

18.25%

Principal Exchange-Traded Funds | Principal Shareholder Yield Index ETF | Principal Shareholder Yield Index ETF Share Class | After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

18.55%

Since Inception

rr_AverageAnnualReturnSinceInception

17.65%

Principal Exchange-Traded Funds | Principal Shareholder Yield Index ETF | Principal Shareholder Yield Index ETF Share Class | After Taxes on Distributions and Sales

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

11.16%

Since Inception

rr_AverageAnnualReturnSinceInception

14.03%

Principal Exchange-Traded Funds | Principal Spectrum Preferred Securities Active ETF

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

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PRINCIPAL SPECTRUM PREFERRED SECURITIES ACTIVE ETF

Objective [Heading]

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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 ("Shares"). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below

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 July 7, 2017, the date operations commenced, through June 30, 2018, the Fund's annualized portfolio turnover rate was 41.0% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

41.00%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

Expense Example [Heading]

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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 funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

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

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

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. Examples of preferred securities include preferred stock, certain depositary receipts, and various types of junior subordinated debt (such debt generally includes the contractual ability to defer payment of interest without accelerating an immediate default event). In particular, the Fund focuses on preferred securities known as “$1,000 par preferred securities” which are issued in large, institutional lot sizes, typically by U.S. and non-U.S. financial services companies (i.e., banking, insurance and commercial finance companies) and other corporations. Preferred securities generally pay fixed and floating rate distributions and are junior to all forms of the company's senior debt, but may have "preference" over common stock in the payment of distributions and the liquidation of a company's assets. The Fund may invest its assets in below investment grade preferred securities (sometimes called “high yield” or "junk") which are rated at the time of purchase Ba1 or lower by Moody's Investors Service, Inc. (“Moody’s”) and BB+ or lower by Standard & Poor’s Rating Service (“S&P”) (if a security is rated differently by the rating agencies, the highest rating is used; if the security has been rated by only one of those agencies, that rating will determine whether the security is below investment grade; If the security has not been rated by either of those agencies, the Sub-Advisor will determine whether the security is of a quality comparable to those rated below investment grade).

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

During the fiscal year ended June 30, 2018, the average ratings of the Fund’s fixed-income assets, based on market value at each month-end, were as follows (all ratings are by Moody’s):

0.00% in securities rated Aaa	44.70% in securities rated Baa	0.00% in securities rated Caa	0.00% in securities rated D
0.00% in securities rated Aa	48.10% in securities rated Ba	0.00% in securities rated Ca	0.00% in securities not rated
7.20% in securities rated A	0.00% in securities rated B	0.00% in securities rated C

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

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

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

Fixed-Income Securities Risk.Fixed-income securities are subject to interest rate, credit quality, and liquidity risks. The market value of fixed-income securities generally declines when interest rates rise, and increased interest rates may adversely affect the liquidity of certain fixed-income securities. Moreover, an issuer of fixed-income securities could default on its payment obligations due to increased interest rates or for other reasons.

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

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

Industry Concentration Risk.A fund that concentrates investments in a particular industry or group of industries has greater exposure than other funds to market, economic and other factors affecting that industry or group of industries.

• Financial Services. A fund concentrating in financial services companies may be more susceptible to adverse economic or regulatory occurrences affecting financial services companies. Financial companies may be adversely affected in certain market cycles, including periods of rising interest rates, which may restrict the availability and increase the cost of capital, and declining economic conditions, which may cause credit losses due to financial difficulties of borrowers. Because many types of financial companies are especially vulnerable to these economic cycles, the Fund’s investments in these companies may lose significant value during such periods.

Liquidity Risk. A Fund is exposed to liquidity risk when trading volume, lack of a market maker, or legal restrictions impair the Fund's ability to sell particular securities or close derivative positions at an advantageous price. Funds with principal investment strategies that involve certain fixed-income securities, securities of companies with smaller market capitalizations, foreign securities, derivatives, high yield bonds and bank loans or securities with substantial market and/or credit risk tend to have the greatest exposure to liquidity risk.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

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, which means funds with longer average portfolio durations may be more volatile than those with shorter durations.

Preferred Securities Risk. Because preferred securities have a lower priority claim on assets or earnings than senior bonds and other debt instruments in a company's capital structure, they are subject to greater credit and liquidation risk than more senior debt instruments. In addition, preferred securities are subject to other risks, such as limited or no voting rights, deferring or skipping distributions, interest rate risk, and redeeming the security prior to any stated maturity date.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

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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 is benchmarked against the BofA Merrill Lynch US Investment Grade Institutional Capital Securities Index. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The Fund’s performance is benchmarked against the BofA Merrill Lynch US Investment Grade Institutional Capital Securities Index. Performance information provides an indication of the risks of investing in the Fund.

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.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

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

Principal Exchange-Traded Funds | Principal Spectrum Preferred Securities Active ETF | Principal Spectrum Preferred Securities Active ETF, Share Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

PREF

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.55%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.55%

^[12]

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 56

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

176

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

307

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 689

Principal Exchange-Traded Funds | Principal Sustainable Momentum Index ETF

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

PRINCIPAL SUSTAINABLE MOMENTUM INDEX ETF

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq US Sustainable Momentum Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 18, 2017, the date operations commenced, through June 30, 2018, the Fund's annualized portfolio turnover rate was 158.1% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

158.10%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 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 that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities (including growth and value stocks) of companies in the Nasdaq US Large Mid Cap Index (the “Parent Index”) that exhibit sustainable price momentum, based on historical stock prices over multiple periods and taking multiple market environments into consideration. The Fund actively trades portfolio securities.

To be eligible for the Index, a security must be a component of the Parent Index, which is composed of equity securities of U.S. issuers with medium and large market capitalizations. Each security is assigned Sustainable Momentum (SUMO) Score based on intermediate factors (3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 month risk-adjusted returns) and long-term factors (36, 48, and 60 month risk-adjusted returns), with volatility adjustments used to determine a composite score. Securities with SUMO scores that rank in the top 15% are included in the Index, in addition to securities already in the Index that rank in the top 35%. Once selected, the securities are weighted, generally giving those in the higher ranking groups relatively more weight. Weighting is also determined in part on whether the Index is in a "high volatility regime" (where the ratio of the 1 month to 12 month standard deviation of the daily returns of the Parent Index exceeds the trailing seven year average of this ratio by a threshold amount).

The Index is rebalanced annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. Market volatility is monitored monthly; if the Index is determined to be in a high volatility regime, there is a special rebalance. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Underlying Index included 137 components, and the Parent Index included 930 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also purchase securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk.If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Medium Market Capitalization Companies.Investments in medium sized companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk.Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Momentum Style Risk. Stocks that previously exhibited high momentum characteristics may not experience positive momentum or may experience more volatility than the market as a whole. In addition, there may be periods when momentum style is out of favor, during which the investment performance of a Fund that uses momentum-based strategies may suffer.

Portfolio Turnover (Active Trading) Risk. High portfolio turnover (more than 100%) caused by actively trading portfolio securities may result in accelerating the realization of taxable gains and losses, lower fund performance and increased brokerage costs.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

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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 is benchmarked against the Nasdaq US Sustainable Momentum Index. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The Fund’s performance is benchmarked against the Nasdaq US Sustainable Momentum Index. Performance information provides an indication of the risks of investing in the Fund.

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.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

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

Principal Exchange-Traded Funds | Principal Sustainable Momentum Index ETF | Principal Sustainable Momentum Index ETF, Share Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

PMOM

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.29%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.29%

^[13]

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 30

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

93

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

163

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 368

Principal Exchange-Traded Funds | Principal U.S. Mega-Cap Multi-Factor Index ETF

Prospectus:

rr_ProspectusTable

Risk/Return [Heading]

rr_RiskReturnHeading

PRINCIPAL U.S. MEGA-CAP MULTI-FACTOR INDEX ETF

Objective [Heading]

rr_ObjectiveHeading

Objective:

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq US Mega Cap Select Leaders Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

October 31, 2019

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 11, 2017, the date operations commenced, through June 30, 2018, the Fund's annualized portfolio turnover rate was 39.8% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

39.80%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 funds.

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

The Example assumes that you invest $10,000 in the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account contractual fee waivers and/or expense reimbursements for the period noted in the table above. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities of companies in the Nasdaq US 500 Large Cap Index (the "Parent Index") that have the largest market capitalizations, with higher weights given to less volatile securities.

The Parent Index is composed of equity securities of U.S. issuers with large market capitalizations. To be eligible for the Index, a security must be in the top 50th percentile of the Parent Index by aggregate company market capitalization. As of June 30, 2018, the market capitalization range of the companies in the Parent Index was between approximately $8.2 billion and $909.8 billion.

The Index employs a modified equal-dollar weighting methodology. With respect to securities of companies in the top 10% of aggregate market capitalization, companies with the largest market capitalizations receive relatively more weight. Securities of the remaining companies are equally weighted and volatility adjusted, which gives higher weight to securities that are more liquid and less volatile.

The Index is rebalanced semi-annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after the Index changes are made public. As of June 30, 2018, the Index included 52 components, and the Parent Index included 500 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also purchase securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund will not concentrate its investments (invest more than 25% of its assets) in a particular industry except to the extent the Index is so concentrated.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Redemption Risk.A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. When creation or redemption baskets involve a cash component, such transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. These transactions may accelerate the realization of taxable income if sales of portfolio securities result in gains and could increase transaction costs.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

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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 is benchmarked against the Nasdaq US Mega Cap Select Leaders Index. Performance information provides an indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The Fund’s performance is benchmarked against the Nasdaq US Mega Cap Select Leaders Index. Performance information provides an indication of the risks of investing in the Fund.

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.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

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

Principal Exchange-Traded Funds | Principal U.S. Mega-Cap Multi-Factor Index ETF | Principal U.S. Mega-Cap Multi-Factor Index ETF, Share Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

USMC

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.15%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Expenses (as a percentage of Assets)

rr_ExpensesOverAssets

0.15%

^[14]

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[15]

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.12%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 12

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

45

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

82

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 189

Principal Exchange-Traded Funds | Principal U.S. Small Cap Index ETF

Prospectus:

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Risk/Return [Heading]

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PRINCIPAL U.S. SMALL-CAP MULTI-FACTOR INDEX ETF

Objective [Heading]

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Objective:

Objective, Primary [Text Block]

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The Fund seeks to provide investment results that closely correspond, before expenses, to the performance of the Nasdaq US Small Cap Select Leaders Index (the "Index").

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 (“Shares”). Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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]

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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 76.3% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

76.30%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

Investors may pay brokerage commissions on their purchases and sales of Shares, which are not reflected in the table or the example below.

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 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. 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]

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Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies that compose the Index at the time of purchase. The Index uses a quantitative model designed to identify equity securities (including growth and value stock) of small-capitalization companies in the Nasdaq US Small Cap Index (the "Parent Index") that exhibit potential for high degrees of sustainable shareholder yield, pricing power and strong momentum, while adjusting for liquidity and quality. As of June 30, 2018, the market capitalization range of the companies comprising the Parent Index was between approximately $8.0 million and $6.8 billion.

To be eligible for the Index, a security must: be a component of the Parent Index; be in the top 90th percentile of the Nasdaq US Benchmark Index in terms of 3-month Average Daily Dollar Volume and have a minimum 3-month trading history, among other factors. One security per issuer is permitted.

Each security is ranked according to three factors:

• The Shareholder Yield (value factor) ranks securities based on the collective financial impact on a company's shareholders from the return of free cash flow through cash dividends, stock repurchases, and debt reduction. This factor is designed to identify securities with low prices relative to their fundamental value.

• The Price Setters (growth factor) ranks securities based on pricing power, which is the extent to which a company can raise the prices of its products without reducing the demand for them.

• The Momentum Factor ranks securities based on recent performance relative to their peers.

Each security has a Shareholder Yield, Price Setters, and Momentum rank that is based on that security's Industry Classification Benchmark ("ICB") within the Index. The ranks are then averaged to determine a rank for each security within each ICB. The ranks are then averaged to determine eligibility for inclusion in the Index. Securities that rank in the top 20% are included in the Index, in addition to securities already in the Index that rank in the top 50%. Securities are weighted by their liquidity-volatility score, in an effort to give greater weight to securities that are more liquid and less volatile. Once an initial weight is determined, a final weight initially caps each security's weight at 0.7%.

The Index is rebalanced semi-annually. Additionally, throughout the year securities that become ineligible for the Index are removed and not replaced. The Fund will make corresponding changes to its portfolio shortly after Index changes are made public. As of June 30, 2018, the Index included 462 components, and the Parent Index included 1,909 components. More detailed information about the Index methodology is provided in the prospectus under Fund Account Information.

The Fund employs a passive investment approach designed to attempt to track the performance of the Index. In seeking its objective, the Fund typically employs a "full replication" strategy which involves investing in all the securities that make up the Index, in the same approximate proportions as the Index. The Fund can, however, use a “sampling” methodology to purchase a subset of the securities in the Index in an effort to hold a portfolio of securities with generally the same risk and return characteristics of the Index. The Fund can also invest in securities not included in the Index that the advisor believes will help the fund track the Index.

The Fund will not concentrate (invest more than 25% of its assets) its investments in a particular industry except to the extent the Index is so concentrated.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund will not concentrate (invest more than 25% of its assets) its investments in a particular industry except to the extent the Index is so concentrated.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

Equity Securities Risk.The value of equity securities could decline if the issuer’s financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Growth Stock Risk. If growth companies do not increase their earnings at a rate expected by investors, the market price of the stock may decline significantly, even if earnings show an absolute increase. Growth company stocks also typically lack the dividend yield that can lessen price declines in market downturns.

• Small Market Capitalization Companies. Investments in smaller companies may involve greater risk and price volatility than investments in larger, more mature companies.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by a fund, or the events that would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock that appears to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Index Fund Risk.An index fund has operating and other expenses while an index does not. As a result, over time, index funds tend to underperform the index. The correlation between fund performance and index performance may also be affected by the type of passive investment approach used by a fund (sampling or replication), changes in securities markets, changes in the composition of the index, and the timing of purchases and sales of fund shares.

Market Trading Risks. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, and disruption to the activities of market makers, authorized participants, or other participants and in the creation/redemption process of the Fund. ANY OF THESE FACTORS MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Momentum Style Risk. Stocks that previously exhibited high momentum characteristics may not experience positive momentum or may experience more volatility than the market as a whole. In addition, there may be periods when momentum style is out of favor, during which the investment performance of a Fund that uses momentum-based strategies may suffer.

Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. When creation or redemption baskets involve a cash component, such transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs, result in changes to expense ratios and increased expenses, and adversely affect underlying fund performance. These transactions may accelerate the realization of taxable income if sales of portfolio securities result in gains and could increase transaction costs.

Risk Lose Money [Text]

rr_RiskLoseMoney

The value of your investment in the Fund changes with the value of the Fund's investments. Many factors affect that value, and it is possible to lose money by investing in the Fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

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

Bar Chart and Performance Table [Heading]

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Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.

The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Life of Fund returns are measured from the date the Fund's shares were first sold (September 21, 2016).

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following information provides some indication of the risks of investing in the Fund. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You may get updated performance information by calling 1-800-787-1621 or online at www.principalfunds.com/etf-funds.The bar chart shows the investment returns of the Fund’s shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Fund). The table shows for the last one, five, and ten calendar year periods (or, if shorter, the life of the Fund), how the Fund’s average annual total returns compare with those of one or more broad measures of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-787-1621

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.principalfunds.com/etf-funds

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 (1)

Bar Chart Closing [Text Block]

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Highest return for a quarter during the period of the bar chart above:	Q3 '17	4.73%
Lowest return for a quarter during the period of the bar chart above:	Q2 '17	1.99%

⁽¹⁾ The year-to-date return as of September 30, 2018 is 13.86%.

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns For the periods ended December 31, 2017

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.

Principal Exchange-Traded Funds | Principal U.S. Small Cap Index ETF | Nasdaq US Small Cap Select Leaders Index

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Nasdaq US Small Cap Select Leaders Index

1 Year

rr_AverageAnnualReturnYear01

13.91%

Since Inception

rr_AverageAnnualReturnSinceInception

20.10%

Principal Exchange-Traded Funds | Principal U.S. Small Cap Index ETF | Principal U.S. Small Cap Index ETF, Share Class

Prospectus:

rr_ProspectusTable

Trading Symbol

dei_TradingSymbol

PSC

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.38%

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

none

Net Expenses (as a percentage of Assets)

rr_NetExpensesOverAssets

0.38%

^[16]

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 39

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

122

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

213

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 480

Annual Return 2017

rr_AnnualReturn2017

13.41%

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Sep. 30, 2018

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

13.86%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

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

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2017

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

4.73%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

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

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2017

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

1.99%

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

13.41%

Since Inception

rr_AverageAnnualReturnSinceInception

19.53%

Principal Exchange-Traded Funds | Principal U.S. Small Cap Index ETF | Principal U.S. Small Cap Index ETF, Share Class | After Taxes on Distributions

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

13.13%

Since Inception

rr_AverageAnnualReturnSinceInception

19.23%

Principal Exchange-Traded Funds | Principal U.S. Small Cap Index ETF | Principal U.S. Small Cap Index ETF, Share Class | After Taxes on Distributions and Sales

Prospectus:

rr_ProspectusTable

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

7.80%

Since Inception

rr_AverageAnnualReturnSinceInception

14.94%

[1] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[2] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[3] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[4] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[5] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[6] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[7] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[8] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[9] PGI has contractually agreed to reduce total annual fund operating expenses for the Fund by waiving a portion of its management fee, to the extent that total expenses exceed 0.29% (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) expressed as a percent of average net assets on an annualized basis. It is expected that the expense limit will continue through the period ending October 31, 2019; however, Principal Exchange-Traded Funds and PGI, the parties to the agreement, may mutually agree to terminate the expense limit prior to the end of the period.

[10] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[11] PGI has contractually agreed to reduce total annual fund operating expenses for the Fund by waiving a portion of its management fee, to the extent that total expenses exceed 0.29% (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) expressed as a percent of average net assets on an annualized basis. It is expected that the expense limit will continue through the period ending October 31, 2019; however, Principal Exchange-Traded Funds and PGI, the parties to the agreement, may mutually agree to terminate the expense limit prior to the end of the period.

[12] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[13] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[14] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.

[15] Principal Global Investors, LLC ("PGI") has contractually agreed to reduce total annual fund operating expenses for the Fund by waiving a portion of its management fee, or reimbursing the Fund, to the extent that total expenses exceed 0.12% (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) expressed as a percent of average net assets on an annualized basis. It is expected that the expense limit will continue through the period ending October 31, 2019; however, Principal Exchange-Traded Funds and PGI, the parties to the agreement, may mutually agree to terminate the expense limit prior to the end of the period.

[16] The investment management agreement (the “Management Agreement”) between the Fund and Principal Global Investors, LLC (“PGI”) provides that, for the duration of the Management Agreement, PGI will pay all operating expenses of the Fund, except for the Management Fee, payments made under each Series 12b-1 plan (if or when such fees are imposed), brokerage commissions and other expenses connected to the execution of portfolio transactions, interest expense, taxes, acquired fund fees and expenses, litigation expenses and other extraordinary expenses.