Label

Element

Value

Risk/Return:

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Registrant Name

dei_EntityRegistrantName

First Trust Exchange-Traded Fund

Prospectus Date

rr_ProspectusDate

May 01, 2020

First Trust Dow Jones Internet Index Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Summary Information

Objective [Heading]

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Investment Objective

Objective, Primary [Text Block]

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The First Trust Dow Jones Internet Index Fund (the "Fund") seeks investment results that correspond generally to the price and yield (before the Fund's fees and expenses) of an equity index called the Dow Jones Internet Composite Index^SM (the "Index").

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

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The following table describes the fees and expenses you may pay if you buy and hold shares of the Fund. Investors purchasing and selling shares may be subject to costs (including customary brokerage commissions) charged by their broker, which are not reflected in the table below.

Shareholder Fees Caption [Text]

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Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

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

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

April 30, 2021

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 28% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

28.00%

Expense Example [Heading]

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Example

Expense Example, No Redemption Narrative [Text Block]

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The example below is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. This example does not take into account customary brokerage commissions that you pay when purchasing or selling shares of the Fund in the secondary market.

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 at current levels. The example assumes that the Fund's investment advisor's agreement to waive fees and/or pay the Fund's expenses to the extent necessary to prevent the operating expenses of the Fund (excluding interest expense, brokerage commissions and other trading expenses, acquired fund fees and expenses, taxes, and extraordinary expenses) from exceeding 0.60% of average daily net assets per year will be terminated following April 30, 2021. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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The Fund will normally invest at least 90% of its net assets (including investment borrowings) in the common stocks that comprise the Index. The Fund, using an indexing investment approach, attempts to replicate, before fees and expenses, the performance of the Index. The Fund's investment advisor seeks a correlation of 0.95 or better (before fees and expenses) between the Fund's performance and the performance of the Index; a figure of 1.00 would represent perfect correlation. The Index is developed, maintained and sponsored by S&P Dow Jones Indices LLC (the "Index Provider"). The Index Provider reserves the right to make exceptions when applying the methodology if the need arises. In addition, the Index Provider may revise Index policy covering rules for selecting companies, treatment of dividends, share counts or other matters.

The Index is designed to measure the performance of the largest and most actively traded securities issued by U.S. companies in the Internet industry. The Index is a composite of its two sub-indices, the Dow Jones Internet Commerce Index and the Dow Jones Internet Services Index, and is composed of securities issued by Internet companies from the two sub-industries represented by these sub-indices: Internet Commerce and Internet Services. For each sub-industry, the sources from which the issuer derives the majority of its sales/revenues are as follows:

• Internet Commerce. Online retail, search, financial services, investment products, social media, advertising, travel platforms and Internet radio.

• Internet Services. Various services performed via the Internet, cloud computing, enterprise software, networking capabilities, website creation tools and digital marketing platforms.

To be eligible for inclusion in the Index, a security must be listed on a qualifying U.S. securities exchange and be issued by a company domiciled in the United States that generates at least 50% of its sales/revenues from the Internet, have a minimum of three months' trading history and have a three-month average float-adjusted market capitalization of at least $100 million. Eligible securities are ranked first by three-month average float-adjusted market capitalization and then by three-month average share volume. A final rank is then calculated based on an equally weighted average of the security's market capitalization and volume rankings. Securities are then sorted in descending order by final rank within the Internet Commerce and Internet Services sub-industries, respectively. The 15 securities from the Internet Commerce sub-industry and 25 securities from the Internet Services sub-industry with the best rankings are selected for inclusion in the Index. Securities selected for inclusion in the Index are then weighted by float-adjusted market capitalization, subject to a single security weight cap of 10%. The aggregate weight of individual securities with weights of 4.5% or more is limited to 45% of the Index. Index composition changes during scheduled reconstitutions are subject to certain buffers designed to limit turnover. The Index may be composed of small, mid and large capitalization companies.

The Index is rebalanced and reconstituted quarterly and the Fund will make corresponding changes to its portfolio shortly after the Index changes are made public. The Index's quarterly rebalance and reconstitution schedule may cause the Fund to experience a higher rate of portfolio turnover. The Fund will be concentrated in an industry or a group of industries to the extent that the Index is so concentrated. As of March 31, 2020, the Index was composed 41 securities and the Fund had significant investments in communication services companies and information technology companies, although this may change from time to time. To the extent the Fund invests a significant portion of its assets in a given jurisdiction or investment sector, the Fund may be exposed to the risks associated with that jurisdiction or investment sector.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

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You could 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 governmental agency. There can be no assurance that the Fund's investment objective will be achieved. The order of the below risk factors does not indicate the significance of any particular risk factor.

AUTHORIZED PARTICIPANT CONCENTRATION RISK. Only an authorized participant may engage in creation or redemption transactions directly with the Fund. A limited number of institutions act as authorized participants for the Fund. To the extent that these institutions exit the business or are unable to proceed with creation and/or redemption orders and no other authorized participant steps forward to create or redeem, the Fund's shares may trade at a premium or discount to the Fund's net asset value and possibly face delisting.

COMMUNICATION SERVICES COMPANIES RISK. Communication services companies may be subject to specific risks associated with legislative or regulatory changes, adverse market conditions, intellectual property use and/or increased competition. Communication services companies are particularly vulnerable to rapid advancements in technology, the innovation of competitors, rapid product obsolescence and government regulation and competition, both domestically and internationally. Additionally, fluctuating domestic and international demand, shifting demographics and often unpredictable changes in consumer tastes can drastically affect a communication services company's profitability. While all companies may be susceptible to network security breaches, certain communication services companies may be particular targets of hacking and potential theft of proprietary or consumer information or disruptions in service, which could have a material adverse effect on their businesses.

CYBER SECURITY RISK. The Fund is susceptible to operational risks through breaches in cyber security. A breach in cyber security refers to both intentional and unintentional events that may cause the Fund to lose proprietary information, suffer data corruption or lose operational capacity. Such events could cause the Fund to incur regulatory penalties, reputational damage, additional compliance costs associated with corrective measures and/or financial loss. Cyber security breaches may involve unauthorized access to the Fund's digital information systems through "hacking" or malicious software coding but may also result from outside attacks such as denial-of-service attacks through efforts to make network services unavailable to intended users. In addition, cyber security breaches of the issuers of securities in which the Fund invests or the Fund's third-party service providers, such as its administrator, transfer agent, custodian, or sub-advisor, as applicable, can also subject the Fund to many of the same risks associated with direct cyber security breaches. Although the Fund has established risk management systems designed to reduce the risks associated with cyber security, there is no guarantee that such efforts will succeed, especially because the Fund does not directly control the cyber security systems of issuers or third-party service providers.

EQUITY SECURITIES RISK. The value of the Fund's shares will fluctuate with changes in the value of the equity securities in which it invests. Equity securities prices fluctuate for several reasons, including changes in investors' perceptions of the financial condition of an issuer or the general condition of the relevant equity market, such as market volatility, or when political or economic events affecting an issuer occur. Common stock prices may be particularly sensitive to rising interest rates, as the cost of capital rises and borrowing costs increase. Equity securities may decline significantly in price over short or extended periods of time, and such declines may occur in the equity market as a whole, or they may occur in only a particular country, company, industry or sector of the market.

INDEX CONSTITUENT RISK. The Fund may be a constituent of one or more indices. As a result, the Fund may be included in one or more index-tracking exchange-traded funds or mutual funds. Being a component security of such a vehicle could greatly affect the trading activity involving the Fund's shares, the size of the Fund and the market volatility of the Fund. Inclusion in an index could increase demand for the Fund and removal from an index could result in outsized selling activity in a relatively short period of time. As a result, the Fund's net asset value could be negatively impacted and the Fund's market price may be below the Fund's net asset value during certain periods. In addition, index rebalances may potentially result in increased trading activity in the Fund's shares.

INDEX PROVIDER RISK. There is no assurance that the Index Provider, or any agents that act on its behalf, will compile the Index accurately, or that the Index will be determined, maintained, constructed, reconstituted, rebalanced, composed, calculated or disseminated accurately. The Index Provider and its agents do not provide any representation or warranty in relation to the quality, accuracy or completeness of data in the Index, and do not guarantee that the Index will be calculated in accordance with its stated methodology. The Advisor's mandate as described in this prospectus is to manage the Fund consistently with the Index provided by the Index Provider. The Advisor relies upon the Index provider and its agents to accurately compile, maintain, construct, reconstitute, rebalance, compose, calculate and disseminate the Index accurately. Therefore, losses or costs associated with any Index Provider or agent errors generally will be borne by the Fund and its shareholders. To correct any such error, the Index Provider or its agents may carry out an unscheduled rebalance of the Index or other modification of Index constituents or weightings. When the Fund in turn rebalances its portfolio, any transaction costs and market exposure arising from such portfolio rebalancing will be borne by the Fund and its shareholders. Unscheduled rebalances also expose the Fund to additional tracking error risk. Errors in respect of the quality, accuracy and completeness of the data used to compile the Index may occur from time to time and may not be identified and corrected by the Index Provider for a period of time or at all, particularly where the Index is less commonly used as a benchmark by funds or advisors. For example, during a period where the Index contains incorrect constituents, the Fund tracking the Index would have market exposure to such constituents and would be underexposed to the Index's other constituents. Such errors may negatively impact the Fund and its shareholders. The Index Provider and its agents rely on various sources of information to assess the criteria of issuers included in the Index, including information that may be based on assumptions and estimates. Neither the Fund nor the Advisor can offer assurances that the Index's calculation methodology or sources of information will provide an accurate assessment of included issuers.

INFORMATION TECHNOLOGY COMPANIES RISK. Information technology companies produce and provide hardware, software and information technology systems and services. These companies may be adversely affected by rapidly changing technologies, short product life cycles, fierce competition, aggressive pricing and reduced profit margins, the loss of patent, copyright and trademark protections, cyclical market patterns, evolving industry standards and frequent new product introductions. In addition, information technology companies are particularly vulnerable to federal, state and local government regulation, and competition and consolidation, both domestically and internationally, including competition from foreign competitors with lower production costs. Information technology companies also heavily rely on intellectual property rights and may be adversely affected by the loss or impairment of those rights.

INTERNET COMPANIES RISK. Internet companies are subject to rapid changes in technology, hacking or other cyber security events, worldwide competition, rapid obsolescence of products and services, loss of patent protections, cyclical market patterns, evolving industry standards, frequent new product introductions and the considerable risk of owning small capitalization companies that have recently begun operations. Many Internet companies have incurred large losses since their inception and may continue to incur large losses in the hope of capturing market share and generating future revenues. Accordingly, many such companies expect to incur significant operating losses for the foreseeable future, and may never be profitable. The markets in which many Internet companies compete face rapidly evolving industry standards, frequent new service and product announcements, introductions and enhancements and changing customer demands. The failure of an Internet company to adapt to such changes could have a material adverse effect on the company's business. In addition, the widespread adoption of new Internet, networking, telecommunications technologies, or other technological changes could require substantial expenditures by an Internet company to modify or adapt its services or infrastructure, which could have a material adverse effect on an Internet company's business.

MARKET MAKER RISK. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares due to a limited number of market markers. Decisions by market makers or authorized participants to reduce their role or step away from these activities in times of market stress could inhibit the effectiveness of the arbitrage process in maintaining the relationship between the underlying values of the Fund's portfolio securities and the Fund's market price. The Fund may rely on a small number of third-party market makers to provide a market for the purchase and sale of shares. Any trading halt or other problem relating to the trading activity of these market makers could result in a dramatic change in the spread between the Fund's net asset value and the price at which the Fund's shares are trading on the Exchange, which could result in a decrease in value of the Fund's shares. This reduced effectiveness could result in Fund shares trading at a discount to net asset value and also in greater than normal intraday bid-ask spreads for Fund shares.

MARKET RISK. Market risk is the risk that a particular security, or shares of the Fund in general, may fall in value. Securities are subject to market fluctuations caused by such factors as economic, political, regulatory or market developments, changes in interest rates and perceived trends in securities prices. Shares of the Fund could decline in value or underperform other investments. In addition, local, regional or global events such as war, acts of terrorism, spread of infectious diseases or other public health issues, recessions, or other events could have a significant negative impact on the Fund and its investments. Such events may affect certain geographic regions, countries, sectors and industries more significantly than others. Such events could adversely affect the prices and liquidity of the Fund's portfolio securities or other instruments and could result in disruptions in the trading markets. Any of such circumstances could have a materially negative impact on the value of the Fund's shares and result in increased market volatility. During any such events, the Fund's shares may trade at increased premiums or discounts to their net asset value.

NON-CORRELATION RISK. The Fund's return may not match the return of the Index for a number of reasons. The Fund incurs operating expenses not applicable to the Index, and may incur costs in buying and selling securities, especially when rebalancing the Fund's portfolio holdings to reflect changes in the composition of the Index. In addition, the Fund's portfolio holdings may not exactly replicate the securities included in the Index or the ratios between the securities included in the Index.

NON-DIVERSIFICATION RISK. The Fund is classified as "non-diversified" under the Investment Company Act of 1940, as amended (the "1940 Act"). As a result, the Fund is only limited as to the percentage of its assets which may be invested in the securities of any one issuer by the diversification requirements imposed by the Internal Revenue Code of 1986, as amended. The Fund may invest a relatively high percentage of its assets in a limited number of issuers. As a result, the Fund may be more susceptible to a single adverse economic or regulatory occurrence affecting one or more of these issuers, experience increased volatility and be highly invested in certain issuers.

PASSIVE INVESTMENT RISK. The Fund is not actively managed. The Fund invests in securities included in or representative of the Index regardless of investment merit. The Fund generally will not attempt to take defensive positions in declining markets. In the event that the Index is no longer calculated, the Index license is terminated or the identity or character of the Index is materially changed, the Fund will seek to engage a replacement index.

PORTFOLIO TURNOVER RISK. High portfolio turnover may result in the Fund paying higher levels of transaction costs and may generate greater tax liabilities for shareholders. Portfolio turnover risk may cause the Fund's performance to be less than expected.

PREMIUM/DISCOUNT RISK. The market price of the Fund's shares will generally fluctuate in accordance with changes in the Fund's net asset value as well as the relative supply of and demand for shares on the Exchange. The Fund's investment advisor cannot predict whether shares will trade below, at or above their net asset value because the shares trade on the Exchange at market prices and not at net asset value. Price differences may be due, in large part, to the fact that supply and demand forces at work in the secondary trading market for shares will be closely related, but not identical, to the same forces influencing the prices of the holdings of the Fund trading individually or in the aggregate at any point in time. However, given that shares can only be purchased and redeemed in Creation Units, and only to and from broker-dealers and large institutional investors that have entered into participation agreements (unlike shares of closed-end funds, which frequently trade at appreciable discounts from, and sometimes at premiums to, their net asset value), the Fund's investment advisor believes that large discounts or premiums to the net asset value of shares should not be sustained. During stressed market conditions, the market for the Fund's shares may become less liquid in response to deteriorating liquidity in the market for the Fund's underlying portfolio holdings, which could in turn lead to differences between the market price of the Fund's shares and their net asset value.

SIGNIFICANT EXPOSURE RISK. To the extent that the Fund invests a large percentage of its assets in a single asset class or industry or sector, an adverse economic, business or political development may affect the value of the Fund's investments more than if the Fund were more broadly diversified. A significant exposure makes the Fund more susceptible to any single occurrence and may subject the Fund to greater market risk than a fund that is more broadly diversified.

SMALLER COMPANIES RISK. Small and/or mid capitalization companies may be more vulnerable to adverse general market or economic developments, and their securities may be less liquid and may experience greater price volatility than larger, more established companies as a result of several factors, including limited trading volumes, fewer products or financial resources, management inexperience and less publicly available information. Accordingly, such companies are generally subject to greater market risk than larger, more established companies.

TRADING ISSUES RISK. Although the shares of the Fund are listed for trading on the Exchange, there can be no assurance that an active trading market for such shares will develop or be maintained. Further, secondary markets may be subject to irregular trading activity and wide bid-ask spreads (which may be especially pronounced for smaller funds). Trading in shares on the Exchange may be halted due to market conditions or for reasons that, in the view of the Exchange, make trading in shares inadvisable. In addition, trading in shares on the Exchange is subject to trading halts caused by extraordinary market volatility pursuant to the Exchange's "circuit breaker" rules. Market makers are under no obligation to make a market in the Fund's shares, and authorized participants are not obligated to submit purchase or redemption orders for Creation Units. In the event market makers cease making a market in the Fund's shares or authorized participants stop submitting purchase or redemption orders for Creation Units, Fund shares may trade at a larger premium or discount to their net asset value. There can be no assurance that the requirements of the Exchange necessary to maintain the listing of the Fund will continue to be met or will remain unchanged. The Fund may have difficulty maintaining its listing on the Exchange in the event the Fund's assets are small or the Fund does not have enough shareholders.

Bar Chart and Performance Table [Heading]

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Annual Total Return

Performance Narrative [Text Block]

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The bar chart and table below illustrate the annual calendar year returns of the Fund based on net asset value as well as the average annual Fund and Index returns. The bar chart and table provide an indication of the risks of investing in the Fund by showing changes in the Fund's performance from year-to-year and by showing how the Fund's average annual total returns based on net asset value compared to those of the Index, a broad-based market index and a market index. See "Total Return Information" for additional performance information regarding the Fund. The Fund's performance information is accessible on the Fund's website at www.ftportfolios.com.

Bar Chart [Heading]

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First Trust Dow Jones Internet Index Fund Calendar Year Total Returns as of 12/31

Bar Chart Closing [Text Block]

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During the periods shown in the chart above:

Best Quarter		Worst Quarter
25.52%	September 30, 2010	-19.04%	September 30, 2011

Performance Table Heading

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Average Annual Total Returns for the Periods Ended December 31, 2019

Performance Table Narrative

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

Returns before taxes do not reflect the effects of any income or capital gains taxes. All after-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of any state or local tax. Returns after taxes on distributions reflect the taxed return on the payment of dividends and capital gains. Returns after taxes on distributions and sale of shares assume you sold your shares at period end, and, therefore, are also adjusted for any capital gains or losses incurred. Returns for the market indices do not include expenses, which are deducted from Fund returns, or taxes.

Your own actual after-tax returns will depend on your specific tax situation and may differ from what is shown here. After-tax returns are not relevant to investors who hold Fund shares in tax-deferred accounts such as individual retirement accounts (IRAs) or employee-sponsored retirement plans.

First Trust Dow Jones Internet Index Fund | First Trust Dow Jones Internet Index Fund

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Management Fees

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0.40%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.12%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.52%

Fee Waiver and Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

none

^[1]

Total Annual Fund Operating Expenses After Fee Waiver and Expense Reimbursement

rr_NetExpensesOverAssets

0.52%

1 Year

rr_ExpenseExampleNoRedemptionYear01

$ 53

3 Years

rr_ExpenseExampleNoRedemptionYear03

167

5 Years

rr_ExpenseExampleNoRedemptionYear05

291

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 653

2010

rr_AnnualReturn2010

36.63%

2011

rr_AnnualReturn2011

(5.74%)

2012

rr_AnnualReturn2012

20.85%

2013

rr_AnnualReturn2013

53.40%

2014

rr_AnnualReturn2014

2.42%

2015

rr_AnnualReturn2015

21.77%

2016

rr_AnnualReturn2016

6.91%

2017

rr_AnnualReturn2017

37.62%

2018

rr_AnnualReturn2018

6.23%

2019

rr_AnnualReturn2019

19.26%

Highest Quarterly Return, Label

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Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2010

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

25.52%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(19.04%)

1 Year

rr_AverageAnnualReturnYear01

19.26%

5 Years

rr_AverageAnnualReturnYear05

17.81%

10 Years

rr_AverageAnnualReturnYear10

18.69%

Since Inception

rr_AverageAnnualReturnSinceInception

15.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 19, 2006

First Trust Dow Jones Internet Index Fund | After tax on distributions | First Trust Dow Jones Internet Index Fund

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

19.26%

5 Years

rr_AverageAnnualReturnYear05

17.81%

10 Years

rr_AverageAnnualReturnYear10

18.69%

Since Inception

rr_AverageAnnualReturnSinceInception

15.43%

First Trust Dow Jones Internet Index Fund | After tax on distributions and sale of fund shares | First Trust Dow Jones Internet Index Fund

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

11.40%

5 Years

rr_AverageAnnualReturnYear05

14.50%

10 Years

rr_AverageAnnualReturnYear10

16.14%

Since Inception

rr_AverageAnnualReturnSinceInception

13.51%

First Trust Dow Jones Internet Index Fund | Dow Jones Internet Composite Index(SM) (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

20.08%

5 Years

rr_AverageAnnualReturnYear05

18.46%

10 Years

rr_AverageAnnualReturnYear10

19.35%

Since Inception

rr_AverageAnnualReturnSinceInception

16.08%

First Trust Dow Jones Internet Index Fund | S&P 500® Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

31.49%

5 Years

rr_AverageAnnualReturnYear05

11.70%

10 Years

rr_AverageAnnualReturnYear10

13.56%

Since Inception

rr_AverageAnnualReturnSinceInception

9.61%

First Trust Dow Jones Internet Index Fund | S&P Composite 1500® Information Technology Index (reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

49.75%

5 Years

rr_AverageAnnualReturnYear05

19.85%

10 Years

rr_AverageAnnualReturnYear10

17.31%

Since Inception

rr_AverageAnnualReturnSinceInception

14.25%

[1] First Trust Advisors L.P., the Fund's investment advisor, has agreed to waive fees and/or reimburse Fund expenses to the extent that the operating expenses of the Fund (excluding interest expense, brokerage commissions and other trading expenses, acquired fund fees and expenses, taxes and extraordinary expenses) exceed 0.60% of its average daily net assets per year (the "Expense Cap") at least through April 30, 2021. Expenses reimbursed and fees waived under such agreement are subject to recovery by the Fund's investment advisor for up to three years from the date the fee was waived or expense was incurred, but no reimbursement payment will be made by the Fund if it results in the Fund exceeding (i) the applicable expense limitation in place for the most recent fiscal year for which such expense limitation was in place, (ii) the applicable expense limitation in place at the time the fees were waived, or (iii) the current expense limitation. The agreement may be terminated by the Trust, on behalf of the Fund, at any time and by the Fund's investment advisor only after April 30, 2021 upon 60 days' written notice.