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Label Element Value
Risk Return Abstract rr_RiskReturnAbstract  
Document Type dei_DocumentType Other
Document Period End Date dei_DocumentPeriodEndDate Mar. 01, 2016
Registrant Name dei_EntityRegistrantName First Trust Series Fund
Central Index Key dei_EntityCentralIndexKey 0001497778
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Mar. 01, 2016
Document Effective Date dei_DocumentEffectiveDate Mar. 01, 2016
Prospectus Date rr_ProspectusDate Mar. 01, 2016
First Trust Preferred Securities and Income Fund  
Risk Return Abstract rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading

SUMMARY INFORMATION
Objective [Heading] rr_ObjectiveHeading

INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The First Trust Preferred Securities and Income Fund (the "Fund") seeks to provide current income and total return.
Expense [Heading] rr_ExpenseHeading

FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other First Trust mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial advisor and in "Share Classes" on page 15 of this prospectus, "Investment in Fund Shares" on page 17 of this prospectus and "Purchase and Redemption of Fund Shares" on page 52 of the Fund's statement of additional information ("SAI").
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption

SHAREHOLDER FEES
(fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption

ANNUAL FUND OPERATING EXPENSES
(expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading

PORTFOLIO TURNOVER
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 123% of the average value of its portfolio.
Expense Example [Heading] rr_ExpenseExampleHeading

EXAMPLE
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

The following example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund's annual operating expenses remain at current levels until February 28, 2017 and then will not exceed 1.50% from March 1, 2017 until February 28, 2026. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading

PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund seeks to achieve its investment objective by investing, under normal market conditions, at least 80% of its net assets (including investment borrowings) in preferred securities and other securities with similar economic characteristics. Securities that have economic characteristics that are similar to preferred securities include certain debt instruments. Such debt instruments are typically issued by corporations, generally in the form of interest bearing notes, or by an affiliated business trust of a corporation, generally in the form of (i) beneficial interests in subordinated debentures or similarly structured securities or (ii) more senior debt securities that pay income and trade in a manner similar to preferred securities. The Fund may also invest in more traditional corporate debt securities and U.S. government securities.

Preferred securities generally pay fixed or adjustable-rate distributions to investors and have preference over common stock in the payment of distributions and the liquidation of a company's assets, but are generally junior to all forms of the company's debt, including both senior and subordinated debt; therefore, the risks and potential rewards of investing in the Fund may at times be similar to the risks and potential rewards of investing in both equity funds and bond funds. Because the issuers of preferred securities are often financial companies, the Fund intends to concentrate (invest at least 25% of its net assets) in the industry or group of industries that comprise the financial sector, which may include banks, thrifts, brokerage firms, broker-dealers, investment banks, finance companies, real estate investment trusts ("REITs") and companies involved in the insurance industry.

Under normal market conditions, the Fund invests at least 60% of its net assets in securities rated investment grade (BBB-/Baa3 or higher) at the time of purchase by at least one independent rating agency, such as Standard & Poor's Ratings Service, a division of The McGraw-Hill Companies, Inc., Moody's Investors Service, Inc., or another nationally recognized statistical rating organization, and unrated securities judged to be of comparable quality by the Fund's sub-advisor. The Fund may invest up to 40% of its net assets in securities rated below investment grade (BB+/Ba1 or lower) at the time of purchase, which are commonly referred to as "high yield" securities or "junk bonds." For securities with a split rating, the highest available rating will be used. In addition, at the time of purchase, at least 80% of the Fund's net assets are issued by issuers that have long-term issuer credit ratings of investment grade by at least one independent rating agency or judged to be of comparable quality by the Fund's sub-advisor, if any issuer is unrated. The Fund may invest in securities of any duration or maturity.

Under normal market conditions, the Fund may invest up to 15% of its net assets in cash and/or cash equivalents. The Fund may invest in securities issued by companies domiciled in the United States, U.S. dollar-denominated depositary receipts, U.S. dollar-denominated foreign securities and non-U.S. dollar-denominated securities. The Fund may invest in Rule 144A Securities, which are generally subject to resale restrictions and may be illiquid.
Risk [Heading] rr_RiskHeading

PRINCIPAL RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

You could lose money by investing in the Fund. There can be no assurance that the Fund will achieve its investment objective. 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.

CONCENTRATION RISK. A fund concentrated in a single industry or sector is likely to present more risks than a fund that is broadly diversified over several industries or sectors. Compared to the broad market, an individual industry or sector may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock, or regulatory changes.

CONTINGENT CAPITAL SECURITIES RISK. Contingent capital securities, also known as "CoCos," are debt or preferred securities typically issued by non-U.S. financial institutions with loss absorption characteristics built into the terms of the security. Such characteristics may include a mandatory conversion into common stock of the issuer under certain circumstances, such as the issuer's capital ratio falling below a certain level. Since the common stock of the issuer may not pay a dividend, investors in these instruments could experience a reduced income rate, potentially to zero, and conversion would depend the subordination of the investor, hence worsening the Fund's standing in a bankruptcy. Some CoCos provide for a reduction in the value or principal amount of the security under certain circumstances. In addition, most CoCos are considered to be high yield or "junk" securities and are therefore subject to the risks of investing in below investment-grade securities.

CREDIT RISK. Credit risk is the risk that an issuer of a security may be unable or unwilling to make dividend, interest and principal payments when due and the related risk that the value of a security may decline because of concerns about the issuer's ability or willingness to make such payments. Credit risk may be heightened if the Fund invests in high yield or "junk" securities. Such securities, while generally offering higher yields than investment grade debt with similar maturities, involve greater risks, including the possibility of dividend or interest deferral, default or bankruptcy, and are regarded as predominantly speculative with respect to the issuer's capacity to pay dividends or interest and repay principal.

DEPOSITARY RECEIPTS RISK. Depositary receipts may be less liquid than the underlying shares in their primary trading market. Any distributions paid to the holders of depositary receipts are usually subject to a fee charged by the depositary. Holders of depositary receipts may have limited voting rights, and investment restrictions in certain countries may adversely impact the value of depositary receipts because such restrictions may limit the ability to convert the equity shares into depositary receipts and vice versa. Such restrictions may cause the equity shares of the underlying issuer to trade at a discount or premium to the market price of the depositary receipts.

FINANCIAL COMPANIES RISK. Financial companies are especially subject to the adverse effects of economic recession, currency exchange rates, government regulation, decreases in the availability of capital, volatile interest rates, portfolio concentrations in geographic markets and in commercial and residential real estate loans, and competition from new entrants in their fields of business.

HIGH YIELD SECURITIES RISK. High yield securities, or "junk bonds," are subject to greater market fluctuations and risk of loss than securities with higher investment ratings. These securities are issued by companies that may have limited operating history, narrowly focused operations, and/or other impediments to the timely payment of periodic interest and principal at maturity. If the economy slows down or dips into recession, the issuers of high yield securities may not have sufficient resources to continue making timely payment of periodic interest and principal at maturity. The market for high yield securities is smaller and less liquid than that for investment grade securities. High yield securities are generally not listed on a national securities exchange but trade in the over-the-counter markets. Due to the smaller, less liquid market for high yield securities, the bid-offer spread on such securities is generally greater than it is for investment grade securities and the purchase or sale of such securities may take longer to complete.

ILLIQUID SECURITIES RISK. Illiquid securities involve the risk that the securities will not be able to be sold at the time desired by the Fund or at prices approximately the value at which the Fund is carrying the securities on its books.

INCOME RISK. Income from the Fund's fixed income investments could decline during periods of falling interest rates.

INTEREST RATE RISK. Interest rate risk is the risk that the value of the fixed income securities held by the Fund will decline because of rising market interest rates. Interest rate risk is generally lower for shorter term investments and higher for longer term investments.

MARKET RISK. Market risk is the risk that a particular security owned by the Fund 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.

NON-U.S. SECURITIES RISK. Non-U.S. securities are subject to higher volatility than securities of domestic issuers due to possible adverse political, social or economic developments; restrictions on foreign investment or exchange of securities; lack of liquidity; currency exchange rates; excessive taxation; government seizure of assets; different legal or accounting standards; and less government supervision and regulation of exchanges in foreign countries.

PORTFOLIO TURNOVER RISK. The Fund's investment strategy tracking the Index may frequently involve buying and selling portfolio securities. High portfolio turnover may result in the Fund paying higher levels of transaction costs and generating greater tax liabilities for shareholders. Portfolio turnover risk may cause the Fund's performance to be less than you expect.

PREFERRED SECURITIES RISK. Preferred securities combine some of the characteristics of both common stocks and bonds. Preferred securities are typically subordinated to bonds and other debt instruments in a company's capital structure, in terms of priority to corporate income, and therefore will be subject to greater credit risk than those debt instruments. Preferred securities are also subject to credit risk, interest rate risk and income risk.

REIT INVESTMENT RISK. Because the Fund invests in REITs, the Fund is subject to the risks associated with investing in real estate, which may include, but are not limited to, fluctuations in the value of underlying properties; defaults by borrowers or tenants; market saturation; changes in general and local operating expenses; and other economic, political or regulatory occurrences affecting companies in the real estate industry. In addition to risks related to investments in real estate generally, investing in REITs involves certain other risks related to their structure and focus, which include, but are not limited to, dependency upon management skills, limited diversification, the risks of locating and managing financing for projects, heavy cash flow dependency, possible default by borrowers, the costs and potential losses of self-liquidation of one or more holdings, the risk of a possible lack of mortgage funds and associated interest rate risks, overbuilding, property vacancies, increases in property taxes and operating expenses, changes in zoning laws, losses due to environmental damages, changes in neighborhood values and appeal to purchasers, the possibility of failing to maintain exemptions from registration under the 1940 Act and, in many cases, relatively small market capitalization, which may result in less market liquidity and greater price volatility. REITs are also subject to the risk that the real estate market may experience an economic downturn generally, which may have a material effect on the real estate in which the REITs invest and their underlying portfolio securities.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading

ANNUAL TOTAL RETURN
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The bar chart and table below illustrate the annual calendar year returns of the Fund's Class A shares as well as the average annual Fund 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 Class A shares' average annual total returns compare to those of a specialized 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.

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. After-tax returns are shown for only Class A shares, and after-tax returns for other Classes will vary. Returns for the market index 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.

Imposition of the Fund's sales load is not reflected in the bar chart below. If the sales load was reflected, returns would be less than those shown.
Bar Chart [Heading] rr_BarChartHeading

FIRST TRUST PREFERRED SECURITIES AND INCOME FUND--TOTAL RETURNS ON CLASS A SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

During the period shown in the chart above:

BEST QUARTER WORST QUARTER
6.75% (March 31, 2012) -5.29% (September 30, 2013)

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

AVERAGE ANNUAL TOTAL RETURNS FOR THE FUND FOR THE PERIODS ENDED DECEMBER 31, 2015
First Trust Preferred Securities and Income Fund | Class A  
Risk Return Abstract rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice none [1]
Maximum Sales Charge (Load) Imposed on Reinvested Dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Exchange Fee rr_ExchangeFee none
Management Fee rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.44% [2]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.49%
Fee Waivers and Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.09%) [3]
Total Annual Fund Operating Expenses After Fee Waivers and Expense Reimbursements rr_NetExpensesOverAssets 1.40% [2]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 586
3 Years rr_ExpenseExampleYear03 891
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,218
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,142
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 586
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 891
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,218
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,142
Annual Return 2012 rr_AnnualReturn2012 16.64%
Annual Return 2013 rr_AnnualReturn2013 (4.49%)
Annual Return 2014 rr_AnnualReturn2014 10.88%
Annual Return 2015 rr_AnnualReturn2015 5.18%
1 Year rr_AverageAnnualReturnYear01 0.45%
Since Inception rr_AverageAnnualReturnSinceInception 5.47%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2011
First Trust Preferred Securities and Income Fund | Class C  
Risk Return Abstract rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00% [1]
Maximum Sales Charge (Load) Imposed on Reinvested Dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Exchange Fee rr_ExchangeFee none
Management Fee rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.35% [2]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.15%
Fee Waivers and Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets none [3]
Total Annual Fund Operating Expenses After Fee Waivers and Expense Reimbursements rr_NetExpensesOverAssets 2.15% [2]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 318
3 Years rr_ExpenseExampleYear03 673
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,154
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,483
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 218
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 673
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,154
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,483
1 Year rr_AverageAnnualReturnYear01 3.39%
Since Inception rr_AverageAnnualReturnSinceInception 5.72%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2011
First Trust Preferred Securities and Income Fund | Class F  
Risk Return Abstract rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice none [1]
Maximum Sales Charge (Load) Imposed on Reinvested Dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Exchange Fee rr_ExchangeFee none
Management Fee rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Other Expenses rr_OtherExpensesOverAssets 0.97% [2]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.92%
Fee Waivers and Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.62%) [3]
Total Annual Fund Operating Expenses After Fee Waivers and Expense Reimbursements rr_NetExpensesOverAssets 1.30% [2]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 132
3 Years rr_ExpenseExampleYear03 486
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 864
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,925
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 132
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 486
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 864
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,925
1 Year rr_AverageAnnualReturnYear01 5.34%
Since Inception rr_AverageAnnualReturnSinceInception 6.66%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 02, 2011
First Trust Preferred Securities and Income Fund | Class I  
Risk Return Abstract rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice none [1]
Maximum Sales Charge (Load) Imposed on Reinvested Dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Exchange Fee rr_ExchangeFee none
Management Fee rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.35% [2]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.15%
Fee Waivers and Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets none [3]
Total Annual Fund Operating Expenses After Fee Waivers and Expense Reimbursements rr_NetExpensesOverAssets 1.15% [2]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 117
3 Years rr_ExpenseExampleYear03 365
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 633
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,398
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 117
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 365
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 633
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,398
1 Year rr_AverageAnnualReturnYear01 5.48%
Since Inception rr_AverageAnnualReturnSinceInception 6.91%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 11, 2011
First Trust Preferred Securities and Income Fund | Class R3  
Risk Return Abstract rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice none [1]
Maximum Sales Charge (Load) Imposed on Reinvested Dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Exchange Fee rr_ExchangeFee none
Management Fee rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses rr_OtherExpensesOverAssets 5.26% [2]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 6.56%
Fee Waivers and Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (4.91%) [3]
Total Annual Fund Operating Expenses After Fee Waivers and Expense Reimbursements rr_NetExpensesOverAssets 1.65% [2]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 168
3 Years rr_ExpenseExampleYear03 594
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,045
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,299
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 168
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 594
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,045
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,299
1 Year rr_AverageAnnualReturnYear01 4.92%
Since Inception rr_AverageAnnualReturnSinceInception 6.11%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 02, 2011
First Trust Preferred Securities and Income Fund | After Taxes on Distributions | Class A  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (1.83%)
Since Inception rr_AverageAnnualReturnSinceInception 3.18%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2011
First Trust Preferred Securities and Income Fund | After Taxes on Distributions and Sales | Class A  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 0.23%
Since Inception rr_AverageAnnualReturnSinceInception 3.22%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 25, 2011
First Trust Preferred Securities and Income Fund | BofA Merrill Lynch Fixed Rate Preferred Securities Index  
Risk Return Abstract rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 7.58%
Since Inception rr_AverageAnnualReturnSinceInception 7.20%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 11, 2011 [4]
First Trust Preferred Securities and Income Fund | BofA Merrill Lynch U.S. Capital Securities Index  
Risk Return Abstract rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 0.86%
Since Inception rr_AverageAnnualReturnSinceInception 7.02%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 11, 2011 [4]
First Trust Preferred Securities and Income Fund | Blended Index  
Risk Return Abstract rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 4.18% [5]
Since Inception rr_AverageAnnualReturnSinceInception 7.13% [5]
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 11, 2011 [4]
First Trust/Confluence Small Cap Value Fund  
Risk Return Abstract rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading

SUMMARY INFORMATION
Objective [Heading] rr_ObjectiveHeading

INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The First Trust/Confluence Small Cap Value Fund (the "Fund") seeks to provide long-term 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. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other First Trust mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial advisor and in "Share Classes" on page 12 of this prospectus, "Investment in Fund Shares" on page 14 of this prospectus and "Purchase and Redemption of Fund Shares" on page 51 of the Fund's statement of additional information ("SAI").
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption

SHAREHOLDER FEES
(fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption

ANNUAL FUND OPERATING EXPENSES
(expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading

PORTFOLIO TURNOVER
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 17% of the average value of its portfolio.
Expense Example [Heading] rr_ExpenseExampleHeading

EXAMPLE
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

The following example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund's annual operating expenses remain at current levels until February 28, 2017 and then will not exceed 1.70% from March 1, 2017 until February 28, 2026. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading

PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The Fund seeks to achieve its investment objective by investing, under normal market conditions, at least 80% of its net assets (including investment borrowings) in equity securities of U.S. listed companies with small market capitalizations ("Small-Cap Companies") at the time of investment. Currently, a company will be considered to be a Small-Cap Company if its market capitalization at the time of purchase is within the range of companies in the Russell 2000 Index or the S&P SmallCap 600 Index during the most recent 12-month period (based on month-end data). Because market capitalization is measured at the time of initial purchase, if the market capitalization of a company included in the Fund grows above "small-cap," the Fund shall not be required to sell such security solely because it is no longer a Small-Cap Company. The market capitalization range of companies in the Russell 2000 Index or the S&P SmallCap 600 Index may vary in a 12-month period. As of December 31, 2015, the market capitalization of the Fund's holdings ranged from approximately $318 million to $4.5 billion.

The portfolio managers seek to invest in Small-Cap Companies that in the portfolio managers' opinion have produced solid returns over extended periods of time. The portfolio managers' investment strategy is based on the rationale that a company which creates superior value, reflected in above-average operating returns, will ultimately have a stock price reflecting that superior performance.

The portfolio managers follow a disciplined, research driven, investment process which seeks to uncover companies trading at discounts to their intrinsic values. By investing in stocks according to a value-based investment philosophy, the portfolio managers seek to enhance the long-term growth potential while limiting downside risk. Companies in which the portfolio managers invest are those that the portfolio managers expect to create above-average growth in value relative to their industries and to the overall market. These companies may include real estate investment trusts ("REITs") and business development companies ("BDCs"). BDCs lend to and invest in private companies, often working with companies that are not large enough to efficiently access the public markets. Each BDC has a unique profile, determined by its respective management team. Some specialize in particular industries, while others apply a more generalized approach and maintain a diversified portfolio. Once such a company is identified, an extensive valuation analysis is performed to determine if its stock price reflects its underlying value. The Fund invests principally in financial and industrials companies.
Risk [Heading] rr_RiskHeading

PRINCIPAL RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

You could lose money by investing in the Fund. There can be no assurance that the Fund will achieve its investment objective. 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.

BDC RISK. The Fund may invest in BDCs which may carry risks similar to those of a private equity or venture capital fund. BDCs are not redeemable at the option of the shareholder and they may trade in the market at a discount to their net asset value. The BDCs held by the Fund may employ the use of leverage their portfolios through borrowings or the issuance of preferred stock. While leverage often serves to increase the yield of a BDC, this leverage also subjects a BDC to increased risks, including the likelihood of increased volatility and the possibility that a BDC's common share income will fall if the dividend rate of the preferred shares or the interest rate on any borrowings rises.

CONCENTRATION RISK. A fund concentrated in a single industry or sector is likely to present more risks than a fund that is broadly diversified over several industries or sectors. Compared to the broad market, an individual industry or sector may be more strongly affected by changes in the economic climate, broad market shifts, moves in a particular dominant stock, or regulatory changes.

EQUITY SECURITIES RISK. Because the Fund invests in equity securities, the value of Fund shares will fluctuate with changes in the value of these equity securities. 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 stock market, such as the current market volatility, or when political or economic events affecting the issuers occur. In addition, common stock prices may be particularly sensitive to rising interest rates, as the cost of capital rises and borrowing costs increase.

FINANCIAL COMPANIES RISK. Financial companies are especially subject to the adverse effects of economic recession, currency exchange rates, government regulation, decreases in the availability of capital, volatile interest rates, portfolio concentrations in geographic markets and in commercial and residential real estate loans, and competition from new entrants in their fields of business.

INDUSTRIALS AND PRODUCER DURABLES COMPANIES RISK. The Fund invests in the securities of industrials and producer durables companies, which convert unfinished goods into finished durables used to manufacture other goods or provide services. These companies produce electrical equipment and components, industrial products, manufactured housing and telecommunications equipment. General risks of these companies include the general state of the economy, intense competition, consolidation, domestic and international politics, excess capacity and consumer demand and spending trends. In addition, they may also be significantly affected by overall capital spending levels, economic cycles, technical obsolescence, delays in modernization, labor relations, government regulations and e-commerce initiatives.

INVESTMENT COMPANIES RISK. If the Fund invests in investment companies, Fund shareholders bear both their proportionate share of Fund expenses and, indirectly, the expenses of the investment companies. Also, the investment companies are subject to the risks of the underlying securities that they hold. In addition, the Fund will incur brokerage costs when purchasing and selling shares of ETFs and closed-end investment companies. Closed-end investment companies may be leveraged, in which case the value and/or yield of their shares will tend to be more volatile than shares of unleveraged funds. In addition, for index-based ETFs, the performance of an ETF may diverge from the performance of such index (commonly known as tracking error). Moreover, shares of closed-end investment companies and ETFs may be sold at a discount from their net asset value.

MARKET CAPITALIZATION RISK. The Fund normally invests at least 80% of its assets in Small-Cap Companies. Because the market capitalization is measured at the time of its initial purchase, the Fund will not be forced to sell a stock because the stock has exceeded or fallen below the market capitalization range. Because of market movement, there can be no assurance that the securities held by the Fund will stay within the given market capitalization range. As a result, the Fund may be exposed to additional risk or investors may not be given the opportunity to invest fully in a certain market capitalization range.

MARKET RISK. Market risk is the risk that a particular security owned by the Fund 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.

REAL ESTATE INVESTMENT RISK. The Fund invests in companies in the real estate industry, including REITs. Therefore, the Fund is subject to the risks associated with investing in real estate, which may include, but are not limited to, fluctuations in the value of underlying properties; defaults by borrowers or tenants; market saturation; changes in general and local economic conditions; decreases in market rates for rents; increases in competition, property taxes, capital expenditures or operating expenses; and other economic, political or regulatory occurrences affecting companies in the real estate industry.

REIT INVESTMENT RISK. Because the Fund invests in REITs, the Fund is subject to the risks associated with investing in real estate, which may include, but are not limited to, fluctuations in the value of underlying properties; defaults by borrowers or tenants; market saturation; changes in general and local operating expenses; and other economic, political or regulatory occurrences affecting companies in the real estate industry. In addition to risks related to investments in real estate generally, investing in REITs involves certain other risks related to their structure and focus, which include, but are not limited to, dependency upon management skills, limited diversification, the risks of locating and managing financing for projects, heavy cash flow dependency, possible default by borrowers, the costs and potential losses of self-liquidation of one or more holdings, the risk of a possible lack of mortgage funds and associated interest rate risks, overbuilding, property vacancies, increases in property taxes and operating expenses, changes in zoning laws, losses due to environmental damages, changes in neighborhood values and appeal to purchasers, the possibility of failing to maintain exemptions from registration under the 1940 Act and, in many cases, relatively small market capitalization, which may result in less market liquidity and greater price volatility. REITs are also subject to the risk that the real estate market may experience an economic downturn generally, which may have a material effect on the real estate in which the REITs invest and their underlying portfolio securities.

SMALL CAP RISK. The Fund invests in Small-Cap Companies. Such 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, products or financial resources, management inexperience and dependence on a few key people, and less publicly available information. Accordingly, such companies are generally subject to greater market risk than larger, more established companies. The market movements of equity securities issued by issuers with smaller capitalizations may be more abrupt or erratic than the market movements of equity securities of larger, more established companies or the stock market in general. Historically, smaller capitalization companies have sometimes gone through extended periods when they did not perform as well as larger companies. In addition, equity securities of Small-Cap Companies may be less liquid than those of larger companies.

SMALL FUND RISK. The Fund currently has fewer assets than larger funds, and like other relatively smaller funds, large inflows and outflows may impact the Fund's market exposure for limited periods of time. This impact may be positive or negative, depending on the direction of market movement during the period affected.

VALUE INVESTING RISK. The Fund focuses its investments on securities that the portfolio managers believe are undervalued or inexpensive relative to other investments. These types of securities may present risks in addition to the general risks associated with investing in them. These securities generally are selected on the basis of an issuer's business and economic fundamentals or the securities' current and projected credit profiles, relative to current market price. Such securities are subject to the risk of misestimating certain fundamental factors. Disciplined adherence to a "value" investment mandate during periods in which that style is "out of favor" can result in significant underperformance relative to overall market indices and other managed investment vehicles that pursue growth style investments and/or flexible style mandates.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading

ANNUAL TOTAL RETURN
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The bar chart and table below illustrate the annual calendar year returns of the Fund's Class A shares as well as the average annual Fund 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 Class A shares' average annual total returns compare to those of two broad-based market indices. 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.

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. After-tax returns are shown for only Class A shares, and after-tax returns for other Classes will vary. Returns for the market index 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.

Imposition of the Fund's sales load is not reflected in the bar chart below. If the sales load was reflected, returns would be less than those shown.
Bar Chart [Heading] rr_BarChartHeading

FIRST TRUST/CONFLUENCE SMALL CAP VALUE FUND--TOTAL RETURNS ON CLASS A SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

During the period shown in the chart above:

BEST QUARTER WORST QUARTER
8.91% (September 30, 2013) -7.82% (September 30, 2015)

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

AVERAGE ANNUAL TOTAL RETURNS FOR THE FUND FOR THE PERIODS ENDED DECEMBER 31, 2015
First Trust/Confluence Small Cap Value Fund | Class A  
Risk Return Abstract rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.50%
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice none [1]
Maximum Sales Charge (Load) Imposed on Reinvested Dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Exchange Fee rr_ExchangeFee none
Management Fee rr_ManagementFeesOverAssets 1.00%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 6.36%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.21% [6]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 7.82%
Fee Waivers and Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (6.01%) [7]
Total Annual Fund Operating Expenses After Fee Waivers and Expense Reimbursements rr_NetExpensesOverAssets 1.81%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 724
3 Years rr_ExpenseExampleYear03 1,157
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,615
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,880
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 724
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 1,157
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,615
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,880
Annual Return 2012 rr_AnnualReturn2012 15.20%
Annual Return 2013 rr_AnnualReturn2013 24.93%
Annual Return 2014 rr_AnnualReturn2014 7.96%
Annual Return 2015 rr_AnnualReturn2015 (3.92%)
1 Year rr_AverageAnnualReturnYear01 (9.20%)
Since Inception rr_AverageAnnualReturnSinceInception 6.75%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 24, 2011
First Trust/Confluence Small Cap Value Fund | Class C  
Risk Return Abstract rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00% [1]
Maximum Sales Charge (Load) Imposed on Reinvested Dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Exchange Fee rr_ExchangeFee none
Management Fee rr_ManagementFeesOverAssets 1.00%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 6.93%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.21% [6]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 8.14%
Fee Waivers and Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (5.58%) [7]
Total Annual Fund Operating Expenses After Fee Waivers and Expense Reimbursements rr_NetExpensesOverAssets 2.56%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 359
3 Years rr_ExpenseExampleYear03 868
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,502
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 3,208
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 259
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 868
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,502
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 3,208
1 Year rr_AverageAnnualReturnYear01 (5.80%)
Since Inception rr_AverageAnnualReturnSinceInception 6.35%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 02, 2011
First Trust/Confluence Small Cap Value Fund | Class I  
Risk Return Abstract rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice none [1]
Maximum Sales Charge (Load) Imposed on Reinvested Dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Exchange Fee rr_ExchangeFee none
Management Fee rr_ManagementFeesOverAssets 1.00%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 7.46%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.21% [6]
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 8.67%
Fee Waivers and Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (7.11%) [7]
Total Annual Fund Operating Expenses After Fee Waivers and Expense Reimbursements rr_NetExpensesOverAssets 1.56%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 159
3 Years rr_ExpenseExampleYear03 566
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 999
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,204
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 159
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 566
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 999
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,204
1 Year rr_AverageAnnualReturnYear01 (4.06%)
Since Inception rr_AverageAnnualReturnSinceInception 8.36%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 11, 2011
First Trust/Confluence Small Cap Value Fund | After Taxes on Distributions | Class A  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (9.52%)
Since Inception rr_AverageAnnualReturnSinceInception 5.77%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 24, 2011
First Trust/Confluence Small Cap Value Fund | After Taxes on Distributions and Sales | Class A  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (4.94%)
Since Inception rr_AverageAnnualReturnSinceInception 5.06%
Inception Date rr_AverageAnnualReturnInceptionDate Feb. 24, 2011
First Trust/Confluence Small Cap Value Fund | Russell 2000(R) Value Index  
Risk Return Abstract rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 (7.47%)
Since Inception rr_AverageAnnualReturnSinceInception 7.39%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 11, 2011 [4]
First Trust/Confluence Small Cap Value Fund | Russell 2000(R) Index  
Risk Return Abstract rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 (4.41%)
Since Inception rr_AverageAnnualReturnSinceInception 8.88%
Inception Date rr_AverageAnnualReturnInceptionDate Jan. 11, 2011 [4]
First Trust Short Duration High Income Fund  
Risk Return Abstract rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading

SUMMARY INFORMATION
Objective [Heading] rr_ObjectiveHeading

INVESTMENT OBJECTIVES
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The First Trust Short Duration High Income Fund (the "Fund") seeks to provide a high level of current income.
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock

As a secondary objective, the Fund seeks 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. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other First Trust mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial advisor and in "Share Classes" on page 15 of this prospectus, "Investment in Fund Shares" on page 17 of this prospectus and "Purchase and Redemption of Fund Shares" on page 51 of the Fund's statement of additional information ("SAI").
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption

SHAREHOLDER FEES
(fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption

ANNUAL FUND OPERATING EXPENSES
(expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading

PORTFOLIO TURNOVER
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 58% of the average value of its portfolio.
Expense Example [Heading] rr_ExpenseExampleHeading

EXAMPLE
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

The following example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund's annual operating expenses remain at current levels until February 28, 2017 and then will not exceed 1.35% from March 1, 2017 until February 28, 2026. 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 market conditions, the Fund invests at least 80% of its net assets (including investment borrowings) in high yield debt securities and bank loans that are rated below-investment grade or unrated. High yield debt securities are below-investment grade debt securities, commonly known as "junk bonds." For purposes of determining whether a security is below-investment grade, the lowest available rating is used.

The Fund has a short duration investment strategy, which seeks to maintain, under normal market conditions, a blended (or weighted average) portfolio duration of three years or less. Duration is a mathematical calculation of the average life of a debt security (or portfolio of debt securities) that serves as a measure of its price risk. In general, each year of duration represents an expected 1% change in the value of a security for every 1% immediate change in interest rates. For example, if a portfolio of bank loans and fixed income securities has an average duration of three years, its value can be expected to fall about 3% if interest rates rise by 1%. Conversely, the portfolio's value can be expected to rise about 3% if interest rates fall by 1%. As a result, prices of instruments with shorter durations tend to be less sensitive to interest rate changes than instruments with longer durations. As the value of a security changes over time, so will its duration.

Bank loans have relatively low durations, i.e., close to zero, which means that the interest rates on loans reset approximately every 30-90 days, on average, however, the inclusion of London Interbank Offered Rate ("LIBOR") floors on certain senior loans or other factors may cause interest rate duration to be longer than 90 days. Accordingly, the Fund's investment in such securities will likely reduce the blended duration of the portfolio and in turn the Fund's overall interest rate sensitivity. "Average duration" is the measure of a debt instrument's or a portfolio's price sensitivity with respect to changes in market yields. The blended duration is the sum of the dollar weighted average duration of the Fund's positions.

Under normal market conditions, the Fund may invest up to 15% of its net assets in non-U.S. securities denominated in non-U.S. currencies. The Fund may also invest in investment grade debt securities and convertible bonds.
Risk [Heading] rr_RiskHeading

PRINCIPAL RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

You could lose money by investing in the Fund. There can be no assurance that the Fund will achieve its investment objectives. 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.

BANK LOANS RISK. An investment in bank loans subjects the Fund to credit risk, which is heightened for bank loans in which the Fund invests because companies that issue such loans tend to be highly leveraged and thus are more susceptible to the risks of interest deferral, default and/or bankruptcy. Senior floating rate loans, in which the Fund may invest, are usually rated below investment grade but may also be unrated. As a result, the risks associated with these senior floating rate loans are similar to the risks of high yield fixed income instruments. An economic downturn would generally lead to a higher non-payment rate, and a senior floating rate loans may lose significant market value before a default occurs. Moreover, any specific collateral used to secure a senior floating rate loans may decline in value or become illiquid, which would adversely affect the senior floating rate loan's value. Unlike the securities markets, there is no central clearinghouse for loan trades, and the loan market has not established enforceable settlement standards or remedies for failure to settle. Therefore, portfolio transactions in senior floating rate loans may have uncertain settlement time periods. Senior floating rate loans are subject to a number of risks described elsewhere in this prospectus, including liquidity risk and the risk of investing in below investment grade fixed income instruments. Furthermore, increases in interest rates may result in greater volatility of senior floating rate loans and average duration may fluctuate with fluctuations in interest rates.

CALL RISK. If an issuer calls higher-yielding securities held by the Fund, performance could be adversely impacted.

CONVERTIBLE BONDS RISK. The market values of convertible bonds tend to decline as interest rates increase and, conversely, to increase as interest rates decline. A convertible bond's market value also tends to reflect the market price of the common stock of the issuing company.

CREDIT RISK. Credit risk is the risk that an issuer of a security may be unable or unwilling to make dividend, interest and principal payments when due and the related risk that the value of a security may decline because of concerns about the issuer's ability or willingness to make such payments. Credit risk may be heightened for the Fund because it invests a substantial portion of its net assets in high yield or "junk" debt. Such securities, while generally offering higher yields than investment grade debt with similar maturities, involve greater risks, including the possibility of dividend or interest deferral, default or bankruptcy, and are regarded as predominantly speculative with respect to the issuer's capacity to pay dividends or interest and repay principal. Credit risk is heightened for loans in which the Fund invests because companies that issue such loans tend to be highly leveraged and thus are more susceptible to the risks of interest deferral, default and/or bankruptcy.

CURRENCY RISK. Because the Fund's net asset value is determined on the basis of U.S. dollars and the Fund invests in non-U.S. dollar-denominated securities, you may lose money if the local currency of a foreign market depreciates against the U.S. dollar, even if the local currency value of the Fund's holdings goes up. The Fund may hedge certain of its non-U.S. dollar holdings.

HIGH YIELD SECURITIES RISK. High yield securities, or "junk bonds," are subject to greater market fluctuations and risk of loss than securities with higher investment ratings. These securities are issued by companies that may have limited operating history, narrowly focused operations, and/or other impediments to the timely payment of periodic interest and principal at maturity. If the economy slows down or dips into recession, the issuers of high yield securities may not have sufficient resources to continue making timely payment of periodic interest and principal at maturity. The market for high yield securities is smaller and less liquid than that for investment grade securities. High yield securities are generally not listed on a national securities exchange but trade in the over-the-counter markets. Due to the smaller, less liquid market for high yield securities, the bid-offer spread on such securities is generally greater than it is for investment grade securities and the purchase or sale of such securities may take longer to complete.

ILLIQUID SECURITIES RISK. Illiquid securities involve the risk that the securities will not be able to be sold at the time desired by the Fund or at prices approximately the value at which the Fund is carrying the securities on its books.

INCOME RISK. If interest rates fall, the income from the Fund's portfolio will likely decline if the Fund holds floating rate debt that will adjust lower with falling interest rates. For loans, interest rates typically reset periodically.

INTEREST RATE RISK. Interest rate risk is the risk that the value of the debt securities in the Fund will decline because of rising market interest rates. Interest rate risk is generally lower for shorter term investments and higher for longer term investments. Duration is a common measure of interest rate risk, which measures a debt security's expected life on a present value basis, taking into account the debt security's yield, interest payments and final maturity. Duration is a reasonably accurate measure of a debt security's price sensitivity to changes in interest rates. The longer the duration of a debt security, the greater the debt security's price sensitivity is to changes in interest rates.

LIQUIDITY RISK. The Fund invests a substantial portion of its assets in lower-quality debt issued by companies that are highly leveraged. Lower-quality debt tends to be less liquid than higher-quality debt. Moreover, smaller debt issues tend to be less liquid than larger debt issues. If the economy experiences a sudden downturn, or if the debt markets for such companies become distressed, the Fund may have particular difficulty selling its assets in sufficient amounts, at reasonable prices and in a sufficiently timely manner to raise the cash necessary to meet any potentially heavy redemption requests by Fund shareholders.

MARKET RISK. Market risk is the risk that a particular security owned by the Fund 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.

NON-U.S. SECURITIES RISK. Non-U.S. securities are subject to higher volatility than securities of domestic issuers due to possible adverse political, social or economic developments; restrictions on foreign investment or exchange of securities; lack of liquidity; currency exchange rates; excessive taxation; government seizure of assets; different legal or accounting standards; and less government supervision and regulation of exchanges in foreign countries.

OTHER DEBT SECURITIES RISK. Secured loans that are not first lien loans that are unsecured and debt securities are subject to many of the same risks that affect senior floating rate loans; however they are often unsecured and/or lower in the issuer's capital structure than senior floating rate loans, and thus may be exposed to greater risk of default and lower recoveries in the event of a default. This risk can be further heightened in the case of below investment grade instruments. Additionally, most fixed income securities are fixed rate and thus are generally more susceptible than floating rate loans to price volatility related to changes in prevailing interest rates.

PREPAYMENT RISK. Loans and other fixed income investments are subject to prepayment risk. The degree to which borrowers prepay loans, whether as a contractual requirement or at their election, may be affected by general business conditions, the financial condition of the borrower and competitive conditions among loan investors, among others. As such, prepayments cannot be predicted with accuracy. Upon a prepayment, either in part or in full, the actual outstanding debt on which the Fund derives interest income will be reduced. The Fund may not be able to reinvest the proceeds received on terms as favorable as the prepaid loan.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading

ANNUAL TOTAL RETURN
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The bar chart and table below illustrate the annual calendar year returns of the Fund's Class A shares as well as the average annual Fund 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 Class A shares' average annual total returns compare to those of a blended benchmark index and two specialized market indices. 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.

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. After-tax returns are shown for only Class A shares, and after-tax returns for other Classes will vary. Returns for the market index 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.

Imposition of the Fund's sales load is not reflected in the bar chart below. If the sales load was reflected, returns would be less than those shown.
Bar Chart [Heading] rr_BarChartHeading

FIRST TRUST SHORT DURATION HIGH INCOME FUND--TOTAL RETURN ON CLASS A SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

During the period shown in the chart above:

BEST QUARTER WORST QUARTER
3.78% (March 31, 2013) -1.83% (December 31, 2015)

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

AVERAGE ANNUAL TOTAL RETURNS FOR THE FUND FOR THE PERIODS ENDED DECEMBER 31, 2015
First Trust Short Duration High Income Fund | Class A  
Risk Return Abstract rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 3.50%
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice none [1]
Maximum Sales Charge (Load) Imposed on Reinvested Dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Exchange Fee rr_ExchangeFee none
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.36%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.26%
Fee Waivers and Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.01%) [8]
Total Annual Fund Operating Expenses After Fee Waivers and Expense Reimbursements rr_NetExpensesOverAssets 1.25%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 473
3 Years rr_ExpenseExampleYear03 735
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,016
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,818
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 473
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 735
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,016
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,818
Annual Return 2013 rr_AnnualReturn2013 7.43%
Annual Return 2014 rr_AnnualReturn2014 2.04%
Annual Return 2015 rr_AnnualReturn2015 (1.49%)
1 Year rr_AverageAnnualReturnYear01 (4.96%)
Since Inception rr_AverageAnnualReturnSinceInception 1.64%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 01, 2012
First Trust Short Duration High Income Fund | Class C  
Risk Return Abstract rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00% [1]
Maximum Sales Charge (Load) Imposed on Reinvested Dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Exchange Fee rr_ExchangeFee none
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses rr_OtherExpensesOverAssets 0.36%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 2.01%
Fee Waivers and Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.01%) [8]
Total Annual Fund Operating Expenses After Fee Waivers and Expense Reimbursements rr_NetExpensesOverAssets 2.00%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 303
3 Years rr_ExpenseExampleYear03 630
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,082
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,337
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 203
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 630
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,082
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,337
1 Year rr_AverageAnnualReturnYear01 (3.18%)
Since Inception rr_AverageAnnualReturnSinceInception 2.02%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 01, 2012
First Trust Short Duration High Income Fund | Class I  
Risk Return Abstract rr_RiskReturnAbstract  
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as a percentage of the lesser of purchase price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice none [1]
Maximum Sales Charge (Load) Imposed on Reinvested Dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Exchange Fee rr_ExchangeFee none
Management Fee rr_ManagementFeesOverAssets 0.65%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.36%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.01%
Fee Waivers and Expense Reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.01%) [8]
Total Annual Fund Operating Expenses After Fee Waivers and Expense Reimbursements rr_NetExpensesOverAssets 1.00%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 102
3 Years rr_ExpenseExampleYear03 321
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 557
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,235
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 102
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 321
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 557
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,235
1 Year rr_AverageAnnualReturnYear01 (1.24%)
Since Inception rr_AverageAnnualReturnSinceInception 3.05%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 01, 2012
First Trust Short Duration High Income Fund | After Taxes on Distributions | Class A  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (6.64%)
Since Inception rr_AverageAnnualReturnSinceInception (0.13%)
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 01, 2012
First Trust Short Duration High Income Fund | After Taxes on Distributions and Sales | Class A  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (2.78%)
Since Inception rr_AverageAnnualReturnSinceInception 0.47%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 01, 2012
First Trust Short Duration High Income Fund | Blended Index  
Risk Return Abstract rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 (2.64%) [9]
Since Inception rr_AverageAnnualReturnSinceInception 2.29% [9]
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 01, 2012 [9],[10]
First Trust Short Duration High Income Fund | BofA Merrill Lynch U.S. High Yield Constrained Index  
Risk Return Abstract rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 (4.61%)
Since Inception rr_AverageAnnualReturnSinceInception 2.27%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 01, 2012 [10]
First Trust Short Duration High Income Fund | S&P/LSTA Leveraged Loan Index  
Risk Return Abstract rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 (0.69%)
Since Inception rr_AverageAnnualReturnSinceInception 2.28%
Inception Date rr_AverageAnnualReturnInceptionDate Nov. 01, 2012 [10]
[1] For Class A shares purchased at net asset value without a sales charge because the purchase amount exceeded $1 million, where the financial intermediary did not waive the sales commission, a contingent deferred sales charge of 1% is imposed on any redemption within 12 months of purchase. The contingent deferred sales charge on Class C shares applies only to redemptions within 12 months of purchase.
[2] Expenses have been restated to reflect the current fiscal year.
[3] The Fund's investment advisor and sub-advisor have agreed to waive fees and reimburse expenses through February 28, 2017 so that Total Annual Fund Operating Expenses (excluding 12b-1 distribution and service fees, interest expenses, taxes, fees incurred in acquiring and disposing of portfolio securities, and extraordinary expenses) do not exceed 1.15% of the average daily net assets of any class of Fund shares. Total Annual Fund Operating Expenses (excluding 12b-1 distribution and service fees, interest expenses, taxes, fees incurred in acquiring and disposing of portfolio securities, and extraordinary expenses) will not exceed 1.50% from March 1, 2017 through February 28, 2026. Fees waived or expenses borne by the Fund's investment advisor and sub-advisor are subject to reimbursement by the Fund 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 at any time if it would result in the Fund's expenses exceeding the applicable expense limitation in place for the most recent fiscal year for which such expense limitation was in place. Expense limitations may be terminated or modified prior to their expiration only with the approval of the Board of Trustees of the First Trust Series Fund.
[4] Since Inception Index returns are based on inception date of the Class I shares.
[5] The Blended Index consists of a 50/50 blend of the BofA Merrill Lynch Fixed Rate Preferred Securities Index and the BofA Merrill Lynch U.S. Capital Securities Index. The Blended Index was added to reflect the diverse allocation of institutional preferred and hybrid securities in the Fund's portfolio. The indexes do not charge management fees or brokerage expenses, and no such fees or expenses were deducted from the performance shown. Indexes are unmanaged and an investor cannot invest directly in an index.
[6] Acquired Fund Fees and Expenses are not taken into consideration in the expense limitation because they are not Fund operating expenses, but rather, are imputed fees and expenses.
[7] The Fund's investment advisor and sub-advisor have agreed to waive fees and reimburse expenses through February 28, 2017 so that Total Annual Fund Operating Expenses (excluding 12b-1 distribution and service fees, interest expenses, taxes, acquired fund fees and expenses, fees incurred in acquiring and disposing of portfolio securities, and extraordinary expenses) do not exceed 1.35% of the average daily net assets of any class of Fund shares. Total Annual Fund Operating Expenses (excluding 12b-1 distribution and service fees, interest expenses, taxes, acquired fund fees and expenses, fees incurred in acquiring and disposing of portfolio securities, and extraordinary expenses) will not exceed 1.70% from March 1, 2017 through February 28, 2026. Fees waived or expenses borne by the Fund's investment advisor and sub-advisor are subject to reimbursement by the Fund 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 at any time if it would result in the Fund's expenses exceeding the applicable expense limitation in place for the most recent fiscal year for which such expense limitation was in place. Expense limitations may be terminated or modified prior to their expiration only with the approval of the Board of Trustees of the First Trust Series Fund.
[8] The Fund's investment advisor has agreed to waive fees and reimburse expenses through February 28, 2017 so that Total Annual Fund Operating Expenses (excluding 12b-1 distribution and service fees, interest expenses, taxes, fees incurred in acquiring and disposing of portfolio securities, and extraordinary expenses) do not exceed 1.00% of the average daily net assets of any class of Fund shares. Total Annual Fund Operating Expenses (excluding 12b-1 distribution and service fees, interest expenses, taxes, fees incurred in acquiring and disposing of portfolio securities, and extraordinary expenses) will not exceed 1.35% from March 1, 2017 through February 28, 2026. Fees waived or expenses borne by the Fund's investment advisor are subject to reimbursement by the Fund 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 at any time if it would result in the Fund's expenses exceeding the applicable expense limitation in place for the most recent fiscal year for which such expense limitation was in place. Expense limitations may be terminated or modified prior to their expiration only with the approval of the Board of Trustees of the First Trust Series Fund.
[9] The Blended Benchmark return is a 50/50 split between the BofA Merrill Lynch U.S. High Yield Constrained Index and the S&P/LSTA Leveraged Loan Index returns.
[10] Since Inception Index returns are based on inception date of the Fund.