First Trust Short Duration High Income Fund Performance Management - First Trust Short Duration High Income Fund |
Oct. 31, 2025 |
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| Prospectus [Line Items] | |
| Bar Chart and Performance Table [Heading] | <span style="color:#000000;font-family:Arial;font-size:9.90pt;font-weight:bold;">Annual Total Return</span> |
| Performance Narrative [Text Block] | The bar chart and table below illustrate the calendar year returns of the Fund’s Class A shares based on net asset value 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 for years 1, 5, 10 and since inception compared to those of a blended benchmark, two market indices and a broad-based securities market index. The Fund’s updated performance information is accessible on the Fund’s website at http://www.ftportfolios.com.On January 3, 2023, the fair value methodology used to value the senior loan investments held by the Fund was changed. Prior to that date, the senior loans were valued using the bid side price provided by a pricing service. After such date, the senior loans were valued using the midpoint between the bid and ask price provided by a pricing service. The change in the Fund’s fair value methodology on January 3, 2023, resulted in a one-time increase in the Fund’s Class A, C, and I’s net asset values of approximately $0.049, $0.048, and $0.052 per share on that date, which represented a positive impact on the Fund’s Class A, C, and I’s performance of 0.28%, 0.27%, and 0.30% respectively.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. |
| Performance Past Does Not Indicate Future [Text] | <span style="color:#000000;font-family:Arial;font-size:9.00pt;">The Fund’s past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.</span> |
| Performance Information Illustrates Variability of Returns [Text] | <span style="font-family:Arial;font-size:9.00pt;margin-left:0%;">The bar chart and table below illustrate the calendar year returns of the Fund’s Class A shares based on net asset value as well as the average annual Fund returns.</span> |
| Performance Additional Market Index [Text] | <span style="color:#000000;font-family:Arial;font-size:8.10pt;font-style:italic;">The Blended Index return is a 50/50 split between the ICE BofA US High Yield Constrained Index and the Morningstar</span><span style="color:#000000;font-family:Arial;font-size:5.5pt;font-style:italic;position:relative;top:-2.75pt;">®</span><span style="color:#000000;font-family:Arial;font-size:8.10pt;font-style:italic;"> LSTA</span><span style="color:#000000;font-family:Arial;font-size:5.5pt;font-style:italic;position:relative;top:-2.75pt;">®</span><span style="color:#000000;font-family:Arial;font-size:8.10pt;font-style:italic;"> US Leveraged Loan Index returns.</span> |
| Bar Chart [Heading] | <span style="font-family:Arial;font-size:9.90pt;font-weight:bold;">First Trust Short Duration High Income Fund</span><span style="font-family:Arial;font-size:9.90pt;font-weight:bold;margin-left:2.75pt;">—Class A Shares</span> <br/><span style="font-family:Arial;font-size:9.90pt;font-weight:bold;">Calendar Year Total Returns as of 12/31</span> |
| Bar Chart Closing [Text Block] | During the periods shown in the chart above:ReturnPeriod EndedBest Quarter6.97%June 30, 2020Worst Quarter-9.70%March 31, 2020 |
| Performance Table Heading | <span style="font-family:Arial;font-size:9.90pt;font-weight:bold;">Average Annual Total Returns for the Periods Ended December 31, 2025</span> |
| Performance Table Uses Highest Federal Rate | <span style="font-family:Arial;font-size:9.00pt;margin-left:0%;">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.</span> |
| Performance Table Not Relevant to Tax Deferred | <span style="color:#000000;font-family:Arial;font-size:9.00pt;margin-left:0%;">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 </span><span style="color:#000000;font-family:Arial;font-size:9.00pt;">(</span><span style="color:#000000;font-family:Arial;font-size:9.00pt;font-style:italic;">IRAs</span><span style="color:#000000;font-family:Arial;font-size:9.00pt;">) or employee-sponsored retirement plans.</span> |
| Performance Table Explanation after Tax Higher | <span style="font-family:Arial;font-size:9.00pt;">Returns after taxes on distributions reflect the taxed return on the payment of dividends </span><span style="font-family:Arial;font-size:9.00pt;margin-left:0%;">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. </span><span style="font-family:Arial;font-size:9.00pt;">After-tax returns are shown for only Class A shares and </span><span style="font-family:Arial;font-size:9.00pt;margin-left:0%;">after-tax returns for other classes will vary.</span><span style="font-family:Arial;font-size:9.00pt;"> Returns for an index do not include expenses, which are deducted from Fund returns, or taxes.</span> |
| Performance Availability Website Address [Text] | <span style="font-family:Arial;font-size:9.00pt;">http://www.ftportfolios.com</span> |
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| Prospectus [Line Items] | |
| Highest Quarterly Return, Label [Optional Text] | <span style="color:#000000;font-family:Arial;font-size:9.00pt;margin-left:0.0pt;">Best Quarter</span> |
| Highest Quarterly Return | 6.97% |
| Highest Quarterly Return, Date | Jun. 30, 2020 |
| Lowest Quarterly Return, Label [Optional Text] | <span style="color:#000000;font-family:Arial;font-size:9.00pt;margin-left:0.0pt;">Worst Quarter</span> |
| Lowest Quarterly Return | (9.70%) |
| Lowest Quarterly Return, Date | Mar. 31, 2020 |