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First Trust SMID Growth Strength ETF Average Annual Total Returns
12 Months Ended 60 Months Ended 102 Months Ended
Mar. 31, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
The SMID Growth Strength Index (reflects no deduction for fees, expenses or taxes)[Member]        
Prospectus [Line Items]        
Average Annual Return, Percent [1],[2]   3.11%
Russell 3000® Index (reflects no deduction for fees, expenses or taxes)[Member]        
Prospectus [Line Items]        
Average Annual Return, Percent   17.15% 13.15% 14.12%
S&P 1000® Index (reflects no deduction for fees, expenses or taxes)[Member]        
Prospectus [Line Items]        
Average Annual Return, Percent   7.04% 8.57% 9.15%
First Trust SMID Growth Strength ETF        
Prospectus [Line Items]        
Average Annual Return, Percent   2.42% 6.69% 7.07%
Performance Inception Date Jun. 20, 2017      
First Trust SMID Growth Strength ETF | After Taxes on Distributions        
Prospectus [Line Items]        
Average Annual Return, Percent   2.42% 5.95% 6.31%
First Trust SMID Growth Strength ETF | After Taxes on Distributions and Sales        
Prospectus [Line Items]        
Average Annual Return, Percent   1.43% 4.89% 5.27%
[1] Performance data is not available for all the periods shown in the table for the index because performance data does not exist for some of the entire periods.
[2] On December 3, 2024, the Fund’s underlying index changed from the Nasdaq Riskalyze US Small CapTM Index to The SMID Growth Strength Index. Therefore, the Fund’s performance and historical returns shown for the periods prior to this date are not necessarily indicative of the performance that the Fund, based on its current Index, would have generated.