v3.25.2
First Trust SMID Capital Strength ETF Average Annual Total Returns
12 Months Ended 60 Months Ended 90 Months Ended
Mar. 31, 2025
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
The SMID Capital Strength Index (reflects no deduction for fees, expenses or taxes)[Member]        
Prospectus [Line Items]        
Average Annual Return, Percent [1],[2]  
Nasdaq Riskalyze US Mid Cap(TM) Index (reflects no deduction for fees, expenses or taxes)[Member]        
Prospectus [Line Items]        
Average Annual Return, Percent   9.22% 9.51% 9.48%
Russell 3000® Index (reflects no deduction for fees, expenses or taxes)[Member]        
Prospectus [Line Items]        
Average Annual Return, Percent   23.81% 13.86% 13.72%
Russell 2500(TM) Index (reflects no deduction for fees, expenses or taxes)[Member]        
Prospectus [Line Items]        
Average Annual Return, Percent   12.00% 8.77% 9.21%
First Trust SMID Capital Strength ETF        
Prospectus [Line Items]        
Average Annual Return, Percent   15.44% 10.18% 9.69%
Performance Inception Date Jun. 20, 2017      
First Trust SMID Capital Strength ETF | After Taxes on Distributions        
Prospectus [Line Items]        
Average Annual Return, Percent   14.89% 9.53% 9.02%
First Trust SMID Capital Strength ETF | After Taxes on Distributions and Sales        
Prospectus [Line Items]        
Average Annual Return, Percent   9.12% 7.73% 7.46%
[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 June 7, 2024, the Fund’s underlying index changed from the Nasdaq Riskalyze US Mid CapTM Index to The SMID Capital 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.