v3.26.1
First Trust Nasdaq-100 Select Equal Weight ETF Average Annual Total Returns
 12 Months Ended 28 Months Ended 34 Months Ended 38 Months Ended 58 Months Ended 59 Months Ended 60 Months Ended 89 Months Ended 101 Months Ended 120 Months Ended 132 Months Ended 227 Months Ended 229 Months Ended 234 Months Ended 236 Months Ended 237 Months Ended 238 Months Ended 268 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
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Dec. 31, 2025
Nasdaq-100 Select Equal Weight(TM) Index (reflects no deduction for fees, expenses or taxes)[Member]                                        
Prospectus [Line Items]                                        
Average Annual Return, Percent [1],[2],[3]                                
Nasdaq-100 Equal Weighted(TM) Index (reflects no deduction for fees, expenses or taxes)[Member]                                        
Prospectus [Line Items]                                        
Average Annual Return, Percent   14.99%           8.20%     13.81% 11.69%                
S&P 500® Index (reflects no deduction for fees, expenses or taxes)[Member]                                        
Prospectus [Line Items]                                        
Average Annual Return, Percent   17.88% 21.88% 24.47% 21.49% 14.19% 14.00% 14.42% 14.37% 14.77% 14.82% 10.87% 11.26% 10.73% 11.26% 11.13% 10.87% 10.96% 10.98% 11.07%
Nasdaq-100 Index® (reflects no deduction for fees, expenses or taxes)[Member]                                        
Prospectus [Line Items]                                        
Average Annual Return, Percent   21.02%           15.30%     19.70% 15.63%                
First Trust Nasdaq-100 Select Equal Weight ETF                                        
Prospectus [Line Items]                                        
Average Annual Return, Percent   14.33%           7.66%     13.18% 11.03%                
Performance Inception Date Apr. 19, 2006                                      
First Trust Nasdaq-100 Select Equal Weight ETF | After Taxes on Distributions                                        
Prospectus [Line Items]                                        
Average Annual Return, Percent   14.13%           7.42%     12.93% 10.80%                
First Trust Nasdaq-100 Select Equal Weight ETF | After Taxes on Distributions and Sales                                        
Prospectus [Line Items]                                        
Average Annual Return, Percent   8.48%           5.90%     10.94% 9.55%                
[1] The Nasdaq-100 Select Equal WeightTM Index began operations on June 23, 2025.
[2] On December 22, 2025, the Fund’s underlying index changed from the Nasdaq-100 Equal WeightedTM Index to the Nasdaq-100 Select Equal WeightTM Index. Therefore, any Fund performance and historical returns shown above that incorporate Fund performance prior to December 22, 2025 reflect performance of the Fund based on the Nasdaq-100 Equal WeightedTM Index and are not necessarily indicative of the performance that the Fund, based on the Nasdaq-100 Select Equal WeightTM Index, would have generated.
[3] 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.