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First Trust Indxx Aerospace and Defense 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
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Indxx US Aerospace & Defense Index (reflects no deduction for fees, expenses or taxes)[Member]                                        
Prospectus [Line Items]                                        
Average Annual Return, Percent   42.13%     26.97%                              
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%
S&P Composite 1500® Aerospace & Defense Index (reflects no deduction for fees, expenses or taxes)[Member]                                        
Prospectus [Line Items]                                        
Average Annual Return, Percent   44.15%     23.80%                              
First Trust Indxx Aerospace and Defense ETF                                        
Prospectus [Line Items]                                        
Average Annual Return, Percent   41.24%     26.20%                              
Performance Inception Date Oct. 25, 2022                                      
First Trust Indxx Aerospace and Defense ETF | After Taxes on Distributions                                        
Prospectus [Line Items]                                        
Average Annual Return, Percent   40.98%     25.89%                              
First Trust Indxx Aerospace and Defense ETF | After Taxes on Distributions and Sales                                        
Prospectus [Line Items]                                        
Average Annual Return, Percent   24.39%     20.85%