v3.25.3
First Trust Financials AlphaDEX Fund Average Annual Total Returns
 12 Months Ended 60 Months Ended 120 Months Ended 164 Months Ended 212 Months Ended
Jul. 31, 2025
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
StrataQuant® Financials Index (reflects no deduction for fees, expenses or taxes)[Member]            
Prospectus [Line Items]            
Average Annual Return, Percent   28.70% 13.82% 12.01%   8.77%
Russell 1000® Index (reflects no deduction for fees, expenses or taxes)[Member]            
Prospectus [Line Items]            
Average Annual Return, Percent   24.51% 14.28% 12.87%   10.12%
S&P 500® Financials Index (reflects no deduction for fees, expenses or taxes)[Member]            
Prospectus [Line Items]            
Average Annual Return, Percent   30.56% 11.70% 11.43%   4.80%
Russell 1000® Financials Index (reflects no deduction for fees, expenses or taxes)[Member]            
Prospectus [Line Items]            
Average Annual Return, Percent [1]   31.83% 14.45% 13.16%  
Russell 3000® Index (reflects no deduction for fees, expenses or taxes)[Member]            
Prospectus [Line Items]            
Average Annual Return, Percent   23.81% 13.86% 12.55% 13.21% 9.93%
First Trust Financials AlphaDEX Fund            
Prospectus [Line Items]            
Average Annual Return, Percent   27.84% 13.07% 11.27%   7.95%
Performance Inception Date May 08, 2007          
First Trust Financials AlphaDEX Fund | After Taxes on Distributions            
Prospectus [Line Items]            
Average Annual Return, Percent   26.74% 11.85% 10.25%   7.09%
First Trust Financials AlphaDEX Fund | After Taxes on Distributions and Sales            
Prospectus [Line Items]            
Average Annual Return, Percent   16.43% 9.77% 8.73%   6.15%
[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.