v3.26.1
First Trust Europe AlphaDEX Fund Average Annual Total Returns
 12 Months Ended 60 Months Ended 120 Months Ended 176 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Nasdaq AlphaDEX® Europe™ Index (reflects no deduction for fees, expenses or taxes)[Member]          
Prospectus [Line Items]          
Average Annual Return, Percent [1]   56.05% 11.68% 10.04%
Nasdaq Developed Markets Europe™ Index (reflects no deduction for fees, expenses or taxes)[Member]          
Prospectus [Line Items]          
Average Annual Return, Percent [1]   36.05% 9.90% 8.35%
MSCI Europe Index (reflects no deduction for fees, expenses or taxes)[Member]          
Prospectus [Line Items]          
Average Annual Return, Percent   35.41% 10.30% 8.52% 6.70%
First Trust Europe AlphaDEX Fund          
Prospectus [Line Items]          
Average Annual Return, Percent   55.13% 10.91% 9.36% 7.16%
Performance Inception Date Apr. 18, 2011        
First Trust Europe AlphaDEX Fund | After Taxes on Distributions          
Prospectus [Line Items]          
Average Annual Return, Percent   52.86% 9.26% 8.03% 5.97%
First Trust Europe AlphaDEX Fund | After Taxes on Distributions and Sales          
Prospectus [Line Items]          
Average Annual Return, Percent   32.51% 7.74% 6.88% 5.18%
[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.