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First Trust Latin America 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® Latin America™ Index (reflects no deduction for fees, expenses or taxes)[Member]          
Prospectus [Line Items]          
Average Annual Return, Percent [1]   57.10% 9.59% 11.41%
Nasdaq Latin America™ Index (reflects no deduction for fees, expenses or taxes)[Member]          
Prospectus [Line Items]          
Average Annual Return, Percent [1]   54.95% 7.72% 8.59%
MSCI EM Latin America Index (reflects no deduction for fees, expenses or taxes)[Member]          
Prospectus [Line Items]          
Average Annual Return, Percent   54.81% 8.65% 8.79% 0.58%
First Trust Latin America AlphaDEX Fund          
Prospectus [Line Items]          
Average Annual Return, Percent   54.67% 8.14% 10.05% 1.93%
Performance Inception Date Apr. 18, 2011        
First Trust Latin America AlphaDEX Fund | After Taxes on Distributions          
Prospectus [Line Items]          
Average Annual Return, Percent   52.36% 6.10% 8.16% 0.39%
First Trust Latin America AlphaDEX Fund | After Taxes on Distributions and Sales          
Prospectus [Line Items]          
Average Annual Return, Percent   32.23% 5.32% 7.18% 0.68%
[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.