v3.26.3
Expense Example, No Redemption - First Trust Flexible Municipal High Income ETF - First Trust Flexible Municipal High Income ETF
Aug. 31, 2025
USD ($)
Prospectus [Line Items]  
Expense Example, No Redemption, 1 Year $ 50
Expense Example, No Redemption, 3 Years 157
Expense Example, No Redemption, 5 Years 274
Expense Example, No Redemption, 10 Years $ 616