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First Trust Nasdaq Pharmaceuticals ETF Average Annual Total Returns
12 Months Ended 60 Months Ended 99 Months Ended
Mar. 31, 2025
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Nasdaq US Smart Pharmaceuticals(TM) Index (reflects no deduction for fees, expenses or taxes)[Member]        
Prospectus [Line Items]        
Average Annual Return, Percent   3.59% 4.77% 5.60%
Nasdaq US Benchmark(TM) Index (reflects no deduction for fees, expenses or taxes)[Member]        
Prospectus [Line Items]        
Average Annual Return, Percent   24.48% 14.04% 14.52%
Nasdaq US Benchmark Pharmaceuticals(TM) Index (reflects no deduction for fees, expenses or taxes)[Member]        
Prospectus [Line Items]        
Average Annual Return, Percent   8.56% 11.54% 11.46%
First Trust Nasdaq Pharmaceuticals ETF        
Prospectus [Line Items]        
Average Annual Return, Percent   2.96% 4.12% 4.92%
Performance Inception Date Sep. 20, 2016      
First Trust Nasdaq Pharmaceuticals ETF | After Taxes on Distributions        
Prospectus [Line Items]        
Average Annual Return, Percent   2.29% 3.59% 4.37%
First Trust Nasdaq Pharmaceuticals ETF | After Taxes on Distributions and Sales        
Prospectus [Line Items]        
Average Annual Return, Percent   1.76% 2.96% 3.62%