v3.26.3
Shareholder Report, Average Annual Return (Details)
 12 Months Ended 60 Months Ended 63 Months Ended 76 Months Ended 78 Months Ended 93 Months Ended 105 Months Ended 109 Months Ended 119 Months Ended
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C000162358 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name First Trust Municipal High Income ETF                
Average Annual Return, Percent 7.59% 0.35%         3.07%    
C000172840 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name First Trust Horizon Managed Volatility Developed International ETF                
Average Annual Return, Percent 17.94% 7.57%             5.94%
C000172841 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name First Trust Horizon Managed Volatility Domestic ETF                
Average Annual Return, Percent 5.06% 5.96%             9.06%
C000187865 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name First Trust California Municipal High Income ETF                
Average Annual Return, Percent 5.57% 0.23%           2.42%  
C000205579 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name First Trust Ultra Short Duration Municipal ETF                
Average Annual Return, Percent 2.37% 2.02%       1.83%      
C000205581 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name First Trust Short Duration Managed Municipal ETF                
Average Annual Return, Percent 2.78% 1.36%       2.15%      
C000216993 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name First Trust Equity Market Neutral ETF                
Average Annual Return, Percent 7.90% 3.80%     2.55%        
C000218390 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name First Trust Horizon Managed Volatility Small/Mid ETF                
Average Annual Return, Percent 12.80% 4.95%   11.77%          
C000223991 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name First Trust New York Municipal High Income ETF                
Average Annual Return, Percent 5.85% 0.13% 0.48%            
MSCI EAFE Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name MSCI EAFE Index                
Average Annual Return, Percent 24.33% 9.31%             9.24%
Standard & Poor's 500 Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name S&P 500® Index                
Average Annual Return, Percent 19.56% 12.86%     15.20%       15.15%
Bloomberg Municipal Bond Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name Bloomberg Municipal Bond Index                
Average Annual Return, Percent 5.27% 0.51% 0.75%     2.50% 2.15% 2.14%  
Russell 3000 Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name Russell 3000® Index                
Average Annual Return, Percent 19.60% 11.82%   19.30%          
Blended Benchmark [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name Blended Benchmark                
Average Annual Return, Percent [1] 4.69% 1.28%         3.06%    
Bloomberg 10 Year California Exempt Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name Bloomberg 10 Year California Exempt Index                
Average Annual Return, Percent 3.62% 0.50%           1.99%  
Bloomberg Municipal Short Term Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name Bloomberg Municipal Short-Term Index                
Average Annual Return, Percent 2.67% 2.40%       1.98%      
Bloomberg Municipal Short 1 5 Year Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name Bloomberg Municipal Short (1-5) Year Index                
Average Annual Return, Percent 2.16% 1.40%       1.98%      
ICE BofA 3 month U S Treasury Bill Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name ICE BofA 3-month U.S. Treasury Bill Index                
Average Annual Return, Percent 3.82% 3.59%     2.84%        
S and P 1000 Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name S&P 1000® Index                
Average Annual Return, Percent 24.91% 8.21%   18.21%          
Bloomberg Municipal New York 12 17 Years Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name Bloomberg Municipal New York 12-17 Years Index                
Average Annual Return, Percent 6.43% 0.60% 0.91%            
[1]
The Blended Benchmark consists of the following two indexes: 50% of the Bloomberg High Yield 10-Year Municipal Index (8-12 years) which is comprised of bonds with a final maturity between 8 and 12 years that are part of the Bloomberg Municipal Bond High Yield Index; and 50% of the Bloomberg Revenue 10-Year Municipal Index (8-12 years), which is comprised of revenue bonds that have a final maturity between 8 and 12 years that are part of the Bloomberg Municipal Bond Index.