v3.26.1
Average Annual Total Returns
 12 Months Ended 60 Months Ended 120 Months Ended 141 Months Ended 178 Months Ended
Mar. 31, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
S&P 500 Index (Class A&I) (reflects no deduction for fees, expenses or taxes)            
Prospectus [Line Items]            
Average Annual Return, Label [Optional Text] S&P 500 Index (Class A&I)(reflects no deduction for fees, expenses or taxes)          
Average Annual Return, Percent   17.88% 14.42% 14.82%   13.69%
S&P 500 Index (Class C) (reflects no deduction for fees, expenses or taxes)            
Prospectus [Line Items]            
Average Annual Return, Label [Optional Text] S&P 500 Index (Class C)(reflects no deduction for fees, expenses or taxes)          
Average Annual Return, Percent   17.88% 14.42% 14.82% 13.67%  
Alerian MLP Total Return Index (Class A&I) (reflects no deduction for fees, expenses or taxes)            
Prospectus [Line Items]            
Average Annual Return, Label [Optional Text] Alerian MLP Total Return Index (Class A&I)(reflects no deduction for fees, expenses or taxes)          
Average Annual Return, Percent   9.76% 25.96% 8.85%   6.01%
Alerian MLP Total Return Index (Class C) (reflects no deduction for fees, expenses or taxes)            
Prospectus [Line Items]            
Average Annual Return, Label [Optional Text] Alerian MLP Total Return Index (Class C)(reflects no deduction for fees, expenses or taxes)          
Average Annual Return, Percent   9.76% 25.96% 8.85% 4.18%  
MainGate MLP Fund Class I            
Prospectus [Line Items]            
Average Annual Return, Label [Optional Text] Return Before Taxes          
Average Annual Return, Percent   2.74% 26.24% 8.31%   6.51%
Performance Inception Date Feb. 17, 2011          
MainGate MLP Fund Class I | After Taxes on Distributions            
Prospectus [Line Items]            
Average Annual Return, Label [Optional Text] Return After Taxes on Distributions          
Average Annual Return, Percent   1.66% 25.24% 7.88%   6.22%
MainGate MLP Fund Class I | After Taxes on Distributions and Sales            
Prospectus [Line Items]            
Average Annual Return, Label [Optional Text] [1] Return After Taxes on Distributions and Sale of Fund Shares*          
Average Annual Return, Percent [1]   2.39% 21.61% 6.72%   5.33%
MainGate MLP Fund Class A            
Prospectus [Line Items]            
Average Annual Return, Label [Optional Text] Return Before Taxes          
Average Annual Return, Percent   (3.45%) 24.46% 7.41%   5.83%
Performance Inception Date Feb. 17, 2011          
MainGate MLP Fund Class C            
Prospectus [Line Items]            
Average Annual Return, Label [Optional Text] Return Before Taxes          
Average Annual Return, Percent   0.73% 24.98% 7.23% 3.45%  
Performance Inception Date Mar. 31, 2014          
[1] In certain cases, the figure representing “Return After Taxes on Distributions and Sale of Fund Shares” may be higher than the other return figures for the same period, since a higher after-tax return results when a capital loss occurs upon redemption and provides an assumed tax deduction that benefits the investor.