v3.25.2
Shareholder Report, Line Graph (Details) - USD ($)
 6 Months Ended 12 Months Ended 24 Months Ended 36 Months Ended 48 Months Ended 60 Months Ended 72 Months Ended 84 Months Ended 96 Months Ended 108 Months Ended 120 Months Ended
May 31, 2015
May 31, 2025
May 31, 2016
May 31, 2017
May 31, 2018
May 31, 2019
May 31, 2020
May 31, 2021
May 31, 2022
May 31, 2023
May 31, 2024
May 31, 2025
C000142690 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Class A Shares - Including sales charges                    
Accumulated Value $ 14,175   $ 10,194 $ 10,880 $ 10,965 $ 10,696 $ 7,253 $ 9,774 $ 12,962 $ 12,491 $ 17,118 $ 20,995
C000142691 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Class C Shares - Including sales charges                    
Accumulated Value 10,000   7,140 7,556 7,561 7,322 4,920 6,579 8,661 8,293 11,273 13,722
C000142692 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Class I Shares                    
Accumulated Value 10,000   7,214 7,713 7,795 7,623 5,184 6,996 9,302 8,994 12,342 15,176
C000142693 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Investor Class Shares - Including sales charges                    
Accumulated Value 9,450   6,796 7,253 7,316 7,136 4,842 6,521 8,645 8,341 11,434 14,016
Russell 3000 Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Russell 3000®Index                    
Accumulated Value 15,000   15,033 17,693 20,358 20,866 23,258 33,471 32,238 32,894 41,967 47,473
Alerian Midstream Energy Select Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Alerian Midstream Energy Select Index                    
Accumulated Value 15,000   11,931 13,864 13,744 13,991 10,347 15,064 19,704 18,344 24,775 31,726
Cushing MLP Premier Tiered Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Cushing MLP Premier Tiered Index                    
Accumulated Value 15,000   11,370 12,079 11,631 11,501 7,506 10,323 13,503 12,571 16,978 21,742
Alerian MLP Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Alerian MLP Index                    
Accumulated Value $ 15,000   $ 11,370 $ 12,079 $ 11,631 $ 11,501 $ 7,506 $ 10,781 $ 13,748 $ 14,825 $ 20,072 $ 23,131
Morningstar Energy Limited Partnership Category Average [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Morningstar Energy Limited Partnership Category Average