v3.26.1
Annual Total Returns
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Future of Energy Fund | A                    
Prospectus [Line Items]                    
Annual Return [Percent] 17.00% [1] 11.68% 10.25% 20.42% 39.93% (27.23%) 11.09% (13.77%) (0.02%) 36.13%
[1] The annual total returns for Class C, I, R and Z shares of the Fund are substantially similar to the annual total returns of Class A shares because the assets of all classes are invested in the same portfolio of securities. The annual total returns differ only to the extent that the classes do not have the same expenses. Class F shares are currently not available for purchase. Class R and Z shares are available on a limited basis.