v3.26.1
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
Jun. 30, 2016
Jun. 30, 2026
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2022
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2026
C000002899                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   The Gabelli Utilities Fund - Class AAA                    
C000239633                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   The Gabelli Utilities Fund - Class C                    
C000034315                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   The Gabelli Utilities Fund - Class I                    
C000002898                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   The Gabelli Utilities Fund - Class A                    
S&P 500 Index                        
Account Value [Line Items]                        
Accumulated Value $ 10,000   $ 11,790 $ 13,484 $ 14,889 $ 16,007 $ 22,537 $ 20,143 $ 24,090 $ 30,006 $ 34,555 $ 42,268
S&P 500 Index                        
Account Value [Line Items]                        
Accumulated Value 10,000   11,790 13,484 14,889 16,007 22,537 20,143 24,090 30,006 34,555 42,268
S&P 500 Index                        
Account Value [Line Items]                        
Accumulated Value 50,000   58,950 67,421 74,446 80,037 112,685 100,717 120,448 150,030 172,775 211,338
S&P 500 Index                        
Account Value [Line Items]                        
Accumulated Value 10,000   11,790 13,484 14,889 16,007 22,537 20,143 24,090 30,006 34,555 42,268
S&P 500 Utilities Index                        
Account Value [Line Items]                        
Accumulated Value 10,000   10,247 10,596 12,613 12,347 14,294 16,338 15,737 16,967 20,938 23,915
Lipper Utility Fund Average                        
Account Value [Line Items]                        
Accumulated Value 10,000   10,310 10,924 12,559 11,794 13,922 15,148 15,091 16,450 20,087 22,994
S&P 500 Utilities Index                        
Account Value [Line Items]                        
Accumulated Value 10,000   10,247 10,596 12,613 12,347 14,294 16,338 15,737 16,967 20,938 23,915
Lipper Utility Fund Average                        
Account Value [Line Items]                        
Accumulated Value 10,000   10,310 10,924 12,559 11,794 13,922 15,148 15,091 16,450 20,087 22,994
S&P 500 Utilities Index                        
Account Value [Line Items]                        
Accumulated Value 50,000   51,235 52,982 63,065 61,734 71,469 81,690 78,683 84,836 104,688 119,575
Lipper Utility Fund Average                        
Account Value [Line Items]                        
Accumulated Value 50,000   51,550 54,622 62,794 58,970 69,608 75,740 75,453 82,251 100,436 114,970
S&P 500 Utilities Index                        
Account Value [Line Items]                        
Accumulated Value 10,000   10,247 10,596 12,613 12,347 14,294 16,338 15,737 16,967 20,938 23,915
Lipper Utility Fund Average                        
Account Value [Line Items]                        
Accumulated Value $ 10,000   $ 10,310 $ 10,924 $ 12,559 $ 11,794 $ 13,922 $ 15,148 $ 15,091 $ 16,450 $ 20,087 $ 22,994