v3.26.1
Shareholder Report
 6 Months Ended
Jun. 30, 2026
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name Gabelli Utilities Fund
Entity Central Index Key 0001087966
Entity Investment Company Type N-1A
Document Period End Date Jun. 30, 2026
C000002899  
Shareholder Report [Line Items]  
Fund Name The Gabelli Utilities Fund
Class Name Class AAA
Trading Symbol GABUX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about The Gabelli Utilities Fund (the "Fund") for the period of January 1, 2026 to June 30, 2026.
Additional Information [Text Block] You can find additional information about the Fund, including the Fund’s prospectus, financial information, holdings, and proxy voting information, at https://gabelli.com/ticker/GABUX/. You can also request  information by contacting us at 800-GABELLI (800-422-3554).
Additional Information Phone Number 800-GABELLI (800-422-3554)
Additional Information Website https://gabelli.com/ticker/GABUX/
Expenses [Text Block]

What were the Fund costs for the last six months? 

(based on a hypothetical $10,000 investment)

Table Summary
Class Name
Costs of a $10k Investment
Costs Paid as a % of a $10k Investment
The Gabelli Utilities Fund - Class AAA
$72
1.38%
Expenses Paid, Amount $ 72
Expense Ratio, Percent 1.38%
Factors Affecting Performance [Text Block]

How did the Fund perform?

For the six months ended June 30, 2026, The Gabelli Utilities Fund underperformed its broad-based benchmark, the S&P 500 Index and outperformed its comparatives, S&P 500 Utilities Index and the Lipper Utility Fund Average. Despite recent volatility, the fundamental outlook for utilities remains strong. Many companies now target annual EPS growth of 6-8% or better; demand from data centers, manufacturing, and electrification drives one of the largest infrastructure investment cycles in decades. Contributors included NextEra Energy, American Electric Power Co., Inc., and Evergy, Inc.  Detractors included Constellation Energy Corp., Sony Group, and Deutsche Telekom AG. 
Performance Past Does Not Indicate Future [Text] Past performance does not guarantee future results.
Line Graph [Table Text Block]
Growth of 10K Chart
Table Summary
The Gabelli Utilities Fund - Class AAA
S&P 500 Index
S&P 500 Utilities Index
Lipper Utility Fund Average
06/16
10,000
10,000
10,000
10,000
06/17
10,427
11,790
10,247
10,310
06/18
10,713
13,484
10,596
10,924
06/19
12,003
14,889
12,613
12,559
06/20
10,776
16,007
12,347
11,794
06/21
13,087
22,537
14,294
13,922
06/22
13,473
20,143
16,338
15,148
06/23
12,977
24,090
15,737
15,091
06/24
13,146
30,006
16,967
16,450
06/25
15,536
34,555
20,938
20,087
06/26
18,094
42,268
23,915
22,994
Average Annual Return [Table Text Block]
Table Summary
6 months
1 Year
5 Year
10 Year
The Gabelli Utilities Fund - Class AAA
9.05%
16.47%
6.69%
6.11%
S&P 500 Index
10.21%
22.32%
13.41%
15.51%
S&P 500 Utilities Index
7.69%
14.22%
10.84%
9.11%
Lipper Utility Fund Average
8.16%
14.47%
10.56%
8.68%
No Deduction of Taxes [Text Block] The table and graph presented above do not reflect the deduction of taxes a shareholder would pay on Fund distributions or the redemption of Fund shares.
AssetsNet $ 1,762,733,327
Holdings Count | Holding 212
Advisory Fees Paid, Amount $ 8,705,471
InvestmentCompanyPortfolioTurnover 2.00%
Additional Fund Statistics [Text Block]

Fund Statistics

  • Total Net Assets$1,762,733,327
  • Number of Portfolio Holdings212
  • Portfolio Turnover Rate2%
  • Management Fees$8,705,471
Holdings [Text Block]

Portfolio Weighting (% of net assets)

Table Summary
Common Stocks
95.0%
U.S. Government Obligations
5.2%
Other Assets and Liabilities (Net)
(0.2)%

Industry Allocation (% of net assets)

Bar Graph showing Allocation by Industry
Table Summary
Industry Weighting
.
Utilities
75.5%
Other
13.5%
Communication Services
6.0%
U.S. Government Obligations
5.2%
Closed-End FundsFootnote Reference*
0.0%
Other Assets and Liabilities (Net)
(0.2)%
FootnoteDescription
Footnote*
Amount represents less than 0.05%
Largest Holdings [Text Block]

Top 10 Holdings (% of net assets)

Table Summary
NextEra Energy Inc.
7.4%
National Fuel Gas Co.
6.2%
American Electric Power Co. Inc.
4.0%
Evergy Inc.
3.8%
WEC Energy Group Inc.
3.1%
Southwest Gas Holdings Inc.
3.0%
Ameren Corp.
2.9%
The AES Corp.
2.4%
ONEOK Inc.
2.3%
Eversource Energy
2.3%
Material Fund Change [Text Block]
Updated Prospectus Phone Number 800-GABELLI (800-422-3554)
Updated Prospectus Email Address <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: justify; text-align-last: left; white-space-collapse: preserve-breaks;">info@gabelli.com</span>
Updated Prospectus Web Address https://gabelli.com/ticker/GABUX/
C000239633  
Shareholder Report [Line Items]  
Fund Name The Gabelli Utilities Fund
Class Name Class C
Trading Symbol GUXPX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about The Gabelli Utilities Fund (the "Fund") for the period of January 1, 2026 to June 30, 2026.
Additional Information [Text Block] You can find additional information about the Fund, including the Fund’s prospectus, financial information, holdings, and proxy voting information, at https://gabelli.com/ticker/GUXPX/. You can also request  information by contacting us at 800-GABELLI (800-422-3554).
Additional Information Phone Number 800-GABELLI (800-422-3554)
Additional Information Website https://gabelli.com/ticker/GUXPX/
Expenses [Text Block]

What were the Fund costs for the last six months? 

(based on a hypothetical $10,000 investment)

Table Summary
Class Name
Costs of a $10k Investment
Costs Paid as a % of a $10k Investment
The Gabelli Utilities Fund - Class C
$110
2.13%
Expenses Paid, Amount $ 110
Expense Ratio, Percent 2.13%
Factors Affecting Performance [Text Block]

How did the Fund perform?

For the six months ended June 30, 2026, The Gabelli Utilities Fund underperformed its broad-based benchmark, the S&P 500 Index and outperformed its comparatives, S&P 500 Utilities Index and the Lipper Utility Fund Average. Despite recent volatility, the fundamental outlook for utilities remains strong. Many companies now target annual EPS growth of 6-8% or better; demand from data centers, manufacturing, and electrification drives one of the largest infrastructure investment cycles in decades. Contributors included NextEra Energy, American Electric Power Co., Inc., and Evergy, Inc.  Detractors included Constellation Energy Corp., Sony Group, and Deutsche Telekom AG. 
Performance Past Does Not Indicate Future [Text] Past performance does not guarantee future results.
Line Graph [Table Text Block]
Growth of 10K Chart
Table Summary
The Gabelli Utilities Fund - Class C
The Gabelli Utilities Fund - Class C (includes sales charge)
S&P 500 Index
S&P 500 Utilities Index
Lipper Utility Fund Average
06/16
10,000
10,000
10,000
10,000
10,000
06/17
10,363
10,363
11,790
10,247
10,310
06/18
10,549
10,549
13,484
10,596
10,924
06/19
11,745
11,745
14,889
12,613
12,559
06/20
10,462
10,462
16,007
12,347
11,794
06/21
12,601
12,601
22,537
14,294
13,922
06/22
12,874
12,874
20,143
16,338
15,148
06/23
12,308
12,308
24,090
15,737
15,091
06/24
12,373
12,373
30,006
16,967
16,450
06/25
14,504
14,504
34,555
20,938
20,087
06/26
16,775
16,775
42,268
23,915
22,994
Average Annual Return [Table Text Block]
Table Summary
6 months
1 Year
5 Year
10 Year
The Gabelli Utilities Fund - Class C
8.64%
15.66%
5.89%
5.31%
The Gabelli Utilities Fund - Class C (includes sales charge)
7.64%
14.66%
5.89%
5.31%
S&P 500 Index
10.21%
22.32%
13.41%
15.51%
S&P 500 Utilities Index
7.69%
14.22%
10.84%
9.11%
Lipper Utility Fund Average
8.16%
14.47%
10.56%
8.68%
No Deduction of Taxes [Text Block] The table and graph presented above do not reflect the deduction of taxes a shareholder would pay on Fund distributions or the redemption of Fund shares.
AssetsNet $ 1,762,733,327
Holdings Count | Holding 212
Advisory Fees Paid, Amount $ 8,705,471
InvestmentCompanyPortfolioTurnover 2.00%
Additional Fund Statistics [Text Block]

Fund Statistics

  • Total Net Assets$1,762,733,327
  • Number of Portfolio Holdings212
  • Portfolio Turnover Rate2%
  • Management Fees$8,705,471
Holdings [Text Block]

Portfolio Weighting (% of net assets)

Table Summary
Common Stocks
95.0%
U.S. Government Obligations
5.2%
Other Assets and Liabilities (Net)
(0.2)%

Industry Allocation (% of net assets)

Bar Graph showing Allocation by Industry
Table Summary
Industry Weighting
.
Utilities
75.5%
Other
13.5%
Communication Services
6.0%
U.S. Government Obligations
5.2%
Closed-End FundsFootnote Reference*
0.0%
Other Assets and Liabilities (Net)
(0.2)%
FootnoteDescription
Footnote*
Amount represents less than 0.05%
Largest Holdings [Text Block]

Top 10 Holdings (% of net assets)

Table Summary
NextEra Energy Inc.
7.4%
National Fuel Gas Co.
6.2%
American Electric Power Co. Inc.
4.0%
Evergy Inc.
3.8%
WEC Energy Group Inc.
3.1%
Southwest Gas Holdings Inc.
3.0%
Ameren Corp.
2.9%
The AES Corp.
2.4%
ONEOK Inc.
2.3%
Eversource Energy
2.3%
Material Fund Change [Text Block]
Updated Prospectus Phone Number 800-GABELLI (800-422-3554)
Updated Prospectus Email Address <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: justify; text-align-last: left; white-space-collapse: preserve-breaks;">info@gabelli.com</span>
Updated Prospectus Web Address https://gabelli.com/ticker/GUXPX/
C000034315  
Shareholder Report [Line Items]  
Fund Name The Gabelli Utilities Fund
Class Name Class I
Trading Symbol GAUIX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about The Gabelli Utilities Fund (the "Fund") for the period of January 1, 2026 to June 30, 2026.
Additional Information [Text Block] You can find additional information about the Fund, including the Fund’s prospectus, financial information, holdings, and proxy voting information, at https://gabelli.com/ticker/GAUIX/. You can also request  information by contacting us at 800-GABELLI (800-422-3554).
Additional Information Phone Number 800-GABELLI (800-422-3554)
Additional Information Website https://gabelli.com/ticker/GAUIX/
Expenses [Text Block]

What were the Fund costs for the last six months? 

(based on a hypothetical $10,000 investment)

Table Summary
Class Name
Costs of a $10k Investment
Costs Paid as a % of a $10k Investment
The Gabelli Utilities Fund - Class I
$59
1.13%
Expenses Paid, Amount $ 59
Expense Ratio, Percent 1.13%
Factors Affecting Performance [Text Block]

How did the Fund perform?

For the six months ended June 30, 2026, The Gabelli Utilities Fund underperformed its broad-based benchmark, the S&P 500 Index and outperformed its comparatives, S&P 500 Utilities Index and the Lipper Utility Fund Average. Despite recent volatility, the fundamental outlook for utilities remains strong. Many companies now target annual EPS growth of 6-8% or better; demand from data centers, manufacturing, and electrification drives one of the largest infrastructure investment cycles in decades. Contributors included NextEra Energy, American Electric Power Co., Inc., and Evergy, Inc.  Detractors included Constellation Energy Corp., Sony Group, and Deutsche Telekom AG. 
Performance Past Does Not Indicate Future [Text] Past performance does not guarantee future results.
Line Graph [Table Text Block]
Growth of 10K Chart
Table Summary
The Gabelli Utilities Fund - Class I
S&P 500 Index
S&P 500 Utilities Index
Lipper Utility Fund Average
06/16
50,000
50,000
50,000
50,000
06/17
52,280
58,950
51,235
51,550
06/18
53,820
67,421
52,982
54,622
06/19
60,472
74,446
63,065
62,794
06/20
54,371
80,037
61,734
58,970
06/21
66,246
112,685
71,469
69,608
06/22
68,383
100,717
81,690
75,740
06/23
66,081
120,448
78,683
75,453
06/24
67,090
150,030
84,836
82,251
06/25
79,403
172,775
104,688
100,436
06/26
92,853
211,338
119,575
114,970
Average Annual Return [Table Text Block]
Table Summary
6 months
1 Year
5 Year
10 Year
The Gabelli Utilities Fund - Class I
9.24%
16.94%
6.99%
6.39%
S&P 500 Index
10.21%
22.32%
13.41%
15.51%
S&P 500 Utilities Index
7.69%
14.22%
10.84%
9.11%
Lipper Utility Fund Average
8.16%
14.47%
10.56%
8.68%
No Deduction of Taxes [Text Block] The table and graph presented above do not reflect the deduction of taxes a shareholder would pay on Fund distributions or the redemption of Fund shares.
AssetsNet $ 1,762,733,327
Holdings Count | Holding 212
Advisory Fees Paid, Amount $ 8,705,471
InvestmentCompanyPortfolioTurnover 2.00%
Additional Fund Statistics [Text Block]

Fund Statistics

  • Total Net Assets$1,762,733,327
  • Number of Portfolio Holdings212
  • Portfolio Turnover Rate2%
  • Management Fees$8,705,471
Holdings [Text Block]

Portfolio Weighting (% of net assets)

Table Summary
Common Stocks
95.0%
U.S. Government Obligations
5.2%
Other Assets and Liabilities (Net)
(0.2)%

Industry Allocation (% of net assets)

Bar Graph showing Allocation by Industry
Table Summary
Industry Weighting
.
Utilities
75.5%
Other
13.5%
Communication Services
6.0%
U.S. Government Obligations
5.2%
Closed-End FundsFootnote Reference*
0.0%
Other Assets and Liabilities (Net)
(0.2)%
FootnoteDescription
Footnote*
Amount represents less than 0.05%
Largest Holdings [Text Block]

Top 10 Holdings (% of net assets)

Table Summary
NextEra Energy Inc.
7.4%
National Fuel Gas Co.
6.2%
American Electric Power Co. Inc.
4.0%
Evergy Inc.
3.8%
WEC Energy Group Inc.
3.1%
Southwest Gas Holdings Inc.
3.0%
Ameren Corp.
2.9%
The AES Corp.
2.4%
ONEOK Inc.
2.3%
Eversource Energy
2.3%
Material Fund Change [Text Block]
Updated Prospectus Phone Number 800-GABELLI (800-422-3554)
Updated Prospectus Email Address <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: justify; text-align-last: left; white-space-collapse: preserve-breaks;">info@gabelli.com</span>
Updated Prospectus Web Address https://gabelli.com/ticker/GAUIX/
C000002898  
Shareholder Report [Line Items]  
Fund Name The Gabelli Utilities Fund
Class Name Class A
Trading Symbol GAUAX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about The Gabelli Utilities Fund (the "Fund") for the period of January 1, 2026 to June 30, 2026.
Additional Information [Text Block] You can find additional information about the Fund, including the Fund’s prospectus, financial information, holdings, and proxy voting information, at https://gabelli.com/ticker/GAUAX/. You can also request  information by contacting us at 800-GABELLI (800-422-3554).
Additional Information Phone Number 800-GABELLI (800-422-3554)
Additional Information Website https://gabelli.com/ticker/GAUAX/
Expenses [Text Block]

What were the Fund costs for the last six months? 

(based on a hypothetical $10,000 investment)

Table Summary
Class Name
Costs of a $10k Investment
Costs Paid as a % of a $10k Investment
The Gabelli Utilities Fund - Class A
$72
1.38%
Expenses Paid, Amount $ 72
Expense Ratio, Percent 1.38%
Factors Affecting Performance [Text Block]

How did the Fund perform?

For the six months ended June 30, 2026, The Gabelli Utilities Fund underperformed its broad-based benchmark, the S&P 500 Index and outperformed its comparatives, S&P 500 Utilities Index and the Lipper Utility Fund Average. Despite recent volatility, the fundamental outlook for utilities remains strong. Many companies now target annual EPS growth of 6-8% or better; demand from data centers, manufacturing, and electrification drives one of the largest infrastructure investment cycles in decades. Contributors included NextEra Energy, American Electric Power Co., Inc., and Evergy, Inc.  Detractors included Constellation Energy Corp., Sony Group, and Deutsche Telekom AG. 
Performance Past Does Not Indicate Future [Text] Past performance does not guarantee future results.
Line Graph [Table Text Block]
Growth of 10K Chart
Table Summary
The Gabelli Utilities Fund - Class A
The Gabelli Utilities Fund - Class A (includes sales charge)
S&P 500 Index
S&P 500 Utilities Index
Lipper Utility Fund Average
06/16
10,000
10,000
10,000
10,000
10,000
06/17
10,435
9,835
11,790
10,247
10,310
06/18
10,705
10,090
13,484
10,596
10,924
06/19
12,010
11,319
14,889
12,613
12,559
06/20
10,765
10,146
16,007
12,347
11,794
06/21
13,072
12,321
22,537
14,294
13,922
06/22
13,465
12,691
20,143
16,338
15,148
06/23
12,971
12,225
24,090
15,737
15,091
06/24
13,141
12,385
30,006
16,967
16,450
06/25
15,526
14,633
34,555
20,938
20,087
06/26
18,090
17,050
42,268
23,915
22,994
Average Annual Return [Table Text Block]
Table Summary
6 months
1 Year
5 Year
10 Year
The Gabelli Utilities Fund - Class A
9.09%
16.52%
6.71%
6.11%
The Gabelli Utilities Fund - Class A (includes sales charge)
2.82%
9.82%
5.46%
5.48%
S&P 500 Index
10.21%
22.32%
13.41%
15.51%
S&P 500 Utilities Index
7.69%
14.22%
10.84%
9.11%
Lipper Utility Fund Average
8.16%
14.47%
10.56%
8.68%
No Deduction of Taxes [Text Block] The table and graph presented above do not reflect the deduction of taxes a shareholder would pay on Fund distributions or the redemption of Fund shares.
AssetsNet $ 1,762,733,327
Holdings Count | Holding 212
Advisory Fees Paid, Amount $ 8,705,471
InvestmentCompanyPortfolioTurnover 2.00%
Additional Fund Statistics [Text Block]

Fund Statistics

  • Total Net Assets$1,762,733,327
  • Number of Portfolio Holdings212
  • Portfolio Turnover Rate2%
  • Management Fees$8,705,471
Holdings [Text Block]

Portfolio Weighting (% of net assets)

Table Summary
Common Stocks
95.0%
U.S. Government Obligations
5.2%
Other Assets and Liabilities (Net)
(0.2)%

Industry Allocation (% of net assets)

Bar Graph showing Allocation by Industry
Table Summary
Industry Weighting
.
Utilities
75.5%
Other
13.5%
Communication Services
6.0%
U.S. Government Obligations
5.2%
Closed-End FundsFootnote Reference*
0.0%
Other Assets and Liabilities (Net)
(0.2)%
FootnoteDescription
Footnote*
Amount represents less than 0.05%
Largest Holdings [Text Block]

Top 10 Holdings (% of net assets)

Table Summary
NextEra Energy Inc.
7.4%
National Fuel Gas Co.
6.2%
American Electric Power Co. Inc.
4.0%
Evergy Inc.
3.8%
WEC Energy Group Inc.
3.1%
Southwest Gas Holdings Inc.
3.0%
Ameren Corp.
2.9%
The AES Corp.
2.4%
ONEOK Inc.
2.3%
Eversource Energy
2.3%
Material Fund Change [Text Block]
Updated Prospectus Phone Number 800-GABELLI (800-422-3554)
Updated Prospectus Email Address <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: justify; text-align-last: left; white-space-collapse: preserve-breaks;">info@gabelli.com</span>
Updated Prospectus Web Address https://gabelli.com/ticker/GAUAX/