v3.25.1
Shareholder Report
 6 Months Ended
Mar. 31, 2025
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name Gabelli 787 Fund, Inc.
Entity Central Index Key 0001394166
Entity Investment Company Type N-1A
Document Period End Date Mar. 31, 2025
C000085566  
Shareholder Report [Line Items]  
Fund Name The Gabelli Enterprise Mergers and Acquisitions Fund
Class Name Class AAA
Trading Symbol EAAAX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about The Gabelli Enterprise Mergers and Acquisitions Fund (the "Fund") for the period of October 1, 2024 to March 31, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You may find additional information about the Fund at www.gabelli.com/funds/open_ends. You may also request  information by contacting us at 800-GABELLI (800-422-3554).
Additional Information Phone Number 800-GABELLI (800-422-3554)
Additional Information Website <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; white-space-collapse: preserve-breaks;">www.gabelli.com/funds/open_ends</span>
Expenses [Text Block]

What were the Fund costs for the last six months? 

(based on a hypothetical $10,000 investment)

Class Name
Costs of a $10k Investment
Costs Paid as a % of a $10k Investment
The Gabelli Enterprise Mergers and Acquisitions Fund - Class AAA
$99
1.95%
Expenses Paid, Amount $ 99
Expense Ratio, Percent 1.95%
Performance Past Does Not Indicate Future [Text] Past performance does not guarantee future results.
Line Graph [Table Text Block]
Growth of 10K Chart
The Gabelli Enterprise Mergers and Acquisitions Fund - Class AAA
S&P 500 Index
Lipper U.S. Treasury Money-Market Fund Average
S&P Merger Arbitrage Index
3/15
10,000
10,000
10,000
10,000
3/16
10,143
10,178
10,001
10,419
3/17
10,966
11,926
10,009
9,996
3/18
11,391
13,594
10,073
10,150
3/19
11,587
14,885
10,249
10,950
3/20
9,859
13,846
10,418
11,061
3/21
13,124
21,649
10,423
12,124
3/22
13,269
25,037
10,424
12,527
3/23
12,541
23,101
10,670
11,971
3/24
13,164
30,004
11,206
12,926
3/25
14,375
32,480
11,735
13,912
Average Annual Return [Table Text Block]
6 months
1 Year
5 Year
10 Year
The Gabelli Enterprise Mergers and Acquisitions Fund - Class AAA
3.37%
9.20%
7.83%
3.70%
S&P 500 Index
(1.97)%
8.25%
18.59%
12.50%
Lipper U.S. Treasury Money-Market Fund Average
2.14%
4.72%
2.41%
1.61%
S&P Merger Arbitrage Index
2.26%
7.63%
4.69%
3.36%
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 $ 49,079,195
Holdings Count | Holding 197
Advisory Fees Paid, Amount $ 149,232
InvestmentCompanyPortfolioTurnover 44.00%
Additional Fund Statistics [Text Block]

Fund Statistics

  • Total Net Assets$49,079,195
  • Number of Portfolio Holdings197
  • Portfolio Turnover Rate44%
  • Management Fees$149,232
Holdings [Text Block]

Top 10 Holdings (% of net assets)

Fox Corp.
5.0%
Vulcan Materials Co.
4.2%
Intra-Cellular Therapies Inc.
3.8%
United States Cellular Corp.
3.2%
Myers Industries Inc.
2.7%
Atlanta Braves Holdings Inc.
2.7%
SurModics Inc.
2.1%
TEGNA Inc.
2.1%
Millicom International Cellular SA
2.0%
TXNM Energy Inc.
2.0%

Portfolio Weighting (% of net assets)

Common Stocks
97.9%
U.S. Government Obligations
1.0%
Rights
0.6%
Closed-End Funds
0.1%
Other Assets and Liabilities (Net)
0.4%

Industry Allocation (% of net assets)

Bar Graph showing Allocation by Industry
Industry Weighting
.
Energy and Utilities
17.0%
Health Care
12.0%
Entertainment
10.0%
Telecommunications
8.5%
Building and Construction
6.4%
Financial Services
6.3%
Wireless Communications
6.2%
Diversified Industrial
5.8%
Other Industry sectors
27.4%
Other Assets and Liabilities (Net)
0.4%
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; white-space-collapse: preserve-breaks;">info@gabelli.com</span>
Updated Prospectus Web 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; white-space-collapse: preserve-breaks;">www.gabelli.com/funds/open_ends</span>
C000049132  
Shareholder Report [Line Items]  
Fund Name The Gabelli Enterprise Mergers and Acquisitions Fund
Class Name Class C
Trading Symbol EMACX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about The Gabelli Enterprise Mergers and Acquisitions Fund (the "Fund") for the period of October 1, 2024 to March 31, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You may find additional information about the Fund at www.gabelli.com/funds/open_ends. You may also request  information by contacting us at 800-GABELLI (800-422-3554).
Additional Information Phone Number 800-GABELLI (800-422-3554)
Additional Information Website <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; white-space-collapse: preserve-breaks;">www.gabelli.com/funds/open_ends</span>
Expenses [Text Block]

What were the Fund costs for the last six months? 

(based on a hypothetical $10,000 investment)

Class Name
Costs of a $10k Investment
Costs Paid as a % of a $10k Investment
The Gabelli Enterprise Mergers and Acquisitions Fund - Class C
$136
2.69%
Expenses Paid, Amount $ 136
Expense Ratio, Percent 2.69%
Performance Past Does Not Indicate Future [Text] Past performance does not guarantee future results.
Line Graph [Table Text Block]
Growth of 10K Chart
The Gabelli Enterprise Mergers and Acquisitions Fund - Class C
The Gabelli Enterprise Mergers and Acquisitions Fund - Class C (includes sales charge)
S&P 500 Index
Lipper U.S. Treasury Money-Market Fund Average
S&P Merger Arbitrage Index
3/15
10,000
10,000
10,000
10,000
10,000
3/16
10,065
9,965
10,178
10,001
10,419
3/17
10,801
10,594
11,926
10,009
9,996
3/18
11,131
10,812
13,594
10,073
10,150
3/19
11,235
10,805
14,885
10,249
10,950
3/20
9,499
9,044
13,846
10,418
11,061
3/21
12,541
11,849
21,649
10,423
12,124
3/22
12,589
11,777
25,037
10,424
12,527
3/23
11,806
10,934
23,101
10,670
11,971
3/24
12,304
11,285
30,004
11,206
12,926
3/25
13,333
12,116
32,480
11,735
13,912
Average Annual Return [Table Text Block]
6 months
1 Year
5 Year
10 Year
The Gabelli Enterprise Mergers and Acquisitions Fund - Class C
2.95%
8.36%
7.01%
2.92%
The Gabelli Enterprise Mergers and Acquisitions Fund - Class C (includes sales charge)
1.95%
7.36%
7.01%
2.92%
S&P 500 Index
(1.97)%
8.25%
18.59%
12.50%
Lipper U.S. Treasury Money-Market Fund Average
2.14%
4.72%
2.41%
1.61%
S&P Merger Arbitrage Index
2.26%
7.63%
4.69%
3.36%
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 $ 49,079,195
Holdings Count | Holding 197
Advisory Fees Paid, Amount $ 149,232
InvestmentCompanyPortfolioTurnover 44.00%
Additional Fund Statistics [Text Block]

Fund Statistics

  • Total Net Assets$49,079,195
  • Number of Portfolio Holdings197
  • Portfolio Turnover Rate44%
  • Management Fees$149,232
Holdings [Text Block]

Top 10 Holdings (% of net assets)

Fox Corp.
5.0%
Vulcan Materials Co.
4.2%
Intra-Cellular Therapies Inc.
3.8%
United States Cellular Corp.
3.2%
Myers Industries Inc.
2.7%
Atlanta Braves Holdings Inc.
2.7%
SurModics Inc.
2.1%
TEGNA Inc.
2.1%
Millicom International Cellular SA
2.0%
TXNM Energy Inc.
2.0%

Portfolio Weighting (% of net assets)

Common Stocks
97.9%
U.S. Government Obligations
1.0%
Rights
0.6%
Closed-End Funds
0.1%
Other Assets and Liabilities (Net)
0.4%

Industry Allocation (% of net assets)

Bar Graph showing Allocation by Industry
Industry Weighting
.
Energy and Utilities
17.0%
Health Care
12.0%
Entertainment
10.0%
Telecommunications
8.5%
Building and Construction
6.4%
Financial Services
6.3%
Wireless Communications
6.2%
Diversified Industrial
5.8%
Other Industry sectors
27.4%
Other Assets and Liabilities (Net)
0.4%
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; white-space-collapse: preserve-breaks;">info@gabelli.com</span>
Updated Prospectus Web 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; white-space-collapse: preserve-breaks;">www.gabelli.com/funds/open_ends</span>
C000049133  
Shareholder Report [Line Items]  
Fund Name The Gabelli Enterprise Mergers and Acquisitions Fund
Class Name Class Y
Trading Symbol EMAYX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about The Gabelli Enterprise Mergers and Acquisitions Fund (the "Fund") for the period of October 1, 2024 to March 31, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You may find additional information about the Fund at www.gabelli.com/funds/open_ends. You may also request  information by contacting us at 800-GABELLI (800-422-3554).
Additional Information Phone Number 800-GABELLI (800-422-3554)
Additional Information Website <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; white-space-collapse: preserve-breaks;">www.gabelli.com/funds/open_ends</span>
Expenses [Text Block]

What were the Fund costs for the last six months? 

(based on a hypothetical $10,000 investment)

Class Name
Costs of a $10k Investment
Costs Paid as a % of a $10k Investment
The Gabelli Enterprise Mergers and Acquisitions Fund - Class Y
$51
1.01%
Expenses Paid, Amount $ 51
Expense Ratio, Percent 1.01%
Performance Past Does Not Indicate Future [Text] Past performance does not guarantee future results.
Line Graph [Table Text Block]
Growth of 10K Chart
The Gabelli Enterprise Mergers and Acquisitions Fund - Class Y
S&P 500 Index
Lipper U.S. Treasury Money-Market Fund Average
S&P Merger Arbitrage Index
3/15
10,000
10,000
10,000
10,000
3/16
10,166
10,178
10,001
10,419
3/17
11,020
11,926
10,009
9,996
3/18
11,470
13,594
10,073
10,150
3/19
11,699
14,885
10,249
10,950
3/20
9,982
13,846
10,418
11,061
3/21
13,342
21,649
10,423
12,124
3/22
13,573
25,037
10,424
12,527
3/23
12,934
23,101
10,670
11,971
3/24
13,689
30,004
11,206
12,926
3/25
15,088
32,480
11,735
13,912
Average Annual Return [Table Text Block]
6 months
1 Year
5 Year
10 Year
The Gabelli Enterprise Mergers and Acquisitions Fund - Class Y
3.85%
10.22%
8.61%
4.20%
S&P 500 Index
(1.97)%
8.25%
18.59%
12.50%
Lipper U.S. Treasury Money-Market Fund Average
2.14%
4.72%
2.41%
1.61%
S&P Merger Arbitrage Index
2.26%
7.63%
4.69%
3.36%
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 $ 49,079,195
Holdings Count | Holding 197
Advisory Fees Paid, Amount $ 149,232
InvestmentCompanyPortfolioTurnover 44.00%
Additional Fund Statistics [Text Block]

Fund Statistics

  • Total Net Assets$49,079,195
  • Number of Portfolio Holdings197
  • Portfolio Turnover Rate44%
  • Management Fees$149,232
Holdings [Text Block]

Top 10 Holdings (% of net assets)

Fox Corp.
5.0%
Vulcan Materials Co.
4.2%
Intra-Cellular Therapies Inc.
3.8%
United States Cellular Corp.
3.2%
Myers Industries Inc.
2.7%
Atlanta Braves Holdings Inc.
2.7%
SurModics Inc.
2.1%
TEGNA Inc.
2.1%
Millicom International Cellular SA
2.0%
TXNM Energy Inc.
2.0%

Portfolio Weighting (% of net assets)

Common Stocks
97.9%
U.S. Government Obligations
1.0%
Rights
0.6%
Closed-End Funds
0.1%
Other Assets and Liabilities (Net)
0.4%

Industry Allocation (% of net assets)

Bar Graph showing Allocation by Industry
Industry Weighting
.
Energy and Utilities
17.0%
Health Care
12.0%
Entertainment
10.0%
Telecommunications
8.5%
Building and Construction
6.4%
Financial Services
6.3%
Wireless Communications
6.2%
Diversified Industrial
5.8%
Other Industry sectors
27.4%
Other Assets and Liabilities (Net)
0.4%
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; white-space-collapse: preserve-breaks;">info@gabelli.com</span>
Updated Prospectus Web 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; white-space-collapse: preserve-breaks;">www.gabelli.com/funds/open_ends</span>
C000049130  
Shareholder Report [Line Items]  
Fund Name The Gabelli Enterprise Mergers and Acquisitions Fund
Class Name Class A
Trading Symbol EMAAX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about The Gabelli Enterprise Mergers and Acquisitions Fund (the "Fund") for the period of October 1, 2024 to March 31, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You may find additional information about the Fund at www.gabelli.com/funds/open_ends. You may also request  information by contacting us at 800-GABELLI (800-422-3554).
Additional Information Phone Number 800-GABELLI (800-422-3554)
Additional Information Website <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; white-space-collapse: preserve-breaks;">www.gabelli.com/funds/open_ends</span>
Expenses [Text Block]

What were the Fund costs for the last six months? 

(based on a hypothetical $10,000 investment)

Class Name
Costs of a $10k Investment
Costs Paid as a % of a $10k Investment
The Gabelli Enterprise Mergers and Acquisitions Fund - Class A
$99
1.95%
Expenses Paid, Amount $ 99
Expense Ratio, Percent 1.95%
Performance Past Does Not Indicate Future [Text] Past performance does not guarantee future results.
Line Graph [Table Text Block]
Growth of 10K Chart
The Gabelli Enterprise Mergers and Acquisitions Fund - Class A
The Gabelli Enterprise Mergers and Acquisitions Fund - Class A (includes sales charge)
S&P 500 Index
Lipper U.S. Treasury Money-Market Fund Average
S&P Merger Arbitrage Index
3/15
10,000
10,000
10,000
10,000
10,000
3/16
10,122
9,540
10,178
10,001
10,419
3/17
10,922
9,702
11,926
10,009
9,996
3/18
11,321
9,478
13,594
10,073
10,150
3/19
11,488
9,065
14,885
10,249
10,950
3/20
9,761
7,260
13,846
10,418
11,061
3/21
12,979
9,098
21,649
10,423
12,124
3/22
13,117
8,666
25,037
10,424
12,527
3/23
12,399
7,720
23,101
10,670
11,971
3/24
13,021
7,642
30,004
11,206
12,926
3/25
14,221
7,866
32,480
11,735
13,912
Average Annual Return [Table Text Block]
6 months
1 Year
5 Year
10 Year
The Gabelli Enterprise Mergers and Acquisitions Fund - Class A
3.40%
9.22%
7.82%
3.58%
The Gabelli Enterprise Mergers and Acquisitions Fund - Class A (includes sales charge)
(2.54)%
2.94%
6.55%
2.97%
S&P 500 Index
(1.97)%
8.25%
18.59%
12.50%
Lipper U.S. Treasury Money-Market Fund Average
2.14%
4.72%
2.41%
1.61%
S&P Merger Arbitrage Index
2.26%
7.63%
4.69%
3.36%
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 $ 49,079,195
Holdings Count | Holding 197
Advisory Fees Paid, Amount $ 149,232
InvestmentCompanyPortfolioTurnover 44.00%
Additional Fund Statistics [Text Block]

Fund Statistics

  • Total Net Assets$49,079,195
  • Number of Portfolio Holdings197
  • Portfolio Turnover Rate44%
  • Management Fees$149,232
Holdings [Text Block]

Top 10 Holdings (% of net assets)

Fox Corp.
5.0%
Vulcan Materials Co.
4.2%
Intra-Cellular Therapies Inc.
3.8%
United States Cellular Corp.
3.2%
Myers Industries Inc.
2.7%
Atlanta Braves Holdings Inc.
2.7%
SurModics Inc.
2.1%
TEGNA Inc.
2.1%
Millicom International Cellular SA
2.0%
TXNM Energy Inc.
2.0%

Portfolio Weighting (% of net assets)

Common Stocks
97.9%
U.S. Government Obligations
1.0%
Rights
0.6%
Closed-End Funds
0.1%
Other Assets and Liabilities (Net)
0.4%

Industry Allocation (% of net assets)

Bar Graph showing Allocation by Industry
Industry Weighting
.
Energy and Utilities
17.0%
Health Care
12.0%
Entertainment
10.0%
Telecommunications
8.5%
Building and Construction
6.4%
Financial Services
6.3%
Wireless Communications
6.2%
Diversified Industrial
5.8%
Other Industry sectors
27.4%
Other Assets and Liabilities (Net)
0.4%
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; white-space-collapse: preserve-breaks;">info@gabelli.com</span>
Updated Prospectus Web 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; white-space-collapse: preserve-breaks;">www.gabelli.com/funds/open_ends</span>