| Form N-CSR Cover | 12 Months Ended |
| Nov. 30, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | General Money Market Fund, Inc. |
| Entity Central Index Key | 0000353560 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Nov. 30, 2024 |
| Shareholder Report | 12 Months Ended | |
| Nov. 30, 2024 USD ($) Holding | ||
| Shareholder Report [Line Items] | ||
| Document Type | N-CSR | |
| Amendment Flag | false | |
| Registrant Name | General Money Market Fund, Inc. | |
| Entity Central Index Key | 0000353560 | |
| Entity Investment Company Type | N-1A | |
| Document Period End Date | Nov. 30, 2024 | |
| C000000265 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Dreyfus Money Market Fund | |
| Class Name | Wealth Shares | |
| Trading Symbol | GMMXX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Dreyfus Money Market Fund (the “Fund”) for the period of December 1, 2023 to November 30, 2024. | |
| Shareholder Report Annual or Semi-Annual | annual shareholder report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.dreyfus.com/products/mm.html#overview | |
| Additional Information Phone Number | 1-800-373-9387 | |
| Additional Information Email | info@bny.com | |
| Additional Information Website | www.dreyfus.com/products/mm.html#overview | |
| Expenses [Text Block] | What were the Fund’s costs for the last year ? (based on a hypothetical $10,000 investment) Share Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Wealth Shares $ 0.54 % | |
| Expenses Paid, Amount | $ 55 | |
| Expense Ratio, Percent | 0.54% | |
| Net Assets | $ 2,154,000,000 | |
| Holdings Count | Holding | 93 | |
| Advisory Fees Paid, Amount | $ 4,183,576 | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 11/30/24 ) Total Advisory Fee Paid During $ 93 $ | |
| Holdings [Text Block] | Portfolio Holdings (as of 11/30/24 ) Allocation of Holdings (Based on Net Assets) | |
| C000000266 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Dreyfus Money Market Fund | |
| Class Name | Service Shares | |
| Trading Symbol | GMBXX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Dreyfus Money Market Fund (the “Fund”) for the period of December 1, 2023 to November 30, 2024. | |
| Shareholder Report Annual or Semi-Annual | annual shareholder report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.dreyfus.com/products/mm.html#overview | |
| Additional Information Phone Number | 1-800-373-9387 | |
| Additional Information Email | info@bny.com | |
| Additional Information Website | www.dreyfus.com/products/mm.html#overview | |
| Expenses [Text Block] | What were the Fund’s costs for the last year ? (based on a hypothetical $10,000 investment) Share Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Service Shares * $ 1.00 % * During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc. If this agreement is not extended in the future, expenses could be higher. | |
| Expenses Paid, Amount | $ 102 | [1] |
| Expense Ratio, Percent | 1% | [1] |
| Net Assets | $ 2,154,000,000 | |
| Holdings Count | Holding | 93 | |
| Advisory Fees Paid, Amount | $ 4,183,576 | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 11/30/24 ) Total Advisory Fee Paid During $ 93 $ | |
| Holdings [Text Block] | Portfolio Holdings (as of 11/30/24 ) Allocation of Holdings (Based on Net Assets) | |
| C000157127 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Dreyfus Money Market Fund | |
| Class Name | Premier Shares | |
| Trading Symbol | GMGXX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Dreyfus Money Market Fund (the “Fund”) for the period of December 1, 2023 to November 30, 2024. | |
| Shareholder Report Annual or Semi-Annual | annual shareholder report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.dreyfus.com/products/mm.html#overview | |
| Additional Information Phone Number | 1-800-373-9387 | |
| Additional Information Email | info@bny.com | |
| Additional Information Website | www.dreyfus.com/products/mm.html#overview | |
| Expenses [Text Block] | What were the Fund’s costs for the last year ? (based on a hypothetical $10,000 investment) Share Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Premier Shares $ 0.28 % | |
| Expenses Paid, Amount | $ 29 | |
| Expense Ratio, Percent | 0.28% | |
| Net Assets | $ 2,154,000,000 | |
| Holdings Count | Holding | 93 | |
| Advisory Fees Paid, Amount | $ 4,183,576 | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 11/30/24 ) Total Advisory Fee Paid During $ 93 $ | |
| Holdings [Text Block] | Portfolio Holdings (as of 11/30/24 ) Allocation of Holdings (Based on Net Assets) | |
| [1]During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc. If this agreement is not extended in the future, expenses could be higher. | ||
| Shareholder Report, Holdings (Details) | Nov. 30, 2024 |
| C000000265 [Member] | Commercial Paper [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 30.20% |
| C000000265 [Member] | Repurchase Agreements [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 48.30% |
| C000000265 [Member] | Negotiable Bank Certificates of Deposit [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.60% |
| C000000265 [Member] | Time Deposits [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.70% |
| C000000265 [Member] | Net Other Assets And Liabilities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.20% |
| C000000266 [Member] | Commercial Paper [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 30.20% |
| C000000266 [Member] | Repurchase Agreements [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 48.30% |
| C000000266 [Member] | Negotiable Bank Certificates of Deposit [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.60% |
| C000000266 [Member] | Time Deposits [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.70% |
| C000000266 [Member] | Net Other Assets And Liabilities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.20% |
| C000157127 [Member] | Commercial Paper [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 30.20% |
| C000157127 [Member] | Repurchase Agreements [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 48.30% |
| C000157127 [Member] | Negotiable Bank Certificates of Deposit [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.60% |
| C000157127 [Member] | Time Deposits [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.70% |
| C000157127 [Member] | Net Other Assets And Liabilities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.20% |
