| Form N-CSR Cover | 6 Months Ended |
| May 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS/A |
| Amendment Flag | true |
| Registrant Name | General Money Market Fund, Inc. |
| Entity Central Index Key | 0000353560 |
| Document Period End Date | May 31, 2024 |
| Shareholder Report | 6 Months Ended | |
| May 31, 2024 USD ($) | ||
| Shareholder Report [Line Items] | ||
| Document Type | N-CSRS/A | |
| Amendment Flag | true | |
| Registrant Name | General Money Market Fund, Inc. | |
| Entity Central Index Key | 0000353560 | |
| Document Period End Date | May 31, 2024 | |
| Wealth Shares | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Dreyfus Money Market Fund | |
| Class Name | Wealth Shares | |
| Trading Symbol | GMMXX | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| Service Shares | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Dreyfus Money Market Fund | |
| Class Name | Service Shares | |
| Trading Symbol | GMBXX | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| Premier Shares | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Dreyfus Money Market Fund | |
| Class Name | Premier Shares | |
| Trading Symbol | GMGXX | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| GENERAL MONEY MARKET FUND, INC | Wealth Shares | ||
| Shareholder Report [Line Items] | ||
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Dreyfus Money Market Fund (the “Fund”) for the period of December 1, 2023 to May 31, 2024. You can find additional information about the Fund at www.dreyfus.com/products/mm.html#overview. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info bnymellon.com. | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.dreyfus.com/products/mm.html#overview. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info@bnymellon.com. | |
| Additional Information Phone Number | 1-800-373-9387 | |
| Additional Information Email | info@bnymellon.com | |
| Additional Information Website | www.dreyfus.com/products/mm.html#overview | |
| Expenses [Text Block] | What were the Fund’s costs for the last six months? (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 $27 0.54% * * Annualized | |
| Expenses Paid, Amount | $ 27 | |
| Expense Ratio, Percent | 0.54% | [1] |
| Net Assets | $ 2,029,000,000 | |
| Holdings Count | 80 | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 5/31/24) Fund Size (Millions) Number of Holdings $2,029 80 | |
| Holdings [Text Block] | Portfolio Holdings (as of 5/31/24) Allocation of Holdings (Based on Net Assets) | |
| Updated Prospectus Web Address | www.dreyfus.com/products/mm.html#overview | |
| GENERAL MONEY MARKET FUND, INC | Service Shares | ||
| Shareholder Report [Line Items] | ||
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Dreyfus Money Market Fund (the “Fund”) for the period of December 1, 2023 to May 31, 2024. You can find additional information about the Fund at www.dreyfus.com/products/mm.html#overview. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info bnymellon.com. | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.dreyfus.com/products/mm.html#overview. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info@bnymellon.com. | |
| Additional Information Phone Number | 1-800-373-9387 | |
| Additional Information Email | info@bnymellon.com | |
| Additional Information Website | www.dreyfus.com/products/mm.html#overview | |
| Expenses [Text Block] | What were the Fund’s costs for the last six months? (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 * $50 0.99% ** * 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. ** Annualized | |
| Expenses Paid, Amount | $ 50 | [2] |
| Expense Ratio, Percent | 0.99% | [2],[3] |
| Net Assets | $ 2,029,000,000 | |
| Holdings Count | 80 | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 5/31/24) Fund Size (Millions) Number of Holdings $2,029 80 | |
| Holdings [Text Block] | Portfolio Holdings (as of 5/31/24) Allocation of Holdings (Based on Net Assets) | |
| Updated Prospectus Web Address | www.dreyfus.com/products/mm.html#overview | |
| GENERAL MONEY MARKET FUND, INC | Premier Shares | ||
| Shareholder Report [Line Items] | ||
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Dreyfus Money Market Fund (the “Fund”) for the period of December 1, 2023 to May 31, 2024. You can find additional information about the Fund at www.dreyfus.com/products/mm.html#overview. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info bnymellon.com. | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.dreyfus.com/products/mm.html#overview. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info@bnymellon.com. | |
| Additional Information Phone Number | 1-800-373-9387 | |
| Additional Information Email | info@bnymellon.com | |
| Additional Information Website | www.dreyfus.com/products/mm.html#overview | |
| Expenses [Text Block] | What were the Fund’s costs for the last six months? (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 $13 0.27% * * Annualized | |
| Expenses Paid, Amount | $ 13 | |
| Expense Ratio, Percent | 0.27% | [4] |
| Net Assets | $ 2,029,000,000 | |
| Holdings Count | 80 | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 5/31/24) Fund Size (Millions) Number of Holdings $2,029 80 | |
| Holdings [Text Block] | Portfolio Holdings (as of 5/31/24) Allocation of Holdings (Based on Net Assets) | |
| Updated Prospectus Web Address | www.dreyfus.com/products/mm.html#overview | |
| [1] Annualized 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. Annualized Annualized | ||
| Shareholder Report, Holdings (Details) - GENERAL MONEY MARKET FUND, INC | May 31, 2024 |
| Wealth Shares | Other | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.20% |
| Wealth Shares | Time Deposits | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.90% |
| Wealth Shares | Negotiable Bank Certificates of Deposit | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.70% |
| Wealth Shares | Commercial Paper | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 32.90% |
| Wealth Shares | Repurchase Agreements | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 50.30% |
| Service Shares | Other | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.20% |
| Service Shares | Time Deposits | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.90% |
| Service Shares | Negotiable Bank Certificates of Deposit | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.70% |
| Service Shares | Commercial Paper | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 32.90% |
| Service Shares | Repurchase Agreements | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 50.30% |
| Premier Shares | Other | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.20% |
| Premier Shares | Time Deposits | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.90% |
| Premier Shares | Negotiable Bank Certificates of Deposit | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.70% |
| Premier Shares | Commercial Paper | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 32.90% |
| Premier Shares | Repurchase Agreements | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 50.30% |
