| Shareholder Report | 6 Months Ended |
| Oct. 31, 2024 USD ($) Holding |
| Shareholder Report [Line Items] | | |
| Document Type | N-CSRS | |
| Amendment Flag | false | |
| Registrant Name | Dreyfus Institutional Reserves Funds | |
| Entity Central Index Key | 0001423799 | |
| Entity Investment Company Type | N-1A | |
| Document Period End Date | Oct. 31, 2024 | |
| Dreyfus Institutional Preferred Treasury Obligations Fund - Institutional Shares | | |
| Shareholder Report [Line Items] | | |
| Fund Name | Dreyfus Institutional Preferred Treasury Obligations Fund | |
| Class Name | Institutional Shares | |
| Trading Symbol | DNSXX | |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Dreyfus Institutional Preferred Treasury Obligations Fund (the “Fund”) for the period of May 1, 2024 to October 31, 2024. | |
| Shareholder Report Annual or Semi-Annual | semi-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 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 Institutional Shares * $ 0.10 % ** * 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. ** Annualized. | |
| Expenses Paid, Amount | $ 5 | [1] |
| Expense Ratio, Percent | 0.10% | [1],[2] |
| Net Assets | $ 744,000,000 | |
| Holdings Count | Holding | 45 | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 10/31/24 ) $ 45 | |
| Holdings [Text Block] | Portfolio Holdings (as of 10/31/24 ) Allocation of Holdings (Based on Net Assets) | |
| Dreyfus Institutional Preferred Treasury Obligations Fund - Hamilton Shares | | |
| Shareholder Report [Line Items] | | |
| Fund Name | Dreyfus Institutional Preferred Treasury Obligations Fund | |
| Class Name | Hamilton Shares | |
| Trading Symbol | DHLXX | |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Dreyfus Institutional Preferred Treasury Obligations Fund (the “Fund”) for the period of May 1, 2024 to October 31, 2024. | |
| Shareholder Report Annual or Semi-Annual | semi-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 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 Hamilton Shares * $ 0.15 % ** * 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. ** Annualized. | |
| Expenses Paid, Amount | $ 8 | [1] |
| Expense Ratio, Percent | 0.15% | [1],[2] |
| Net Assets | $ 744,000,000 | |
| Holdings Count | Holding | 45 | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 10/31/24 ) $ 45 | |
| Holdings [Text Block] | Not FDIC Insured. Not Bank-Guaranteed. May Lose Value Portfolio Holdings (as of 10/31/24 ) 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.[2]Annualized. |
