| Form N-CSR Cover | 6 Months Ended |
| May 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | Dreyfus Institutional Liquidity Funds |
| Entity Central Index Key | 0001717375 |
| Document Period End Date | May 31, 2024 |
| Shareholder Report | 6 Months Ended |
| May 31, 2024 USD ($) | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | Dreyfus Institutional Liquidity Funds |
| Entity Central Index Key | 0001717375 |
| Document Period End Date | May 31, 2024 |
| Dreyfus Treasury and Agency Liquidity Money Market Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Dreyfus Treasury and Agency Liquidity Money Market Fund |
| Class Name | Dreyfus Treasury and Agency Liquidity Money Market Fund |
| Trading Symbol | DTLXX |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report |
| Dreyfus Treasury and Agency Liquidity Money Market Fund | Dreyfus Treasury and Agency Liquidity Money Market Fund | |
| Shareholder Report [Line Items] | |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Dreyfus Treasury and Agency Liquidity 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) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Dreyfus Treasury and Agency Liquidity Money Market Fund $9 0.09% |
| Expenses Paid, Amount | $ 9 |
| Expense Ratio, Percent | 0.09% |
| Net Assets | $ 12,681,000,000 |
| Holdings Count | 10 |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 5/31/24) Fund Size (Millions) Number of Holdings $12,681 10 |
| 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 |
| Shareholder Report, Holdings (Details) - Dreyfus Treasury and Agency Liquidity Money Market Fund - Dreyfus Treasury and Agency Liquidity Money Market Fund | May 31, 2024 |
| Other | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | (0.30%) |
| U.S. Treasury Floating Rate Notes | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.50% |
| Repurchase Agreements | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 94.80% |
