| Form N-CSR Cover | 12 Months Ended |
| Nov. 30, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | Dreyfus Institutional Liquidity Funds |
| Entity Central Index Key | 0001717375 |
| 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 | Dreyfus Institutional Liquidity Funds |
| Entity Central Index Key | 0001717375 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Nov. 30, 2024 |
| C000195671 [Member] | |
| 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 |
| Annual or Semi-Annual Statement [Text Block] | This 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 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) Fund Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Dreyfus Treasury and Agency Liquidity Money Market Fund $ 0.09 % |
| Expenses Paid, Amount | $ 9 |
| Expense Ratio, Percent | 0.09% |
| Net Assets | $ 9,316,000,000 |
| Holdings Count | Holding | 9 |
| Advisory Fees Paid, Amount | $ 8,408,424 |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 11/30/24 ) Total Advisory Fee Paid During $ 9 $ |
| Holdings [Text Block] | Portfolio Holdings (as of 11/30/24 ) Allocation of Holdings (Based on Net Assets) |
| Shareholder Report, Holdings (Details) - C000195671 [Member] | Nov. 30, 2024 |
| Repurchase Agreements [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 97.30% |
| U S Treasury Floating Rate Notes [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| Net Other Assets and Liabilities [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | (0.30%) |
