| Cover | May 12, 2024 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Mar. 12, 2024 |
| Entity Registrant Name | LAFAYETTE SQUARE USA, INC. |
| Entity Incorporation, State or Country Code | DE |
| Securities Act File Number | 814-01427 |
| Entity Tax Identification Number | 87-2807075 |
| Entity Address, Address Line One | 175 SW 7th St |
| Entity Address, Address Line Two | Unit 1911 |
| Entity Address, City or Town | Miami |
| Entity Address, State or Province | FL |
| Entity Address, Postal Zip Code | 33130-2992 |
| City Area Code | 786 |
| Local Phone Number | -7096 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | true |
| Entity Central Index Key | 0001849089 |
| Amendment Flag | false |
