| Cover | Jul. 25, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jul. 25, 2021 |
| Entity File Number | 000-55188 |
| Entity Registrant Name | Benefit Street Partners Realty Trust, Inc. |
| Entity Central Index Key | 0001562528 |
| Entity Tax Identification Number | 46-1406086 |
| Entity Incorporation, State or Country Code | MD |
| Entity Address, Address Line One | 9 West 57th Street |
| Entity Address, Address Line Two | Suite 4920 |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10019 |
| City Area Code | 212 |
| Local Phone Number | 588-6770 |
| Written Communications | true |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
