| Cover | Oct. 19, 2021 |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 19, 2021 |
| Current Fiscal Year End Date | --12-31 |
| Entity File Number | 000-55188 |
| Entity Registrant Name | Franklin BSP 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 | 1345 Avenue of the Americas |
| Entity Address, Address Line Two | Suite 32A |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10105 |
| City Area Code | 212 |
| Local Phone Number | 588-6770 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | FBRT |
| Security Exchange Name | NYSE |
| Series E Preferred Stock [Member] | |
| Title of 12(b) Security | 7.50% Series E Cumulative Redeemable Preferred Stock, par value $0.01 per share |
| Trading Symbol | FBRT PRE |
| Security Exchange Name | NYSE |
