Variable Interest Entities and Collateralized Loan Obligations - Schedule of Weighted Average Spreads and Maturities for Loan Collateral and Borrowings (Details) - Collateralized Loan Obligation	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
TRTX 2018-FL2 | Collateral (Loan Investments)
Debt Instrument [Line Items]
Weighted Average Spread (%)	3.33%	3.82%
Weighted Average Maturity (Years)	4 years 10 months 24 days	4 years 2 months 12 days
TRTX 2018-FL2 | Debt (Notes Issued)
Debt Instrument [Line Items]
Weighted Average Spread (%)	1.45%	1.45%
Weighted Average Maturity (Years)	16 years 10 months 24 days	17 years 10 months 24 days
TRTX 2019-FL3 | Collateral (Loan Investments)
Debt Instrument [Line Items]
Weighted Average Spread (%)	3.20%	3.33%
Weighted Average Maturity (Years)	4 years 1 month 6 days	4 years 1 month 6 days
TRTX 2019-FL3 | Debt (Notes Issued)
Debt Instrument [Line Items]
Weighted Average Spread (%)	1.44%	1.44%
Weighted Average Maturity (Years)	13 years 9 months 18 days	14 years 9 months 18 days