Other Assets and Liabilities - Summary of Components of Other Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Held-to-maturity, Past Due [Line Items]
Debt securities held-to-maturity	$ 77,754		$ 77,445
CECL reserve	(122)	$ (889)	(1,723)	$ (4,119)	$ (5,122)	$ 0
Debt securities held-to-maturity, net	77,632		75,722
Loan portfolio payments held by servicer	80,540		73,224
Accrued interest receivable	72,485		66,757
2021 FL4 CLO restricted cash	50,000		0	$ 0
Derivative assets	19,860		522
Collateral deposited under derivative agreements	2,710		51,050
Prepaid expenses	411		973
Prepaid taxes	0		376
Other	659		1,195
Total	$ 304,297		$ 269,819