Variable Interest Entities - Summary of Investment in Subordinate MBS Backed by Assets Held in Consolidated VIEs (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Asset-backed financings at fair value	$ (72,922)	$ 58,474	$ (64,151)	$ 66,108
Interest income	176,734	158,926	472,128	474,629
Net investment income	80,864	163,429	226,267	344,247
Loans at fair value	1,429,525		1,429,525		$ 1,433,820
Asset-backed financings at fair value	1,334,797		1,334,797		1,336,731
Variable Interest Entities [Member]
Loans at fair value	75,360	(54,082)	71,381	(61,318)
Loans at fair value	1,427,575		1,427,575		1,431,689
Asset-backed financings at fair value	1,334,797		1,334,797		1,336,731
Variable Interest Entities [Member] | Subordinate Mortgage Backed Securities [Member]
Loans at fair value	75,360	(54,082)	71,381	(61,318)
Asset-backed financings at fair value	(72,922)	58,474	(64,151)	66,108
Interest income	16,037	9,505	41,594	38,315
Interest expense	10,838	13,652	34,918	38,796
Net investment income	7,637	$ 245	13,906	$ 4,309
Loans at fair value	1,427,575		1,427,575		1,431,689
Asset-backed financings at fair value	1,334,797		1,334,797		1,336,731
Retained subordinate MBS at fair value pledged to secure Assets sold under agreements to repurchase	$ 83,417		$ 83,417		$ 85,344