Investment Securities - Purchases, Sales and Redemptions, and Principal Collections for All Investment Securities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Debt Securities, Available-for-sale [Line Items]
Purchases/fundings	$ 5,536	$ 0	$ 6,988	$ 86,058
Sales and redemptions	1,427	0	1,722	0
Principal collections	36,331	4,251	87,679	19,431
HTM Securities
Debt Securities, Available-for-sale [Line Items]
Purchases/fundings	5,536	0	6,988	86,058
Sales and redemptions	0		0	0
Principal collections	33,762	609	79,543	2,549
Equity Security
Debt Securities, Available-for-sale [Line Items]
Purchases/fundings	0	0	0	0
Sales and redemptions	878	0	1,173	0
Principal collections	0	0	0	0
Securitization VIEs
Debt Securities, Available-for-sale [Line Items]
Purchases/fundings	0	0	0	(289,833)
Sales and redemptions	0	0	0	0
Principal collections	(13,624)	(21,802)	(54,071)	(64,555)
RMBS | Available-for-sale
Debt Securities, Available-for-sale [Line Items]
Purchases/fundings	0	0	0	0
Sales and redemptions	549	0	549	0
Principal collections	2,468	3,412	7,451	16,200
RMBS | Fair value option
Debt Securities, Available-for-sale [Line Items]
Purchases/fundings	0	0	0	226,152
Sales and redemptions	0	0	0	0
Principal collections	12,979	16,914	41,776	58,843
CMBS | Fair value option
Debt Securities, Available-for-sale [Line Items]
Purchases/fundings	0	0	0	63,681
Sales and redemptions	0	0	0	0
Principal collections	$ 746	$ 5,118	$ 12,980	$ 6,394