Use of Special Purpose Entities (SPE) and Variable Interest Entities (VIE) - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended			12 Months Ended
	Aug. 31, 2022	Mar. 31, 2022	Mar. 31, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Loss on extinguishment of debt	$ 500	$ 600		$ (2,214)	$ 1,583	$ 0
Payments to acquire other investments				100	98	477
Realized gains (losses), net				27,549	21,451	(148,058)
Proceeds from divestiture of interest in consolidated subsidiaries				100,666	8,108	5,751
Deconsolidation gain (loss) amount				0	0	(54,118)
Unrealized (losses) gains, net				(321,081)	95,649	(160,161)
VIE, Primary Beneficiary
Variable Interest Entity [Line Items]
Principal balance				14,700	203,500
Loss on extinguishment of debt				1,600
Consolidated SLST
Variable Interest Entity [Line Items]
Proceeds from sale of other investments						62,600
Realized gains (losses), net						2,400
Consolidated SLST | VIE, Primary Beneficiary
Variable Interest Entity [Line Items]
Investment in Consolidated SLST limited to securities owned, net carrying value				$ 191,500	$ 230,300
Payments to acquire other investments						$ 40,000
Consolidated K-Series | VIE, Primary Beneficiary
Variable Interest Entity [Line Items]
Deconsolidation of financial instruments			$ 17,400,000
IOs and mezzanine securities transferred to available-for-sale securities from consolidated K-series due to de-consolidation			237,300
Consolidated K-Series | VIE, Primary Beneficiary | Multi-family loans
Variable Interest Entity [Line Items]
Collateralized debt obligations			16,600,000
Consolidated K-Series | VIE, Primary Beneficiary | First Loss POs And Mezzanine Securities
Variable Interest Entity [Line Items]
Proceeds from divestiture of interest in consolidated subsidiaries			555,200
Deconsolidation gain (loss) amount			(54,100)
Unrealized (losses) gains, net			$ 168,500