Investment Securities - Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities	$ 102,076	$ 113,386
Credit loss allowance	12,994	3,182
HTM debt securities	604,942	676,652
Total investment securities	721,593	815,804
VIE eliminations
Debt Securities, Available-for-sale [Line Items]
Equity security	(1,641,787)	(1,666,921)
CMBS
Debt Securities, Available-for-sale [Line Items]
Credit loss allowance	492	172
HTM debt securities	569,867	577,681
CMBS | Non- Controlling Interests
Debt Securities, Available-for-sale [Line Items]
Equity security	187,300	198,900
Before consolidation of securitization VIEs
Debt Securities, Available-for-sale [Line Items]
HTM debt securities	591,948	673,470
Equity security, fair value	8,829	9,840
Total investment securities	2,363,380	2,482,725
Before consolidation of securitization VIEs | RMBS
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities	102,076	113,386
Equity security	451,191	423,183
Before consolidation of securitization VIEs | CMBS
Debt Securities, Available-for-sale [Line Items]
Equity security	$ 1,209,336	$ 1,262,846