Investment Securities - Summary of Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities	$ 134,406	$ 143,980
HTM debt securities	704,691	691,746
Total investment securities	869,189	860,984
Credit loss allowance	3,385	8,610
VIE eliminations
Debt Securities, Available-for-sale [Line Items]
Equity security	(1,543,145)	(1,491,786)
CMBS
Debt Securities, Available-for-sale [Line Items]
HTM debt securities	533,372	538,506
Credit loss allowance	228	3,140
CMBS \| Non- Controlling Interests
Debt Securities, Available-for-sale [Line Items]
Equity security	190,600	182,600
Before consolidation of securitization VIEs
Debt Securities, Available-for-sale [Line Items]
HTM debt securities	701,306	683,136
Equity security, fair value	11,619	11,624
Total investment securities	2,412,334	2,352,770
Before consolidation of securitization VIEs \| RMBS
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities	134,406	143,980
Equity security	311,292	250,424
Before consolidation of securitization VIEs \| CMBS
Debt Securities, Available-for-sale [Line Items]
Equity security	$ 1,253,711	$ 1,263,606

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