Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Measurements, Recurring
Assets carried at fair value
Equity investments	$ 179,746	$ 239,631
Assets of disposal group held for sale	38,428	0
Total	3,932,820	4,136,097
Liabilities carried at fair value
Total	634,495	839,419
Fair Value, Measurements, Recurring \| Interest Rate Cap
Assets carried at fair value
Interest rate caps	2,473	0
Fair Value, Measurements, Recurring \| Consolidated SLST \| VIE, Primary Beneficiary
Assets carried at fair value
Residential loans:	827,582	1,070,882
Fair Value, Measurements, Recurring \| Residential loans
Assets carried at fair value
Residential loans:	1,081,384	1,703,290
Fair Value, Measurements, Recurring \| Residential loans held in securitization trusts
Assets carried at fair value
Residential loans:	1,616,114	801,429
Fair Value, Measurements, Recurring \| Multi-family loans
Assets carried at fair value
Multi-family loans	87,534	120,021
Fair Value, Measurements, Recurring \| Non-Agency RMBS
Assets carried at fair value
Investment securities available for sale:	68,570	128,019
Fair Value, Measurements, Recurring \| CMBS
Assets carried at fair value
Investment securities available for sale:	30,133	33,146
Fair Value, Measurements, Recurring \| ABS
Assets carried at fair value
Investment securities available for sale:	856	39,679
Fair Value, Measurements, Recurring \| Consolidated SLST CDOs \| Consolidated SLST \| VIE, Primary Beneficiary
Liabilities carried at fair value
Multi-family collateralized debt obligations	634,495	839,419
Level 1 \| Fair Value, Measurements, Recurring
Assets carried at fair value
Equity investments	0	0
Assets of disposal group held for sale	0	0
Total	0	0
Liabilities carried at fair value
Total	0	0
Level 1 \| Fair Value, Measurements, Recurring \| Interest Rate Cap
Assets carried at fair value
Interest rate caps	0	0
Level 1 \| Fair Value, Measurements, Recurring \| Consolidated SLST \| VIE, Primary Beneficiary
Assets carried at fair value
Residential loans:	0	0
Level 1 \| Fair Value, Measurements, Recurring \| Residential loans
Assets carried at fair value
Residential loans:	0	0
Level 1 \| Fair Value, Measurements, Recurring \| Residential loans held in securitization trusts
Assets carried at fair value
Residential loans:	0	0
Level 1 \| Fair Value, Measurements, Recurring \| Multi-family loans
Assets carried at fair value
Multi-family loans	0	0
Level 1 \| Fair Value, Measurements, Recurring \| Non-Agency RMBS
Assets carried at fair value
Investment securities available for sale:	0	0
Level 1 \| Fair Value, Measurements, Recurring \| CMBS
Assets carried at fair value
Investment securities available for sale:	0	0
Level 1 \| Fair Value, Measurements, Recurring \| ABS
Assets carried at fair value
Investment securities available for sale:	0	0
Level 1 \| Fair Value, Measurements, Recurring \| Consolidated SLST CDOs \| Consolidated SLST \| VIE, Primary Beneficiary
Liabilities carried at fair value
Multi-family collateralized debt obligations	0	0
Level 2
Assets carried at fair value
Investment securities available for sale:	99,559	200,844
Level 2 \| Fair Value, Measurements, Recurring
Assets carried at fair value
Equity investments	0	0
Assets of disposal group held for sale	29,418	0
Total	131,450	200,844
Liabilities carried at fair value
Total	0	0
Level 2 \| Fair Value, Measurements, Recurring \| Interest Rate Cap
Assets carried at fair value
Interest rate caps	2,473	0
Level 2 \| Fair Value, Measurements, Recurring \| Consolidated SLST \| VIE, Primary Beneficiary
Assets carried at fair value
Residential loans:	0	0
Level 2 \| Fair Value, Measurements, Recurring \| Residential loans
Assets carried at fair value
Residential loans:	0	0
Level 2 \| Fair Value, Measurements, Recurring \| Residential loans held in securitization trusts
Assets carried at fair value
Residential loans:	0	0
Level 2 \| Fair Value, Measurements, Recurring \| Multi-family loans
Assets carried at fair value
Multi-family loans	0	0
Level 2 \| Fair Value, Measurements, Recurring \| Non-Agency RMBS
Assets carried at fair value
Investment securities available for sale:	68,570	128,019
Level 2 \| Fair Value, Measurements, Recurring \| CMBS
Assets carried at fair value
Investment securities available for sale:	30,133	33,146
Level 2 \| Fair Value, Measurements, Recurring \| ABS
Assets carried at fair value
Investment securities available for sale:	856	39,679
Level 2 \| Fair Value, Measurements, Recurring \| Consolidated SLST CDOs \| Consolidated SLST \| VIE, Primary Beneficiary
Liabilities carried at fair value
Multi-family collateralized debt obligations	0	0
Level 3
Assets carried at fair value
Equity investments	179,746	239,631
Level 3 \| Fair Value, Measurements, Recurring
Assets carried at fair value
Equity investments	179,746	239,631
Assets of disposal group held for sale	9,010	0
Total	3,801,370	3,935,253
Liabilities carried at fair value
Total	634,495	839,419
Level 3 \| Fair Value, Measurements, Recurring \| Interest Rate Cap
Assets carried at fair value
Interest rate caps	0	0
Level 3 \| Fair Value, Measurements, Recurring \| Consolidated SLST \| VIE, Primary Beneficiary
Assets carried at fair value
Residential loans:	827,582	1,070,882
Liabilities carried at fair value
Multi-family collateralized debt obligations		839,419
Level 3 \| Fair Value, Measurements, Recurring \| Residential loans
Assets carried at fair value
Residential loans:	1,081,384	1,703,290
Level 3 \| Fair Value, Measurements, Recurring \| Residential loans held in securitization trusts
Assets carried at fair value
Residential loans:	1,616,114	801,429
Level 3 \| Fair Value, Measurements, Recurring \| Multi-family loans
Assets carried at fair value
Multi-family loans	87,534	120,021
Level 3 \| Fair Value, Measurements, Recurring \| Non-Agency RMBS
Assets carried at fair value
Investment securities available for sale:	0	0
Level 3 \| Fair Value, Measurements, Recurring \| CMBS
Assets carried at fair value
Investment securities available for sale:	0	0
Level 3 \| Fair Value, Measurements, Recurring \| ABS
Assets carried at fair value
Investment securities available for sale:	0	0
Level 3 \| Fair Value, Measurements, Recurring \| Consolidated SLST CDOs \| Consolidated SLST \| VIE, Primary Beneficiary
Liabilities carried at fair value
Multi-family collateralized debt obligations	$ 634,495	$ 839,419

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