Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Assets carried at fair value
Investment securities available for sale:	$ 23,516	$ 29,520
Fair Value, Measurements, Recurring
Assets carried at fair value
Equity investments	205,814	239,631
Assets of disposal group held for sale	39,430	0
Total	4,377,898	4,136,097
Liabilities carried at fair value
Total	660,069	839,419
Fair Value, Measurements, Recurring \| Interest Rate Cap
Derivative assets:
Fair Value	963	0
Fair Value, Measurements, Recurring \| Residential loans
Assets carried at fair value
Residential loans, at fair value	1,661,318	1,703,290
Fair Value, Measurements, Recurring \| Residential loans \| Consolidated SLST \| VIE, Primary Beneficiary
Assets carried at fair value
Residential loans, at fair value	860,785	1,070,882
Fair Value, Measurements, Recurring \| Residential loans held in securitization trusts
Assets carried at fair value
Residential loans, at fair value	1,411,073	801,429
Fair Value, Measurements, Recurring \| Multi-family loans
Assets carried at fair value
Multi-family loans	95,829	120,021
Fair Value, Measurements, Recurring \| Non-Agency RMBS
Assets carried at fair value
Investment securities available for sale:	71,229	128,019
Fair Value, Measurements, Recurring \| CMBS
Assets carried at fair value
Investment securities available for sale:	30,346	33,146
Fair Value, Measurements, Recurring \| ABS
Assets carried at fair value
Investment securities available for sale:	1,111	39,679
Fair Value, Measurements, Recurring \| Consolidated SLST CDOs \| Consolidated SLST \| VIE, Primary Beneficiary
Liabilities carried at fair value
Consolidated SLST CDOs	660,069	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
Derivative assets:
Fair Value	0	0
Level 1 \| Fair Value, Measurements, Recurring \| Residential loans
Assets carried at fair value
Residential loans, at fair value	0	0
Level 1 \| Fair Value, Measurements, Recurring \| Residential loans \| Consolidated SLST \| VIE, Primary Beneficiary
Assets carried at fair value
Residential loans, at fair value	0	0
Level 1 \| Fair Value, Measurements, Recurring \| Residential loans held in securitization trusts
Assets carried at fair value
Residential loans, at fair value	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
Consolidated SLST CDOs	0	0
Level 2
Assets carried at fair value
Investment securities available for sale:	102,686	200,844
Level 2 \| Fair Value, Measurements, Recurring
Assets carried at fair value
Equity investments	0	0
Assets of disposal group held for sale	29,494	0
Total	133,143	200,844
Liabilities carried at fair value
Total	0	0
Level 2 \| Fair Value, Measurements, Recurring \| Interest Rate Cap
Derivative assets:
Fair Value	963	0
Level 2 \| Fair Value, Measurements, Recurring \| Residential loans
Assets carried at fair value
Residential loans, at fair value	0	0
Level 2 \| Fair Value, Measurements, Recurring \| Residential loans \| Consolidated SLST \| VIE, Primary Beneficiary
Assets carried at fair value
Residential loans, at fair value	0	0
Level 2 \| Fair Value, Measurements, Recurring \| Residential loans held in securitization trusts
Assets carried at fair value
Residential loans, at fair value	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:	71,229	128,019
Level 2 \| Fair Value, Measurements, Recurring \| CMBS
Assets carried at fair value
Investment securities available for sale:	30,346	33,146
Level 2 \| Fair Value, Measurements, Recurring \| ABS
Assets carried at fair value
Investment securities available for sale:	1,111	39,679
Level 2 \| Fair Value, Measurements, Recurring \| Consolidated SLST CDOs \| Consolidated SLST \| VIE, Primary Beneficiary
Liabilities carried at fair value
Consolidated SLST CDOs	0	0
Level 3
Assets carried at fair value
Equity investments	205,814	239,631
Level 3 \| Fair Value, Measurements, Recurring
Assets carried at fair value
Equity investments	205,814	239,631
Assets of disposal group held for sale	9,936	0
Total	4,244,755	3,935,253
Liabilities carried at fair value
Total	660,069	839,419
Level 3 \| Fair Value, Measurements, Recurring \| Interest Rate Cap
Derivative assets:
Fair Value	0	0
Level 3 \| Fair Value, Measurements, Recurring \| Residential loans
Assets carried at fair value
Residential loans, at fair value	1,661,318	1,703,290
Level 3 \| Fair Value, Measurements, Recurring \| Residential loans \| Consolidated SLST \| VIE, Primary Beneficiary
Assets carried at fair value
Residential loans, at fair value	860,785	1,070,882
Level 3 \| Fair Value, Measurements, Recurring \| Residential loans held in securitization trusts
Assets carried at fair value
Residential loans, at fair value	1,411,073	801,429
Level 3 \| Fair Value, Measurements, Recurring \| Multi-family loans
Assets carried at fair value
Multi-family loans	95,829	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
Consolidated SLST CDOs	$ 660,069	$ 839,419

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value portion of assets classified as held for sale.

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Fair value portion of investments accounted under the equity method.

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Fair value of financial and nonfinancial obligations.

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