Fair Value of Financial Instruments - Valuation for Level 3 Assets (Details) $ in Thousands	9 Months Ended
Sep. 30, 2022 USD ($) securitization	Sep. 30, 2021 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 3,935,253	$ 3,471,854
Total (losses)/gains (realized/unrealized)
Included in earnings	(332,778)	83,305
Transfers out	(2,741)	(3,787)
Transfers to securitization trust, net	0	0
Transfer to disposal group held for sale	0
Funding/Contributions	28,086	53,200
Paydowns/Distributions	(1,039,373)	(864,268)
Sales		(67,452)
Purchases	1,656,308	975,781
Balance at the end of period	4,244,755	3,648,633
Consolidated SLST \| VIE, Primary Beneficiary \| Residential loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	1,070,882	1,266,785
Total (losses)/gains (realized/unrealized)
Included in earnings	(113,257)	(16,522)
Transfers out	0	0
Transfers to securitization trust, net	0	0
Transfer to disposal group held for sale	0
Funding/Contributions	0	0
Paydowns/Distributions	(96,840)	(113,258)
Sales		0
Purchases	0	0
Balance at the end of period	860,785	1,137,005
Residential loans \| Residential loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	1,703,290	1,090,930
Total (losses)/gains (realized/unrealized)
Included in earnings	(109,846)	28,094
Transfers out	(1,511)	(2,080)
Transfers to securitization trust, net	(1,049,673)	(236,751)
Transfer to disposal group held for sale	0
Funding/Contributions	0	0
Paydowns/Distributions	(468,669)	(464,097)
Sales		(65,076)
Purchases	1,587,727	974,199
Balance at the end of period	$ 1,661,318	1,325,219
Number of securitizations completed \| securitization	3
Residential loans held in securitization trusts \| Residential loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 801,429	691,451
Total (losses)/gains (realized/unrealized)
Included in earnings	(130,217)	34,901
Transfers out	(1,230)	(1,707)
Transfers to securitization trust, net	1,049,673	236,751
Transfer to disposal group held for sale	0
Funding/Contributions	0	0
Paydowns/Distributions	(377,163)	(149,019)
Sales		(2,376)
Purchases	68,581	1,582
Balance at the end of period	1,411,073	811,583
Multi-family loans \| Multi-family loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	120,021	163,593
Total (losses)/gains (realized/unrealized)
Included in earnings	6,658	14,811
Transfers out	0	0
Transfers to securitization trust, net	0	0
Transfer to disposal group held for sale	0
Funding/Contributions	0	7,970
Paydowns/Distributions	(30,850)	(66,562)
Sales		0
Purchases	0	0
Balance at the end of period	95,829	119,812
Equity investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		259,095
Total (losses)/gains (realized/unrealized)
Included in earnings		22,021
Funding/Contributions		45,230
Paydowns/Distributions		(71,332)
Equity investments \| Equity investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	239,631	259,095
Total (losses)/gains (realized/unrealized)
Included in earnings	13,884	22,021
Transfers out	0	0
Transfers to securitization trust, net	0	0
Transfer to disposal group held for sale	(9,936)
Funding/Contributions	28,086	45,230
Paydowns/Distributions	(65,851)	(71,332)
Sales		0
Purchases	0	0
Balance at the end of period	205,814	$ 255,014
Equity investments in disposal group held for sale \| Equity investments in disposal group held for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	0
Total (losses)/gains (realized/unrealized)
Included in earnings	0
Transfers out	0
Transfers to securitization trust, net	0
Transfer to disposal group held for sale	9,936
Funding/Contributions	0
Paydowns/Distributions	0
Purchases	0
Balance at the end of period	$ 9,936

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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers Out of Level 3 to Out of Securitization Trust, Net

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Number Of Securitizations Completed

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Publisher FASB
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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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