Fair Value of Financial Instruments - Changes in Unrealized Gains (Losses) Included in Earnings for Level 3 (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Unrealized (losses) gains, net	Unrealized (losses) gains, net	Unrealized (losses) gains, net
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Unrealized (losses) gains, net	Unrealized (losses) gains, net	Unrealized (losses) gains, net
Level 3 \| Consolidated SLST \| VIE, Primary Beneficiary
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Multi-family loans held in securitization trusts, at fair value	$ (124,834)	$ (31,128)	$ 33,479
Consolidated SLST	92,431	54,960	(65,552)
Level 3 \| Residential loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Multi-family loans held in securitization trusts, at fair value	(57,892)	31,222	16,449
Level 3 \| Residential loans held in securitization trusts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Multi-family loans held in securitization trusts, at fair value	(219,647)	35,570	17,785
Level 3 \| Multi-family loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Multi-family loans held in securitization trusts, at fair value	(1,737)	1,924	(682)
Level 3 \| Investments in unconsolidated entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Multi-family loans held in securitization trusts, at fair value	(4,338)	3,990	256
Level 3 \| Equity investments in disposal group held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Multi-family loans held in securitization trusts, at fair value	$ (1,430)	$ 0	$ 0

Indicates line item in statement in which net income is reported that includes unrealized gain (loss) from asset measured at fair value using unobservable input (level 3) and still held.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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

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