Fair Value of Financial Instruments - Valuation for Level 3 Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 3,935,253,000	$ 3,471,854,000	$ 20,659,268,000
Total (losses)/gains (realized/unrealized)
Included in earnings	(375,144,000)	99,416,000	138,979,000
Transfers in			500,793,000
Transfers out	(18,858,000)	(4,133,000)	(254,525,000)
Transfers to securitization trust, net	0	0	0
Transfer to disposal group held for sale	0
Funding/Contributions	28,086,000	145,143,000	80,500,000
Paydowns/Distributions	(1,501,232,000)	(1,281,879,000)	(744,378,000)
Recovery of charge-off			35,000
Sales		(77,127,000)	(17,478,375,000)
Purchases	1,733,265,000	1,581,979,000	569,557,000
Balance at the end of period	$ 3,801,370,000	$ 3,935,253,000	$ 3,471,854,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Total non-interest (loss) income	Total non-interest (loss) income	Total non-interest (loss) income
VIE, Primary Beneficiary
Total (losses)/gains (realized/unrealized)
Sales			$ 16,589,867,000
VIE, Primary Beneficiary | Consolidated SLST
Total (losses)/gains (realized/unrealized)
Sales			(22,226,000)
VIE, Primary Beneficiary | Consolidated K-Series
Total (losses)/gains (realized/unrealized)
Sales			16,612,093,000
Residential loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 1,703,290,000	$ 1,090,930,000	1,429,754,000
Total (losses)/gains (realized/unrealized)
Included in earnings	(111,879,000)	36,844,000	(9,240,000)
Transfers in			164,279,000
Transfers out	(17,052,000)	(2,080,000)	(6,017,000)
Transfers to securitization trust, net	(1,422,577,000)	(305,433,000)	(651,911,000)
Transfer to disposal group held for sale	0
Funding/Contributions	0	0	0
Paydowns/Distributions	(712,214,000)	(618,790,000)	(308,600,000)
Recovery of charge-off			0
Sales		(74,751,000)	(96,892,000)
Purchases	1,641,816,000	1,576,570,000	569,557,000
Balance at the end of period	1,081,384,000	1,703,290,000	1,090,930,000
Residential loans | VIE, Primary Beneficiary | Consolidated SLST
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	1,070,882,000	1,266,785,000	1,328,886,000
Total (losses)/gains (realized/unrealized)
Included in earnings	(128,236,000)	(35,953,000)	27,898,000
Transfers in			0
Transfers out	0	0	0
Transfers to securitization trust, net	0	0	0
Transfer to disposal group held for sale	0
Funding/Contributions	0	0	0
Paydowns/Distributions	(115,064,000)	(159,950,000)	(89,999,000)
Recovery of charge-off			0
Sales		0	0
Purchases	0	0	0
Balance at the end of period	827,582,000	1,070,882,000	1,266,785,000
Residential loans held in securitization trusts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	801,429,000	691,451,000	0
Total (losses)/gains (realized/unrealized)
Included in earnings	(162,518,000)	43,001,000	31,402,000
Transfers in			46,572,000
Transfers out	(1,806,000)	(2,053,000)	(2,492,000)
Transfers to securitization trust, net	1,422,577,000	305,433,000	651,911,000
Transfer to disposal group held for sale	0
Funding/Contributions	0	0	0
Paydowns/Distributions	(535,017,000)	(239,436,000)	(35,942,000)
Recovery of charge-off			0
Sales		(2,376,000)	0
Purchases	91,449,000	5,409,000	0
Balance at the end of period	1,616,114,000	801,429,000	691,451,000
Multi-family loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	120,021,000	163,593,000
Total (losses)/gains (realized/unrealized)
Included in earnings	9,531,000	18,795,000
Transfers out	0	0
Transfers to securitization trust, net	0	0
Transfer to disposal group held for sale	0
Funding/Contributions	0	37,678,000
Paydowns/Distributions	(42,018,000)	(100,045,000)
Sales		0
Purchases	0	0
Balance at the end of period	87,534,000	120,021,000	163,593,000
Multi-family loans | VIE, Primary Beneficiary | Consolidated K-Series
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		0	17,816,746,000
Total (losses)/gains (realized/unrealized)
Included in earnings			41,795,000
Transfers in			0
Transfers out			(237,297,000)
Transfers to securitization trust, net			0
Funding/Contributions			0
Paydowns/Distributions			(239,796,000)
Recovery of charge-off			35,000
Sales			(17,381,483,000)
Purchases			0
Balance at the end of period			0
Preferred equity and mezzanine loan investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		163,593,000	0
Total (losses)/gains (realized/unrealized)
Included in earnings			20,454,000
Transfers in			182,465,000
Transfers out			(8,719,000)
Transfers to securitization trust, net			0
Funding/Contributions			14,164,000
Paydowns/Distributions			(44,771,000)
Recovery of charge-off			0
Sales			0
Purchases			0
Balance at the end of period			163,593,000
Equity investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	239,631,000	259,095,000	83,882,000
Total (losses)/gains (realized/unrealized)
Included in earnings	18,884,000	36,729,000	26,670,000
Transfers in			107,477,000
Transfers out	0	0	0
Transfers to securitization trust, net	0	0	0
Transfer to disposal group held for sale	(9,936,000)
Funding/Contributions	28,086,000	107,465,000	66,336,000
Paydowns/Distributions	(96,919,000)	(163,658,000)	(25,270,000)
Recovery of charge-off			0
Sales		0	0
Purchases	0	0	0
Balance at the end of period	179,746,000	239,631,000	$ 259,095,000
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	(926,000)
Transfers out	0
Transfers to securitization trust, net	0
Transfer to disposal group held for sale	9,936,000
Funding/Contributions	0
Paydowns/Distributions	0
Purchases	0
Balance at the end of period	$ 9,010,000	$ 0