Fair Value - Level III (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Changes in financial assets classified as Level III
Balance at the beginning of the period	$ 38,156,506	$ 42,980,382
Total realized and unrealized gains (losses):
Change in fair value / gain on sale	(1,099,605)	(1,450,387)
Net accretion	$ 1,075	$ 1,167
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]	Available-for-sale securities	Available-for-sale securities
Included in OCI	$ (867)	$ (1,291)
Purchases / Originations	231,109	289,508
Sales	(297,319)	(218,597)
Issuances		(3,166)
Cash repayments / receipts	(118,786)	(50,442)
Transfers into Level III	(7,595)	(465,410)
Transfers out of Level III	1,341,388
Transfers out of Level III		601,090
Deconsolidation of VIEs	(62,423)	(616,945)
Balance at the end of the period	38,143,483	41,065,909
Amount of unrealized gains (losses) attributable to assets
Included in earnings	(1,117,823)	(1,460,680)
Included in OCI	(867)	(1,291)
Loans under fair value option
Changes in financial assets classified as Level III
Balance at the beginning of the period	2,516,008	2,645,637
Total realized and unrealized gains (losses):
Change in fair value / gain on sale	58,404	(29,013)
Net accretion	0	0
Included in OCI	0	0
Purchases / Originations	231,109	289,508
Sales	(297,319)	(218,597)
Issuances		0
Cash repayments / receipts	(54,628)	(45,316)
Transfers into Level III	0	0
Transfers out of Level III	(6,938)
Transfers out of Level III		0
Deconsolidation of VIEs	0	0
Balance at the end of the period	2,446,636	2,642,219
Amount of unrealized gains (losses) attributable to assets
Included in earnings	39,054	(40,815)
Included in OCI	0	0
RMBS
Changes in financial assets classified as Level III
Balance at the beginning of the period	93,806	102,368
Total realized and unrealized gains (losses):
Change in fair value / gain on sale	0	0
Net accretion	1,075	1,167
Included in OCI	(867)	(1,291)
Purchases / Originations	0	0
Sales	0	0
Issuances		0
Cash repayments / receipts	(2,073)	(1,925)
Transfers into Level III	0	0
Transfers out of Level III	0
Transfers out of Level III		0
Deconsolidation of VIEs	0	0
Balance at the end of the period	91,941	100,319
Amount of unrealized gains (losses) attributable to assets
Included in earnings	1,075	1,167
Included in OCI	(867)	(1,291)
CMBS
Changes in financial assets classified as Level III
Balance at the beginning of the period	27,345	18,600
Total realized and unrealized gains (losses):
Change in fair value / gain on sale	(29)	607
Net accretion	0	0
Included in OCI	0	0
Purchases / Originations	0	0
Sales	0	0
Issuances		0
Cash repayments / receipts	(45)	(63)
Transfers into Level III	0	0
Transfers out of Level III	0
Transfers out of Level III		0
Deconsolidation of VIEs	0	342
Balance at the end of the period	27,271	19,486
Amount of unrealized gains (losses) attributable to assets
Included in earnings	28	949
Included in OCI	0	0
Woodstar Fund investments
Changes in financial assets classified as Level III
Balance at the beginning of the period	2,073,533	2,012,833
Total realized and unrealized gains (losses):
Change in fair value / gain on sale	(8,035)	(3,896)
Net accretion	0	0
Included in OCI	0	0
Purchases / Originations	0	0
Sales	0	0
Issuances		0
Cash repayments / receipts	0	0
Transfers into Level III	0	0
Transfers out of Level III	0
Transfers out of Level III		0
Deconsolidation of VIEs	0	0
Balance at the end of the period	2,065,498	2,008,937
Amount of unrealized gains (losses) attributable to assets
Included in earnings	(8,035)	(3,896)
Included in OCI	0	0
Domestic servicing rights
Changes in financial assets classified as Level III
Balance at the beginning of the period	22,390	19,384
Total realized and unrealized gains (losses):
Change in fair value / gain on sale	753	228
Net accretion	0	0
Included in OCI	0	0
Purchases / Originations	0	0
Sales	0	0
Issuances		0
Cash repayments / receipts	0	0
Transfers into Level III	0	0
Transfers out of Level III	0
Transfers out of Level III		0
Deconsolidation of VIEs	0	0
Balance at the end of the period	23,143	19,612
Amount of unrealized gains (losses) attributable to assets
Included in earnings	753	228
Included in OCI	0	0
VIE Assets
Changes in financial assets classified as Level III
Balance at the beginning of the period	38,937,576	43,786,356
Total realized and unrealized gains (losses):
Change in fair value / gain on sale	(1,404,497)	(1,530,426)
Net accretion	0	0
Included in OCI	0	0
Purchases / Originations	0	0
Sales	0	0
Issuances		0
Cash repayments / receipts	0	0
Transfers into Level III	0	0
Transfers out of Level III	0
Transfers out of Level III		0
Deconsolidation of VIEs	(62,461)	(622,077)
Balance at the end of the period	37,470,618	41,633,853
Amount of unrealized gains (losses) attributable to assets
Included in earnings	(1,404,497)	(1,530,426)
Included in OCI	0	0
VIE Liabilities
Changes in financial assets classified as Level III
Balance at the beginning of the period	(5,514,152)	(5,604,796)
Total realized and unrealized gains (losses):
Change in fair value / gain on sale	253,799	112,113
Net accretion	0	0
Included in OCI	0	0
Purchases / Originations	0	0
Sales	0	0
Issuances		(3,166)
Cash repayments / receipts	(62,040)	(3,138)
Transfers into Level III	(7,595)	(465,410)
Transfers out of Level III	1,348,326
Transfers out of Level III		601,090
Deconsolidation of VIEs	38	4,790
Balance at the end of the period	(3,981,624)	(5,358,517)
Amount of unrealized gains (losses) attributable to assets
Included in earnings	253,799	112,113
Included in OCI	$ 0	$ 0