Valuation (Significant Unobservable Inputs Rollforward) (Details) - Level 3 - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	$ 15,509,523	$ 13,474,349	$ 14,661,702	$ 12,917,482
Assets, Accreted Discounts/Amortized Premiums	(12,109)	(442)	(32,412)	(1,090)
Assets, Realized Gain (Loss)	14,735	(11,829)	12,433	(18,111)
Assets, Change In Net Unrealized Gain/(Loss)	232,225	273,486	729,555	680,801
Assets, Purchases	2,442,359	1,504,179	6,026,847	3,988,693
Assets, Sales	(1,793,021)	(1,074,190)	(5,011,311)	(3,388,078)
Assets, Transfers into Level 3	8,021	9,409	25,060	15,678
Assets, Transfers out of Level 3	(31,519)	(13,890)	(41,660)	(34,303)
Assets, Ending Balance	16,370,214	14,161,072	16,370,214	14,161,072
Liabilities, Beginning Balance	(12,191,075)	(10,687,197)	(11,368,709)	(10,120,668)
Liabilities, Accreted Discounts/Amortized Premiums	(1,808)	(2,890)	(5,101)	(3,532)
Liabilities, Realized Gain/(Loss)	1	590	(1,382)	0
Liabilities, Change In Net Unrealized Gain/(Loss)	(187,879)	(202,542)	(537,960)	(518,181)
Liabilities Purchases/Payments	282,333	569,386	814,921	1,191,137
Liabilities, Sales/Issuance	(485,145)	(559,819)	(1,485,342)	(1,431,228)
Liabilities, Transfers into Level 3	0	0	0	0
Liabilities, Transfers out of Level 3	0	0	0	0
Liabilities, Ending Balance	(12,583,573)	(10,882,472)	(12,583,573)	(10,882,472)
Non-Agency RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets	262,571		262,571
CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets	22,171		22,171
CLOs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets	32,673		32,673
Asset-backed securities, backed by consumer loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total assets	87,580		87,580
Other secured borrowings, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Beginning Balance	(2,127,225)	(1,585,838)	(1,934,309)	(1,424,668)
Liabilities, Accreted Discounts/Amortized Premiums	(1,808)	(2,890)	(5,101)	(3,532)
Liabilities, Realized Gain/(Loss)	0	0	0	0
Liabilities, Change In Net Unrealized Gain/(Loss)	(13,969)	(59,288)	(75,298)	(73,327)
Liabilities Purchases/Payments	49,807	41,442	144,167	115,638
Liabilities, Sales/Issuance	(120,799)	(207,181)	(343,453)	(427,866)
Liabilities, Transfers into Level 3	0	0	0	0
Liabilities, Transfers out of Level 3	0	0	0	0
Liabilities, Ending Balance	(2,213,994)	(1,813,755)	(2,213,994)	(1,813,755)
Change in unrealized gains (losses), liabilities	(13,969)	(59,288)	(75,299)	(73,327)
Unsecured Borrowings
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Beginning Balance	(249,036)	(269,069)	(281,912)	(272,765)
Liabilities, Accreted Discounts/Amortized Premiums	0	0	0	0
Liabilities, Realized Gain/(Loss)	0	0	(1,383)	0
Liabilities, Change In Net Unrealized Gain/(Loss)	(2,891)	(9,059)	(3,563)	(5,363)
Liabilities Purchases/Payments	0	0	34,931	0
Liabilities, Sales/Issuance	0	0	0	0
Liabilities, Transfers into Level 3	0	0	0	0
Liabilities, Transfers out of Level 3	0	0	0	0
Liabilities, Ending Balance	(251,927)	(278,128)	(251,927)	(278,128)
Change in unrealized gains (losses), liabilities	(2,890)	(9,059)	(4,717)	(5,363)
HMBS-related obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Beginning Balance	(9,814,811)	(8,832,058)	(9,150,883)	(8,423,235)
Liabilities, Accreted Discounts/Amortized Premiums	0	0	0	0
Liabilities, Realized Gain/(Loss)	0	0	0	0
Liabilities, Change In Net Unrealized Gain/(Loss)	(171,019)	(133,837)	(460,701)	(439,491)
Liabilities Purchases/Payments	232,526	527,944	635,823	1,075,499
Liabilities, Sales/Issuance	(364,345)	(352,638)	(1,141,888)	(1,003,362)
Liabilities, Transfers into Level 3	0	0	0	0
Liabilities, Transfers out of Level 3	0	0	0	0
Liabilities, Ending Balance	(10,117,649)	(8,790,589)	(10,117,649)	(8,790,589)
Change in unrealized gains (losses), liabilities	(171,019)	(133,837)	(460,701)	(439,491)
Loan Purchase Commitments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Beginning Balance			(1,602)
Liabilities, Accreted Discounts/Amortized Premiums			0
Liabilities, Realized Gain/(Loss)			0
Liabilities, Change In Net Unrealized Gain/(Loss)			1,602
Liabilities Purchases/Payments			0
Liabilities, Sales/Issuance			0
Liabilities, Transfers into Level 3			0
Liabilities, Transfers out of Level 3			0
Liabilities, Ending Balance	0		0
Servicing-related asset
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Beginning Balance		(232)
Liabilities, Accreted Discounts/Amortized Premiums		0
Liabilities, Realized Gain/(Loss)		590
Liabilities, Change In Net Unrealized Gain/(Loss)		(358)
Liabilities Purchases/Payments		0
Liabilities, Sales/Issuance		0
Liabilities, Transfers into Level 3		0
Liabilities, Transfers out of Level 3		0
Liabilities, Ending Balance		0		0
Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Change in unrealized gain (loss), assets	(3,101)	6,909	2,591	11,552
Securities | Agency RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	8,883	7,482	10,660	5,512
Assets, Accreted Discounts/Amortized Premiums	(438)	(317)	(1,130)	(688)
Assets, Realized Gain (Loss)	(5)	91	(16)	59
Assets, Change In Net Unrealized Gain/(Loss)	138	586	690	207
Assets, Purchases	158	4,656	1,161	5,564
Assets, Sales	0	(983)	(848)	(1,114)
Assets, Transfers into Level 3	555	277	2,151	2,935
Assets, Transfers out of Level 3	(536)	(256)	(3,913)	(939)
Assets, Ending Balance	8,755	11,536	8,755	11,536
Securities | Non-Agency RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	258,932	84,811	153,188	155,240
Assets, Accreted Discounts/Amortized Premiums	(11,944)	(1,130)	(31,114)	(2,684)
Assets, Realized Gain (Loss)	690	(326)	2,386	(4,186)
Assets, Change In Net Unrealized Gain/(Loss)	(5,181)	3,428	2,278	24,159
Assets, Purchases	63,690	29,207	207,501	51,618
Assets, Sales	(18,762)	(19,579)	(52,511)	(121,468)
Assets, Transfers into Level 3	6,129	918	13,148	2,069
Assets, Transfers out of Level 3	(30,983)	(9,452)	(32,305)	(16,871)
Assets, Ending Balance	262,571	87,877	262,571	87,877
Securities | CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	21,615	18,245	21,399	14,143
Assets, Accreted Discounts/Amortized Premiums	456	197	903	635
Assets, Realized Gain (Loss)	99	157	(389)	294
Assets, Change In Net Unrealized Gain/(Loss)	256	406	108	(190)
Assets, Purchases	0	0	0	6,092
Assets, Sales	(1,592)	(3,483)	(4,169)	(4,580)
Assets, Transfers into Level 3	1,337	6,111	9,761	6,963
Assets, Transfers out of Level 3	0	2,240	5,442	3,964
Assets, Ending Balance	22,171	19,393	22,171	19,393
Securities | CLOs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	20,794	35,697	22,678	20,439
Assets, Accreted Discounts/Amortized Premiums	(857)	(1,513)	(3,156)	(2,189)
Assets, Realized Gain (Loss)	428	363	574	(3,061)
Assets, Change In Net Unrealized Gain/(Loss)	(834)	(193)	(2,520)	905
Assets, Purchases	33,281	0	44,405	69,421
Assets, Sales	(20,139)	(8,611)	(29,308)	(50,793)
Assets, Transfers into Level 3	0	2,103	0	3,711
Assets, Transfers out of Level 3	0	(1,942)	0	(12,529)
Assets, Ending Balance	32,673	25,904	32,673	25,904
Securities | Asset-backed securities, backed by consumer loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	55,186	68,924	60,227	74,226
Assets, Accreted Discounts/Amortized Premiums	(1,722)	(1,304)	(5,193)	(5,129)
Assets, Realized Gain (Loss)	(1,042)	(5,469)	(5,498)	(7,734)
Assets, Change In Net Unrealized Gain/(Loss)	389	2,869	1,365	2,949
Assets, Purchases	5,670	7,113	19,294	23,212
Assets, Sales	(4,424)	(6,422)	(16,138)	(21,813)
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	54,057	65,711	54,057	65,711
Securities | Other asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	21,999	31,196	35,483	7,696
Assets, Accreted Discounts/Amortized Premiums	(1,277)	(178)	(1,280)	(23)
Assets, Realized Gain (Loss)	3,621	0	6,936	0
Assets, Change In Net Unrealized Gain/(Loss)	(586)	2,291	(2,584)	3,936
Assets, Purchases	14,555	1,062	16,603	23,456
Assets, Sales	(4,789)	(1,884)	(21,635)	(2,578)
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	33,523	32,487	33,523	32,487
Securities | Corporate debt securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	13,607	15,066	14,352	8,041
Assets, Accreted Discounts/Amortized Premiums	0	0	0	0
Assets, Realized Gain (Loss)	(261)	637	(3)	160
Assets, Change In Net Unrealized Gain/(Loss)	(519)	(1,030)	(1,015)	(350)
Assets, Purchases	2,898	6,232	9,162	15,641
Assets, Sales	(1,572)	(7,239)	(8,343)	(9,826)
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	14,153	13,666	14,153	13,666
Securities | Corporate equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	9,039	10,162	9,759	12,294
Assets, Accreted Discounts/Amortized Premiums	0	0	0	0
Assets, Realized Gain (Loss)	0	0	(348)	549
Assets, Change In Net Unrealized Gain/(Loss)	756	(98)	1,445	(605)
Assets, Purchases	932	156	1,953	320
Assets, Sales	0	0	(2,082)	(2,338)
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	10,727	10,220	10,727	10,220
Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Change in unrealized gain (loss), assets	232,291	261,765	650,936	635,425
Loans | Residential mortgage loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	3,107,555	3,101,615	3,539,534	3,093,912
Assets, Accreted Discounts/Amortized Premiums	1,299	(218)	767	(2,042)
Assets, Realized Gain (Loss)	7,609	(7,250)	18,893	(12,716)
Assets, Change In Net Unrealized Gain/(Loss)	10,845	83,967	54,683	104,743
Assets, Purchases	1,309,295	867,769	3,225,311	2,063,012
Assets, Sales	(1,201,806)	(427,650)	(3,604,391)	(1,628,676)
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	3,234,797	3,618,233	3,234,797	3,618,233
Loans | Commercial mortgage loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	435,222	266,220	350,515	266,595
Assets, Accreted Discounts/Amortized Premiums	(49)	31	0	31
Assets, Realized Gain (Loss)	0	0	(9,699)	(44)
Assets, Change In Net Unrealized Gain/(Loss)	79	(1,775)	11,803	43
Assets, Purchases	134,943	52,597	290,452	268,006
Assets, Sales	(24,521)	(23,811)	(97,397)	(241,369)
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	545,674	293,262	545,674	293,262
Loans | Consumer loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	271	949	477	1,759
Assets, Accreted Discounts/Amortized Premiums	(20)	(51)	(100)	(286)
Assets, Realized Gain (Loss)	26	(9)	52	17
Assets, Change In Net Unrealized Gain/(Loss)	(18)	(4)	(41)	(1)
Assets, Purchases	11	13	28	153
Assets, Sales	(62)	(228)	(208)	(972)
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	208	670	208	670
Loans | Corporate loan [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	19,709	4,933	11,767	5,819
Assets, Accreted Discounts/Amortized Premiums	0	0	0	0
Assets, Realized Gain (Loss)	0	0	(1,644)	0
Assets, Change In Net Unrealized Gain/(Loss)	(11)	(1,188)	1,740	(1,288)
Assets, Purchases	74,090	100	142,179	828
Assets, Sales	(75,484)	(100)	(135,738)	(1,614)
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	18,304	3,745	18,304	3,745
Loans | Reverse mortgage loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	11,105,608	9,472,389	10,097,279	8,938,551
Assets, Accreted Discounts/Amortized Premiums	(179)	0	(312)	0
Assets, Realized Gain (Loss)	0	(19)	0	(19)
Assets, Change In Net Unrealized Gain/(Loss)	223,787	180,728	613,060	532,180
Assets, Purchases	634,152	478,484	1,659,036	1,217,247
Assets, Sales	(231,052)	(527,706)	(636,747)	(1,084,083)
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	11,732,316	9,603,876	11,732,316	9,603,876
Forward MSR-related Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	81,256	158,031	77,848	163,336
Assets, Accreted Discounts/Amortized Premiums	2,622	4,041	8,203	11,285
Assets, Realized Gain (Loss)	0	0	0	0
Assets, Change In Net Unrealized Gain/(Loss)	(2,160)	(4,521)	9,836	(1,579)
Assets, Purchases	0	0	0	0
Assets, Sales	(7,024)	(7,720)	(21,193)	(23,211)
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	74,694	149,831	74,694	149,831
Change in unrealized gain (loss), assets	(2,160)	(4,521)	9,836	(1,579)
Mortgage servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	29,276	29,538	29,766	29,580
Assets, Accreted Discounts/Amortized Premiums	0	0	0	0
Assets, Realized Gain (Loss)	0	0	0	0
Assets, Change In Net Unrealized Gain/(Loss)	(221)	(661)	(711)	(703)
Assets, Purchases	0	0	0	0
Assets, Sales	0	0	0	0
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	29,055	28,877	29,055	28,877
Change in unrealized gain (loss), assets	(221)	(661)	(711)	(703)
Servicing-related asset
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance				1,327
Assets, Accreted Discounts/Amortized Premiums				0
Assets, Realized Gain (Loss)				590
Assets, Change In Net Unrealized Gain/(Loss)				(1,917)
Assets, Purchases				0
Assets, Sales				0
Assets, Transfers into Level 3				0
Assets, Transfers out of Level 3				0
Assets, Ending Balance		0		0
Loan commitments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	8,785	5,623	6,692	2,584
Assets, Accreted Discounts/Amortized Premiums	0	0	0	0
Assets, Realized Gain (Loss)	0	0	0	0
Assets, Change In Net Unrealized Gain/(Loss)	42	332	2,135	3,371
Assets, Purchases	0	0	0	0
Assets, Sales	0	0	0	0
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	8,827	5,955	8,827	5,955
Change in unrealized gain (loss), assets	8,004	332	8,823	1,348
Investment in unconsolidated entities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	307,722	163,182	220,078	116,414
Assets, Accreted Discounts/Amortized Premiums	0	0	0	0
Assets, Realized Gain (Loss)	3,570	0	1,189	7,948
Assets, Change In Net Unrealized Gain/(Loss)	9,504	7,281	37,260	13,601
Assets, Purchases	168,684	56,785	409,762	244,116
Assets, Sales	(201,794)	(38,773)	(380,603)	(193,604)
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	287,686	188,475	287,686	188,475
Change in unrealized gain (loss), assets	6,073	3,854	21,816	6,055
Financial Derivatives - Assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Change in unrealized gain (loss), assets	13	(3)	13	(2)
Financial Derivatives - Assets | Credit default swaps on asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance		8		8
Assets, Accreted Discounts/Amortized Premiums		0		0
Assets, Realized Gain (Loss)		0		(1)
Assets, Change In Net Unrealized Gain/(Loss)		(2)		(2)
Assets, Purchases		0		1
Assets, Sales		0		0
Assets, Transfers into Level 3		0		0
Assets, Transfers out of Level 3		0		0
Assets, Ending Balance		6		6
Financial Derivatives - Assets | Total return swaps
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	0	3	0	6
Assets, Accreted Discounts/Amortized Premiums	0	0	0	0
Assets, Realized Gain (Loss)	0	(4)	0	33
Assets, Change In Net Unrealized Gain/(Loss)	13	(3)	13	(6)
Assets, Purchases	0	5	0	6
Assets, Sales	0	(1)	0	(39)
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	13	0	13	0
Loan Purchase Commitments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Assets, Beginning Balance	4,064	275	0	0
Assets, Accreted Discounts/Amortized Premiums	0	0	0	0
Assets, Realized Gain (Loss)	0	0	0	0
Assets, Change In Net Unrealized Gain/(Loss)	(4,054)	1,073	10	1,348
Assets, Purchases	0	0	0	0
Assets, Sales	0	0	0	0
Assets, Transfers into Level 3	0	0	0	0
Assets, Transfers out of Level 3	0	0	0	0
Assets, Ending Balance	10	1,348	10	1,348
Change in unrealized gain (loss), assets	(2,334)	$ 1,073	10	$ 3,371
Financial Derivatives - Liabilities | Credit default swaps on asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities, Beginning Balance	3		3
Liabilities, Accreted Discounts/Amortized Premiums	0		0
Liabilities, Realized Gain/(Loss)	1		1
Liabilities, Change In Net Unrealized Gain/(Loss)	0		0
Liabilities Purchases/Payments	0		0
Liabilities, Sales/Issuance	(1)		(1)
Liabilities, Transfers into Level 3	0		0
Liabilities, Transfers out of Level 3	0		0
Liabilities, Ending Balance	$ 3		$ 3