Fair Value - Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Details) - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Loans held for investment
Assets
Beginning balance	$ 19,190,065	$ 18,123,991
Total gain (loss) included in earnings	1,473,731	1,753,126
Purchases and additions	3,322,290	2,870,747
Sales and settlements	(2,949,938)	(2,256,238)
Transfers in (out) between categories	(1,030,664)	(1,301,561)
Ending balance	20,005,484	19,190,065
Loans held for investment, subject to nonrecourse debt
Assets
Beginning balance	9,288,403	8,272,393
Total gain (loss) included in earnings	966,349	639,122
Purchases and additions	24,735	41,134
Sales and settlements	(1,085,448)	(988,337)
Transfers in (out) between categories	832,138	1,324,091
Ending balance	10,026,177	9,288,403
Loans held for sale
Assets
Beginning balance	0
Total gain (loss) included in earnings	(1,305)
Purchases and additions	71,971
Sales and settlements	(220,520)
Transfers in (out) between categories	185,977
Ending balance	36,123	0
MSR
Assets
Beginning balance	0	6,436
Total gain (loss) included in earnings		(920)
Purchases and additions		0
Sales and settlements		(5,516)
Transfers in (out) between categories		0
Ending balance		0
Retained bonds
Assets
Beginning balance	40,407	44,297
Total gain (loss) included in earnings	1,903	(684)
Purchases and additions	0	0
Sales and settlements	(3,625)	(3,206)
Transfers in (out) between categories	0	0
Ending balance	38,685	40,407
HMBS related obligations
Liabilities
Beginning balance	(18,444,370)	(17,353,720)
Total gain (loss) included in earnings	(1,116,201)	(1,340,956)
Purchases and additions	(2,006,384)	(2,003,170)
Settlements	2,654,729	2,253,476
Ending balance	(18,912,226)	(18,444,370)
Nonrecourse debt
Liabilities
Beginning balance	(8,954,068)	(7,904,200)
Total gain (loss) included in earnings	(733,504)	(644,705)
Purchases and additions	(4,991,431)	(3,177,025)
Settlements	4,942,510	2,771,862
Ending balance	(9,736,493)	(8,954,068)
Deferred purchase price liabilities
Liabilities
Beginning balance	(16,684)	(8,855)
Total gain (loss) included in earnings	1,931	(7,966)
Purchases and additions	0	0
Settlements	2,206	137
Ending balance	$ (12,547)	$ (16,684)