Loan Sales and Servicing Activities - Summary of Cash Flows with Transferees (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Cash flows:
Sales proceeds	$ 26,168,605	$ 21,651,096	$ 70,706,054	$ 60,061,205
Servicing fees received	363,121	303,224	1,048,099	853,962
Allowance for losses rollforward
Balance at beginning of period	68,671	70,070	73,991	78,992
Provision (reversal of provision) for losses	9,583	(2,554)	13,974	(7,603)
Charge-offs, net	(4,346)	(1,872)	(14,057)	(5,745)
Balance at end of period	73,908	$ 65,644	73,908	$ 65,644
Period end information:
Unpaid principal balance of loans outstanding	393,947,146		393,947,146		$ 352,790,614
30-89 days	16,324,494		16,324,494		13,775,493
90 days or more - Not in foreclosure	7,380,142		7,380,142		6,754,282
90 days or more - In foreclosure	666,480		666,480		618,694
90 days or more - Foreclosed	4,471		4,471		7,565
Bankruptcy	$ 1,685,409		$ 1,685,409		$ 1,415,614