Fair Value - Level 3 Unobservable Inputs, Mortgage Servicing Rights, Effect of Change In Inputs on Fair Value (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2022 USD ($) item	Dec. 31, 2021 USD ($) item
MSR and pool characteristics
Carrying value	$ 5,661,672,000	$ 3,878,078,000
Mortgage servicing liabilities | Level 3
Prepayment speed
Annual per-loan cost of servicing	1,208	1,406
Total | Mortgage servicing rights | Level 3
MSR and pool characteristics
Carrying value	5,661,672,000	3,878,078,000
Unpaid principal balance of underlying loans	$ 303,800,226,000	$ 278,324,780,000
Weighted-average note interest rate (as a percent)	3.30%	3.20%
Weighted-average servicing fee rate (as a percent)	0.36%	0.34%
Pricing spread
Effect on fair value of 5% adverse change	$ (80,798,000)	$ (59,577,000)
Effect on fair value of 10% adverse change	(159,312,000)	(117,352,000)
Effect on fair value of 20% adverse change	(309,839,000)	(227,791,000)
Prepayment speed
Effect on fair value of 5% adverse change	(75,034,000)	(80,109,000)
Effect on fair value of 10% adverse change	(147,692,000)	(157,252,000)
Effect on fair value of 20% adverse change	(286,318,000)	(303,259,000)
Annual per-loan cost of servicing
Effect on fair value of 5% adverse change	(38,133,000)	(32,979,000)
Effect on fair value of 10% adverse change	(76,265,000)	(65,958,000)
Effect on fair value of 20% adverse change	(152,531,000)	(131,916,000)
Total | Mortgage servicing rights | Level 3 | Minimum
Prepayment speed
Annual per-loan cost of servicing	80	79
Total | Mortgage servicing rights | Level 3 | Maximum
Prepayment speed
Annual per-loan cost of servicing	149	197
Total | Mortgage servicing rights | Level 3 | Weighted average
Prepayment speed
Annual per-loan cost of servicing	$ 106	$ 108
Total | Mortgage servicing rights | Pricing spread | Level 3 | Minimum
Inputs
Input | item	4.9	5.3
Total | Mortgage servicing rights | Pricing spread | Level 3 | Maximum
Inputs
Input | item	14.8	15.5
Total | Mortgage servicing rights | Pricing spread | Level 3 | Weighted average
Inputs
Input | item	6.9	7.7
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Minimum
Inputs
Input | item	5.1	7.9
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Maximum
Inputs
Input | item	17.1	26.7
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Weighted average
Inputs
Input | item	7.6	10.7
Total | Mortgage servicing rights | Life | Level 3 | Minimum
Inputs
Input | item	3.8	3.1
Total | Mortgage servicing rights | Life | Level 3 | Maximum
Inputs
Input | item	9.3	7.7
Total | Mortgage servicing rights | Life | Level 3 | Weighted average
Inputs
Input | item	8.3	6.8