Fair Value - Level 3 Unobservable Inputs, Mortgage Servicing Rights, Effect of Change In Inputs on Fair Value (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2023 USD ($) item	Dec. 31, 2022 USD ($) item
MSR and pool characteristics
Carrying value	$ 6,003,390,000	$ 5,953,621,000
Mortgage servicing liabilities | Level 3
Prepayment speed
Annual per-loan cost of servicing	1,136	1,177
Total | Mortgage servicing rights | Level 3
MSR and pool characteristics
Carrying value	6,003,390,000	5,953,621,000
Unpaid principal balance of underlying loans	$ 321,263,982,000	$ 314,567,639,000
Weighted-average note interest rate (as a percent)	3.50%	3.40%
Weighted-average servicing fee rate (as a percent)	0.37%	0.36%
Pricing spread
Effect on fair value of 5% adverse change	$ (80,273,000)	$ (81,021,000)
Effect on fair value of 10% adverse change	(158,416,000)	(159,863,000)
Effect on fair value of 20% adverse change	(308,614,000)	(311,329,000)
Prepayment speed
Effect on fair value of 5% adverse change	(85,106,000)	(77,346,000)
Effect on fair value of 10% adverse change	(167,216,000)	(152,192,000)
Effect on fair value of 20% adverse change	(323,085,000)	(294,872,000)
Annual per-loan cost of servicing
Effect on fair value of 5% adverse change	(41,653,000)	(41,263,000)
Effect on fair value of 10% adverse change	(83,305,000)	(82,527,000)
Effect on fair value of 20% adverse change	(166,610,000)	(165,053,000)
Total | Mortgage servicing rights | Level 3 | Minimum
Prepayment speed
Annual per-loan cost of servicing	68	68
Total | Mortgage servicing rights | Level 3 | Maximum
Prepayment speed
Annual per-loan cost of servicing	144	144
Total | Mortgage servicing rights | Level 3 | Weighted average
Prepayment speed
Annual per-loan cost of servicing	$ 108	$ 109
Total | Mortgage servicing rights | Pricing spread | Level 3 | Minimum
Inputs
Input | item	4.9	4.9
Total | Mortgage servicing rights | Pricing spread | Level 3 | Maximum
Inputs
Input | item	14.2	14.3
Total | Mortgage servicing rights | Pricing spread | Level 3 | Weighted average
Inputs
Input | item	6.5	6.5
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Minimum
Inputs
Input | item	5.2	5.0
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Maximum
Inputs
Input | item	18.0	17.7
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Weighted average
Inputs
Input | item	8.2	7.5
Total | Mortgage servicing rights | Life | Level 3 | Minimum
Inputs
Input | item	3.7	3.7
Total | Mortgage servicing rights | Life | Level 3 | Maximum
Inputs
Input | item	9.0	9.3
Total | Mortgage servicing rights | Life | Level 3 | Weighted average
Inputs
Input | item	8.1	8.4