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, 2024 USD ($) Y	Dec. 31, 2023 USD ($) Y
MSR and pool characteristics
Carrying value	$ 7,752,292,000	$ 7,099,348,000
Mortgage servicing liabilities | Level 3
Prepayment speed
Annual per-loan cost of servicing	1,001	1,043
Total | Mortgage servicing rights | Level 3
MSR and pool characteristics
Carrying value	7,752,292,000	7,099,348,000
Unpaid principal balance of underlying loans	$ 410,031,301,000	$ 370,244,119,000
Weighted-average note interest rate (as a percent)	4.40%	4.10%
Weighted-average servicing fee rate (as a percent)	0.38%	0.38%
Pricing spread
Effect on fair value of 5% adverse change	$ (101,071,000)	$ (94,307,000)
Effect on fair value of 10% adverse change	(199,523,000)	(186,129,000)
Effect on fair value of 20% adverse change	(388,935,000)	(362,671,000)
Prepayment speed
Effect on fair value of 5% adverse change	(133,350,000)	(107,757,000)
Effect on fair value of 10% adverse change	(261,595,000)	(211,643,000)
Effect on fair value of 20% adverse change	(503,923,000)	(408,638,000)
Annual per-loan cost of servicing
Effect on fair value of 5% adverse change	(46,687,000)	(44,572,000)
Effect on fair value of 10% adverse change	(93,373,000)	(89,145,000)
Effect on fair value of 20% adverse change	(186,746,000)	(178,289,000)
Total | Mortgage servicing rights | Level 3 | Minimum
Prepayment speed
Annual per-loan cost of servicing	68	70
Total | Mortgage servicing rights | Level 3 | Maximum
Prepayment speed
Annual per-loan cost of servicing	131	135
Total | Mortgage servicing rights | Level 3 | Weighted average
Prepayment speed
Annual per-loan cost of servicing	$ 106	$ 107
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Minimum
Inputs
Input	0.063	0.061
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Maximum
Inputs
Input	0.189	0.178
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Weighted average
Inputs
Input	0.091	0.083
Total | Mortgage servicing rights | Life | Level 3 | Minimum
Inputs
Input | Y	2.7	3.0
Total | Mortgage servicing rights | Life | Level 3 | Maximum
Inputs
Input | Y	8.8	9.0
Total | Mortgage servicing rights | Life | Level 3 | Weighted average
Inputs
Input | Y	7.7	8.1
Total | Mortgage servicing rights | Pricing spread | Level 3 | Minimum
Inputs
Input	0.050	0.055
Total | Mortgage servicing rights | Pricing spread | Level 3 | Maximum
Inputs
Input	0.113	0.126
Total | Mortgage servicing rights | Pricing spread | Level 3 | Weighted average
Inputs
Input	0.063	0.064