Fair Value - Level 3 Unobservable Inputs, Mortgage Servicing Rights - Initial Recognition (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2025 USD ($) Y	Sep. 30, 2024 USD ($) Y	Sep. 30, 2025 USD ($) Y	Sep. 30, 2024 USD ($) Y	Dec. 31, 2024 USD ($) Y
Mortgage servicing rights
Inputs
Amount recognized	$ 700,326,000	$ 578,982,000	$ 2,165,213,000	$ 1,532,709,000
Total | Mortgage servicing rights | Level 3 | Minimum
Inputs:
Annual per-loan cost of servicing			70		$ 68
Total | Mortgage servicing rights | Level 3 | Maximum
Inputs:
Annual per-loan cost of servicing			127		130
Total | Mortgage servicing rights | Level 3 | Weighted average
Inputs:
Annual per-loan cost of servicing			$ 106		$ 105
Total | Mortgage servicing rights | Pricing spread | Level 3 | Minimum
Inputs:
Input					0.05
Total | Mortgage servicing rights | Pricing spread | Level 3 | Maximum
Inputs:
Input					0.113
Total | Mortgage servicing rights | Pricing spread | Level 3 | Weighted average
Inputs:
Input					0.062
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Minimum
Inputs:
Input	0.06		0.06		0.059
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Maximum
Inputs:
Input	0.227		0.227		0.177
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Weighted average
Inputs:
Input	0.089		0.089		0.078
Total | Mortgage servicing rights | Life | Level 3 | Minimum
Inputs:
Input | Y	2.5		2.5		2.7
Total | Mortgage servicing rights | Life | Level 3 | Maximum
Inputs:
Input | Y	9		9		9.1
Total | Mortgage servicing rights | Life | Level 3 | Weighted average
Inputs:
Input | Y	8		8		8.4
Total | Mortgage servicing rights | Option-adjusted spread | Level 3 | Minimum
Inputs:
Input	0.021		0.021
Total | Mortgage servicing rights | Option-adjusted spread | Level 3 | Maximum
Inputs:
Input	0.132		0.132
Total | Mortgage servicing rights | Option-adjusted spread | Level 3 | Weighted average
Inputs:
Input	0.049		0.049
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Level 3
Inputs
Amount recognized	$ 700,326,000	578,982,000	$ 2,165,213,000	1,532,709,000
Unpaid principal balance of underlying loans	$ 33,438,395,000	$ 25,922,146,000	$ 95,800,375,000	$ 70,148,676,000
Weighted-average servicing fee rate (as a percent)	0.39%	0.46%	0.42%	0.44%
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Level 3 | Minimum
Inputs:
Annual per-loan cost of servicing	$ 69	$ 69	$ 69	$ 69
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Level 3 | Maximum
Inputs:
Annual per-loan cost of servicing	127	127	127	127
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Level 3 | Weighted average
Inputs:
Annual per-loan cost of servicing	$ 98	$ 102	$ 99	$ 100
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Minimum
Inputs:
Input	0.049	0.049		0.049
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Maximum
Inputs:
Input	0.126	0.126		0.126
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Weighted average
Inputs:
Input	0.055	0.057	0.055	0.061
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Minimum
Inputs:
Input	0.067	0.079	0.066	0.073
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Maximum
Inputs:
Input	0.16	0.258	0.16	0.258
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Weighted average
Inputs:
Input	0.092	0.115	0.088	0.105
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Minimum
Inputs:
Input	3.7	3.7	3.7	3.5
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Maximum
Inputs:
Input	10.1	9.3	10.2	9.7
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Weighted average
Inputs:
Input | Y	8.4	7.4	8.6	7.7