Fair Value - Level 3 Unobservable Inputs, Mortgage Servicing Rights - Initial Recognition (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024 USD ($) Y	Sep. 30, 2023 USD ($) Y	Sep. 30, 2024 USD ($) Y	Sep. 30, 2023 USD ($) Y	Dec. 31, 2023 USD ($) Y
Mortgage servicing rights
Inputs
Amount recognized	$ 578,982,000	$ 450,936,000	$ 1,532,709,000	$ 1,299,992,000
Total | Mortgage servicing rights | Level 3 | Minimum
Inputs:
Annual per-loan cost of servicing			68		$ 70
Total | Mortgage servicing rights | Level 3 | Maximum
Inputs:
Annual per-loan cost of servicing			131		135
Total | Mortgage servicing rights | Level 3 | Weighted average
Inputs:
Annual per-loan cost of servicing			$ 106		$ 107
Total | Mortgage servicing rights | Pricing spread | Level 3 | Minimum
Inputs:
Input	0.050		0.050		0.055
Total | Mortgage servicing rights | Pricing spread | Level 3 | Maximum
Inputs:
Input	0.113		0.113		0.126
Total | Mortgage servicing rights | Pricing spread | Level 3 | Weighted average
Inputs:
Input	0.063		0.063		0.064
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Minimum
Inputs:
Input	0.063		0.063		0.061
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Maximum
Inputs:
Input	0.189		0.189		0.178
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Weighted average
Inputs:
Input	0.091		0.091		0.083
Total | Mortgage servicing rights | Life | Level 3 | Minimum
Inputs:
Input | Y	2.7		2.7		3.0
Total | Mortgage servicing rights | Life | Level 3 | Maximum
Inputs:
Input | Y	8.8		8.8		9.0
Total | Mortgage servicing rights | Life | Level 3 | Weighted average
Inputs:
Input | Y	7.7		7.7		8.1
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Level 3
Inputs
Amount recognized	$ 578,982,000	450,936,000	$ 1,532,709,000	1,299,992,000
Unpaid principal balance of underlying loans	$ 25,922,146,000	$ 21,861,437,000	$ 70,148,676,000	$ 60,549,919,000
Weighted-average servicing fee rate (as a percent)	0.46%	0.42%	0.44%	0.47%
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	$ 68	$ 69	$ 68
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	$ 102	$ 97	$ 100	$ 99
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Minimum
Inputs:
Input	0.049	0.055	0.049	0.055
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	0.126
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Weighted average
Inputs:
Input	0.057	0.061	0.061	0.070
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Minimum
Inputs:
Input	0.079	0.075	0.073	0.075
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Maximum
Inputs:
Input	0.258	0.204	0.258	0.232
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Weighted average
Inputs:
Input	0.115	0.103	0.105	0.109
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Minimum
Inputs:
Input	3.7	3.6	3.5	3.0
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Maximum
Inputs:
Input	9.3	9.4	9.7	9.4
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Weighted average
Inputs:
Input | Y	7.4	7.7	7.7	7.6