Fair Value - Level 3 Unobservable Inputs, Mortgage Servicing Rights - Initial Recognition (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2025 USD ($) Y	Mar. 31, 2024 USD ($) Y	Dec. 31, 2024 USD ($) Y
Mortgage servicing rights
Inputs
Amount recognized	$ 650,349,000	$ 412,520,000
Total | Mortgage servicing rights | Level 3 | Minimum
Inputs:
Annual per-loan cost of servicing	68		$ 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	$ 105		$ 105
Total | Mortgage servicing rights | Pricing spread | Level 3 | Minimum
Inputs:
Input	0.049		0.05
Total | Mortgage servicing rights | Pricing spread | Level 3 | Maximum
Inputs:
Input	0.114		0.113
Total | Mortgage servicing rights | Pricing spread | Level 3 | Weighted average
Inputs:
Input	0.061		0.062
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Minimum
Inputs:
Input	0.062		0.059
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Maximum
Inputs:
Input	0.186		0.177
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Weighted average
Inputs:
Input	0.088		0.078
Total | Mortgage servicing rights | Life | Level 3 | Minimum
Inputs:
Input | Y	2.7		2.7
Total | Mortgage servicing rights | Life | Level 3 | Maximum
Inputs:
Input | Y	8.8		9.1
Total | Mortgage servicing rights | Life | Level 3 | Weighted average
Inputs:
Input | Y	8.1		8.4
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Level 3
Inputs
Amount recognized	$ 650,349,000	412,520,000
Unpaid principal balance of underlying loans	$ 27,664,977,000	$ 19,484,815,000
Weighted-average servicing fee rate (as a percent)	0.43%	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	$ 70	$ 71
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
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	$ 101	$ 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
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
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Weighted average
Inputs:
Input	0.055	0.063
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Minimum
Inputs:
Input	0.066	0.079
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Maximum
Inputs:
Input	0.15	0.159
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Weighted average
Inputs:
Input	0.088	0.11
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Minimum
Inputs:
Input | Y	3.8	3.5
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Maximum
Inputs:
Input | Y	10.2	9.3
Total | Mortgage servicing rights | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Weighted average
Inputs:
Input | Y	8.7	7.5