Fair Value - Level 3 Unobservable Inputs, Mortgage Servicing Rights - Initial Recognition (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023 USD ($) item	Sep. 30, 2022 USD ($) item	Sep. 30, 2023 USD ($) item	Sep. 30, 2022 USD ($) item	Dec. 31, 2022 USD ($) item
Mortgage servicing rights
Inputs
Amount recognized | $	$ 450,936,000	$ 345,077,000	$ 1,299,992,000	$ 1,359,632,000
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 | $			135		144
Total | Mortgage servicing rights | Level 3 | Weighted average
Inputs:
Annual per-loan cost of servicing | $			$ 107		$ 109
Total | Mortgage servicing rights | Pricing spread | Level 3 | Minimum
Inputs:
Input	5.6		5.6		4.9
Total | Mortgage servicing rights | Pricing spread | Level 3 | Maximum
Inputs:
Input	12.6		12.6		14.3
Total | Mortgage servicing rights | Pricing spread | Level 3 | Weighted average
Inputs:
Input	6.5		6.5		6.5
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Minimum
Inputs:
Input	5.4		5.4		5.0
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Maximum
Inputs:
Input	16.4		16.4		17.7
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Weighted average
Inputs:
Input	6.7		6.7		7.5
Total | Mortgage servicing rights | Life | Level 3 | Minimum
Inputs:
Input	3.2		3.2		3.7
Total | Mortgage servicing rights | Life | Level 3 | Maximum
Inputs:
Input	9.4		9.4		9.3
Total | Mortgage servicing rights | Life | Level 3 | Weighted average
Inputs:
Input	8.8		8.8		8.4
Total | MSRs at the time of initial recognition, excluding MSR purchases | Level 3
Inputs
Amount recognized | $	$ 450,936,000	345,077,000	$ 1,299,992,000	1,359,632,000
Unpaid principal balance of underlying loans | $	$ 21,861,437,000	$ 16,003,556,000	$ 60,549,919,000	$ 65,956,748,000
Weighted-average servicing fee rate (as a percent)	0.42%	0.49%	0.47%	0.44%
Total | MSRs at the time of initial recognition, excluding MSR purchases | Level 3 | Minimum
Inputs:
Annual per-loan cost of servicing | $	$ 68	$ 79	$ 68	$ 79
Total | MSRs at the time of initial recognition, excluding MSR purchases | Level 3 | Maximum
Inputs:
Annual per-loan cost of servicing | $	127	116	127	177
Total | MSRs at the time of initial recognition, excluding MSR purchases | Level 3 | Weighted average
Inputs:
Annual per-loan cost of servicing | $	$ 97	$ 105	$ 99	$ 104
Total | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Minimum
Inputs:
Input	5.5	5.5	5.5	5.5
Total | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Maximum
Inputs:
Input	12.6	11.4	12.6	16.1
Total | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Weighted average
Inputs:
Input	6.1	8.1	7.0	7.8
Total | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Minimum
Inputs:
Input	7.5	6.8	7.5	5.7
Total | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Maximum
Inputs:
Input	20.4	19.1	23.2	23.4
Total | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Weighted average
Inputs:
Input	10.3	11.1	10.9	9.0
Total | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Minimum
Inputs:
Input	3.6	4.0	3.0	3.7
Total | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Maximum
Inputs:
Input	9.4	8.1	9.4	9.2
Total | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Weighted average
Inputs:
Input	7.7	7.4	7.6	8.1