Fair Value - Level 3 Unobservable Inputs, Mortgage Servicing Rights - Initial Recognition (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022 USD ($) item	Sep. 30, 2021 USD ($) item	Sep. 30, 2022 USD ($) item	Sep. 30, 2021 USD ($) item	Dec. 31, 2021 USD ($) item
Mortgage servicing rights
Inputs
Amount recognized | $	$ 345,077,000	$ 432,429,000	$ 1,359,632,000	$ 1,386,324,000
Total | Mortgage servicing rights | Level 3 | Minimum
Inputs:
Annual per-loan cost of servicing | $			80		$ 79
Total | Mortgage servicing rights | Level 3 | Maximum
Inputs:
Annual per-loan cost of servicing | $			149		197
Total | Mortgage servicing rights | Level 3 | Weighted average
Inputs:
Annual per-loan cost of servicing | $			$ 106		$ 108
Total | Mortgage servicing rights | Pricing spread | Level 3 | Minimum
Inputs:
Input	4.9		4.9		5.3
Total | Mortgage servicing rights | Pricing spread | Level 3 | Maximum
Inputs:
Input	14.8		14.8		15.5
Total | Mortgage servicing rights | Pricing spread | Level 3 | Weighted average
Inputs:
Input	6.9		6.9		7.7
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Minimum
Inputs:
Input	5.1		5.1		7.9
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Maximum
Inputs:
Input	17.1		17.1		26.7
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Weighted average
Inputs:
Input	7.6		7.6		10.7
Total | Mortgage servicing rights | Life | Level 3 | Minimum
Inputs:
Input	3.8		3.8		3.1
Total | Mortgage servicing rights | Life | Level 3 | Maximum
Inputs:
Input	9.3		9.3		7.7
Total | Mortgage servicing rights | Life | Level 3 | Weighted average
Inputs:
Input	8.3		8.3		6.8
Total | MSRs at the time of initial recognition, excluding MSR purchases | Level 3
Inputs
Amount recognized | $	$ 345,077,000	432,429,000	$ 1,359,632,000	1,386,324,000
Unpaid principal balance of underlying loans | $	$ 16,003,556,000	$ 33,697,228,000	$ 65,956,748,000	$ 105,470,580,000
Weighted-average servicing fee rate (as a percent)	0.49%	0.34%	0.44%	0.33%
Total | MSRs at the time of initial recognition, excluding MSR purchases | Level 3 | Minimum
Inputs:
Annual per-loan cost of servicing | $	$ 79	$ 80	$ 79	$ 80
Total | MSRs at the time of initial recognition, excluding MSR purchases | Level 3 | Maximum
Inputs:
Annual per-loan cost of servicing | $	116	117	177	117
Total | MSRs at the time of initial recognition, excluding MSR purchases | Level 3 | Weighted average
Inputs:
Annual per-loan cost of servicing | $	$ 105	$ 102	$ 104	$ 104
Total | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Minimum
Inputs:
Input	5.5	6.0	5.5	6.0
Total | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Maximum
Inputs:
Input	11.4	16.9	16.1	16.9
Total | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Weighted average
Inputs:
Input	8.1	8.5	7.8	9.0
Total | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Minimum
Inputs:
Input	6.8	7.2	5.7	6.2
Total | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Maximum
Inputs:
Input	19.1	31.0	23.4	31.0
Total | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Weighted average
Inputs:
Input	11.1	9.2	9.0	8.5
Total | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Minimum
Inputs:
Input	4.0	3.0	3.7	3.0
Total | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Maximum
Inputs:
Input	8.1	8.4	9.2	9.0
Total | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Weighted average
Inputs:
Input	7.4	7.7	8.1	8.1