Fair Value - Level 3 Unobservable Inputs, Mortgage Servicing Rights - Initial Recognition (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2022 USD ($) item	Jun. 30, 2021 USD ($) item	Jun. 30, 2022 USD ($) item	Jun. 30, 2021 USD ($) item	Dec. 31, 2021 USD ($) item
Mortgage servicing rights
Inputs
Amount recognized | $	$ 398,253,000	$ 483,362,000	$ 1,014,555,000	$ 953,895,000
Total | Mortgage servicing rights | Level 3 | Minimum
Inputs:
Annual per-loan cost of servicing | $			79		$ 79
Total | Mortgage servicing rights | Level 3 | Maximum
Inputs:
Annual per-loan cost of servicing | $			156		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	5.5		5.5		7.9
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Maximum
Inputs:
Input	19.0		19.0		26.7
Total | Mortgage servicing rights | Annual total prepayment speed | Level 3 | Weighted average
Inputs:
Input	8.2		8.2		10.7
Total | Mortgage servicing rights | Life | Level 3 | Minimum
Inputs:
Input	2.0		2.0		3.1
Total | Mortgage servicing rights | Life | Level 3 | Maximum
Inputs:
Input	9.2		9.2		7.7
Total | Mortgage servicing rights | Life | Level 3 | Weighted average
Inputs:
Input	8.0		8.0		6.8
Total | MSRs at the time of initial recognition, excluding MSR purchases | Level 3
Inputs
Amount recognized | $	$ 398,253,000	483,362,000	$ 1,014,555,000	953,895,000
Unpaid principal balance of underlying loans | $	$ 19,377,222,000	$ 36,830,098,000	$ 49,953,192,000	$ 71,773,352,000
Weighted-average servicing fee rate (as a percent)	0.42%	0.33%	0.43%	0.33%
Total | MSRs at the time of initial recognition, excluding MSR purchases | Level 3 | Minimum
Inputs:
Annual per-loan cost of servicing | $	$ 80	$ 80	$ 80	$ 81
Total | MSRs at the time of initial recognition, excluding MSR purchases | Level 3 | Maximum
Inputs:
Annual per-loan cost of servicing | $	146	117	176	117
Total | MSRs at the time of initial recognition, excluding MSR purchases | Level 3 | Weighted average
Inputs:
Annual per-loan cost of servicing | $	$ 103	$ 104	$ 104	$ 104
Total | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Minimum
Inputs:
Input	5.7	6.0	5.7	6.0
Total | MSRs at the time of initial recognition, excluding MSR purchases | Pricing spread | Level 3 | Maximum
Inputs:
Input	11.7	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	8.2	8.9	7.7	9.2
Total | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Minimum
Inputs:
Input	5.7	6.7	5.7	6.2
Total | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Maximum
Inputs:
Input	19.3	17.7	23.4	16.7
Total | MSRs at the time of initial recognition, excluding MSR purchases | Annual total prepayment speed | Level 3 | Weighted average
Inputs:
Input	8.4	8.5	8.3	8.1
Total | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Minimum
Inputs:
Input	4.3	4.0	3.7	4.1
Total | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Maximum
Inputs:
Input	9.2	8.8	9.2	9.0
Total | MSRs at the time of initial recognition, excluding MSR purchases | Life | Level 3 | Weighted average
Inputs:
Input	8.5	8.1	8.4	8.3