Mortgage Servicing Rights - Summary of Adverse Changes to Weighted-Average Assumptions on the Fair Value of Servicing Rights (Details) - Mortgage servicing rights - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Actual
Option adjusted spread (percent)	5.60%	5.90%
Constant prepayment rate (as a percent)	7.30%	7.90%
Weighted average cost to service per loan	$ 69	$ 68
10% adverse change
Option adjusted spread (percent)	1,114,000,000	1,012,000,000
Constant prepayment rate (as a percent)	1,100,000,000	1,000,000,000
Weighted average cost to service per loan	1,124,000,000	1,023,000,000
20% adverse change
Option adjusted spread (percent)	1,094,000,000	992,000,000
Constant prepayment rate (as a percent)	1,068,000,000	970,000,000
Weighted average cost to service per loan	$ 1,114,000,000	$ 1,013,000,000