Mortgage Servicing Rights - Summary of Income and Fees (Details) - Residential first mortgage - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Servicing Assets at Fair Value
Decrease in MSR fair value due to pay-offs, pay-downs, run-off, model changes and other	$ (99)	$ (109)	$ (89)
Changes in fair value due to interest rate risk	57	(50)	(76)
Net (loss) return on mortgage servicing rights
Servicing Assets at Fair Value
Servicing fees, ancillary income and late fees	115	107	96
Decrease in MSR fair value due to pay-offs, pay-downs, run-off, model changes and other	(99)	(109)	(89)
Changes in fair value due to interest rate risk	57	(50)	(76)
Gain (loss) on MSR derivatives	(37)	65	76
Net transaction costs	(13)	(3)	(1)
Total return (loss) included in net return on mortgage servicing rights	23	10	6
Loan administration income
Servicing Assets at Fair Value
Servicing fees, ancillary income and late fees	140	126	106
Charges on subserviced custodial balances	(10)	(29)	(67)
Other servicing charges	(9)	(13)	(9)
Total income on mortgage loans subserviced, included in loan administration	$ 121	$ 84	$ 30