Mortgage Servicing Rights - Summary of Income and Fees (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Servicing Assets at Fair Value [Line Items]
Decrease in MSR fair value due to pay-offs, pay-downs, run-off, model changes, and other (1)	$ (105)	$ (80)	$ (8)
Changes in fair value due to interest rate risk	30	1	10
Total return (loss) included in net return on mortgage servicing rights	73	103	6
Total income (loss) on mortgage loans subserviced, included in loan administration income	(22)	(17)	3
Residential first mortgage loans
Servicing Assets at Fair Value [Line Items]
Servicing fees, ancillary income and late fees	202	227	20
Decrease in MSR fair value due to pay-offs, pay-downs, run-off, model changes, and other (1)	(105)	(80)	(8)
Changes in fair value due to interest rate risk	30	1	10
Gain on MSR derivatives	(54)	(47)	(16)
Net transaction costs	0	2	0
Residential first mortgage loans | Loan administration income on mortgage loans subserviced
Servicing Assets at Fair Value [Line Items]
Servicing fees, ancillary income and late fees	117	154	11
Charges on subserviced custodial balances	(141)	(168)	(8)
Other servicing charges	$ 2	$ (3)	$ 0