Mortgage Servicing Rights - Summary of Income and Fees (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2023
Servicing Assets at Fair Value [Line Items]
Decrease in MSR fair value due to pay-offs, pay-downs, run-off, model changes and other	$ (20)	$ (54)
Changes in fair value due to interest rate risk	57	59
Residential first mortgage loans
Servicing Assets at Fair Value [Line Items]
Servicing fees, ancillary income and late fees	59	169
Decrease in MSR fair value due to pay-offs, pay-downs, run-off, model changes and other	(20)	(54)
Changes in fair value due to interest rate risk	57	59
Gain on MSR derivatives	(73)	(105)
Net transaction costs	0	1
Total return (loss) included in net return on mortgage servicing rights	23	70
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	42	116
Charges on subserviced custodial balances	(55)	(124)
Other servicing charges	(1)	(3)
Total loss on mortgage loans subserviced, included in loan administration income	$ (14)	$ (11)