Mortgage Servicing Rights - Summary of Income and Fees (Details) - Residential first mortgage loans - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Servicing Assets at Fair Value [Line Items]
Decreases in MSR fair value due to pay-offs, pay-downs, run-off, model changes, and other	$ (15)	$ (32)	$ (23)	$ (71)
Changes in fair value due to interest rate risk	49	(22)	96	51
Net return (loss) on mortgage servicing rights
Servicing Assets at Fair Value [Line Items]
Servicing fees, ancillary income and late fees	32	29	62	60
Decreases in MSR fair value due to pay-offs, pay-downs, run-off, model changes, and other	(15)	(32)	(23)	(71)
Changes in fair value due to interest rate risk	49	(22)	96	51
Loss on MSR derivatives	(43)	27	(84)	(38)
Net transaction costs	(1)	(7)	0	(7)
Total return included in net return on mortgage servicing rights	22	(5)	51	(5)
Loan administration income on mortgage loans subserviced
Servicing Assets at Fair Value [Line Items]
Servicing fees, ancillary income and late fees	37	33	74	65
Charges on subserviced custodial balances	(4)	(2)	(6)	(5)
Other servicing charges	0	(2)	(2)	(5)
Total income on mortgage loans subserviced, included in loan administration	$ 33	$ 29	$ 66	$ 55