Goodwill and Mortgage Servicing Rights - Mortgage Servicing Rights (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Mortgage servicing rights activity
Fair value at beginning of period	$ 4,699	$ 6,130	$ 6,030
MSR activity:
Originations of MSRs	944	1,384	931
Purchase of MSRs	248	105	315
Disposition of MSRs	(176)	(789)	(636)
Net additions/(Dispositions)	1,016	700	610
Changes due to collection/realization of expected cash flows	(899)	(951)	(740)
Changes in valuation due to inputs and assumptions:
Changes due to market interest rates and other	(1,568)	(893)	300
Changes in valuation due to other inputs and assumptions:
Projected cash flows (e.g., cost to service)	(54)	(333)	15
Discount rates	199	153	24
Prepayment model changes and other	(117)	(107)	(109)
Total changes in valuation due to other inputs and assumptions	28	(287)	(70)
Total changes in valuation due to inputs and assumptions	(1,540)	(1,180)	230
Fair value at December 31,	3,276	4,699	6,130
Change in unrealized gains/(losses) included in income related to MSRs held at December 31,	(1,540)	(1,180)	230
Contractual service fees, late fees and other ancillary fees included in income	1,325	1,639	1,778
Third-party mortgage loans serviced at December 31,	448,000	522,000	521,000
Servicer advances, net of an allowance for uncollectible amounts, at December 31,	$ 1,800	$ 2,000	$ 3,000