Goodwill and Mortgage Servicing Rights - Mortgage Servicing Rights (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Mortgage servicing rights activity [Abstract]
Fair value at beginning of period	$ 6,130	$ 6,030	$ 6,096
MSR activity:
Originations of MSRs	1,384	931	1,103
Purchase of MSRs	105	315	0
Disposition of MSRs	(789)	(636)	(140)
Net additions	700	610	963
Changes due to collection/realization of expected cash flows	(951)	(740)	(797)
Changes in valuation due to inputs and assumptions:
Changes due to market interest rates and other	(893)	300	(202)
Changes in valuation due to other inputs and assumptions:
Projected cash flows (e.g., cost to service)	(333)	15	(102)
Discount rates	153	24	(19)
Prepayment model changes and other	(107)	(109)	91
Total changes in valuation due to other inputs and assumptions	(287)	(70)	(30)
Total changes in valuation due to inputs and assumptions	(1,180)	230	(232)
Fair value at December 31,	4,699	6,130	6,030
Change in unrealized gains/(losses) included in income related to MSRs held	(1,180)	230	(232)
Contractual service fees, late fees and other ancillary fees included in income	1,639	1,778	1,886
Third-party mortgage loans serviced	522,000	521,000	555,000
Servicer advances, net of an allowance for uncollectible amounts	$ 2,000	$ 3,000	$ 4,000