Goodwill and Mortgage Servicing Rights - Mortgage Servicing Rights (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Mortgage servicing rights activity [Abstract]
Fair value at beginning of period	$ 6,030	$ 6,096	$ 6,608
MSR activity:
Originations of MSRs	931	1,103	679
Purchase of MSRs	315	0	0
Disposition of MSRs	(636)	(140)	(109)
Net additions	610	963	570
Changes due to collection/realization of expected cash flows	(740)	(797)	(919)
Changes in valuation due to inputs and assumptions:
Changes due to market interest rates and other	300	(202)	(72)
Changes in valuation due to other inputs and assumptions:
Projected cash flows (e.g., cost to service)	15	(102)	(35)
Discount rates	24	(19)	7
Prepayment model changes and other	(109)	91	(63)
Total changes in valuation due to other inputs and assumptions	(70)	(30)	(91)
Total changes in valuation due to inputs and assumptions	230	(232)	(163)
Fair value at December 31,	6,130	6,030	6,096
Change in unrealized gains/(losses) included in income related to MSRs held	230	(232)	(163)
Contractual service fees, late fees and other ancillary fees included in income	1,778	1,886	2,124
Third-party mortgage loans serviced	521,000	555,000	593,300
Servicer advances, net of an allowance for uncollectible amounts	$ 3,000	$ 4,000	$ 4,700