Goodwill and Mortgage Servicing Rights - Mortgage Servicing Rights (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Mortgage servicing rights activity [Abstract]
Fair value at beginning of period	$ 5,957	$ 6,202	$ 6,130	$ 6,030
MSR activity:
Originations of MSRs	424	157	756	333
Purchase of MSRs	2	79	106	146
Disposition of MSRs	(217)	(104)	(328)	(399)
Net additions/(dispositions)	209	132	534	80
Changes due to collection/realization of expected cash flows	(247)	(187)	(446)	(347)
Changes in valuation due to inputs and assumptions:
Changes due to market interest rates and other	(540)	103	(841)	485
Changes in valuation due to other inputs and assumptions:
Projected cash flows (e.g., cost to service)	(350)	0	(350)	0
Discount rates	153	0	153	24
Prepayment model changes and other	(89)	(9)	(87)	(31)
Total changes in valuation due to other inputs and assumptions	(286)	(9)	(284)	(7)
Total changes in valuation due to inputs and assumptions	(826)	94	(1,125)	478
Fair value at end of period	5,093	6,241	5,093	6,241
Change in unrealized gains/(losses) included in income related to MSRs	(826)	94	(1,125)	478
Contractual service fees, late fees and other ancillary fees included in income	437	446	857	911
Third-party mortgage loans serviced	527,000	534,000	527,000	534,000
Servicer advances, net of an allowance for uncollectible amounts	$ 2,200	$ 3,300	$ 2,200	$ 3,300