Goodwill and Mortgage Servicing Rights - Mortgage Servicing Rights (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Mortgage servicing rights activity [Abstract]
Fair value at beginning of period	$ 6,130	$ 6,030
MSR activity:
Originations of MSRs	332	176
Purchase of MSRs	104	67
Disposition of MSRs	(111)	(295)
Net additions/(dispositions)	325	(52)
Changes due to collection/realization of expected cash flows	(199)	(160)
Changes in valuation due to inputs and assumptions:
Changes due to market interest rates and other	(301)	382
Changes in valuation due to other inputs and assumptions:
Projected cash flows (e.g., cost to service)	0	0
Discount rates	0	24
Prepayment model changes and other	2	(22)
Total changes in valuation due to other inputs and assumptions	2	2
Total changes in valuation due to inputs and assumptions	(299)	384
Fair value at end of period	5,957	6,202
Change in unrealized gains/(losses) included in income related to MSRs	(299)	384
Contractual service fees, late fees and other ancillary fees included in income	420	465
Third-party mortgage loans serviced	530,000	540,000
Servicer advances, net of an allowance for uncollectible amounts	$ 2,600	$ 3,600