Goodwill and Mortgage Servicing Rights - Mortgage Servicing Rights (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Mortgage servicing rights activity [Abstract]
Fair value at beginning of period	$ 6,241	$ 5,753	$ 6,030	$ 6,096
MSR activity:
Originations of MSRs	278	253	611	624
Purchase of MSRs	13	0	159	0
Disposition of MSRs	(2)	(2)	(401)	(140)
Net additions/(dispositions)	289	251	369	484
Changes due to collection/realization of expected cash flows	(195)	(200)	(542)	(619)
Changes in valuation due to inputs and assumptions:
Changes due to market interest rates and other	150	(67)	635	(188)
Changes in valuation due to other inputs and assumptions:
Projected cash flows (e.g., cost to service)	14	(116)	14	(102)
Discount rates	0	0	24	(19)
Prepayment model changes and other	(66)	117	(97)	86
Total changes in valuation due to other inputs and assumptions	(52)	1	(59)	(35)
Total changes in valuation due to inputs and assumptions	98	(66)	576	(223)
Fair value at end of period	6,433	5,738	6,433	5,738
Change in unrealized gains/(losses) included in income related to MSRs	98	(66)	576	(223)
Contractual service fees, late fees and other ancillary fees included in income	428	463	1,339	1,427
Third-party mortgage loans serviced	528,000	558,000	528,000	558,000
Net servicer advances	$ 3,100	$ 3,900	$ 3,100	$ 3,900