Goodwill and Mortgage Servicing Rights - Mortgage Servicing Rights (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Mortgage servicing rights activity [Abstract]
Fair value at beginning of period	$ 5,093	$ 6,241	$ 6,130	$ 6,030
MSR activity:
Originations of MSRs	390	278	1,146	611
Purchase of MSRs	(2)	13	104	159
Disposition of MSRs	(359)	(2)	(687)	(401)
Net additions/(dispositions)	29	289	563	369
Changes due to collection/realization of expected cash flows	(256)	(195)	(702)	(542)
Changes in valuation due to inputs and assumptions:
Changes due to market interest rates and other	(433)	150	(1,274)	635
Changes in valuation due to other inputs and assumptions:
Projected cash flows (e.g., cost to service)	17	14	(333)	14
Discount rates	0	0	153	24
Prepayment model changes and other	(31)	(66)	(118)	(97)
Total changes in valuation due to other inputs and assumptions	(14)	(52)	(298)	(59)
Total changes in valuation due to inputs and assumptions	(447)	98	(1,572)	576
Fair value at end of period	4,419	6,433	4,419	6,433
Change in unrealized gains/(losses) included in income related to MSRs	(447)	98	(1,572)	576
Contractual service fees, late fees and other ancillary fees included in income	397	428	1,254	1,339
Third-party mortgage loans serviced	537,000	528,000	537,000	528,000
Servicer advances, net of an allowance for uncollectible amounts	$ 2,000	$ 3,100	$ 2,000	$ 3,100