Goodwill and Mortgage Servicing Rights - Mortgage Servicing Rights (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Mortgage servicing rights activity [Abstract]
Fair value at beginning of period	$ 4,470	$ 3,267	$ 3,276	$ 4,699
MSR activity:
Originations of MSRs	419	164	823	435
Purchase of MSRs	395	5	574	7
Disposition of MSRs	(25)	2	(24)	(73)
Net additions/(dispositions)	789	171	1,373	369
Changes due to collection/realization of expected cash flows	(182)	(247)	(369)	(495)
Changes in valuation due to inputs and assumptions:
Changes due to market interest rates and other	(500)	(144)	336	(1,514)
Changes in valuation due to other inputs and assumptions:
Projected cash flows (e.g., cost to service)	1	3	(23)	2
Discount rates	0	0	0	0
Prepayment model changes and other	(29)	30	(44)	19
Total changes in valuation due to other inputs and assumptions	(28)	33	(67)	21
Total changes in valuation due to inputs and assumptions	(528)	(111)	269	(1,493)
Fair value at end of period	4,549	3,080	4,549	3,080
Changes in unrealized gains/(losses) included in income related to MSRs	(528)	(111)	269	(1,493)
Contractual service fees, late fees and other ancillary fees included in income	307	329	598	693
Third-party mortgage loans serviced	465,000	483,000	465,000	483,000
Servicer advances, net of an allowance for uncollectible amounts	$ 1,700	$ 1,700	$ 1,700	$ 1,700