Goodwill and Mortgage Servicing Rights - Mortgage Servicing Rights (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Mortgage Servicing Rights [Roll Forward]
Fair value at beginning of period	$ 4,549	$ 3,080	$ 3,276	$ 4,699
MSR activity:
Originations of MSRs	429	204	1,252	639
Purchase of MSRs	584	17	1,158	24
Disposition of MSRs	1	(104)	(23)	(177)
Net additions/(dispositions)	1,014	117	2,387	486
Changes due to collection/realization of expected cash flows	(201)	(215)	(570)	(710)
Changes in valuation due to inputs and assumptions:
Changes due to market interest rates and other	133	(59)	469	(1,573)
Changes in valuation due to other inputs and assumptions:
Projected cash flows (e.g., cost to service)	119	(82)	96	(80)
Discount rates	0	199	0	199
Prepayment model changes and other	(263)	(24)	(307)	(5)
Total changes in valuation due to other inputs and assumptions	(144)	93	(211)	114
Total changes in valuation due to inputs and assumptions	(11)	34	258	(1,459)
Fair value at end of period	5,351	3,016	5,351	3,016
Changes in unrealized gains/(losses) included in income related to MSRs	(11)	34	258	(1,459)
Contractual service fees, late fees and other ancillary fees included in income	334	333	932	1,026
Third-party mortgage loans serviced	510,000	456,000	510,000	456,000
Servicer advances, net of an allowance for uncollectible amounts	$ 1,700	$ 1,700	$ 1,700	$ 1,700