Asset Quality - Changes in Allowance for Loan and Lease Losses by Loan Category (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 1,438	$ 1,359	$ 1,626	$ 900
Provision	(196)	445	(270)	784
Charge-offs	(71)	(110)	(206)	(211)
Recoveries	49	14	70	31
Ending balance	1,220	1,708	1,220	1,708
Total ALLL, including discontinued operations	1,250	1,751	1,250	1,751	$ 1,471	$ 1,662	$ 1,402	$ 910
Total provision, including discontinued operations	(198)	445	(275)	787
Total charge-offs, including discontinued operations	(72)	(112)	(208)	(215)
Total recoveries, including discontinued operations	49	16	71	34
Provision (credit) for losses on lending-related commitments	(26)	37	(45)	57
Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				204
Total ALLL, including discontinued operations								235
Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				1,104
Total ALLL, including discontinued operations								$ 1,145
Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	937	818	1,099	751
Provision	(135)	366	(195)	616
Charge-offs	(45)	(77)	(157)	(142)
Recoveries	38	6	48	12
Ending balance	795	1,113	795	1,113
Commercial Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				(124)
Commercial Loans | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				627
Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	501	541	527	149
Provision	(61)	79	(75)	168
Charge-offs	(26)	(33)	(49)	(69)
Recoveries	11	8	22	19
Ending balance	425	595	425	595
Consumer Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				328
Consumer Loans | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				477
Commercial and Industrial | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	596	542	678	551
Provision	(88)	249	(105)	436
Charge-offs	(41)	(71)	(114)	(131)
Recoveries	32	5	40	10
Ending balance	499	725	499	725
Commercial and Industrial | Commercial Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				(141)
Commercial and Industrial | Commercial Loans | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				410
Commercial mortgage | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	256	207	327	143
Provision	(31)	87	(68)	137
Charge-offs	(4)	(2)	(39)	(5)
Recoveries	6	0	7	1
Ending balance	227	292	227	292
Commercial mortgage | Commercial Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				16
Commercial mortgage | Commercial Loans | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				159
Construction | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	45	25	47	22
Provision	(10)	16	(12)	26
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	35	41	35	41
Construction | Commercial Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				(7)
Construction | Commercial Loans | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				15
Commercial real estate loans | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	301	232	374	165
Provision	(41)	103	(80)	163
Charge-offs	(4)	(2)	0	(5)
Recoveries	6	0	0	1
Ending balance	262	333	262	333
Commercial real estate loans | Commercial Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				9
Commercial real estate loans | Commercial Loans | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				174
Commercial lease financing | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	40	44	47	35
Provision	(6)	14	(10)	17
Charge-offs	0	(4)	(4)	(6)
Recoveries	0	1	1	1
Ending balance	34	55	34	55
Commercial lease financing | Commercial Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				8
Commercial lease financing | Commercial Loans | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				43
Real estate — residential mortgage | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	100	89	102	7
Provision	(13)	14	(16)	19
Charge-offs	(1)	(2)	(1)	(2)
Recoveries	0	0	1	0
Ending balance	86	101	86	101
Real estate — residential mortgage | Consumer Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				77
Real estate — residential mortgage | Consumer Loans | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				84
Home equity loans | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	157	184	171	31
Provision	(18)	14	(31)	22
Charge-offs	(4)	(2)	(6)	(6)
Recoveries	1	1	2	3
Ending balance	136	197	136	197
Home equity loans | Consumer Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				147
Home equity loans | Consumer Loans | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				178
Consumer direct loans | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	126	116	128	34
Provision	(6)	22	(2)	51
Charge-offs	(7)	(10)	(15)	(22)
Recoveries	2	2	4	4
Ending balance	115	130	115	130
Consumer direct loans | Consumer Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				63
Consumer direct loans | Consumer Loans | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				97
Credit cards | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	80	104	87	47
Provision	(6)	13	(9)	44
Charge-offs	(9)	(12)	(15)	(23)
Recoveries	3	2	5	4
Ending balance	68	107	68	107
Credit cards | Consumer Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				35
Credit cards | Consumer Loans | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				82
Consumer indirect loans | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	38	48	39	30
Provision	(18)	16	(17)	32
Charge-offs	(5)	(7)	(12)	(16)
Recoveries	5	3	10	8
Ending balance	20	60	20	60
Consumer indirect loans | Consumer Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				6
Consumer indirect loans | Consumer Loans | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				36
Discontinued Operations
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	33	43	36	10
Provision	(2)	0	(5)	3
Charge-offs	(1)	(2)	(2)	(4)
Recoveries	0	2	1	3
Ending balance	$ 30	$ 43	$ 30	43
Discontinued Operations | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				31
Discontinued Operations | Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				$ 41