Asset Quality - Changes in Allowance for Loan and Lease Losses by Loan Category (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 1,220	$ 1,708	$ 1,626	$ 900
Provision	(107)	150	(377)	934
Charge-offs	(66)	(151)	(272)	(362)
Recoveries	37	23	107	54
Ending balance	1,084	1,730	1,084	1,730
Total ALLL, including discontinued operations, beginning balance	1,250	1,751	1,662	910
Total provision, including discontinued operations	(108)	149	(383)	936
Total charge-offs, including discontinued operations	(67)	(151)	(275)	(366)
Total recoveries, including discontinued operations	38	23	109	57
Total ALLL, including discontinued operations, ending balance	1,113	1,772	1,113	1,772
Provision (credit) for losses on lending-related commitments	0	10	(45)	67
Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				204
Total ALLL, including discontinued operations, beginning balance				235
Adjusted balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				1,104
Total ALLL, including discontinued operations, beginning balance				1,145
Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	795	1,113	1,099	751
Provision	(89)	181	(284)	797
Charge-offs	(28)	(124)	(185)	(266)
Recoveries	27	11	75	23
Ending balance	705	1,181	705	1,181
Commercial Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				(124)
Commercial Loans | 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	425	595	527	149
Provision	(18)	(31)	(93)	137
Charge-offs	(38)	(27)	(87)	(96)
Recoveries	10	12	32	31
Ending balance	379	549	379	549
Consumer Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				328
Consumer Loans | 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	499	725	678	551
Provision	(30)	177	(135)	613
Charge-offs	(27)	(101)	(141)	(232)
Recoveries	20	9	60	19
Ending balance	462	810	462	810
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 | 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	227	292	327	143
Provision	(44)	(2)	(112)	135
Charge-offs	0	(13)	(39)	(18)
Recoveries	1	2	8	3
Ending balance	184	279	184	279
Commercial mortgage | Commercial Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				16
Commercial mortgage | Commercial Loans | 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	35	41	47	22
Provision	(8)	(7)	(20)	19
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	27	34	27	34
Construction | Commercial Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				(7)
Construction | Commercial Loans | 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	262	333	374	165
Provision	(52)	(9)	(132)	154
Charge-offs	0	(13)	0	(18)
Recoveries	1	2	0	3
Ending balance	211	313	211	313
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 | 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	34	55	47	35
Provision	(7)	13	(17)	30
Charge-offs	(1)	(10)	(5)	(16)
Recoveries	6	0	7	1
Ending balance	32	58	32	58
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 | 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	86	101	102	7
Provision	(1)	2	(17)	21
Charge-offs	2	0	1	(2)
Recoveries	1	1	2	1
Ending balance	88	104	88	104
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 | 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	136	197	171	31
Provision	(13)	(13)	(44)	9
Charge-offs	(1)	(4)	(7)	(10)
Recoveries	2	3	4	6
Ending balance	124	183	124	183
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 | 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	115	130	128	34
Provision	(5)	1	(7)	52
Charge-offs	(7)	(8)	(22)	(30)
Recoveries	2	2	6	6
Ending balance	105	125	105	125
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 | 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	68	107	87	47
Provision	(4)	(5)	(13)	39
Charge-offs	(6)	(9)	(21)	(32)
Recoveries	1	2	6	6
Ending balance	59	95	59	95
Credit cards | Consumer Loans | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				35
Credit cards | Consumer Loans | 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	20	60	39	30
Provision	5	(16)	(12)	16
Charge-offs	(26)	(6)	(38)	(22)
Recoveries	4	4	14	12
Ending balance	3	42	3	42
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 | 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	30	43	36	10
Provision	(1)	(1)	(6)	2
Charge-offs	(1)	0	(3)	(4)
Recoveries	1	0	2	3
Ending balance	$ 29	$ 42	$ 29	42
Discontinued Operations | Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				31
Discontinued Operations | Adjusted balance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance				$ 41