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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 1,359	$ 883	$ 900	$ 883
Provision	445	72	784	136
Charge-offs	(110)	(84)	(211)	(211)
Recoveries	14	19	31	31
Ending balance	1,708	890	1,708	890
Total ALLL, including discontinued operations	1,751	902	1,751	902	$ 1,402	$ 1,145	$ 910	$ 896	$ 897
Total provision, including discontinued operations	445	74	787	140
Total charge-offs, including discontinued operations	(112)	(88)	(215)	(215)
Total recoveries, including discontinued operations	16	20	34	34
Provision for losses on lending-related commitments	37	2	57	0
Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	818	737	751	743
Provision	366	48	616	83
Charge-offs	(77)	(47)	(142)	(142)
Recoveries	6	9	12	12
Ending balance	1,113	747	1,113	747
Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	541	146		140
Provision	79	24	168	53
Charge-offs	(33)	(37)	(69)	(69)
Recoveries	8	10	19	19
Ending balance	595	143	595	143
Commercial and industrial | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	542	530	551	532
Provision	249	43	436	67
Charge-offs	(71)	(30)	(131)	(131)
Recoveries	5	6	10	10
Ending balance	725	549	725	549
Commercial mortgage | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	207	144	143	142
Provision	87	(5)	137	1
Charge-offs	(2)	(1)	(5)	(5)
Recoveries	0	1	1	1
Ending balance	292	139	292	139
Real estate — construction | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	25	28		33
Provision	16	(4)	26	(5)
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	41	24	41	24
Commercial real estate loans | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	232	172	165	175
Provision	103	(9)	163	(4)
Charge-offs	(2)	(1)	(5)	(5)
Recoveries	0	1	1	1
Ending balance	333	163	333	163
Commercial lease financing | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	44	35		36
Provision	14	14	17	20
Charge-offs	(4)	(16)	(6)	(6)
Recoveries	1	2	1	1
Ending balance	55	35	55	35
Real estate — residential mortgage | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	89	8	7	7
Provision	14	0	19	1
Charge-offs	(2)	(1)	(2)	(2)
Recoveries	0	0	0	0
Ending balance	101	7	101	7
Home equity loans | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	184	36	31	35
Provision	14	4	22	7
Charge-offs	(2)	(6)	(6)	(6)
Recoveries	1	2	3	3
Ending balance	197	36	197	36
Consumer direct loans | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	116	33		30
Provision	22	7	51	19
Charge-offs	(10)	(10)	(22)	(22)
Recoveries	2	2	4	4
Ending balance	130	32	130	32
Credit cards | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	104	47	47	48
Provision	13	7	44	15
Charge-offs	(12)	(12)	(23)	(23)
Recoveries	2	2	4	4
Ending balance	107	44	107	44
Consumer indirect loans | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	48	22	30	20
Provision	16	6	32	11
Charge-offs	(7)	(8)	(16)	(16)
Recoveries	3	4	8	8
Ending balance	60	24	60	24
Discontinued operations
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	43	13	10	14
Provision	0	2	3	4
Charge-offs	(2)	(4)	(4)	(4)
Recoveries	2	1	3	3
Ending balance	$ 43	$ 12	43	$ 12
Continuing operations | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			149
Continuing operations | Real estate — construction | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			22
Continuing operations | Commercial lease financing | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			35
Continuing operations | Consumer direct loans | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			34
Impact of ASC 326 Adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			204
Total ALLL, including discontinued operations							$ 235
Impact of ASC 326 Adoption | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			(124)
Impact of ASC 326 Adoption | Commercial and industrial | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			(141)
Impact of ASC 326 Adoption | Commercial mortgage | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			16
Impact of ASC 326 Adoption | Commercial real estate loans | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			9
Impact of ASC 326 Adoption | Real estate — residential mortgage | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			77
Impact of ASC 326 Adoption | Home equity loans | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			147
Impact of ASC 326 Adoption | Credit cards | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			35
Impact of ASC 326 Adoption | Consumer indirect loans | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			6
Impact of ASC 326 Adoption | Discontinued operations
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			31
Impact of ASC 326 Adoption | Continuing operations | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			328
Impact of ASC 326 Adoption | Continuing operations | Real estate — construction | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			(7)
Impact of ASC 326 Adoption | Continuing operations | Commercial lease financing | Commercial Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			8
Impact of ASC 326 Adoption | Continuing operations | Consumer direct loans | Consumer Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			$ 63