Asset Quality - Changes in Allowance for Loan and Lease Losses by Loan Category (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 897	$ 893
Provision	66	60
Charge-offs	(91)	(76)
Recoveries	24	20
Ending balance	896	897
Provision (credit) for losses on lending-related commitments	(2)	3
Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	883	877
Provision	64	58
Charge-offs	(87)	(72)
Recoveries	23	18
Ending balance	883	881
Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	743	735
Provision	35	38
Charge-offs	(53)	(39)
Recoveries	12	8
Ending balance	737	742
Continuing Operations [Member] | Commercial and Industrial [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	532	529
Provision	24	35
Charge-offs	(36)	(37)
Recoveries	10	6
Ending balance	530	533
Continuing Operations [Member] | Commercial Real Estate: Commercial Mortgage [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	142	133
Provision	6	4
Charge-offs	(5)	(1)
Recoveries	1	0
Ending balance	144	136
Continuing Operations [Member] | RE Construction [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	33	30
Provision	(1)	2
Charge-offs	(4)	0
Recoveries	0	1
Ending balance	28	33
Continuing Operations [Member] | Commercial Real Estate [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	175	163
Provision	5	6
Charge-offs	(9)	(1)
Recoveries	1	1
Ending balance	172	169
Continuing Operations [Member] | Commercial Lease Financing [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	36	43
Provision	6	(3)
Charge-offs	(8)	(1)
Recoveries	1	1
Ending balance	35	40
Continuing Operations [Member] | Real Estate - Residential Mortgage [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	7	7
Provision	1	3
Charge-offs	(1)	(1)
Recoveries	1	0
Ending balance	8	9
Continuing Operations [Member] | Home Equity Loans [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	35	43
Provision	3	(4)
Charge-offs	(4)	(4)
Recoveries	2	3
Ending balance	36	38
Continuing Operations [Member] | Consumer Direct Loans [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	30	28
Provision	12	5
Charge-offs	(10)	(8)
Recoveries	1	2
Ending balance	33	27
Continuing Operations [Member] | Credit Cards [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	48	44
Provision	8	12
Charge-offs	(11)	(12)
Recoveries	2	1
Ending balance	47	45
Continuing Operations [Member] | Consumer Indirect Loans [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	20	20
Provision	5	4
Charge-offs	(8)	(8)
Recoveries	5	4
Ending balance	22	20
Continuing Operations [Member] | Consumer Loans [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	140	142
Provision	29	20
Charge-offs	(34)	(33)
Recoveries	11	10
Ending balance	146	139
Discontinued Operations [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	14	16
Provision	2	2
Charge-offs	(4)	(4)
Recoveries	1	2
Ending balance	$ 13	$ 16