Asset Quality - Breakdown of Allowance for Loan and Lease Losses and Corresponding Loan Balances (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance, Total ALLL - Including Discontinued Operations	$ 18	$ 21
Collectively Evaluated for Impairment, Allowance, Total ALLL - Including Discontinued Operations	873	871
Purchased Credit Impaired, Allowance, Total ALLL - Including Discontinued Operations	5	5
Loans, Outstanding, Total ALLL - Including Discontinued Operations	91,197	90,625
Individually Evaluated for Impairment, Outstanding, Total ALLL - Including Discontinued Operations	472	470
Collectively Evaluated for Impairment, Outstanding, Total ALLL - Including Discontinued Operations	90,174	89,580
Purchased Credit Impaired, Outstanding, Total ALLL - Including Discontinued Operations	551	575
Continuing Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	16	19
Collectively Evaluated for Impairment, Allowance	862	859
Purchase Credit Impairment, Allowance	5	5
Total loans	90,178	89,552
Individually Evaluated for Impairment, Outstanding	449	447
Collectively Evaluated for Impairment, Outstanding	89,178	88,530
Purchase Credit Impairment, Outstanding	551	575
Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	2	5
Collectively Evaluated for Impairment, Allowance	732	734
Purchase Credit Impairment, Allowance	3	4
Total loans	66,745	66,310
Individually Evaluated for Impairment, Outstanding	230	228
Collectively Evaluated for Impairment, Outstanding	66,284	65,841
Purchase Credit Impairment, Outstanding	231	241
Continuing Operations [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	14	14
Collectively Evaluated for Impairment, Allowance	130	125
Purchase Credit Impairment, Allowance	2	1
Total loans	23,433	23,242
Individually Evaluated for Impairment, Outstanding	219	219
Collectively Evaluated for Impairment, Outstanding	22,894	22,689
Purchase Credit Impairment, Outstanding	320	334
Discontinued Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	2	2
Collectively Evaluated for Impairment, Allowance	11	12
Purchase Credit Impairment, Allowance	0	0
Total loans	1,019	1,073
Individually Evaluated for Impairment, Outstanding	23	23
Collectively Evaluated for Impairment, Outstanding	996	1,050
Purchase Credit Impairment, Outstanding	0	0
Commercial and Industrial [Member] | Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	2	5
Collectively Evaluated for Impairment, Allowance	527	526
Purchase Credit Impairment, Allowance	1	1
Total loans	46,474	45,753
Individually Evaluated for Impairment, Outstanding	169	162
Collectively Evaluated for Impairment, Outstanding	46,247	45,530
Purchase Credit Impairment, Outstanding	58	61
Commercial Real Estate: Commercial Mortgage [Member] | Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	0	0
Collectively Evaluated for Impairment, Allowance	142	139
Purchase Credit Impairment, Allowance	2	3
Total loans	14,344	14,285
Individually Evaluated for Impairment, Outstanding	61	66
Collectively Evaluated for Impairment, Outstanding	14,111	14,041
Purchase Credit Impairment, Outstanding	172	178
Commercial Real Estate: Construction [Member] | Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	0	0
Collectively Evaluated for Impairment, Allowance	28	33
Purchase Credit Impairment, Allowance	0	0
Total loans	1,420	1,666
Individually Evaluated for Impairment, Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	1,419	1,664
Purchase Credit Impairment, Outstanding	1	2
Commercial Real Estate Loans [Member] | Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	0	0
Collectively Evaluated for Impairment, Allowance	170	172
Purchase Credit Impairment, Allowance	2	3
Total loans	15,764	15,951
Individually Evaluated for Impairment, Outstanding	61	66
Collectively Evaluated for Impairment, Outstanding	15,530	15,705
Purchase Credit Impairment, Outstanding	173	180
Commercial Lease Financing [Member] | Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	0	0
Collectively Evaluated for Impairment, Allowance	35	36
Purchase Credit Impairment, Allowance	0	0
Total loans	4,507	4,606
Individually Evaluated for Impairment, Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	4,507	4,606
Purchase Credit Impairment, Outstanding	0	0
Real Estate - Residential Mortgage [Member] | Continuing Operations [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	3	3
Collectively Evaluated for Impairment, Allowance	4	4
Purchase Credit Impairment, Allowance	1	0
Total loans	5,615	5,513
Individually Evaluated for Impairment, Outstanding	47	49
Collectively Evaluated for Impairment, Outstanding	5,267	5,150
Purchase Credit Impairment, Outstanding	301	314
Home Equity Loans [Member] | Continuing Operations [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	8	8
Collectively Evaluated for Impairment, Allowance	27	26
Purchase Credit Impairment, Allowance	1	1
Total loans	10,846	11,142
Individually Evaluated for Impairment, Outstanding	128	127
Collectively Evaluated for Impairment, Outstanding	10,702	10,998
Purchase Credit Impairment, Outstanding	16	17
Consumer Direct Loans [Member] | Continuing Operations [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	0	0
Collectively Evaluated for Impairment, Allowance	33	30
Purchase Credit Impairment, Allowance	0	0
Total loans	2,165	1,809
Individually Evaluated for Impairment, Outstanding	4	4
Collectively Evaluated for Impairment, Outstanding	2,158	1,802
Purchase Credit Impairment, Outstanding	3	3
Consumer Credit Card Financing Receivable [Member] | Continuing Operations [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	0	0
Collectively Evaluated for Impairment, Allowance	47	48
Purchase Credit Impairment, Allowance	0	0
Total loans	1,086	1,144
Individually Evaluated for Impairment, Outstanding	3	3
Collectively Evaluated for Impairment, Outstanding	1,083	1,141
Purchase Credit Impairment, Outstanding	0	0
Consumer Indirect Loans [Member] | Continuing Operations [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Individually Evaluated for Impairment, Allowance	3	3
Collectively Evaluated for Impairment, Allowance	19	17
Purchase Credit Impairment, Allowance	0	0
Total loans	3,721	3,634
Individually Evaluated for Impairment, Outstanding	37	36
Collectively Evaluated for Impairment, Outstanding	3,684	3,598
Purchase Credit Impairment, Outstanding	0	0
Education Lending [Member] | Discontinued Operations [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans at fair value	$ 2	$ 2