Asset Quality - Breakdown of Allowance for Loan and Lease Losses and Corresponding Loan Balances (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance, Total ALLL - Including Discontinued Operations	$ 33	$ 21
Collectively Evaluated for Impairment, Allowance, Total ALLL - Including Discontinued Operations	867	871
Purchased Credit Impaired, Allowance, Total ALLL - Including Discontinued Operations	4	5
Loans, Outstanding, Total ALLL - Including Discontinued Operations	93,675	90,625
Individually Evaluated for Impairment, Outstanding, Total ALLL - Including Discontinued Operations	540	470
Collectively Evaluated for Impairment, Outstanding, Total ALLL - Including Discontinued Operations	92,638	89,580
Purchased Credit Impaired, Outstanding, Total ALLL - Including Discontinued Operations	497	575
Continuing Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	31	19
Collectively Evaluated for Impairment, Allowance	858	859
Purchase Credit Impairment, Allowance	4	5
Total loans	92,760	89,552
Individually Evaluated for Impairment, Outstanding	517	447
Collectively Evaluated for Impairment, Outstanding	91,746	88,530
Purchase Credit Impairment, Outstanding	497	575
Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	15	5
Collectively Evaluated for Impairment, Allowance	728	734
Purchase Credit Impairment, Allowance	3	4
Total loans	67,479	66,310
Individually Evaluated for Impairment, Outstanding	306	228
Collectively Evaluated for Impairment, Outstanding	66,975	65,841
Purchase Credit Impairment, Outstanding	198	241
Continuing Operations [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	16	14
Collectively Evaluated for Impairment, Allowance	130	125
Purchase Credit Impairment, Allowance	1	1
Total loans	25,281	23,242
Individually Evaluated for Impairment, Outstanding	211	219
Collectively Evaluated for Impairment, Outstanding	24,771	22,689
Purchase Credit Impairment, Outstanding	299	334
Discontinued Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	2	2
Collectively Evaluated for Impairment, Allowance	9	12
Purchase Credit Impairment, Allowance	0	0
Total loans	915	1,073
Individually Evaluated for Impairment, Outstanding	23	23
Collectively Evaluated for Impairment, Outstanding	892	1,050
Purchase Credit Impairment, Outstanding	0	0
Commercial and Industrial [Member] | Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	15	5
Collectively Evaluated for Impairment, Allowance	538	526
Purchase Credit Impairment, Allowance	1	1
Total loans	48,362	45,753
Individually Evaluated for Impairment, Outstanding	234	162
Collectively Evaluated for Impairment, Outstanding	48,078	45,530
Purchase Credit Impairment, Outstanding	50	61
Commercial Mortgage [Member] | Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	0	0
Collectively Evaluated for Impairment, Allowance	132	139
Purchase Credit Impairment, Allowance	2	3
Total loans	13,167	14,285
Individually Evaluated for Impairment, Outstanding	72	66
Collectively Evaluated for Impairment, Outstanding	12,948	14,041
Purchase Credit Impairment, Outstanding	147	178
Commercial Real Estate: Construction [Member] | Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	0	0
Collectively Evaluated for Impairment, Allowance	23	33
Purchase Credit Impairment, Allowance	0	0
Total loans	1,480	1,666
Individually Evaluated for Impairment, Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	1,479	1,664
Purchase Credit Impairment, Outstanding	1	2
Commercial Real Estate Loans [Member] | Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	0	0
Collectively Evaluated for Impairment, Allowance	155	172
Purchase Credit Impairment, Allowance	2	3
Total loans	14,647	15,951
Individually Evaluated for Impairment, Outstanding	72	66
Collectively Evaluated for Impairment, Outstanding	14,427	15,705
Purchase Credit Impairment, Outstanding	148	180
Commercial Lease Financing [Member] | Continuing Operations [Member] | Commercial Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	0	0
Collectively Evaluated for Impairment, Allowance	35	36
Purchase Credit Impairment, Allowance	0	0
Total loans	4,470	4,606
Individually Evaluated for Impairment, Outstanding	0	0
Collectively Evaluated for Impairment, Outstanding	4,470	4,606
Purchase Credit Impairment, Outstanding	0	0
Real Estate - Residential Mortgage [Member] | Continuing Operations [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	4	3
Collectively Evaluated for Impairment, Allowance	2	4
Purchase Credit Impairment, Allowance	1	0
Total loans	6,527	5,513
Individually Evaluated for Impairment, Outstanding	43	49
Collectively Evaluated for Impairment, Outstanding	6,202	5,150
Purchase Credit Impairment, Outstanding	282	314
Home Equity Loans [Member] | Continuing Operations [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	9	8
Collectively Evaluated for Impairment, Allowance	24	26
Purchase Credit Impairment, Allowance	0	1
Total loans	10,456	11,142
Individually Evaluated for Impairment, Outstanding	126	127
Collectively Evaluated for Impairment, Outstanding	10,316	10,998
Purchase Credit Impairment, Outstanding	14	17
Consumer Direct Loans [Member] | Continuing Operations [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	0	0
Collectively Evaluated for Impairment, Allowance	34	30
Purchase Credit Impairment, Allowance	0	0
Total loans	2,789	1,809
Individually Evaluated for Impairment, Outstanding	4	4
Collectively Evaluated for Impairment, Outstanding	2,782	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 Loss [Line Items]
Individually Evaluated for Impairment, Allowance	0	0
Collectively Evaluated for Impairment, Allowance	46	48
Purchase Credit Impairment, Allowance	0	0
Total loans	1,105	1,144
Individually Evaluated for Impairment, Outstanding	3	3
Collectively Evaluated for Impairment, Outstanding	1,102	1,141
Purchase Credit Impairment, Outstanding	0	0
Consumer Indirect Loans [Member] | Continuing Operations [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Impairment, Allowance	3	3
Collectively Evaluated for Impairment, Allowance	24	17
Purchase Credit Impairment, Allowance	0	0
Total loans	4,404	3,634
Individually Evaluated for Impairment, Outstanding	35	36
Collectively Evaluated for Impairment, Outstanding	4,369	3,598
Purchase Credit Impairment, Outstanding	0	0
Education Lending [Member] | Discontinued Operations [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans at fair value	$ 2	$ 2