Credit Quality - Recorded Investment in Portfolio Loans and Leases by Age and Class (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans and Leases	$ 108,355	$ 94,487
Total Past Due	736	599
Total portfolio loans and leases	109,091	95,086
90-Days past Due and Still Accruing	128	93
30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	444	326
90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	292	273
Commercial and Industrial Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans and Leases	50,877	44,213
Total Past Due	227	127
Total portfolio loans and leases	51,104	44,340
90-Days past Due and Still Accruing	19	4
Commercial and Industrial Loans | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	144	32
Commercial and Industrial Loans | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	83	95
Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans and Leases	4,503	3,277
Total Past Due	20	7
Total portfolio loans and leases	4,523	3,284
90-Days past Due and Still Accruing	6	2
Commercial Mortgage Loans, Owner-occupied | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	3	1
Commercial Mortgage Loans, Owner-occupied | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	17	6
Commercial Mortgage Loans, Nonowner-Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans and Leases	6,169	3,688
Total Past Due	25	2
Total portfolio loans and leases	6,194	3,690
90-Days past Due and Still Accruing	5	0
Commercial Mortgage Loans, Nonowner-Occupied | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	18	1
Commercial Mortgage Loans, Nonowner-Occupied | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	7	1
Commercial construction loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans and Leases	5,263	4,657
Total Past Due	1	0
Total portfolio loans and leases	5,264	4,657
90-Days past Due and Still Accruing	1	0
Commercial construction loans | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	0
Commercial construction loans | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1	0
Commercial Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans and Leases	3,675	3,597
Total Past Due	2	3
Total portfolio loans and leases	3,677	3,600
90-Days past Due and Still Accruing	0	0
Commercial Leases | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2	1
Commercial Leases | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	0	2
Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans and Leases	16,483	15,227
Total Past Due	102	98
Total portfolio loans and leases	16,585	15,325
90-Days past Due and Still Accruing	47	38
Residential Mortgage | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	32	37
Residential Mortgage | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	70	61
Home Equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans and Leases	6,199	6,280
Total Past Due	126	122
Total portfolio loans and leases	6,325	6,402
90-Days past Due and Still Accruing	1	0
Home Equity | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	69	71
Home Equity | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	57	51
Indirect secured consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans and Leases	10,273	8,844
Total Past Due	130	132
Total portfolio loans and leases	10,403	8,976
90-Days past Due and Still Accruing	11	12
Indirect secured consumer loans | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	117	119
Indirect secured consumer loans | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	13	13
Credit Card
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans and Leases	2,351	2,381
Total Past Due	85	89
Total portfolio loans and leases	2,436	2,470
90-Days past Due and Still Accruing	37	37
Credit Card | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	44	47
Credit Card | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	41	42
Other consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans and Leases	2,562	2,323
Total Past Due	18	19
Total portfolio loans and leases	2,580	2,342
90-Days past Due and Still Accruing	1	0
Other consumer loans | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	15	17
Other consumer loans | 90 Days and Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 3	$ 2