Credit Quality - Summary of the Credit Risk Profile of the Commercial Portfolio Segment by Class (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Modifications [Line Items]
Total loans and leases	$ 109,091	$ 95,086
Commercial and Industrial Loans
Financing Receivable, Modifications [Line Items]
Total loans and leases	51,104	44,340
Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Modifications [Line Items]
Total loans and leases	4,523	3,284
Commercial Mortgage Loans, Nonowner-Occupied
Financing Receivable, Modifications [Line Items]
Total loans and leases	6,194	3,690
Commercial Construction Loans
Financing Receivable, Modifications [Line Items]
Total loans and leases	5,264	4,657
Commercial Leases
Financing Receivable, Modifications [Line Items]
Total loans and leases	3,677	3,600
Commercial Portfolio Segment
Financing Receivable, Modifications [Line Items]
Total loans and leases	70,762	59,571
Commercial Portfolio Segment | Commercial and Industrial Loans
Financing Receivable, Modifications [Line Items]
Total loans and leases	51,104	44,340
Commercial Portfolio Segment | Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Modifications [Line Items]
Total loans and leases	4,523	3,284
Commercial Portfolio Segment | Commercial Mortgage Loans, Nonowner-Occupied
Financing Receivable, Modifications [Line Items]
Total loans and leases	6,194	3,690
Commercial Portfolio Segment | Commercial Construction Loans
Financing Receivable, Modifications [Line Items]
Total loans and leases	5,264	4,657
Commercial Portfolio Segment | Commercial Leases
Financing Receivable, Modifications [Line Items]
Total loans and leases	3,677	3,600
Pass | Commercial Portfolio Segment
Financing Receivable, Modifications [Line Items]
Total loans and leases	67,488	57,581
Pass | Commercial Portfolio Segment | Commercial and Industrial Loans
Financing Receivable, Modifications [Line Items]
Total loans and leases	48,610	42,695
Pass | Commercial Portfolio Segment | Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Modifications [Line Items]
Total loans and leases	4,206	3,122
Pass | Commercial Portfolio Segment | Commercial Mortgage Loans, Nonowner-Occupied
Financing Receivable, Modifications [Line Items]
Total loans and leases	5,880	3,632
Pass | Commercial Portfolio Segment | Commercial Construction Loans
Financing Receivable, Modifications [Line Items]
Total loans and leases	5,218	4,657
Pass | Commercial Portfolio Segment | Commercial Leases
Financing Receivable, Modifications [Line Items]
Total loans and leases	3,574	3,475
Special Mention | Commercial Portfolio Segment
Financing Receivable, Modifications [Line Items]
Total loans and leases	1,332	901
Special Mention | Commercial Portfolio Segment | Commercial and Industrial Loans
Financing Receivable, Modifications [Line Items]
Total loans and leases	1,101	779
Special Mention | Commercial Portfolio Segment | Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Modifications [Line Items]
Total loans and leases	103	23
Special Mention | Commercial Portfolio Segment | Commercial Mortgage Loans, Nonowner-Occupied
Financing Receivable, Modifications [Line Items]
Total loans and leases	95	27
Special Mention | Commercial Portfolio Segment | Commercial Construction Loans
Financing Receivable, Modifications [Line Items]
Total loans and leases	5	0
Special Mention | Commercial Portfolio Segment | Commercial Leases
Financing Receivable, Modifications [Line Items]
Total loans and leases	28	72
Substandard | Commercial Portfolio Segment
Financing Receivable, Modifications [Line Items]
Total loans and leases	1,936	1,076
Substandard | Commercial Portfolio Segment | Commercial and Industrial Loans
Financing Receivable, Modifications [Line Items]
Total loans and leases	1,387	853
Substandard | Commercial Portfolio Segment | Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Modifications [Line Items]
Total loans and leases	214	139
Substandard | Commercial Portfolio Segment | Commercial Mortgage Loans, Nonowner-Occupied
Financing Receivable, Modifications [Line Items]
Total loans and leases	219	31
Substandard | Commercial Portfolio Segment | Commercial Construction Loans
Financing Receivable, Modifications [Line Items]
Total loans and leases	41	0
Substandard | Commercial Portfolio Segment | Commercial Leases
Financing Receivable, Modifications [Line Items]
Total loans and leases	75	53
Doubtful | Commercial Portfolio Segment
Financing Receivable, Modifications [Line Items]
Total loans and leases	6	13
Doubtful | Commercial Portfolio Segment | Commercial and Industrial Loans
Financing Receivable, Modifications [Line Items]
Total loans and leases	6	13
Doubtful | Commercial Portfolio Segment | Commercial Mortgage Loans, Owner-occupied
Financing Receivable, Modifications [Line Items]
Total loans and leases	0	0
Doubtful | Commercial Portfolio Segment | Commercial Mortgage Loans, Nonowner-Occupied
Financing Receivable, Modifications [Line Items]
Total loans and leases	0	0
Doubtful | Commercial Portfolio Segment | Commercial Construction Loans
Financing Receivable, Modifications [Line Items]
Total loans and leases	0	0
Doubtful | Commercial Portfolio Segment | Commercial Leases
Financing Receivable, Modifications [Line Items]
Total loans and leases	$ 0	$ 0