Loans and Leases - Recorded Investment in Each Class of Total Loans and Leases by Credit Quality Indicator (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 23,294	$ 19,757
Commercial and Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	22,533	18,888
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	98	27
Lease Financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	663	842
Investment grade
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	18,627	15,758
Investment grade | Commercial and Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	17,866	14,889
Investment grade | Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	98	27
Investment grade | Lease Financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	663	842
Speculative
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	4,638	3,984
Speculative | Commercial and Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	4,638	3,984
Speculative | Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	0
Speculative | Lease Financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0	0
Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	29
Special Mention | Commercial and Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	29
Special Mention | Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	0
Special Mention | Lease Financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases	$ 0
Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases		15
Substandard | Commercial and Financial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases		15
Substandard | Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases		0
Substandard | Lease Financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases		$ 0