Loans and ACL - Schedule of Credit Exposure Credit Risk Profile by Internal Loan Risk Rating, Excluding PCI Loans (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable [Line Items]
Loans and leases	$ 143,701	$ 143,322
Commercial | Commercial and industrial
Financing Receivable [Line Items]
Loans and leases	59,153	57,739
Commercial | Commercial and industrial | Pass
Financing Receivable [Line Items]
Loans and leases	57,700	55,881
Commercial | Commercial and industrial | Special mention
Financing Receivable [Line Items]
Loans and leases	268	343
Commercial | Commercial and industrial | Substandard-performing
Financing Receivable [Line Items]
Loans and leases	926	1,146
Commercial | Commercial and industrial | Nonperforming
Financing Receivable [Line Items]
Loans and leases	259	369
Commercial | CRE
Financing Receivable [Line Items]
Loans and leases	21,263	19,764
Commercial | CRE | Pass
Financing Receivable [Line Items]
Loans and leases	20,862	19,186
Commercial | CRE | Special mention
Financing Receivable [Line Items]
Loans and leases	48	162
Commercial | CRE | Substandard-performing
Financing Receivable [Line Items]
Loans and leases	308	359
Commercial | CRE | Nonperforming
Financing Receivable [Line Items]
Loans and leases	45	57
Commercial | Lease financing
Financing Receivable [Line Items]
Loans and leases	1,911	1,677
Commercial | Lease financing | Pass
Financing Receivable [Line Items]
Loans and leases	1,881	1,641
Commercial | Lease financing | Special mention
Financing Receivable [Line Items]
Loans and leases	6	4
Commercial | Lease financing | Substandard-performing
Financing Receivable [Line Items]
Loans and leases	23	28
Commercial | Lease financing | Nonperforming
Financing Receivable [Line Items]
Loans and leases	1	4
Retail | Residential mortgage
Financing Receivable [Line Items]
Loans and leases	28,725	29,921
Retail | Residential mortgage | Performing
Financing Receivable [Line Items]
Loans and leases	28,596	29,749
Retail | Residential mortgage | Nonperforming
Financing Receivable [Line Items]
Loans and leases	129	172
Retail | Direct
Financing Receivable [Line Items]
Loans and leases	11,891	12,092
Retail | Direct | Performing
Financing Receivable [Line Items]
Loans and leases	11,827	12,029
Retail | Direct | Nonperforming
Financing Receivable [Line Items]
Loans and leases	64	63
Retail | Indirect
Financing Receivable [Line Items]
Loans and leases	17,235	18,564
Retail | Indirect | Performing
Financing Receivable [Line Items]
Loans and leases	17,163	18,493
Retail | Indirect | Nonperforming
Financing Receivable [Line Items]
Loans and leases	$ 72	$ 71