Loans and ACL - Risk Rating (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Loans and leases	$ 146,183	$ 143,701
Commercial | Commercial & Industrial
Loans and leases	60,474	59,153
Commercial | Commercial & Industrial | Pass
Loans and leases	59,246	57,700
Commercial | Commercial & Industrial | Special mention
Loans and leases	189	268
Commercial | Commercial & Industrial | Substandard-performing
Loans and leases	796	926
Commercial | Commercial & Industrial | Nonperforming
Loans and leases	243	259
Commercial | CRE
Loans and leases	21,610	21,263
Commercial | CRE | Pass
Loans and leases	21,273	20,862
Commercial | CRE | Special mention
Loans and leases	38	48
Commercial | CRE | Substandard-performing
Loans and leases	238	308
Commercial | CRE | Nonperforming
Loans and leases	61	45
Commercial | Lease Financing
Loans and leases	1,924	1,911
Commercial | Lease Financing | Pass
Loans and leases	1,905	1,881
Commercial | Lease Financing | Special mention
Loans and leases	6	6
Commercial | Lease Financing | Substandard-performing
Loans and leases	4	23
Commercial | Lease Financing | Nonperforming
Loans and leases	9	1
Retail | Residential mortgage
Loans and leases	29,965	28,725
Retail | Residential mortgage | Performing
Loans and leases	29,846	28,596
Retail | Residential mortgage | Nonperforming
Loans and leases	119	129
Retail | Direct
Loans and leases	11,661	11,891
Retail | Direct | Performing
Loans and leases	11,603	11,827
Retail | Direct | Nonperforming
Loans and leases	58	64
Retail | Indirect
Loans and leases	17,140	17,235
Retail | Indirect | Performing
Loans and leases	17,072	17,163
Retail | Indirect | Nonperforming
Loans and leases	$ 68	$ 72