Loans and ACL - Risk Rating (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Loans and leases	$ 146,690	$ 143,701
Commercial | Commercial & Industrial
Loans and leases	59,722	59,153
Commercial | Commercial & Industrial | Pass
Loans and leases	58,609	57,700
Commercial | Commercial & Industrial | Special mention
Loans and leases	173	268
Commercial | Commercial & Industrial | Substandard-performing
Loans and leases	702	926
Commercial | Commercial & Industrial | Nonperforming
Loans and leases	238	259
Commercial | CRE
Loans and leases	21,466	21,263
Commercial | CRE | Pass
Loans and leases	21,122	20,862
Commercial | CRE | Special mention
Loans and leases	57	48
Commercial | CRE | Substandard-performing
Loans and leases	241	308
Commercial | CRE | Nonperforming
Loans and leases	46	45
Commercial | Lease Financing
Loans and leases	2,028	1,911
Commercial | Lease Financing | Pass
Loans and leases	2,016	1,881
Commercial | Lease Financing | Special mention
Loans and leases	2	6
Commercial | Lease Financing | Substandard-performing
Loans and leases	4	23
Commercial | Lease Financing | Nonperforming
Loans and leases	6	1
Retail | Residential mortgage
Loans and leases	30,821	28,725
Retail | Residential mortgage | Performing
Loans and leases	30,701	28,596
Retail | Residential mortgage | Nonperforming
Loans and leases	120	129
Retail | Direct
Loans and leases	11,618	11,891
Retail | Direct | Performing
Loans and leases	11,563	11,827
Retail | Direct | Nonperforming
Loans and leases	55	64
Retail | Indirect
Loans and leases	17,468	17,235
Retail | Indirect | Performing
Loans and leases	17,396	17,163
Retail | Indirect | Nonperforming
Loans and leases	$ 72	$ 72