Loans and ACL - Risk Rating (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Loans and leases	$ 143,017	$ 143,701
Commercial | Commercial & Industrial
Loans and leases	59,132	59,153
Commercial | Commercial & Industrial | Pass
Loans and leases	57,844	57,700
Commercial | Commercial & Industrial | Special mention
Loans and leases	155	268
Commercial | Commercial & Industrial | Substandard-performing
Loans and leases	876	926
Commercial | Commercial & Industrial | Nonperforming
Loans and leases	257	259
Commercial | CRE
Loans and leases	21,497	21,263
Commercial | CRE | Pass
Loans and leases	21,127	20,862
Commercial | CRE | Special mention
Loans and leases	29	48
Commercial | CRE | Substandard-performing
Loans and leases	274	308
Commercial | CRE | Nonperforming
Loans and leases	67	45
Commercial | Lease Financing
Loans and leases	1,886	1,911
Commercial | Lease Financing | Pass
Loans and leases	1,867	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	13	1
Retail | Residential mortgage
Loans and leases	28,792	28,725
Retail | Residential mortgage | Performing
Loans and leases	28,665	28,596
Retail | Residential mortgage | Nonperforming
Loans and leases	127	129
Retail | Direct
Loans and leases	11,675	11,891
Retail | Direct | Performing
Loans and leases	11,611	11,827
Retail | Direct | Nonperforming
Loans and leases	64	64
Retail | Indirect
Loans and leases	16,680	17,235
Retail | Indirect | Performing
Loans and leases	16,606	17,163
Retail | Indirect | Nonperforming
Loans and leases	$ 74	$ 72