Loans and ACL (Commercial Credit Exposure Credit Risk Profile by Internal Loan Risk Rating) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Loans and leases	$ 119,884	$ 115,917
Commercial and Industrial [Member]
Loans and leases	41,454	38,508
Commercial and Industrial [Member] | Pass [Member]
Loans and leases	40,055	36,804
Commercial and Industrial [Member] | Special Mention [Member]
Loans and leases	163	219
Commercial and Industrial [Member] | Substandard Performing [Member]
Loans and leases	997	1,122
Commercial and Industrial [Member] | Nonperforming [Member]
Loans and leases	239	363
CRE Income Producing Properties [Member]
Loans and leases	10,722	10,228
CRE Income Producing Properties [Member] | Pass [Member]
Loans and leases	10,253	9,527
CRE Income Producing Properties [Member] | Special Mention [Member]
Loans and leases	67	52
CRE Income Producing Properties [Member] | Substandard Performing [Member]
Loans and leases	328	536
CRE Income Producing Properties [Member] | Nonperforming [Member]
Loans and leases	74	113
CRE Construction And Development [Member]
Loans and leases	2,735	2,382
CRE Construction And Development [Member] | Pass [Member]
Loans and leases	2,615	2,150
CRE Construction And Development [Member] | Special Mention [Member]
Loans and leases	7	17
CRE Construction And Development [Member] | Substandard Performing [Member]
Loans and leases	87	164
CRE Construction And Development [Member] | Nonperforming [Member]
Loans and leases	26	51
Commercial Other Lending Subsidiaries [Member]
Loans and leases	5,356	4,502
Commercial Other Lending Subsidiaries [Member] | Pass [Member]
Loans and leases	5,317	4,464
Commercial Other Lending Subsidiaries [Member] | Special Mention [Member]
Loans and leases	10	8
Commercial Other Lending Subsidiaries [Member] | Substandard Performing [Member]
Loans and leases	25	29
Commercial Other Lending Subsidiaries [Member] | Nonperforming [Member]
Loans and leases	$ 4	$ 1