Loans and ACL (Commercial Credit Exposure Credit Risk Profile by Internal Loan Risk Rating) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Loans and leases	$ 118,689	$ 115,917
Commercial and Industrial, Excluding Covered [Member]
Loans and leases	40,048	38,508
Commercial and Industrial, Excluding Covered [Member] | Pass Grade Credit [Member]
Loans and leases	38,555	36,804
Commercial and Industrial, Excluding Covered [Member] | Special Mention Grade Credit [Member]
Loans and leases	230	219
Commercial and Industrial, Excluding Covered [Member] | Substandard Performing [Member]
Loans and leases	1,004	1,122
Commercial and Industrial, Excluding Covered [Member] | Nonperforming [Member]
Loans and leases	259	363
CRE Income Producing Properties, Excluding Covered [Member]
Loans and leases	10,662	10,228
CRE Income Producing Properties, Excluding Covered [Member] | Pass Grade Credit [Member]
Loans and leases	10,158	9,528
CRE Income Producing Properties, Excluding Covered [Member] | Special Mention Grade Credit [Member]
Loans and leases	52	52
CRE Income Producing Properties, Excluding Covered [Member] | Substandard Performing [Member]
Loans and leases	371	536
CRE Income Producing Properties, Excluding Covered [Member] | Nonperforming [Member]
Loans and leases	81	112
CRE Construction And Development, Excluding Covered [Member]
Loans and leases	2,733	2,382
CRE Construction And Development, Excluding Covered [Member] | Pass Grade Credit [Member]
Loans and leases	2,577	2,149
CRE Construction And Development, Excluding Covered [Member] | Special Mention Grade Credit [Member]
Loans and leases	6	17
CRE Construction And Development, Excluding Covered [Member] | Substandard Performing [Member]
Loans and leases	113	164
CRE Construction And Development, Excluding Covered [Member] | Nonperforming [Member]
Loans and leases	37	52
Commercial Other Lending Subsidiaries, Excluding Covered [Member]
Loans and leases	5,263	4,502
Commercial Other Lending Subsidiaries, Excluding Covered [Member] | Pass Grade Credit [Member]
Loans and leases	5,230	4,464
Commercial Other Lending Subsidiaries, Excluding Covered [Member] | Special Mention Grade Credit [Member]
Loans and leases	5	8
Commercial Other Lending Subsidiaries, Excluding Covered [Member] | Substandard Performing [Member]
Loans and leases	19	29
Commercial Other Lending Subsidiaries, Excluding Covered [Member] | Nonperforming [Member]
Loans and leases	$ 9	$ 1