Loans and Allowance for Credit Losses, PCI Loans Outstanding (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2008
PCI loans [Abstract]
Purchased Credit Impaired Loans (carrying value)	$ 24,236	$ 26,727	$ 58,797
Total PCI loans (unpaid principal balance)	34,320	38,229	98,182
Total Commercial [Member]
PCI loans [Abstract]
Purchased Credit Impaired Loans (carrying value)	1,859	2,504	18,704
Commercial and Industrial Loans [Member]
PCI loans [Abstract]
Purchased Credit Impaired Loans (carrying value)	246	215	4,580
Commercial Real Estate Mortgage [Member]
PCI loans [Abstract]
Purchased Credit Impaired Loans (carrying value)	973	1,136	5,803
Commercial Real Estate Construction [Member]
PCI loans [Abstract]
Purchased Credit Impaired Loans (carrying value)	237	433	6,462
Foreign Loans [Member]
PCI loans [Abstract]
Purchased Credit Impaired Loans (carrying value)	403	720	1,859
Total Consumer [Member]
PCI loans [Abstract]
Purchased Credit Impaired Loans (carrying value)	22,377	24,223	40,093
Real estate 1-4 family first mortgage [Member]
PCI loans [Abstract]
Purchased Credit Impaired Loans (carrying value)	22,271	24,100	39,214
Real estate 1-4 family junior lien mortgage [Member]
PCI loans [Abstract]
Purchased Credit Impaired Loans (carrying value)	106	123	728
Automobile [Member]
PCI loans [Abstract]
Purchased Credit Impaired Loans (carrying value)	$ 0	$ 0	$ 151