Loans and Allowance for Credit Losses, Troubled Debt Restructurings, Current Defaults (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	$ 152	$ 139	$ 257	$ 301
Total Commercial [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	88	37	120	96
Commercial and Industrial Loans [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	38	16	46	30
Commercial Real Estate Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	49	21	72	63
Commercial Real Estate Construction [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	1	0	2	3
Total Consumer [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	64	102	137	205
Real estate 1-4 family first mortgage [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	42	78	94	157
Real estate 1-4 family junior lien mortgage [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	4	8	8	15
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	14	13	27	26
Automobile [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	3	3	6	7
Other revolving credit and installment [Member]
Financing Receivable, Modifications [Line Items]
Recorded investment of defaults	$ 1	$ 0	$ 2	$ 0