Loans and Allowance for Credit Losses, Commitments to Lend (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	$ 510,876	$ 497,242
Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	306,664	299,817
Commercial and Industrial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	283,008	278,093
Commercial Real Estate Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	7,542	6,134
Commercial Real Estate Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	16,114	15,587
Commercial Lease Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	0	3
Total Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	204,212	197,425
Real estate 1-4 family first mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	36,114	32,055
Real estate 1-4 family junior lien mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	44,348	45,492
Credit Card [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	97,184	95,062
Other revolving credit and installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	$ 26,566	$ 24,816