Loans and Allowance for Credit Losses, Commitments to Lend (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	$ 430,214	$ 423,665
Total Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	248,150	239,323
Commercial and Industrial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	223,784	215,626
Commercial Real Estate Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	6,887	6,165
Commercial Real Estate Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	9,328	9,109
Foreign Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	8,151	8,423
Total Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	182,064	184,342
Real estate 1-4 family first mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	37,064	42,657
Real estate 1-4 family junior lien mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	50,237	50,934
Credit Card [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	73,911	70,960
Other revolving credit and installment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unfunded credit commitments	$ 20,852	$ 19,791