Premises and Equipment - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Capital Leased Assets, Gross	$ 6	$ 7
Operating Leases, Rent Expense	219	184	179
Depreciation, Depletion and Amortization	$ 188	$ 181	$ 177