Other Non-Interest Income and Expense (Narrative) (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other Non Operating Income And Expenses [Line Items]
Minimum percentage of the aggregate total net interest income and total non interest income required for amounts to be stated separately	1.00%	1.00%	1.00%