Summary of Interest Foregone on Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Interest Income That Would Have Been Recognized Had Impaired Loans Performed in Accordance With Their Original Terms	$ 1,382	$ 3,063	$ 4,315	$ 7,143
Less: Interest Income Recognized on Impaired Loans	(1,111)	(1,522)	(3,456)	(2,815)
Interest Foregone on Impaired Loans	$ 271	$ 1,541	$ 859	$ 4,328