Foreclosed Real Estate and Repossessed Personal Property - Changes in Foreclosed Real Estate Portfolio (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Foreclosed Assets [Line Items]
Foreclosed real estate, beginning of period	$ 10,911	$ 27,663
Plus: New foreclosed real estate	1,270	2,276
Less: Proceeds from sale of foreclosed real estate	(765)	(1,922)
Plus: Gain (loss) on sale of foreclosed real estate	57	16
Less: Writedowns and losses charged to expense	(416)	(1,332)
Foreclosed real estate, end of period	$ 11,057	$ 26,701