Income Taxes - Provision for Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Expense Benefit [Line Items]
Federal, Currently payable	$ 6,423	$ 245	$ 4,784
State, Currently payable	50	50	50
Total current income tax expense benefit	6,473	295	4,834
Federal, Deferred	(1,152)	713	(2,347)
State, Deferred	838	710	237
Total deferred income tax expense benefit	(314)	1,423	(2,110)
Income tax provision	$ 6,159	$ 1,718	$ 2,724