Investment Securities - Schedule of Gross Unrealized Losses and Fair Value of Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months Unrealized Losses	$ (792)	$ (386)	$ (444)
12 Months or More Unrealized Losses	(604)	(581)	(481)
Total Unrealized Losses	(1,396)	(967)	(925)
Less Than 12 Months Fair Value	74,592	44,540	55,880
12 Months or More Fair Value	6,131	8,682	8,903
Total Fair Value	80,723	53,222	64,783
U.S. government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months Unrealized Losses		(6)	(44)
Total Unrealized Losses		(6)	(44)
Less Than 12 Months Fair Value		4,994	8,960
Total Fair Value		4,994	8,960
State, county and municipal securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months Unrealized Losses	(138)	(199)	(166)
12 Months or More Unrealized Losses	(9)	(11)
Total Unrealized Losses	(147)	(210)	(166)
Less Than 12 Months Fair Value	19,159	15,595	8,960
12 Months or More Fair Value	505	505
Total Fair Value	19,664	16,100	8,960
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months Unrealized Losses	(6)
12 Months or More Unrealized Losses	(594)	(547)	(471)
Total Unrealized Losses	(600)	(547)	(471)
Less Than 12 Months Fair Value	244		100
12 Months or More Fair Value	4,506	4,560	6,611
Total Fair Value	4,750	4,560	6,711
Mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months Unrealized Losses	(648)	(181)	(234)
12 Months or More Unrealized Losses	(1)	(23)	(10)
Total Unrealized Losses	(649)	(204)	(244)
Less Than 12 Months Fair Value	55,189	23,951	37,860
12 Months or More Fair Value	1,120	3,617	2,292
Total Fair Value	$ 56,309	$ 27,568	$ 40,152