Investment Securities - Schedule of Gross Unrealized Losses and Fair Value of Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months Fair Value	$ 151,072	$ 44,540	$ 47,313
12 Months or More Fair Value	8,042	8,682	9,490
Total Fair Value	159,114	53,222	56,803
Less Than 12 Months Unrealized Losses	(6,641)	(386)	(399)
12 Months or More Unrealized Losses	(1,156)	(581)	(589)
Total Unrealized Losses	(7,797)	(967)	(988)
U.S. Government Agencies [Member]
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months Fair Value	13,917	4,994
12 Months or More Fair Value
Total Fair Value	13,917	4,994
Less Than 12 Months Unrealized Losses	(1,028)	(6)
12 Months or More Unrealized Losses
Total Unrealized Losses	(1,028)	(6)
State, County and Municipal Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months Fair Value	46,516	15,595	14,653
12 Months or More Fair Value	3,807	505	505
Total Fair Value	50,323	16,100	15,158
Less Than 12 Months Unrealized Losses	(1,735)	(199)	(132)
12 Months or More Unrealized Losses	(300)	(11)	(12)
Total Unrealized Losses	(2,035)	(210)	(144)
Corporate Debt Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
12 Months or More Fair Value	4,235	4,560	5,551
Total Fair Value	4,235	4,560	5,551
12 Months or More Unrealized Losses	(856)	(547)	(560)
Total Unrealized Losses	(856)	(547)	(560)
Mortgage-Backed Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months Fair Value	90,639	23,951	32,660
12 Months or More Fair Value		3,617	3,434
Total Fair Value	90,639	27,568	36,094
Less Than 12 Months Unrealized Losses	(3,878)	(181)	(267)
12 Months or More Unrealized Losses		(23)	(17)
Total Unrealized Losses	$ (3,878)	$ (204)	$ (284)