Investment Securities - Schedule of Gross Unrealized Losses and Fair Value of Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 56,043	$ 51,798	$ 103,393
12 Months or More, Fair Value	47,020	81,155	44,459
Total Fair Value	103,063	132,953	147,852
Less Than 12 Months, Unrealized Losses	(464)	(291)	(3,052)
12 Months or More, Unrealized Losses	(1,200)	(1,820)	(2,290)
Total Unrealized Losses	(1,664)	(2,111)	(5,342)
US Government Agencies [Member]
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months, Fair Value			9,353
12 Months or More, Fair Value	4,958	14,678	4,792
Total Fair Value	4,958	14,678	14,145
Less Than 12 Months, Unrealized Losses			(595)
12 Months or More, Unrealized Losses	(42)	(275)	(208)
Total Unrealized Losses	(42)	(275)	(803)
State, County and Municipal Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months, Fair Value	4,675	15,038	38,937
12 Months or More, Fair Value	10,579	19,665	3,612
Total Fair Value	15,254	34,703	42,549
Less Than 12 Months, Unrealized Losses	(34)	(70)	(1,238)
12 Months or More, Unrealized Losses	(201)	(363)	(243)
Total Unrealized Losses	(235)	(433)	(1,481)
Corporate Debt Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months, Fair Value	5,007
12 Months or More, Fair Value			4,871
Total Fair Value	5,007		4,871
Less Than 12 Months, Unrealized Losses	(52)
12 Months or More, Unrealized Losses			(209)
Total Unrealized Losses	(52)		(209)
Mortgage-Backed Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months, Fair Value	46,361	36,760	55,103
12 Months or More, Fair Value	31,483	46,812	31,184
Total Fair Value	77,844	83,572	86,287
Less Than 12 Months, Unrealized Losses	(378)	(221)	(1,219)
12 Months or More, Unrealized Losses	(957)	(1,182)	(1,630)
Total Unrealized Losses	$ (1,335)	$ (1,403)	$ (2,849)