Securities - Schedule of Gross Unrealized Losses and Fair Value of Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	$ 51,798	$ 156,316
12 Months or More, Estimated Fair Value	81,155	32,008
Total Estimated Fair Value	132,953	188,324
Less Than 12 Months, Unrealized Losses	(291)	(5,396)
12 Months or More, Unrealized Losses	(1,820)	(2,098)
Total Unrealized Losses	(2,111)	(7,494)
US Government Agencies [Member]
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value		13,926
12 Months or More, Estimated Fair Value	14,678
Total Estimated Fair Value	14,678	13,926
Less Than 12 Months, Unrealized Losses		(1,021)
12 Months or More, Unrealized Losses	(275)
Total Unrealized Losses	(275)	(1,021)
State, County and Municipal Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	15,038	47,401
12 Months or More, Estimated Fair Value	19,665	3,794
Total Estimated Fair Value	34,703	51,195
Less Than 12 Months, Unrealized Losses	(70)	(1,882)
12 Months or More, Unrealized Losses	(363)	(292)
Total Unrealized Losses	(433)	(2,174)
Corporate Debt Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
12 Months or More, Estimated Fair Value		4,826
Total Estimated Fair Value		4,826
12 Months or More, Unrealized Losses		(261)
Total Unrealized Losses		(261)
Mortgage-Backed Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Less Than 12 Months, Estimated Fair Value	36,760	94,989
12 Months or More, Estimated Fair Value	46,812	23,388
Total Estimated Fair Value	83,572	118,377
Less Than 12 Months, Unrealized Losses	(221)	(2,493)
12 Months or More, Unrealized Losses	(1,182)	(1,545)
Total Unrealized Losses	$ (1,403)	$ (4,038)