Securities - Unrealized Loss Positions (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	$ 34,816	$ 16,932
Less than 12 months, Unrealized Loss	(860)	(163)
12 months or more, Fair Value	1,308	4,900
12 months or more, Unrealized Loss	(12)	(53)
Fair Value, Total	36,124	21,832
Total Unrealized Loss	(872)	(216)
Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	995	495
Less than 12 months, Unrealized Loss	(5)	(5)
Fair Value, Total	995	495
Total Unrealized Loss	(5)	(5)
US Government Agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	20,933	13,871
Less than 12 months, Unrealized Loss	(396)	(141)
12 months or more, Fair Value	1,308	1,619
12 months or more, Unrealized Loss	(12)	(15)
Fair Value, Total	22,241	15,490
Total Unrealized Loss	(408)	(156)
State and Municipal Obligations
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	12,888	2,566
Less than 12 months, Unrealized Loss	(459)	(17)
12 months or more, Fair Value		3,281
12 months or more, Unrealized Loss		(38)
Fair Value, Total	12,888	5,847
Total Unrealized Loss	$ (459)	$ (55)