Securities - Unrealized Loss Positions (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	$ 25,759	$ 34,816
Less than 12 months, Unrealized Loss	(478)	(860)
12 months or more, Fair Value	5,745	1,308
12 months or more, Unrealized Loss	(133)	(12)
Fair Value, Total	31,504	36,124
Total Unrealized Loss	(611)	(872)
Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	500	995
Less than 12 months, Unrealized Loss	(1)	(5)
Fair Value, Total	500	995
Total Unrealized Loss	(1)	(5)
US Government Agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	18,052	20,933
Less than 12 months, Unrealized Loss	(298)	(396)
12 months or more, Fair Value	4,792	1,308
12 months or more, Unrealized Loss	(88)	(12)
Fair Value, Total	22,844	22,241
Total Unrealized Loss	(386)	(408)
State and Municipal Obligations
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	7,207	12,888
Less than 12 months, Unrealized Loss	(179)	(459)
12 months or more, Fair Value	953
12 months or more, Unrealized Loss	(45)
Fair Value, Total	8,160	12,888
Total Unrealized Loss	$ (224)	$ (459)