Securities - Unrealized Loss Positions (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	$ 42,463	$ 28,304
Less than 12 months, Unrealized Loss	(1,147)	(370)
12 months or more, Fair Value	19,726	21,971
12 months or more, Unrealized Loss	(984)	(474)
Fair Value, Total	62,189	50,275
Total Unrealized Loss	(2,131)	(844)
US Government Agencies Agencies and Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	31,602	25,053
Less than 12 months, Unrealized Loss	(1,046)	(353)
12 months or more, Fair Value	14,323	16,184
12 months or more, Unrealized Loss	(661)	(334)
Fair Value, Total	45,925	41,237
Total Unrealized Loss	(1,707)	(687)
State and Municipal Obligations
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	10,363	2,753
Less than 12 months, Unrealized Loss	(99)	(15)
12 months or more, Fair Value	5,403	5,787
12 months or more, Unrealized Loss	(323)	(140)
Fair Value, Total	15,766	8,540
Total Unrealized Loss	(422)	(155)
Corporate Bonds
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	498	498
Less than 12 months, Unrealized Loss	(2)	(2)
Fair Value, Total	498	498
Total Unrealized Loss	$ (2)	$ (2)