Securities - Securities with Unrealized Losses Not Recognized in Income (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	$ 73,027	$ 65,891
12 Months or less, Unrealized Loss	(984)	(1,185)
More than 12 months, Fair Value	3,441	4,261
More than 12 months, Unrealized Loss	(58)	(63)
Total Fair Value	76,468	70,152
Total Unrealized Loss	(1,042)	(1,248)
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	14,197	13,271
12 Months or less, Unrealized Loss	(57)	(61)
More than 12 months, Fair Value	851	893
More than 12 months, Unrealized Loss	(15)	(16)
Total Fair Value	15,048	14,164
Total Unrealized Loss	(72)	(77)
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	16,584	17,167
12 Months or less, Unrealized Loss	(412)	(558)
More than 12 months, Fair Value	515	519
More than 12 months, Unrealized Loss	(17)	(16)
Total Fair Value	17,099	17,686
Total Unrealized Loss	(429)	(574)
Mortgage-backed Securities in Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	42,246	35,453
12 Months or less, Unrealized Loss	(515)	(566)
More than 12 months, Fair Value	2,075	2,849
More than 12 months, Unrealized Loss	(26)	(31)
Total Fair Value	44,321	38,302
Total Unrealized Loss	$ (541)	$ (597)