Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net income, Before tax amount	$ 3,012	$ 3,113	$ 2,800	$ 3,053	$ 2,514	$ 2,935	$ 2,517	$ 2,837	$ 11,978	$ 10,803	$ 11,642
Net unrealized holding (losses) gains on securities, Before tax amount:
Unrealized holding (losses) gains arising during the period, Before tax amount									(4,192)	(1,419)	7,657
Reclassification adjustment for gains included in net income, Before tax amount									(674)	(783)	(1,112)
Unrealized holding (losses) gains arising during the period, Tax expense (benefit)									(1,426)	(483)	2,604
Reclassification adjustment for gains included in net income, Tax expense (benefit)									(229)	(266)	(378)
Unrealized holding (losses) gains arising during the period, Net of tax amount									(2,766)	(936)	5,053
Reclassification adjustment for gains included in net income, Net of tax amount									(445)	(517)	(734)
Other comprehensive (loss) income, Before tax amount									(4,866)	(2,202)	6,545
Total comprehensive income, Before tax amount									7,112	8,601	18,187
Tax expense (benefit)	743	821	702	788	571	715	583	701	3,054	2,570	2,644
Other comprehensive (loss) income, Tax expense (benefit)									(1,655)	(749)	2,226
Total comprehensive income, Tax expense (benefit)									1,399	1,821	4,870
Net income	$ 2,269	$ 2,292	$ 2,098	$ 2,265	$ 1,943	$ 2,220	$ 1,934	$ 2,136	8,924	8,233	8,998
Other comprehensive (loss) income, Net of tax amount									(3,211)	(1,453)	4,319
Total comprehensive income, Net of tax amount									$ 5,713	$ 6,780	$ 13,317