Earnings Per Share - Reconciliation of Basic and Diluted Income (Loss) Per Share (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic EPS:
Net income	$ 1,240,000	$ 1,403,000	$ 4,051,000	$ 3,479,000
Average common shares outstanding	6,211,636	6,236,075	6,203,453	6,227,955
Earnings per share	$ 0.20	$ 0.22	$ 0.65	$ 0.56
Diluted EPS
Net income	$ 1,240,000	$ 1,403,000	$ 4,051,000	$ 3,479,000
Average common shares outstanding	6,211,636	6,236,075	6,203,453	6,227,955
Dilutive effect of stock options	0	0	0	0
Average diluted shares outstanding	6,211,636	6,236,075	6,203,453	6,227,955
Earnings per share, diluted	$ 0.20	$ 0.22	$ 0.65	$ 0.56