Stockholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended				6 Months Ended		23 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Aug. 30, 2016
Equity [Abstract]
Common stock repurchase authorized								$ 5,000,000
Repurchase of common stock, shares			54,768		2,000	133,208	238,204
Repurchase of common stock, value			$ 1,030,000		$ 35,622	$ 2,537,000	$ 4,601,000
Common stock repurchase, average price per share					$ 17.81		$ 19.31
Dividends declared, per share	$ 0.19	$ 0.19	$ 0.17	$ 0.17	$ 0.38	$ 0.34
Dividends paid, per share	$ 0.19	$ 0.19	$ 0.17	$ 0.17
Dividend payments, amount	$ 2,217,000		$ 1,971,000		$ 4,432,926	$ 3,942,000