Stockholders' Equity - Additional Information (Detail) - USD ($)	2 Months Ended	3 Months Ended									12 Months Ended
	Feb. 24, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 30, 2016
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase authorized														$ 5,000,000
Repurchase of common stock, shares											54,176	0	0
Repurchase of common stock, value											$ 1,143,913
Common stock repurchase, average price per share											$ 21.11
Share repurchase program, remaining amount		$ 3,856,000									$ 3,856,000
Dividends declared, per share		$ 0.17	$ 0.17	$ 0.17	$ 0.17	$ 0.14	$ 0.14	$ 0.14	$ 0.14	$ 0.11	$ 0.68	$ 0.56	$ 0.33
Dividends paid, per share		$ 0.17	$ 0.17	$ 0.17	$ 0.17	$ 0.14	$ 0.14	$ 0.14	$ 0.14	$ 0.11
Dividend payments, amount											$ 7,746,655	$ 6,337,568	$ 3,697,588
Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock, shares	35,496
Repurchase of common stock, value	$ 721,000
Common stock repurchase, average price per share	$ 20.32