Shareholders' Equity - Summary of Certain Information about Stock Options (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted-average grant-date fair value of option grants for the period	$ 2.45	$ 2.53	$ 2.62	$ 2.83
Options in-the-money at period end	1,261,705	766,101	1,261,705	766,101
Aggregate intrinsic value of options exercised	$ 31,338	$ 226,430	$ 89,171	$ 568,516