Stock-Based Compensation (Textual 2 Stock Option) - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation option awards contractual term	10 years
Portion of initial stock options granted to employees that vests on employee's first anniversary	25.00%
Portion of initial stock options granted to employees that vests ratably over three years after completion of first year of service	75.00%
Option awards vesting period, after completion of one year of service	3 years
Vesting period	4 years
Vesting period for initial stock options granted to directors	4 years
Vesting period for subsequent stock options granted to directors	1 year
Proceeds from exercise of employee stock options	$ 4,402	$ 1,039
Options granted, weighted average fair value per share	$ 7.81	$ 4.44
Service option awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expenses	$ 10,000
Unrecognized compensation expenses, weighted average period	1 year 4 months 24 days