401 (K) PLAN - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Expense related to 401 (K) Plan	$ 1.4	$ 1.2	$ 0.9
Defined contribution plan, employers matching contribution, service period	3 years		1 year
Defined contribution plan, employers matching contribution, vesting percentage after one years of service			100.00%
Description of 401(k) plan	The Company sponsors a 401 (k) Plan (“the Plan”) which is a defined contribution plan. It is available to all employees who are age 21 or older. Participants may make voluntary contributions and the Company makes matching contributions according to the Plan’s matching formula. For employees who started before January 1, 2016, matching contributions fully vest after one year of service. For employees who started on and after January 1, 2016, matching contributions vest on a straight line basis over three years. The expense related to the Plan primarily consists of the Company’s matching contributions.
Age limit for eligibility to participate in the defined contribution plan	21 years