STOCKHOLDERS' EQUITY - Summary of Stock Option Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Stock Options
Outstanding, beginning balance (in shares)	1,115
Granted (in shares)	0
Exercised (in shares)	(361)
Forfeited (in shares)	(27)
Outstanding, ending balance (in shares)	727
Exercisable (in shares)	527
Unvested (in shares)	240
Weighted Average Exercise Price
Outstanding, beginning balance (in dollars per share) | $ / shares	$ 6.13
Granted (in dollars per share) | $ / shares	0.00
Exercised (in dollars per share) | $ / shares	6.20
Forfeited (in dollars per share) | $ / shares	13.17
Outstanding, ending balance (in dollars per share) | $ / shares	5.82
Exercisable (in dollars per share) | $ / shares	4.81
Unvested (in dollars per share) | $ / shares	$ 9.16
Weighted average remaining contractual term, outstanding	6 years 4 months 1 day
Weighted average remaining contractual term, exercisable	5 years 7 months 25 days
Weighted average remaining contractual term, unvested	8 years 4 months 6 days
Aggregate intrinsic value, outstanding | $	$ 12,495
Aggregate intrinsic value, exercisable | $	9,590
Aggregate intrinsic value, unvested | $	$ 3,326
Market-based Performance Stock Options
Weighted Average Exercise Price
Attainment level percentage	100.00%
Additional issuance if performance targets met (in shares)	40