NET INCOME (LOSS) PER SHARE - BASIC AND DILUTED NET INCOME (LOSS) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income (loss)	$ (7,758)	$ (14,845)	$ 62,125	$ (27,710)
Denominator:
Shares used in calculating basic net income (loss) per share (in shares)	30,527	29,193	30,116	29,109
Stock options, ESPP, Restricted Stock and RSUs (in shares)	0	0	958	0
Shares used in computation of diluted net income (loss) per share (in shares)	30,527	29,193	31,074	29,109
Basic net loss per share (in dollars per share)	$ (0.25)	$ (0.51)	$ 2.06	$ (0.95)
Diluted net loss per share (in dollars per share)	$ (0.25)	$ (0.51)	$ 2.00	$ (0.95)
Options to purchase shares of common stock (in shares)			371
Average fair value price per share of common stock (in dollars per share)			$ 11.81