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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income (loss)	$ (8,620)	$ (7,758)	$ (19,636)	$ 62,125
Denominator:
Weighted-average common stock outstanding, basic (in shares)	31,578	30,527	31,335	30,116
Stock options, restricted stock, restricted stock units and employee stock purchase plan (in shares)	0	0	0	958
Shares used in computation of diluted net income (loss) per share (in shares)	31,578	30,527	31,335	31,074
Basic net income (loss) per share (in dollars per share)	$ (0.27)	$ (0.25)	$ (0.63)	$ 2.06
Diluted net income (loss) per share (in dollars per share)	$ (0.27)	$ (0.25)	$ (0.63)	$ 2.00