NET INCOME (LOSS) PER SHARE - BASIC AND DILUTED NET INCOME (LOSS) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net income (loss)	$ (11,016)	$ 69,883
Denominator:
Weighted-average common stock outstanding, basic (in shares)	31,089	29,700
Stock options, restricted stock, restricted stock units and employee stock purchase plan (in shares)	0	866
Shares used in computation of diluted net income (loss) per share (in shares)	31,089	30,566
Basic net (loss) per share (in dollars per share)	$ (0.35)	$ 2.35
Diluted net income (loss) per share (in dollars per share)	$ (0.35)	$ 2.29