NET INCOME (LOSS) PER SHARE - Reconciliation used in Computing Basic and Diluted Net Income (Loss) per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Income (loss) from continuing operations									$ 54,343	$ (45,291)	$ (40,030)
Income from discontinued operations, net of tax									0	0	649
Net income (loss) used in computing basic net income (loss) per share	$ (3,142)	$ (4,640)	$ (7,758)	$ 69,883	$ (12,294)	$ (5,287)	$ (14,845)	$ (12,865)	$ 54,343	$ (45,291)	$ (39,381)
Denominator:
Shares used in computation of basic net income (loss) per share (weighted average common shares outstanding) (in shares)	30,814	30,780	30,527	29,700	29,250	29,245	29,193	29,024	30,459	29,179	28,759
Dilutive potential common shares:
Stock options, ESPP, Restricted Stock and RSUs (in shares)									948	0	0
Shares used in computation of diluted net income (loss) per share (in shares)	30,814	30,780	30,527	30,566	29,250	29,245	29,193	29,024	31,407	29,179	28,759
Basic net income (loss) per share:
Continuing operations (in dollars per share)									$ 1.78	$ (1.55)	$ (1.39)
Discontinued operations (in dollars per share)									0.00	0.00	0.02
Total (in dollars per share)	$ (0.10)	$ (0.15)	$ (0.25)	$ 2.35	$ (0.42)	$ (0.18)	$ (0.51)	$ (0.44)	1.78	(1.55)	(1.37)
Diluted net income (loss) per share:
Continuing operations (in dollars per share)									1.73	(1.55)	(1.39)
Discontinued operations (in dollars per share)									0.00	0.00	0.02
Total (in dollars per shares)	$ (0.10)	$ (0.15)	$ (0.25)	$ 2.29	$ (0.42)	$ (0.18)	$ (0.51)	$ (0.44)	$ 1.73	$ (1.55)	$ (1.37)