THE COMPANY AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Basic and diluted earnings per share (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) segment $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net income (loss) | $	$ (19,425)	$ 18,518	$ 92,894
Basic and diluted shares:
Weighted average ordinary shares outstanding (in shares)	50,310	48,145	46,365
Effect of dilutive shares (in shares)	0	1,381	1,413
Shares used to compute diluted net income (loss) per share (in shares)	50,310	49,526	47,778
Net income (loss) per share - basic (in USD per share) | $ / shares	$ (0.39)	$ 0.38	$ 2.00
Net income (loss) per share - diluted (in USD per share) | $ / shares	$ (0.39)	$ 0.37	$ 1.94
Segment reporting
Number of reportable segments | segment	1
Share options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	4,500	500	500