COMPREHENSIVE LOSS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in accumulated other comprehensive income (loss) by component
Balance	$ 290,105	$ 211,660	$ 319,795
Balance	265,431	290,105	211,660
Unrealized Gain (Loss) on Marketable Securities
Changes in accumulated other comprehensive income (loss) by component
Balance	(289)	9	82
Other comprehensive (loss) gain before reclassifications	234	(298)	(73)
Net current-period other comprehensive (loss) gain	234	(298)	(73)
Balance	(55)	(289)	9
Foreign Currency Items
Changes in accumulated other comprehensive income (loss) by component
Balance	2,596	2,581	2,586
Other comprehensive (loss) gain before reclassifications		15	(5)
Net current-period other comprehensive (loss) gain		15	(5)
Balance	2,596	2,596	2,581
Accumulated Other Comprehensive Income
Changes in accumulated other comprehensive income (loss) by component
Balance	2,307	2,590	2,668
Other comprehensive (loss) gain before reclassifications	234	(283)	(78)
Net current-period other comprehensive (loss) gain	234	(283)	(78)
Balance	$ 2,541	$ 2,307	$ 2,590