SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Prepaid and other current assets	$ 16,411		$ 16,411		$ 13,784	$ 11,881
Deferred income tax assets	75,484		75,484		19,626	20,156
Accumulated deficit	(607,182)		(607,182)		$ (706,981)	(708,354)
Income Statement Related Disclosures [Abstract]
Revenue	197,057	$ 171,494	562,193	$ 456,782
Income tax benefit (expense)	10,534	(4,292)	63,716	(3,109)
Net income from continuing operations	28,362	$ 10,131	109,068	$ 25,936
Balances without adoption of ASC Topic 606
Balance Sheet Related Disclosures [Abstract]
Prepaid and other current assets	12,103		12,103			11,881
Deferred income tax assets	76,014		76,014			20,156
Accumulated deficit	(610,960)		(610,960)			(708,354)
Income Statement Related Disclosures [Abstract]
Revenue	196,316		560,560
Income tax benefit (expense)	10,733		64,146
Net income from continuing operations	27,820		107,865
Adjustments due to ASC Topic 606 | Accounting Standards Update 2014-09
Balance Sheet Related Disclosures [Abstract]
Prepaid and other current assets	4,308		4,308			1,903
Deferred income tax assets	(530)		(530)			(530)
Accumulated deficit	3,778		3,778			$ 1,373
Income Statement Related Disclosures [Abstract]
Revenue	741		1,633
Income tax benefit (expense)	(199)		(430)
Net income from continuing operations	$ 542		$ 1,203