THE COMPANY AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Adoption of ASU 2014-09 (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	$ 255,311	$ 150,745
Operating expense by segment:	266,067	149,357
Operating income (loss)	(10,756)	1,388
Net loss	(9,114)	$ 25,887
North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	236,026
Operating expense by segment:	241,391
Operating income (loss)	(5,365)
Europe
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	19,285
Operating expense by segment:	24,676
Operating income (loss)	(5,391)
Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	255,311
Operating expense by segment:	272,160
Operating income (loss)	(16,849)
Net loss	(13,714)
Under ASC 605 | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	236,026
Operating expense by segment:	247,431
Operating income (loss)	(11,405)
Under ASC 605 | Europe
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	19,285
Operating expense by segment:	24,729
Operating income (loss)	(5,444)
Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	0
Operating expense by segment:	(6,093)
Operating income (loss)	6,093
Net loss	4,600
Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09 | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	0
Operating expense by segment:	(6,040)
Operating income (loss)	6,040
Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09 | Europe
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	0
Operating expense by segment:	(53)
Operating income (loss)	$ 53