THE COMPANY AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Adoption of ASU 2014-09 (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	$ 294,822	$ 180,711	$ 550,133	$ 331,456
Operating costs and expenses by segment:	271,560	183,547	537,627	332,904
Operating income (loss)	23,262	(2,836)	12,506	(1,448)
Net earnings	23,023	$ (25)	13,909	$ 25,862
North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	277,505
Operating costs and expenses by segment:	251,395		492,786
Operating income (loss)	26,110
Europe
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	17,317
Operating costs and expenses by segment:	20,165		44,841
Operating income (loss)	(2,848)
Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	294,822		550,133
Operating costs and expenses by segment:	273,678		545,838
Operating income (loss)	21,144		4,295
Net earnings	21,445		7,731
Under ASC 605 | North America
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	277,505		513,531
Operating costs and expenses by segment:	253,460		500,891
Operating income (loss)	24,045		12,640
Under ASC 605 | Europe
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue by segment:	17,317		36,602
Operating costs and expenses by segment:	20,218		44,947
Operating income (loss)	(2,901)		(8,345)
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		0
Operating costs and expenses by segment:	(2,118)		(8,211)
Operating income (loss)	2,118		8,211
Net earnings	1,578		6,178
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		0
Operating costs and expenses by segment:	(2,065)		(8,105)
Operating income (loss)	2,065		8,105
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		0
Operating costs and expenses by segment:	(53)		(106)
Operating income (loss)	$ 53		$ 106