SEGMENTS INFORMATION - Revenues from External Customers and Operating Profit/(Loss) Before Unallocated Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 445,647	$ 348,977	$ 869,795	$ 673,628
Operating profit	54,237	40,682	102,934	71,648
North America
Segment Reporting Information [Line Items]
Revenues	257,103	194,025	488,299	372,328
Operating profit	51,221	43,622	95,181	80,714
Europe
Segment Reporting Information [Line Items]
Revenues	171,495	141,319	344,838	274,026
Operating profit	26,568	20,658	55,458	40,469
Russia
Segment Reporting Information [Line Items]
Revenues	17,380	13,677	37,166	27,370
Operating profit	2,321	1,895	7,668	5,444
Operating Segments
Segment Reporting Information [Line Items]
Revenues	445,978	349,021	870,303	673,724
Operating profit	$ 80,110	$ 66,175	$ 158,307	$ 126,627