SEGMENTS INFORMATION - Revenues from External Customers and Operating Profit/(Loss) Before Unallocated Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 377,523	$ 298,293	$ 1,051,151	$ 846,607
Operating profit	49,248	33,902	120,896	96,313
Russia
Segment Reporting Information [Line Items]
Revenues	14,079	9,861	40,614	29,331
Operating Segments
Segment Reporting Information [Line Items]
Revenues	378,290	298,354	1,052,014	847,145
Operating profit	73,198	55,455	199,825	158,730
Operating Segments | North America
Segment Reporting Information [Line Items]
Revenues	206,389	161,655	578,717	466,255
Operating profit	45,529	34,699	126,243	103,693
Operating Segments | Europe
Segment Reporting Information [Line Items]
Revenues	157,446	126,265	431,472	349,834
Operating profit	25,984	19,548	66,453	49,793
Operating Segments | Russia
Segment Reporting Information [Line Items]
Revenues	14,455	10,434	41,825	31,056
Operating profit	$ 1,685	$ 1,208	$ 7,129	$ 5,244