SEGMENTS INFORMATION - Revenues from External Customers and Segment Operating Profit Before Unallocated Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Revenues	$ 298,293	$ 236,049	$ 846,607	$ 653,875
Operating profit	33,902	27,776	96,313	74,202
Russia
Segment Reporting Information [Line Items]
Revenues	9,833	9,469	29,269	26,526
Operating Segments
Segment Reporting Information [Line Items]
Revenues	298,354	236,174	847,145	654,437
Operating profit	55,455	47,721	158,730	130,834
Operating Segments | North America
Segment Reporting Information [Line Items]
Revenues	161,655	121,746	466,255	330,228
Operating profit	34,699	28,906	103,693	78,720
Operating Segments | Europe
Segment Reporting Information [Line Items]
Revenues	126,265	103,514	349,834	292,826
Operating profit	19,548	17,021	49,793	49,031
Operating Segments | Russia
Segment Reporting Information [Line Items]
Revenues	10,434	9,707	31,056	27,432
Operating profit	1,208	1,626	5,244	3,095
Operating Segments | Other
Segment Reporting Information [Line Items]
Revenues	0	1,207	0	3,951
Operating profit	$ 0	$ 168	$ 0	$ (12)