SEGMENTS INFORMATION - Revenues from External Customers and Segment Operating Profit Before Unallocated Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Revenues	$ 283,832	$ 217,781	$ 548,314	$ 417,826
Operating profit	32,080	23,606	62,411	46,426
Russia
Segment Reporting Information [Line Items]
Revenues	10,484	9,798	19,436	17,057
Operating Segments
Segment Reporting Information [Line Items]
Revenues	283,977	218,069	548,791	418,263
Operating profit	54,628	44,433	103,275	83,113
Operating Segments | North America
Segment Reporting Information [Line Items]
Revenues	157,110	108,213	304,600	208,482
Operating profit	38,339	25,746	68,994	49,814
Operating Segments | Europe
Segment Reporting Information [Line Items]
Revenues	115,726	98,160	223,569	189,312
Operating profit	13,413	16,670	30,245	32,010
Operating Segments | Russia
Segment Reporting Information [Line Items]
Revenues	11,141	10,212	20,622	17,725
Operating profit	2,876	1,740	4,036	1,469
Operating Segments | Other
Segment Reporting Information [Line Items]
Revenues	0	1,484	0	2,744
Operating profit	$ 0	$ 277	$ 0	$ (180)