SEGMENT INFORMATION Schedule of Segment Revenues from External Customers and Segment Operating Profit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 399,297	$ 377,523	$ 348,977	$ 324,651	$ 313,525	$ 298,293	$ 283,832	$ 264,482	$ 1,450,448	$ 1,160,132	$ 914,128
Operating profit/(loss)	$ 52,050	$ 49,248	$ 40,682	$ 30,966	$ 37,383	$ 33,902	$ 32,080	$ 30,331	172,946	133,696	105,967
Russia
Segment Reporting Information [Line Items]
Revenues									61,222	40,944	36,585
Operating Segments
Segment Reporting Information [Line Items]
Revenues									1,452,287	1,160,815	914,966
Operating profit/(loss)									275,326	218,121	186,133
Operating Segments | North America
Segment Reporting Information [Line Items]
Revenues									796,126	642,216	471,603
Operating profit/(loss)									169,340	143,021	112,312
Operating Segments | Europe
Segment Reporting Information [Line Items]
Revenues									593,167	474,988	400,460
Operating profit/(loss)									92,080	67,545	68,717
Operating Segments | Russia
Segment Reporting Information [Line Items]
Revenues									62,994	43,611	37,992
Operating profit/(loss)									13,906	7,555	5,198
Operating Segments | Other
Segment Reporting Information [Line Items]
Revenues									0	0	4,911
Operating profit/(loss)									$ 0	$ 0	$ (94)