SEGMENT INFORMATION (Revenues from External Customers and Operating Profit/(Loss) Before Unallocated Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Operating profit/(loss)	$ 78,270	$ 64,560	$ 54,237	$ 48,697	$ 52,050	$ 49,248	$ 40,682	$ 30,966	$ 245,764	$ 172,946	$ 133,696
North America Segment
Segment Reporting Information [Line Items]
Segment Revenues									1,077,094	796,126	642,216
Operating profit/(loss)									221,846	169,340	143,021
North America Segment | North America
Segment Reporting Information [Line Items]
Segment Revenues									1,046,333
Europe Segment
Segment Reporting Information [Line Items]
Segment Revenues									693,867	593,167	474,988
Operating profit/(loss)									115,876	92,080	67,545
Europe Segment | North America
Segment Reporting Information [Line Items]
Segment Revenues									52,859
Russia Segment
Segment Reporting Information [Line Items]
Segment Revenues									73,148	62,994	43,611
Operating profit/(loss)									11,377	13,906	7,555
Russia Segment | North America
Segment Reporting Information [Line Items]
Segment Revenues									75
Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues									1,844,109	1,452,287	1,160,815
Operating profit/(loss)									349,099	$ 275,326	$ 218,121
Operating Segments | North America
Segment Reporting Information [Line Items]
Segment Revenues									$ 1,099,267