GOODWILL AND INTANGIBLE ASSETS Goodwill (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Goodwill [Roll Forward]
Gross Balance, December 31, 2019	$ 1,130,600
Accumulated impairment losses, beginning balance	(462,612)
Balance, December 31, 2019	667,988
Foreign currency	(52,389)
Balance, March 31, 2020	615,599
Accumulated impairment losses, ending balance	(462,612)
Gross Balance, March 31, 2020	1,078,211
Bulgaria
Goodwill [Roll Forward]
Gross Balance, December 31, 2019	173,146
Accumulated impairment losses, beginning balance	(144,639)
Balance, December 31, 2019	28,507
Foreign currency	(705)
Balance, March 31, 2020	27,802
Accumulated impairment losses, ending balance	(144,639)
Gross Balance, March 31, 2020	172,441
Czech Republic
Goodwill [Roll Forward]
Gross Balance, December 31, 2019	805,396
Accumulated impairment losses, beginning balance	(287,545)
Balance, December 31, 2019	517,851
Foreign currency	(48,216)
Balance, March 31, 2020	469,635
Accumulated impairment losses, ending balance	(287,545)
Gross Balance, March 31, 2020	757,180
Romania
Goodwill [Roll Forward]
Gross Balance, December 31, 2019	83,521
Accumulated impairment losses, beginning balance	(11,028)
Balance, December 31, 2019	72,493
Foreign currency	(2,239)
Balance, March 31, 2020	70,254
Accumulated impairment losses, ending balance	(11,028)
Gross Balance, March 31, 2020	81,282
Slovak Republic
Goodwill [Roll Forward]
Gross Balance, December 31, 2019	49,137
Accumulated impairment losses, beginning balance	0
Balance, December 31, 2019	49,137
Foreign currency	(1,229)
Balance, March 31, 2020	47,908
Accumulated impairment losses, ending balance	0
Gross Balance, March 31, 2020	47,908
Slovenia
Goodwill [Roll Forward]
Gross Balance, December 31, 2019	19,400
Accumulated impairment losses, beginning balance	(19,400)
Balance, December 31, 2019	0
Foreign currency	0
Balance, March 31, 2020	0
Accumulated impairment losses, ending balance	(19,400)
Gross Balance, March 31, 2020	$ 19,400