GOODWILL AND INTANGIBLE ASSETS Goodwill (Details) $ in Thousands	6 Months Ended
Jun. 30, 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	(28,574)
Balance, June 30, 2020	639,414
Accumulated impairment losses, ending balance	(462,612)
Gross Balance, June 30, 2020	1,102,026
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	(91)
Balance, June 30, 2020	28,416
Accumulated impairment losses, ending balance	(144,639)
Gross Balance, June 30, 2020	173,055
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	(27,283)
Balance, June 30, 2020	490,568
Accumulated impairment losses, ending balance	(287,545)
Gross Balance, June 30, 2020	778,113
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	(1,035)
Balance, June 30, 2020	71,458
Accumulated impairment losses, ending balance	(11,028)
Gross Balance, June 30, 2020	82,486
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	(165)
Balance, June 30, 2020	48,972
Accumulated impairment losses, ending balance	0
Gross Balance, June 30, 2020	48,972
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, June 30, 2020	0
Accumulated impairment losses, ending balance	(19,400)
Gross Balance, June 30, 2020	$ 19,400

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=120320667&loc=SL49117168-202975

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-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

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