DISCONTINUED OPERATIONS AND ASSETS HELD FOR SALE - Discontinued Operations - Croatia, Slovenia, and Romania (Details) - USD ($) $ / shares in Units, $ 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
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenues										$ 126,499	$ 111,839	$ 116,931
Cost of revenues										88,763	89,438	92,605
Selling, general and administrative expenses										22,265	16,344	19,718
Operating income										15,471	6,057	4,608
Interest expense	[1]									18,579	20,835	19,699
Other non-operating income / (expense), net										729	(413)	(2,370)
Loss from discontinued operations, before tax										(2,379)	(15,191)	(17,461)
Provision for income taxes										2,247	981	547
Loss from discontinued operations, net of tax, before loss on sale										(4,626)	(16,172)	(18,008)
Loss on sale of divested businesses, net of tax										0	0	(11,388)
Loss from discontinued operations, net of tax (Note 3)		$ 4,121	$ (5,988)	$ 2,533	$ (5,292)		$ (8,054)	$ (2,101)	$ (5,816)	$ (4,626)	$ (16,172)	$ (29,396)
Loss from discontinued operations, net of tax per share - basic (in dollars per share)		$ 0.02	$ (0.04)	$ 0.01	$ (0.04)	$ 0.00	$ (0.05)	$ (0.02)	$ (0.04)	$ (0.03)	$ (0.10)	$ (0.20)
Loss from discontinued operations, net of tax per share - diluted (in dollars per share)		$ 0.01	$ (0.04)	$ 0.00	$ (0.04)	$ 0.00	$ (0.05)	$ (0.02)	$ (0.04)	$ (0.03)	$ (0.10)	$ (0.20)
Net cash (used in) / provided by discontinued operations - operating activities										$ (4,206)	$ (25,900)	$ 5,347
Net cash used in discontinued operations - investing activities										(4,082)	(5,961)	(265)
Net cash used in discontinued operations - financing activities										$ (285)	$ (247)	(329)
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations, net of tax per share - basic (in dollars per share)										$ (0.03)	$ (0.10)
Loss from discontinued operations, net of tax per share - diluted (in dollars per share)										$ (0.03)	$ (0.10)
Croatia And Slovenia | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenues										$ 126,499	$ 111,839	109,646
Cost of revenues										88,763	89,438	85,925
Selling, general and administrative expenses										22,265	16,344	17,185
Operating income										15,471	6,057	6,536
Interest expense										18,579	20,835	19,677
Other non-operating income / (expense), net										729	(413)	(2,330)
Loss from discontinued operations, before tax										(2,379)	(15,191)	(15,471)
Provision for income taxes										2,247	981	638
Loss from discontinued operations, net of tax, before loss on sale										(4,626)	(16,172)	$ (16,109)
Loss from discontinued operations, net of tax per share - basic (in dollars per share)												$ (0.11)
Loss from discontinued operations, net of tax per share - diluted (in dollars per share)												$ (0.11)
Net cash (used in) / provided by discontinued operations - operating activities										(4,206)	(25,900)	$ 8,366
Net cash used in discontinued operations - investing activities										(6,128)	(7,155)	(6,863)
Net cash used in discontinued operations - financing activities										(285)	(247)	(253)
Romania | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenues												7,285
Cost of revenues												6,680
Selling, general and administrative expenses												2,533
Operating income												(1,928)
Interest expense												22
Other non-operating income / (expense), net												(40)
Loss from discontinued operations, before tax												(1,990)
Provision for income taxes												(91)
Loss from discontinued operations, net of tax, before loss on sale												(1,899)
Loss on sale of divested businesses, net of tax	[2]											(11,388)
Loss from discontinued operations, net of tax (Note 3)												(13,287)
Cumulative translation adjustment into net income												7,700
Reclassification of accumulated losses attributable to noncontrolling interest of USS												$ (3,700)
Loss from discontinued operations, net of tax per share - basic (in dollars per share)												$ (0.09)
Loss from discontinued operations, net of tax per share - diluted (in dollars per share)												$ (0.09)
Net cash (used in) / provided by discontinued operations - operating activities										0	0	$ (3,019)
Net cash used in discontinued operations - investing activities										2,046	1,194	6,598
Net cash used in discontinued operations - financing activities										$ 0	$ 0	$ (76)

[1] (1) For the years ended December 31, 2017, 2016 and 2015, we paid US$ 17.4 million, US$ 33.3 million and US$ 3.5 million, respectively, of interest and Guarantee Fees associated with the 2018 Euro Term Loan, both as defined in Note 5, "Long-term Debt and Other Financing Arrangements". These payments were allocated to net cash (used in) / provided by discontinued operations - operating activities in our Consolidated Statements of Cash Flows as we are required to apply the expected proceeds from the sale of our Croatia and Slovenia operations towards the repayment of the remaining principal amounts owing in respect of the 2018 Euro Term Loan (see Note 5, "Long-term Debt and Other Financing Arrangements").

[2] Amount includes realized gains / losses on completed disposal transactions in 2015. The amount includes losses related to the reclassification of the cumulative translation adjustment into net income of US$ 7.7 million and the reclassification of accumulated losses attributable to noncontrolling interest of US$ 3.7 million.