BASIS OF PRESENTATION - Statement of Cash Flows Impact (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss	$ (191,327)	$ (46,282)	$ (211,638)	$ (76,398)
Depreciation, depletion and amortization	26,396	39,497	52,431	76,064
Accretion of asset retirement obligation and receivable			17,302	22,437
Share-based compensation	25	1,133	1,860	2,480
Non-cash interest expense			4,782	4,639
Amortization of deferred financing costs			5,162	5,193
Gain on derivative instruments			0	(1,904)
(Gain) loss on foreign exchange	(264)	1,137	(1,575)	1,602
Loss (income) from equity affiliates	67	(1,400)	(1,109)	(2,919)
Distributions from equity affiliates			1,262	3,403
Deferred income tax benefit			(712)	(774)
Other			182	(1,752)
Receivables			13,826	11,360
Inventories			(33,275)	7,706
Accounts payable and accrued expenses			(14,403)	(20,919)
Interest payable			6,715	532
Deferred revenue			2,908	(4,924)
Unbilled revenues			12,234	(12,449)
Other assets and liabilities			(20,602)	17,596
Asset retirement obligation			(20,176)	(20,819)
Net cash provided by (used in) operating activities			(40,082)	10,154
Additions to property, plant and equipment			(11,773)	(13,104)
Proceeds from sales of restricted investments			23,623	21,605
Purchases of restricted investments			(23,252)	(24,731)
Cash payments related to acquisitions and other			0	(3,580)
Proceeds from sales of assets			2,087	783
Receipts from loan and lease receivables			0	50,488
Other			(399)	(969)
Net cash (used in) provided by investing activities			(9,714)	30,492
Repayments of long-term debt			(66,996)	(44,324)
Borrowings on revolving lines of credit			122,400	113,200
Repayments of revolving lines of credit			(122,400)	(113,200)
Other			0	(364)
Net cash provided by (used in) financing activities			17,040	(44,688)
Effect of exchange rate changes on cash			1,186	463
Net (decrease) increase in cash and cash equivalents, including restricted cash			(31,570)	(3,579)
Cash and cash equivalents, including restricted cash, beginning of period			152,439	129,615	$ 129,615
Cash and cash equivalents, including restricted cash, end of period	$ 120,869	126,036	120,869	126,036	152,439
Cash paid for interest			41,978	48,931
Accrued purchases of property and equipment			5,495	1,009
Capital leases and other financing sources			$ 0	480
As Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss		(50,520)		(87,821)
Depreciation, depletion and amortization		39,497		76,064
Accretion of asset retirement obligation and receivable				22,437
Share-based compensation				2,480
Non-cash interest expense				4,639
Amortization of deferred financing costs				5,193
Gain on derivative instruments				(1,904)
(Gain) loss on foreign exchange		1,185		1,652
Loss (income) from equity affiliates		(1,400)		(2,919)
Distributions from equity affiliates				3,403
Deferred income tax benefit				(965)
Other				(1,752)
Receivables				11,360
Inventories				7,706
Accounts payable and accrued expenses				(20,919)
Interest payable				532
Deferred revenue				(5,809)
Unbilled revenues				0
Other assets and liabilities				17,596
Asset retirement obligation				(20,819)
Net cash provided by (used in) operating activities				10,154
Additions to property, plant and equipment				(13,104)
Proceeds from sales of restricted investments				21,605
Purchases of restricted investments				(23,614)
Cash payments related to acquisitions and other				(3,580)
Proceeds from sales of assets				783
Receipts from loan and lease receivables				50,488
Other				(969)
Net cash (used in) provided by investing activities				31,609
Repayments of long-term debt				(44,324)
Borrowings on revolving lines of credit				113,200
Repayments of revolving lines of credit				(113,200)
Other				(364)
Net cash provided by (used in) financing activities				(44,688)
Effect of exchange rate changes on cash				463
Net (decrease) increase in cash and cash equivalents, including restricted cash				(2,462)
Cash and cash equivalents, including restricted cash, beginning of period				60,082	60,082
Cash and cash equivalents, including restricted cash, end of period		57,620		57,620
Cash paid for interest				48,931
Accrued purchases of property and equipment				1,009
Capital leases and other financing sources				480
Accounting Standards Update 2014-09 | Adjustments for New Revenue Standard
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss		4,238		11,423
Depreciation, depletion and amortization		0		0
Accretion of asset retirement obligation and receivable				0
Share-based compensation				0
Non-cash interest expense				0
Amortization of deferred financing costs				0
Gain on derivative instruments				0
(Gain) loss on foreign exchange		(48)		(50)
Loss (income) from equity affiliates		0		0
Distributions from equity affiliates				0
Deferred income tax benefit				191
Other				0
Receivables				0
Inventories				0
Accounts payable and accrued expenses				0
Interest payable				0
Deferred revenue				885
Unbilled revenues				(12,449)
Other assets and liabilities				0
Asset retirement obligation				0
Net cash provided by (used in) operating activities				0
Additions to property, plant and equipment				0
Proceeds from sales of restricted investments				0
Purchases of restricted investments				0
Cash payments related to acquisitions and other				0
Proceeds from sales of assets				0
Receipts from loan and lease receivables				0
Other				0
Net cash (used in) provided by investing activities				0
Repayments of long-term debt				0
Borrowings on revolving lines of credit				0
Repayments of revolving lines of credit				0
Other				0
Net cash provided by (used in) financing activities				0
Effect of exchange rate changes on cash				0
Net (decrease) increase in cash and cash equivalents, including restricted cash				0
Cash and cash equivalents, including restricted cash, beginning of period				0	0
Cash and cash equivalents, including restricted cash, end of period		0		0
Cash paid for interest				0
Accrued purchases of property and equipment				0
Capital leases and other financing sources				0
Accounting Standards Update 2016-18 | Adjustments for New Revenue Standard
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net loss				0
Depreciation, depletion and amortization				0
Accretion of asset retirement obligation and receivable				0
Share-based compensation				0
Non-cash interest expense				0
Amortization of deferred financing costs				0
Gain on derivative instruments				0
(Gain) loss on foreign exchange				0
Loss (income) from equity affiliates				0
Distributions from equity affiliates				0
Deferred income tax benefit				0
Other				0
Receivables				0
Inventories				0
Accounts payable and accrued expenses				0
Interest payable				0
Deferred revenue				0
Unbilled revenues				0
Other assets and liabilities				0
Asset retirement obligation				0
Net cash provided by (used in) operating activities				0
Additions to property, plant and equipment				0
Proceeds from sales of restricted investments				0
Purchases of restricted investments				(1,117)
Cash payments related to acquisitions and other				0
Proceeds from sales of assets				0
Receipts from loan and lease receivables				0
Other				0
Net cash (used in) provided by investing activities				(1,117)
Repayments of long-term debt				0
Borrowings on revolving lines of credit				0
Repayments of revolving lines of credit				0
Other				0
Net cash provided by (used in) financing activities				0
Effect of exchange rate changes on cash				0
Net (decrease) increase in cash and cash equivalents, including restricted cash				(1,117)
Cash and cash equivalents, including restricted cash, beginning of period				69,533	$ 69,533
Cash and cash equivalents, including restricted cash, end of period		$ 68,416		68,416
Cash paid for interest				0
Accrued purchases of property and equipment				0
Capital leases and other financing sources				$ 0