BASIS OF PRESENTATION - Statement of Operations Impact (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 276,312	$ 327,314	$ 571,989	$ 674,326
Cost of sales (exclusive of depreciation, depletion and amortization, shown separately)	227,066	272,317	452,226	557,337
Depreciation, depletion and amortization	26,396	39,497	52,431	76,064
Selling and administrative	38,954	28,327	73,293	56,902
Heritage health benefit expenses	914	1,001	1,802	1,995
(Gain) loss on sale/disposal of assets	(2,401)	133	(2,397)	(34)
Derivative loss (gain)	0	481	0	(1,904)
Loss (income) from equity affiliates	67	(1,400)	(1,109)	(2,919)
Total costs, expenses and other	434,297	340,356	719,547	687,441
Operating income (loss)	(157,985)	(13,042)	(147,558)	(13,115)
Interest expense	(30,816)	(30,109)	(60,899)	(59,371)
Interest income	1,174	1,038	2,217	1,931
Gain (loss) on foreign exchange	264	(1,137)	1,575	(1,602)
Other expense	(2,838)	(3,434)	(5,882)	(5,015)
Total other income (expense)	(34,054)	(33,642)	(64,827)	(64,057)
Loss before income taxes	(192,039)	(46,684)	(212,385)	(77,172)
Income tax benefit	(712)	(402)	(747)	(774)
Net loss	(191,327)	(46,282)	(211,638)	(76,398)
Less net loss attributable to noncontrolling interest	(5,260)	(138)	(5,982)	(637)
Net loss applicable to common shareholders	$ (186,067)	$ (46,144)	$ (205,656)	$ (75,761)
Basic and diluted (in dollars per share)	$ (9.91)	$ (2.47)	$ (11.00)	$ (4.07)
Basic and diluted (shares)	18,772	18,700	18,700	18,636
Adjustments for New Revenue Standard | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues		$ 4,289		$ 11,564
Cost of sales (exclusive of depreciation, depletion and amortization, shown separately)		0		0
Depreciation, depletion and amortization		0		0
Selling and administrative		0		0
Heritage health benefit expenses		0		0
(Gain) loss on sale/disposal of assets		0		0
Derivative loss (gain)		0		0
Loss (income) from equity affiliates		0		0
Total costs, expenses and other		0		0
Operating income (loss)		4,289		11,564
Interest expense		0		0
Interest income		0		0
Gain (loss) on foreign exchange		48		50
Other expense		0		0
Total other income (expense)		48		50
Loss before income taxes		4,337		11,614
Income tax benefit		99		191
Net loss		4,238		11,423
Less net loss attributable to noncontrolling interest		0		0
Net loss applicable to common shareholders		$ 4,238		$ 11,423
Basic and diluted (in dollars per share)		$ 0.22		$ 0.61
Basic and diluted (shares)		0		0
Adjustments for New Revenue Standard | Accounting Standards Update 2014-09, Revised Recognition Period
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues		$ 0		$ 0
Cost of sales (exclusive of depreciation, depletion and amortization, shown separately)		408		824
Depreciation, depletion and amortization		0		0
Selling and administrative		(1,839)		(3,690)
Heritage health benefit expenses		(2,305)		(4,609)
(Gain) loss on sale/disposal of assets		0		0
Derivative loss (gain)		0		0
Loss (income) from equity affiliates		0		0
Total costs, expenses and other		(3,736)		(7,475)
Operating income (loss)		3,736		7,475
Interest expense		0		0
Interest income		0		0
Gain (loss) on foreign exchange		0		0
Other expense		(3,736)		(7,475)
Total other income (expense)		(3,736)		(7,475)
Loss before income taxes		0		0
Income tax benefit		0		0
Net loss		0		0
Less net loss attributable to noncontrolling interest		0		0
Net loss applicable to common shareholders		$ 0		$ 0
Basic and diluted (in dollars per share)		$ 0.00		$ 0.00
Basic and diluted (shares)		0		0
As Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues		$ 323,025		$ 662,762
Cost of sales (exclusive of depreciation, depletion and amortization, shown separately)		271,909		556,513
Depreciation, depletion and amortization		39,497		76,064
Selling and administrative		30,166		60,592
Heritage health benefit expenses		3,306		6,604
(Gain) loss on sale/disposal of assets		133		(34)
Derivative loss (gain)		481		(1,904)
Loss (income) from equity affiliates		(1,400)		(2,919)
Total costs, expenses and other		344,092		694,916
Operating income (loss)		(21,067)		(32,154)
Interest expense		(30,109)		(59,371)
Interest income		1,038		1,931
Gain (loss) on foreign exchange		(1,185)		(1,652)
Other expense		302		2,460
Total other income (expense)		(29,954)		(56,632)
Loss before income taxes		(51,021)		(88,786)
Income tax benefit		(501)		(965)
Net loss		(50,520)		(87,821)
Less net loss attributable to noncontrolling interest		(138)		(637)
Net loss applicable to common shareholders		$ (50,382)		$ (87,184)
Basic and diluted (in dollars per share)		$ (2.69)		$ (4.68)
Basic and diluted (shares)		18,700		18,636