Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenues	$ 276,312	$ 327,314	$ 571,989	$ 674,326
Costs, expenses and other:
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)
Loss on impairment	143,324	0	143,324	0
Derivative loss (gain)	0	481	0	(1,904)
Loss (income) from equity affiliates	67	(1,400)	(1,109)	(2,919)
Other operating income	23	0	23	0
Total costs, expenses and other	434,297	340,356	719,547	687,441
Operating loss	(157,985)	(13,042)	(147,558)	(13,115)
Other (expense) income:
Interest expense	(30,816)	(30,109)	(60,899)	(59,371)
Loss on extinguishment of debt	(1,838)	0	(1,838)	0
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)
Net loss per share applicable to common shareholders:
Basic and diluted (in dollars per share)	$ (9.91)	$ (2.47)	$ (11.00)	$ (4.07)
Weighted average number of common shares outstanding:
Basic and diluted (shares)	18,772	18,700	18,700	18,636