Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Revenues	$ 358,011	$ 371,772	$ 1,020,772	$ 1,085,223
Costs, expenses and other:
Cost of sales	280,012	285,428	836,525	864,735
Depreciation, depletion and amortization	38,066	40,860	114,131	113,097
Selling and administrative	28,115	25,655	88,706	80,667
Heritage health benefit expenses	3,349	3,265	9,953	9,502
Loss (gain) on sale/disposal of assets	236	548	202	(1,369)
Derivative (gain) loss	(4,667)	5,442	(6,571)	2,164
Income from equity affiliates	(1,355)	(1,547)	(4,274)	(4,127)
Other operating loss	0	3,368	0	5,065
Total costs, expenses and other	343,756	363,019	1,038,672	1,069,734
Operating income (loss)	14,255	8,753	(17,900)	15,489
Other (expense) income:
Interest expense	(30,017)	(30,882)	(89,388)	(90,669)
Interest income	1,012	1,374	2,942	5,521
(Loss) gain on foreign exchange	(1,739)	220	(3,391)	(1,531)
Other (loss) income	(3,251)	303	(793)	435
Total other income (expense)	(33,995)	(28,985)	(90,630)	(86,244)
Loss before income taxes	(19,740)	(20,232)	(108,530)	(70,755)
Income tax benefit	(440)	(1,625)	(1,406)	(49,660)
Net loss	(19,300)	(18,607)	(107,124)	(21,095)
Less net loss attributable to noncontrolling interest	(78)	(239)	(715)	(1,545)
Net loss applicable to common shareholders	$ (19,222)	$ (18,368)	$ (106,409)	$ (19,550)
Net loss per share applicable to common shareholders:
Basic and diluted (in dollars per share)	$ (1.03)	$ (0.99)	$ (5.70)	$ (1.06)
Weighted average number of common shares outstanding:
Basic and diluted (shares)	18,742	18,570	18,672	18,458