Summary Unaudited Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	Oct. 17, 2016	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
Summary of the unaudited quarterly results of operations for the period
Revenue		$ 213,893	$ 248,884	$ 229,201	$ 195,728	$ 227,928	$ 217,073	$ 174,188	$ 181,249	$ 887,706	$ 800,438	$ 1,124,111
Operating income (loss)		(2,441)	11,848	2,484	(6,951)	36,131	10,861	45,920	(25,645)	4,940	67,268	(81,391)
Net income (loss)		$ 17,839	$ 2,577	$ (6,948)	$ (20,108)	$ 24,511	$ (1,584)	$ 35,289	$ (36,375)	$ (6,639)	$ 21,841	$ (204,900)
Income (loss) per common share from continuing operations attributable to the controlling interest:
Basic		$ 0.24	$ 0.03	$ (0.09)	$ (0.3)	$ 0.4	$ (0.03)	$ 0.58	$ (0.59)	$ (0.09)	$ 0.36	$ (3.36)
Diluted		0.23	0.03	(0.09)	(0.3)	0.39	(0.03)	0.57	(0.59)	(0.09)	0.35	$ (3.36)
Closing stock price		$ 4.45	$ 3.66	$ 3.53	$ 4.58	$ 5.61	$ 5.44	$ 2.06	$ 1.95	$ 4.45	$ 5.61
Premium on early retirement of debt					$ (900)					$ 880	$ 0	$ 0
Write-off of deferred financing costs and original issue discount					$ 700					702	1,254	0
Revenue from Business interuptions insurance proceeds			$ 3,100
Impairments									$ 4,200	0	4,609	91,541
Non-cash credit to depreciation and depletion expense		$ 2,800				$ 13,900		$ 37,300		2,900	53,300
Debt restructuring costs	$ 4,700					$ 200	$ 4,500			$ 23	$ 4,665	$ 0