Income Taxes (Income Tax Expense (Benefit)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Successor
Income Tax Examination [Line Items]
Income tax provision (benefit) at statutory rate	$ 13,118		$ 31,496
Percentage depletion allowance	(5,692)		(12,731)
State taxes, net of effect of federal taxes	408		891
Change in valuation allowance	(8,316)		(20,218)
Other, net	801		1,721
Income Tax Expense (Benefit)	$ 319		$ 1,159
Predecessor
Income Tax Examination [Line Items]
Income tax provision (benefit) at statutory rate		$ (61,645)		$ (134,380)
Percentage depletion allowance		5,909		(19,758)
State taxes, net of effect of federal taxes		(2,571)		(7,061)
Change in valuation allowance		58,665		159,227
Other, net		(603)		616
Income Tax Expense (Benefit)		$ (245)		$ (1,356)