Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2015	Dec. 31, 2014
Predecessor [Member]
Income Tax Examination [Line Items]
Income tax provision (benefit) at statutory rate		$ 433,109	$ (1,150,283)	$ (186,452)
Percentage depletion allowance		(3,681)	(19,035)	(12,692)
State taxes, net of effect of federal taxes		(46,122)	(76,445)	(3,903)
Reversal of cancellation of indebtedness income		(1,493,162)	0	0
Worthless stock deduction		(80,077)	0	0
Change in valuation allowance		1,185,326	865,146	226,929
Other, net		(19)	7,237	1,752
Provision for (benefit from) income taxes		$ (4,626)	$ (373,380)	$ 25,634
Successor [Member]
Income Tax Examination [Line Items]
Income tax provision (benefit) at statutory rate	$ 12,112
Percentage depletion allowance	(4,292)
State taxes, net of effect of federal taxes	633
Reversal of cancellation of indebtedness income	0
Worthless stock deduction	0
Change in valuation allowance	(7,655)
Other, net	358
Provision for (benefit from) income taxes	$ 1,156