Property, Plant and Equipment (Narrative) (Details) - USD ($)		4 Months Ended	8 Months Ended	12 Months Ended
		Dec. 31, 2016	Aug. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property Plant And Equipment [Line Items]
Non-cash investing activities capital expenditures, reflected within the changes in accounts payable and accrued liabilities		$ 300,000
Non cash investing activities capital expenditures included in operating activities		31,000,000
Impairments of Unproved Gas And Oil Properties		0
Asset impairment		0
Gain (loss) on asset sales and disposal	[1]	$ 180,000
Predecessor
Property Plant And Equipment [Line Items]
Non-cash investing activities capital expenditures, reflected within the changes in accounts payable and accrued liabilities			$ 18,700,000	$ 22,600,000	$ 25,000,000
Non cash investing activities capital expenditures included in operating activities			7,700,000
Impairments of Unproved Gas And Oil Properties			0	6,600,000	0
Asset impairment			0	966,635,000	573,774,000
Gain (loss) on asset sales and disposal	[1]		$ (479,000)	(1,181,000)	(1,869,000)
Predecessor | Barnett and Coal-bed Methane
Property Plant And Equipment [Line Items]
Asset impairment				960,000,000
Predecessor | Appalachian Basin
Property Plant And Equipment [Line Items]
Asset impairment					555,700,000
Predecessor | Reclassification out of Accumulated Other Comprehensive Income
Property Plant And Equipment [Line Items]
Future hedge gains reclassified from accumulated other comprehensive income				$ 85,800,000	$ 82,300,000

[1] Gain (loss) on asset sales and disposal, reorganization items, net, gain on early extinguishment of debt, interest expense and income tax (expense) benefit have not been allocated to reportable segments as it would be impracticable to reasonably do so for the periods presented.