Subsequent Events (Details) - USD ($)		9 Months Ended
	Oct. 20, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Subsequent Event [Line Items]
Proceeds from sale of property		$ 0	$ 11,643,000
Tug Hill | Scenario, Forecast | Disposal Group, Disposed of by Sale
Subsequent Event [Line Items]
Escrow deposit	$ 31,000,000
7 1⁄2% Senior Notes due 2022
Subsequent Event [Line Items]
Interest rate				7.50%
Senior Notes | 7 1⁄2% Senior Notes due 2022
Subsequent Event [Line Items]
Interest rate		7.50%
RSA | Scenario, Forecast
Subsequent Event [Line Items]
Elimination of debt outstanding	850,000,000
Reduction in annual interest payments	46,000,000
RSA | Senior Notes | 7 1⁄2% Senior Notes due 2022
Subsequent Event [Line Items]
Interest rate		7.50%
Subsequent Event | Tug Hill | Disposal Group, Disposed of by Sale
Subsequent Event [Line Items]
Proceeds from sale of property	360,000,000
Escrow deposit	5,000,000
Maximum title and environmental defect loss	$ 10,000,000
Period for court approval of PSA and other matters	30 days
Subsequent Event | RSA
Subsequent Event [Line Items]
Minimum percentage of decrease in debt outstanding	66.66%
Percentage of decrease in debt outstanding	85.40%
Percentage of common stock issued in reorganization	95.00%
Percentage of common stock issued in reorganization to existing shareholders	5.00%
Repayments of debt	$ 225,000,000
Percentage of warrants issued in reorganization	15.00%
Subsequent Event | RSA | Minimum
Subsequent Event [Line Items]
Estimate of unsecured claims	$ 17,000,000
Subsequent Event | RSA | Maximum
Subsequent Event [Line Items]
Estimate of unsecured claims	27,000,000
Subsequent Event | RSA | Appalachia regions of Pennsylvania and West Virginia
Subsequent Event [Line Items]
Minimum proceeds from sale property	350,000,000
Minimum payment of net cash proceeds from the sale of properties	$ 150,000,000
Payment of excess net cash proceeds from sale of properties	85.00%