Asset Retirement Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance of ARO, beginning	$ 94,060		$ 108,533		$ 118,023
Liabilities incurred	981		2,266		2,772
Liabilities settled	(686)		(1,543)		(5,525)
Accretion expense	7,108		7,859		8,192
Accretion expense of discontinued operations			251		1,197
Revision in estimated cash flows			692
Reclassification associated with held for sale properties	(11,473)	[1]	(23,747)	[2]	(14,929)	[3]
Balance of ARO, end	$ 89,990		$ 94,060		$ 108,533

[1] Asset retirement obligation associated with certain San Juan Basin properties included as liabilities related to assets held for sale in current liabilities on the balance sheet at December 31, 2015.

[2] Asset retirement obligation associated with certain San Juan Basin properties included as liabilities related to assets held for sale in current liabilities on the balance sheet at December 31, 2014.

[3] Asset retirement obligation associated with North Louisiana/East Texas properties.