Discontinued Operations and Held for Sale Properties (Balance Sheet) (Details) - San Juan Basin properties - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets of Disposal Group, Including Discontinued Operation [Abstract]
Inventories	$ 3,651	$ 0
Oil and natural gas properties	305,386	1,166,124
Less accumulated depreciation, depletion and amortization	(219,059)	(770,327)
Other property and equipment, net	3,761	0
Total assets held-for-sale	93,739	395,797
Liabilities of Disposal Group, Including Discontinued Operation [Abstract]
Other long-term liabilities	(12,789)	(24,230)
Total liabilities held-for-sale	(12,789)	(24,230)
Total held-for-sale properties	$ 80,950	$ 371,567