Decommissioning and Other Asset Retirement Obligations (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Decommissioning and Other Asset Retirement Obligations Detail [Table]
Beginning balance for the period, as reported	$ 54,591	$ 57,449
Activity in the period:
Accretion of liability	404	806
Retirement obligations incurred	0	0
Revisions in estimated cash flows	92	213
Settlement of retirement obligations	(64)	(3,445)
Ending balance as of June 30	55,023	55,023
Value of asset retirement obligations associated with non-operated properties	$ 9,500	$ 9,500	$ 9,100