Decommissioning and Other Asset Retirement Obligations (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2014
Decommissioning and Other Asset Retirement Obligations Detail [Table]
Beginning balance for the period, as reported	$ 59,408	$ 62,741
Activity in the period:
Accretion of liability	571	1,413
Retirement obligations incurred	0	0
Revisions in estimated cash flows	1,110	1,347
Settlement of retirement obligations	(1,113)	(5,525)
Ending balance as of June 30	59,976	59,976
Value of asset retirement obligations associated with non-operated properties	$ 8,800	$ 8,800	$ 8,400