Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2016

Asset Retirement Obligation [Abstract]

Schedule Of Asset Retirement Obligations

		December 31,
		2016		2015
Asset retirement obligations at beginning of period	$	146,210	$	127,240
Accretion expense		10,252		9,122
Liabilities incurred		1,317		7,352
Liabilities settled		(170)		(1,861)
Revisions of estimated liabilities		(436)		4,357
Asset retirement obligations at end of period		157,173		146,210
Less: current asset retirement obligations		(239)		(305)
Long-term asset retirement obligations	$	156,934	$	145,905