Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2012

Asset Retirement Obligation Disclosure [Abstract]

ScheduleOfChangeInAssetRetirementObligationTableTextBlock

		2012		2011
Beginning balance		$	80,313	$	65,155
	Accretion		5,543		5,162
	New obligations		15		2,257
	Changes in estimates of existing obligations (1)		(18,231)		8,116
	Property Dispositions & Settlements		-		(377)
Ending balance		$	67,640	$	80,313
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• Changes in estimates of existing obligations are primarily due to the annual review process, which considers various factors including inflation rates, current estimates for removal cost, discount rates, and the estimated remaining life of assets.The increase in 2011 is primarily attributed to a decrease in the discount rate. The decrease in 2012 is primarily attributed to a decrease in removal cost estimates.