Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2012

AssetRetirementObligationDisclosureAbstract

ScheduleOfChangeInAssetRetirementObligationTableTextBlock

		2012		2011
Beginning balance		$	302,768	$	251,644
	Accretion		23,052		19,866
	New obligations		2,556		530
	Changes in estimates of existing obligations (1)		10,895		74,039
	Property dispositions/obligations settled		(42,401)		(43,311)
Ending balance		$	296,870	$	302,768

• The change in estimates of existing obligations in 2012 are primarily due to an increase of $13 million related to changes in the timing and method of abandonment of our Eminence natural gas storage caverns that were associated with a leak in 2010. The 2011 change in estimates of existing obligations included revisions of $35 million primarily due to increases in the inflation rate and estimated removal costs, which are among several factors considered for revision in the annual review process. The 2011 revision also included an increase of $39 million related to changes in the timing and method of abandonment of our Eminence natural gas storage caverns.