Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2013

Asset Retirement Obligation Disclosure [Abstract]

Schedule of change in asset retirement obligation

During 2013 and 2012, our overall asset retirement obligation changed as follows (in thousands):

	2013			2012
Beginning balance	$	296,870		$	302,768
Accretion	31,461			23,052
New obligations	2,225			2,556
Changes in estimates of existing obligations (1)	(27,628		)	10,895
Property dispositions/obligations settled	(28,941		)	(42,401		)
Ending balance	$	273,987		$	296,870

(1) The 2013 changes in estimates of existing obligations reflects decreases of $36 million, primarily due to a revision in the estimated remaining life of the assets, which is among several factors considered in the annual review process, including inflation rates, current estimates for removal cost and discount rates. These decreases are partially offset by an increase of $9 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 2012 changes in estimates of existing obligations is 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.