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	$	67,640		$	80,313
Accretion	5,708			5,543
New obligations	51			15
Changes in estimates of existing obligations (1)	(12,577		)	(18,231		)
Property Dispositions & Settlements	(69		)	—
Ending balance	$	60,753		$	67,640

(1) 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 decrease in 2012 is primarily attributed to a decrease in removal cost estimates. The decrease in 2013 is primarily attributed to increases in the discount rate and the remaining life of the applicable property.