Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2012

Asset Retirement Obligations

Schedule of changes in carrying amount of asset retirement obligations

Changes in the carrying amount of our AROs were as follows (in thousands):

	2012			2011
Balance at January 1	$	199,633		$	188,757
Accretion expense		13,189			12,469
Revisions to estimated cash flows		33,444			5,913
Payments		(5,632	)		(7,506	)
Balance at December 31		240,634			199,633
Less: current portion		(1,643	)		(6,926	)
Asset retirement obligation, net of current portion	$	238,991		$	192,707