Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2011

Asset Retirement Obligations [Abstract]

ARO operating costs

	Three Months Ended				Nine Months Ended
	September 30				September 30
in thousands	2011		2010		2011		2010
ARO Operating Costs
Accretion		$1,894		$2,081		$6,189		$6,525
Depreciation		1,947		3,050		5,342		9,390
Total		$3,841		$5,131		$11,531		$15,915

Reconciliations of ARO

	Three Months Ended						Nine Months Ended
	September 30						September 30
in thousands	2011			2010			2011			2010
Asset Retirement Obligations
Balance at beginning of period		$160,733			$162,168			$162,730			$167,757
Liabilities incurred		1,456			1,016			1,734			2,457
Liabilities settled		(6,238	)		(4,762	)		(12,202	)		(8,879	)
Accretion expense		1,894			2,081			6,189			6,525
Revisions up (down)		139			(288	)		(467	)		(7,645	)
Balance at end of period		$157,984			$160,215			$157,984			$160,215