Asset Retirement Obligations (table)

12 Months Ended

Dec. 31, 2014

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations Table

The following table provides a summary of changes in asset retirement obligations:

	Year Ended December 31,
thousands	2014			2013
Carrying amount of asset retirement obligations at beginning of year	$	78,035		$	66,723
Liabilities incurred	13,769			14,143
Liabilities settled	(4,181		)	(1,943		)
Accretion expense	4,846			4,326
Revisions in estimated liabilities	16,623			(5,214		)
Carrying amount of asset retirement obligations at end of year	$	109,092		$	78,035