Asset Retirement Obligations (Tables)

3 Months Ended

Mar. 31, 2012

Asset Retirement Obligations

Schedule of changes in the entity's AROs

	(in millions)
Obligation at December 31, 2011	$	131.6
Accretion expense		2.4
Liabilities incurred		0.4
Expenditures		(2.0	)
Obligation at March 31, 2012	$	132.4

Schedule of AROs reported in accrued expenses and other noncurrent liabilities on the entity's consolidated balance sheet

	March 31, 2012		December 31, 2011
	(in millions)
Current portion	$	16.2	$	13.8
Noncurrent portion		116.2		117.8
	$	132.4	$	131.6