Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2013

Asset Retirement Obligations

Schedule of changes in the entity's AROs

	(in millions)
Obligation at December 31, 2012	$	145.0
Accretion expense		7.8
Liabilities incurred		1.1
Expenditures		(3.6	)
Changes in estimate		7.8
Obligation at September 30, 2013	$	158.1

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

	September 30, 2013		December 31, 2012
	(in millions)
Current portion	$	9.4	$	12.3
Noncurrent portion		148.7		132.7
	$	158.1	$	145.0