Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2012

Asset Retirement Obligation [Abstract]

Asset retirement obligations roll forward

The following is a reconciliation of the changes in the asset retirement obligation from January 1, 2012, to September 30, 2012, respectively:

	Asset Retirement Obligations
	2012
	(in millions)
ARO liability at January 1,	$	163.9
Accretion	7.7
Liabilities incurred	5.2
Liabilities settled	(0.2		)
ARO liability at September 30,	$	176.6