Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2013

Asset Retirement Obligation [Abstract]

Asset retirement obligations roll forward

The following is a reconciliation of the changes in the Company's asset retirement obligation from January 1, 2013, to September 30, 2013:

	Asset Retirement Obligations
	2013
	(in millions)
ARO liability at January 1,	$	193.1
Accretion	7.2
Liabilities incurred	8.7
Revisions	(25.3		)
Liabilities settled	(13.5		)
ARO liability at September 30,	$	170.2