Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2012

Asset Retirement Obligations (Tables) [Abstract]

Change in Asset Retirement Obligations

The following table presents the change in our AROs during 2012 and 2011:

	2012			2011
	(Millions of Dollars)
Balance as of January 1	$	55.5		$	52.6
Liabilities Incurred	—			0.6
Liabilities Settled	(14.0		)	(2.2		)
Accretion	2.8			3.0
Cash Flow Revisions	—			1.5
Balance as of December 31	$	44.3		$	55.5