Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2011

Asset Retirement Obligations [Abstract]

Change to asset retirement obligations

	2011			2010
	(Millions of dollars)
Asset retirement obligations at January 1	$	1,358		$	1,297
Liabilities incurred		25			255
Liabilities settled or disposed of		(334	)		(282	)
Accretion expense		96			78
Revisions of estimated liabilities		947			(6	)
Foreign currency translation		(21	)		16
Asset retirement obligations at December 31		2,071			1,358
Less: current obligations		227			155
Long-term obligations at December 31	$	1,844		$	1,203