Asset Retirement Obligations Asset Retirement Obligations (Notes)

12 Months Ended

Dec. 31, 2011

Asset Retirement Obligations [Abstract]

ASSET RETIREMENT OBLIGATIONS [Text Block]

ASSET RETIREMENT OBLIGATIONS

We have recorded AROs for requirements imposed by certain regulations pertaining to hazardous materials disposal and other cleanup obligations. Our AROs primarily include regulatory or contractual obligations for the expected demolition or removal of assets and related hazardous materials, if applicable, of equipment or piping at our refineries. We have also recorded obligations related to underground storage tank removal at our leased retail stations. Changes in AROs for the years ended December 31, 2011 and 2010, were as follows (in millions):

	2011			2010
Balance at beginning of year (current and noncurrent)	$	30		$	34
Additions to accrual	3			2
Accretion expense	2			2
Settlements	(8		)	(7		)
Changes in timing and amount of estimated cash flows	(1		)	(1		)
Balance at end of year	$	26		$	30