Accrued Expenses and Other Long-Term Liabilities, Asset Retirement Obligations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009
Asset Retirement Obligations Rollforward Analysis
Balance as of beginning of year	$ 101	$ 179	$ 72
Additions to accrual	4	3	98
Reductions to accrual	0	(34)	0
Accretion expense	4	7	14
Settlements	(22)	(54)	(5)
Balance as of end of year	$ 87	$ 101	$ 179
Maximum Years in Which Underground Storage Tanks Remain in Service at Owned Retail Location	25