Acquisitions and Investments (Acquisitions of Convenience Stores) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended						12 Months Ended
	Jul. 31, 2012 Store		May 31, 2012 Parcels Store		May 31, 2011 Store		Dec. 31, 2013 Store		Dec. 31, 2012
Business Acquisition [Line Items]
Goodwill, Acquired During Period							$ 8	[1]	$ 88	[1]
Speedway [Member]
Business Acquisition [Line Items]
Number of convenience stores acquired	10		87		23		9
Goodwill, Acquired During Period	$ 5	[1]	$ 83	[1]	$ 9	[1]	$ 8	[1]	$ 88	[1]
Number of undeveloped real estate parcels acquired for future development			2

[1] See Note 5 for information on the acquisitions.