Acquisitions and Investments (Acquisitions of Convenience Stores) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2014		Dec. 31, 2013 Store
Business Acquisition [Line Items]
Goodwill acquired during period	$ 600
Speedway
Business Acquisition [Line Items]
Number of convenience stores acquired			9
Goodwill acquired during period	$ 600	[1]	$ 8

[1] See Note 4 for information on the acquisitions.