Basis of Presentation and Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended		12 Months Ended
	May 31, 2011	Jan. 21, 2011	Dec. 31, 2012 plants refineries retail_sites branded_wholesale_sites
Basis of Presentation and Summary of Significant Accounting Policies (Textual)
Number of refineries owned			16
Combined total throughput capacity of petroleum refining			3,000,000
Number of company-owned and leased retail sites			1,880
Number of branded wholesale sites			5,450
Number of ethanol plants owned			10
Combined capacity of ethanol (gallons per year)			1,100,000,000
Date of joint venture agreement		Jan. 21, 2011
Feed capacity of diesel plants		10,000
Estimated aggregate cost to construct diesel plant		$ 368
Date of joint venture construction financing agreement	May 31, 2011
Maximum amount of joint venture construction financing	$ 221
Maximum percentage of joint venture construction costs financed	0.60
Maximum maturity period (in months) of temporary cash investments			3 months
Period (in years) of estimated undiscounted future costs resulted in environmental liabilities			20 years
Variable Interest Entity, Primary Beneficiary [Member]
Basis of Presentation and Summary of Significant Accounting Policies (Textual)
Joint venture ownership percentage			50.00%
Variable Interest Entity, Not Primary Beneficiary [Member]
Basis of Presentation and Summary of Significant Accounting Policies (Textual)
Joint venture ownership percentage			50.00%
Minimum [Member]
Basis of Presentation and Summary of Significant Accounting Policies (Textual)
Property, plant and equipment, useful life			25 years
Maximum [Member]
Basis of Presentation and Summary of Significant Accounting Policies (Textual)
Property, plant and equipment, useful life			30 years