Segment Information - Total Assets by Reportable Segment (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 29,003	$ 27,223
Operating Segments [Member] | Refining & Marketing [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	20,379	17,052
Operating Segments [Member] | Speedway [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	2,036	1,947
Operating Segments [Member] | Pipeline Transportation [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,943	1,950
Corporate and Other [Member] | Corporate And Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 4,645	$ 6,274