Segment Information (Total Assets By Reportable Segment) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	$ 30,460	$ 28,385
Operating Segments | Refining & Marketing
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	19,751	19,573
Operating Segments | Speedway
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	5,296	2,064
Operating Segments | Pipeline Transportation
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	2,407	1,947
Corporate and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total consolidated assets	$ 3,006	$ 4,801