Segment Information - Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	$ 363	[1],[2],[3]	$ 283	[1],[2],[3]	$ 734	[1],[2]	$ 1,857	[1],[2]
Plus: Items not allocated to segments:
Capital expenditures	322	[4],[5]	277	[4],[5]	570	[4],[5]	1,846	[4],[5]
Operating Segments
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	343	[2]	251	[2]	683	[2]	1,797	[2],[6]
Less: Investments in equity method investees	41		6		164		11
Corporate and Other
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	20	[2],[3]	32	[2],[3]	51	[1],[2]	60	[1],[2]
Plus: Items not allocated to segments:
Capital expenditures not allocated to segments	13		28		38		52
Capitalized interest	$ 7		$ 4		$ 13		$ 8

[1] The six months ended June 30, 2013 includes the acquisition of the Galveston Bay Refinery and Related Assets, comprised of total consideration, excluding inventory and other current assets, plus assumed liabilities. Total consideration includes the base purchase price and a fair-value estimate of $600 million for the contingent consideration. See Note 4 to the unaudited consolidated financial statements.

[2] Capital expenditures include changes in capital accruals, acquisitions and investments in affiliates.

[3] Includes capitalized interest $7 million and $4 million for the three months ended June 30, 2014 and 2013, respectively, and $13 million and $8 million for the six months ended June 30, 2014 and 2013, respectively.

[4] Capital expenditures include changes in capital accruals and acquisitions.

[5] See Note 16 for a reconciliation of total capital expenditures to additions to property, plant and equipment as reported in the consolidated statements of cash flows.

[6] The Refining & Marketing and Pipeline Transportation segments include the acquisition of the Galveston Bay Refinery and Related Assets. See Note 4.