Exit and Disposal Costs - Components and Changes in Restructuring Accruals (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013
Restructuring Cost and Reserve [Line Items]
Provision	$ 44
Discontinued operations-Downstream businesses [Member]
Restructuring Cost and Reserve [Line Items]
Provision	33	122
General and Administrative Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Provision	9	52
Exploration and Production [Member] | Operating Costs and Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Provision	1	45
Exploration and Production [Member] | Exploration Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Provision	$ 1	$ 16