Exit and Disposal Costs - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Restructuring Cost and Reserve [Line Items]
Enhanced benefit arrangements	$ 30
Continuing Operations [Member] | Exploration and Production [Member]
Restructuring Cost and Reserve [Line Items]
Enhanced benefit arrangements	5
Continuing Operations [Member] | Retail Marketing and Other [Member]
Restructuring Cost and Reserve [Line Items]
Enhanced benefit arrangements	10
Continuing Operations [Member] | Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Enhanced benefit arrangements	10
Discontinued Operations [Member]
Restructuring Cost and Reserve [Line Items]
Enhanced benefit arrangements	$ 5