Derivative Instruments - Effect of Derivative Instruments - Statement of Income Table (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Derivative [Line Items]
Total (gains) losses on derivatives, net	$ (392)		$ (308)		$ 469
Gathering, Processing, and Marketing Sales and Gains (Losses) on Derivatives, Net [Member]
Derivative [Line Items]
Total (gains) losses on derivatives, net	(392)		(308)		469
Commodity Derivatives [Member] | Gathering, Processing, and Marketing Sales [Member]
Derivative [Line Items]
Total (gains) losses on derivatives, net	6	[1]	18	[1]	8	[1]
Commodity Derivatives [Member] | (Gains) Losses on Derivatives, net [Member]
Derivative [Line Items]
Total (gains) losses on derivatives, net	141		(387)		(562)
Interest-Rate and Other Derivatives [Member] | (Gains) Losses on Derivatives, net [Member]
Derivative [Line Items]
Total (gains) losses on derivatives, net	$ (539)		$ 61		$ 1,023

[1] Represents the effect of marketing and trading derivative activities.