Derivative Instruments and Hedging Activities - Commodity Derivative Activity Recorded in Statement of Consolidated Operations (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
Derivative Instruments, Gain (Loss) [Line Items]
Loss on cash flow hedges reclassified from accumulated other comprehensive loss		$ (11)		$ (20)
Loss on derivatives recognized in income			Oil and Gas Production Revenues
Realized gain (loss)	(174)	247	(194)	147
Loss on derivatives recognized in income			Derivative instrument gains (losses), net
Derivatives Not Designated as Cash Flow Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized gain (loss)	(125)	5	(221)	(47)
Unrealized gain (loss)	(49)	242	27	194
Gain (loss) on derivatives not designated as cash flow hedges	$ (174)	$ 247	$ (194)	$ 147