Derivative Instruments and Hedging Activities - Commodity Derivative Activity Recorded in Statement of Consolidated Operations (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on cash flow hedges reclassified from accumulated other comprehensive loss		$ 2		$ (18)
Gain (Loss) on derivatives recognized in income			Oil and Gas Production Revenues
Gain (Loss) on derivatives recognized in income			Revenues and other Other
Realized loss	273	(422)	79	(275)
Gain (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 loss	(41)	(91)	(262)	(138)
Unrealized gain (loss)	314	(331)	341	(137)
Gain (loss) on derivatives not designated as cash flow hedges	273	(422)	79	(275)
Revenues and Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Loss for ineffectiveness on cash flow hedges		$ (1)		$ (1)