Derivative Instruments and Hedging Activities - Commodity Derivative Activity Recorded in Statement of Consolidated Operations (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Oil and Gas Production Revenues [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on cash flow hedges reclassified from accumulated other comprehensive loss		$ (9)
Oil and Gas Production Revenues [Member] | Derivatives Not Designated as Cash Flow Hedging Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Realized loss	(96)	(52)
Unrealized gain (loss)	76	(48)
Derivative Instrument Losses, Net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on derivatives not designated as cash flow hedges	$ (20)	$ (100)