Derivatives and Other Financial Instruments - Schedule of Gains and Losses on Derivative Excluded from Assessment of Effectiveness Recognized in Current Earnings (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss expected to be recognized into earnings over the next 12 months	$ 23
Amount of gain or (loss) recognized in earnings related amount excluded from the assessment of hedge effectiveness	(1)	3
Earnings recognized in relation to ineffective portion of the hedging relationship		$ (1)	$ 1