Financial Instruments - Summary of Reconciliation of Net Carrying Amount of Derivative Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Net derivative asset as of January 1	$ 11
Loss for the period included in net loss	(14)
Proceeds from settlement of foreign exchange derivative contracts	(2)
Settlement of interest rate derivative contracts	3
Termination of foreign currency derivative contracts (settlement pending)	(2)
Net derivative liability as of June 30	$ (4)