Schedule Of Derivative Instruments, Gain or Loss In Statement Of Financial Performance (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in net income (loss)	$ 2	$ 0	$ 4	$ (19)
Fair Value Derivatives | Interest rate contracts | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in net income (loss)	$ 2	$ 3	$ 6	$ 14