Financial Instruments - Schedule of Interest Rate Swap Agreements Designated as Cash Flow Hedges (Detail) (Pay-Fixed Interest Rate Swaps [Member], USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Maturity Date, 2014 [Member]
Derivative Instruments [Line Items]
Fair Value	$ (6)
Notional Amount	500
Pay-fixed interest rate swaps	Dec. 31, 2014
Maturity Date, 2016 [Member]
Derivative Instruments [Line Items]
Fair Value	(269)
Notional Amount	3,000
Pay-fixed interest rate swaps	Dec. 31, 2016
Maturity Date, 2017 [Member]
Derivative Instruments [Line Items]
Fair Value	(48)
Notional Amount	$ 1,000
Pay-fixed interest rate swaps	Dec. 31, 2017