Fair Value Measurements - Fair Values of Derivative Instruments in Condensed Consolidated Balance Sheets (Detail) (Derivatives Designated as Hedging Instruments, Interest rate contracts, USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Derivatives Designated as Hedging Instruments | Interest rate contracts
Derivatives Fair Value [Line Items]
Accounts Payable and Other Current Liabilities	$ 1	$ 6
Other Non-Current Liabilities	$ 12	$ 16