Net Interest Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Interest Income Expense Net
Interest expense, net of capitalized interest	$ 51	$ 31	$ 106	$ 85
Interest income	(6)	(6)	(19)	(20)
Net interest expense	$ 45	$ 25	$ 87	$ 65