Intangible Assets - Amortization Expense Charged to Income for Intangible Assets (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
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization expenses	$ 80	$ 84	$ 244	$ 245