Intangible Assets - Amortization Expense Charged to Income for Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization expenses	$ 81	$ 80	$ 163	$ 161