Goodwill and Other Intangible Assets - Additional Information (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
Finite And Indefinite Intangible Assets [Line Items]
Goodwill deductible for income tax purposes	$ 108		$ 108
Amortization expense, intangible assets	74	73	228	217
Amortization expense, computer software	$ 38	$ 38	$ 120	$ 111