Intangible Assets - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Customer loyalty payments in cash	$ 60	$ 38
Balance of accrued commissions and incentives	266		211
Other current assets reclassified as customer loyalty payments within other intangible assets			50
Other non-current assets reclassified as customer loyalty payments within other intangible assets			68
Customer Relationships [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Amortization expense	61	61
Customer Loyalty Payments [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Balance of accrued commissions and incentives	22		15
Amortization expense	$ 45	$ 48