Intangible Assets - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Customer loyalty payments in cash	$ 26	$ 12
Balances of accrued commission and incentives	308		253
Acquired Intangible Assets [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Amortization expense	19	20
Customer Loyalty Payments [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Balances of accrued commission and incentives	52		35
Amortization expense	$ 18	$ 14