Intangible Assets - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	May 31, 2014	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 Acquired Intangible Assets [Member]	Jun. 30, 2013 Acquired Intangible Assets [Member]	Jun. 30, 2014 Acquired Intangible Assets [Member]	Jun. 30, 2013 Acquired Intangible Assets [Member]	Jun. 30, 2014 Customer Loyalty Payments [Member]	Jun. 30, 2013 Customer Loyalty Payments [Member]	Jun. 30, 2014 Customer Loyalty Payments [Member]	Jun. 30, 2013 Customer Loyalty Payments [Member]	Dec. 31, 2013 Customer Loyalty Payments [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Goodwill acquired	$ 14	$ 14
Acquisition of goodwill paid in cash	10
Deferred consideration to be paid	4
Customer loyalty payments in cash		45	36
Balances of accrued commission and incentives		298		253					62		62		35
Amortization expense					$ 20	$ 20	$ 39	$ 40	$ 19	$ 15	$ 37	$ 29