Intangible Assets - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended	6 Months Ended
	Dec. 31, 2012	Jun. 30, 2013 Customer Relationships [Member]	Jun. 30, 2012 Customer Relationships [Member]	Jun. 30, 2013 Customer Loyalty Payments [Member]	Jun. 30, 2012 Customer Loyalty Payments [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
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
Amortization expense		$ 40	$ 41	$ 29	$ 31