Property and Equipment, Net - Summary of Property and Equipment (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Cost	$ 986	$ 947
Accumulated depreciation	(585)	(531)
Net	401	416
Capitalized software [Member]
Property, Plant and Equipment [Line Items]
Cost	640	629
Accumulated depreciation	(429)	(386)
Net	211	243
Computer equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	274	274
Accumulated depreciation	(148)	(138)
Net	126	136
Building and leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Cost	15	12
Accumulated depreciation	(8)	(7)
Net	7	5
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Cost	57	32
Net	$ 57	$ 32