Property and Equipment, Net (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Summary of Property and equipment
Cost	$ 960	$ 947
Accumulated depreciation	(558)	(531)
Net	402	416
Capitalized software [Member]
Summary of Property and equipment
Cost	633	629
Accumulated depreciation	(408)	(386)
Net	225	243
Computer Equipment [Member]
Summary of Property and equipment
Cost	268	274
Accumulated depreciation	(143)	(138)
Net	125	136
Building and leasehold improvements [Member]
Summary of Property and equipment
Cost	13	12
Accumulated depreciation	(7)	(7)
Net	6	5
Construction in progress [Member]
Summary of Property and equipment
Cost	46	32
Net	$ 46	$ 32

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

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Gross amount of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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- Definition

Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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