Schedule of Property and Equipment Net (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Abstract]
Land	$ 51us-gaap_Land	$ 56us-gaap_Land
Buildings and leasehold improvements	565us-gaap_BuildingsAndImprovementsGross	549us-gaap_BuildingsAndImprovementsGross
Capitalized software	485	494
Furniture, fixtures and equipment	392us-gaap_FurnitureAndFixturesGross	374us-gaap_FurnitureAndFixturesGross
Buses and support vehicles	78	74
Projects in process	82us-gaap_ConstructionInProgressGross	64us-gaap_ConstructionInProgressGross
Property and Equipment, gross	1,653us-gaap_PropertyPlantAndEquipmentGross	1,611us-gaap_PropertyPlantAndEquipmentGross
Less: Accumulated depreciation and amortization	(1,015)	(997)
Property, Plant and Equipment, Net, Total	$ 638us-gaap_PropertyPlantAndEquipmentNet	$ 614us-gaap_PropertyPlantAndEquipmentNet

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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- Definition

Amount before accumulated depreciation of building structures held for productive use including addition, improvement, or renovation to the structure, including, but not limited to, interior masonry, interior flooring, electrical, and plumbing.

+ References

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- Definition

Amount before accumulated amortization of capitalized costs for computer software, including but not limited to, acquired and internally developed computer software.

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- Definition

Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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- Definition

Amount before accumulated depreciation of equipment commonly used in offices and stores that have no permanent connection to the structure of a building or utilities. Examples include, but are not limited to, desks, chairs, tables, and bookcases.

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- Definition

Amount before accumulated depletion of real estate held for productive use, excluding land held for sale.

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Amount before accumulated depreciation, depletion and amortization of 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, and furniture and fixtures.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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- Definition

Period end book value of vehicles owned by the public utility.

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No definition available.

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