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

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The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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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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Other Financial Data - Components of Fixed Assets, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fixed Assets, net
Fixed assets, gross	$ 1,733	$ 1,746
Less: Accumulated depreciation	1,169	1,196
Fixed assets, net	564	550
Depreciation of fixed assets	187	162	$ 164
Software
Fixed Assets, net
Fixed assets, gross	680	677
Leasehold improvements
Fixed Assets, net
Fixed assets, gross	349	369
Computer equipment
Fixed Assets, net
Fixed assets, gross	295	258
Furniture, fixtures and equipment
Fixed Assets, net
Fixed assets, gross	240	252
Construction in progress
Fixed Assets, net
Fixed assets, gross	79	75
Other
Fixed Assets, net
Fixed assets, gross	$ 90	$ 115