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 amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Remaining amortization period of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Summary of Significant Accounting Policies - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property and Equipment
Property and equipment, gross	$ 8,188	$ 8,396
Less accumulated depreciation	(5,226)	(5,513)
Property and equipment, net	2,962	2,883
Depreciation expense	464	471	$ 425
Land
Property and Equipment
Property and equipment, gross	72	73
Equipment
Property and Equipment
Property and equipment, gross	$ 1,613	1,603
Equipment \| Minimum
Property and Equipment
Estimated useful lives	10 years
Equipment \| Maximum
Property and Equipment
Estimated useful lives	50 years
Equipment
Property and Equipment
Property and equipment, gross	$ 6,012	6,362
Equipment \| Minimum
Property and Equipment
Estimated useful lives	2 years
Amortization period of software costs included in equipment	3 years
Equipment \| Maximum
Property and Equipment
Estimated useful lives	25 years
Amortization period of software costs included in equipment	10 years
Construction in progress
Property and Equipment
Property and equipment, gross	$ 491	$ 358