Commitments and Contingencies (Capital Lease Obligations) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Capital Leased Assets [Line Items]
Debt and capital lease obligations	$ 122	$ 67
Less accumulated depreciation and amortization	(12)	(14)
Property and equipment, net	10	9
Rental Equipment
Capital Leased Assets [Line Items]
Depreciation and amortization	22	21	$ 20
Capital leased assets	257	203
Less accumulated depreciation and amortization	(86)	(80)
Property and equipment, net	171	123
Non-rental Equipment
Capital Leased Assets [Line Items]
Depreciation and amortization	1	2	$ 3
Non-rental vehicles
Capital Leased Assets [Line Items]
Capital leased assets	6	2
Buildings
Capital Leased Assets [Line Items]
Capital leased assets	$ 16	$ 21

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Amount before accumulated depreciation of leased physical assets used in the normal conduct of business to produce goods and services.

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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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The total gross amount less the charge for the use of the long-lived depreciable assets subject to a lease meeting the criteria for capitalization.

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The charge for the use of long-lived depreciable capital leased assets for the period.

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