Leases - Narrative (Details) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Leased Assets [Line Items]
Impaired direct financing receivables	$ 0	$ 0
Rent expense	141,000,000	130,000,000	$ 127,000,000
Contingent rentals from operating leases	377,000,000	357,000,000	342,000,000
Direct Financing Leases
Operating Leased Assets [Line Items]
Contingent rental income	$ 18,000,000	$ 15,000,000	$ 12,000,000
Trucks and Tractors
Operating Leased Assets [Line Items]
Minimum lease term of revenue earning equipment	3 years
Maximum lease term of revenue earning equipment	7 years
Trailers
Operating Leased Assets [Line Items]
Maximum lease term of revenue earning equipment	10 years

The increases or decreases in lease payments that result from changes occurring after the inception of the lease in the factors (other than the passage of time) on which lease payments are based, except that any escalation of minimum lease payments relating to increases in construction or acquisition cost of the leased property or for increases in some measure of cost or value during the construction or preconstruction period, are excluded from contingent rentals. Contingent rentals also may include amounts for which the triggering events have not yet occurred or the specified targets for which have not yet been achieved (such as sales based percentage rent), but which events are considered probable of occurring or which specified targets are considered probable of being achieved.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration