Investments and Acquisitions (Narrative) (Details) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Schedule of Investments [Line Items]
Acquisitions of freight management companies	$ 21
Contingent consideration	$ 8
Contingent consideration, expected payment timing	2 years

Line items represent reporting 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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
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-Section 12
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