Goodwill (Details) - USD ($) $ in Thousands			3 Months Ended	12 Months Ended
	Oct. 01, 2018	Oct. 01, 2017	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Goodwill			$ 424,725	$ 424,725	$ 415,993
Accumulated impairment losses				(44,734)	(29,221)	$ (29,221)
Goodwill				475,206	395,504	386,772
Foreign currency translation adjustment				(475)	2,226
Acquisitions				95,690	6,506
Goodwill				519,940	424,725	415,993
Goodwill impairment charge	$ 0	$ 0	15,513	15,513	0	0
Fleet Management Solutions
Goodwill [Roll Forward]
Goodwill			237,176	237,176	228,832
Accumulated impairment losses				(25,835)	(10,322)	(10,322)
Goodwill				243,606	226,854	218,510
Foreign currency translation adjustment				(1)	1,838
Acquisitions				32,266	6,506
Goodwill				269,441	237,176	228,832
Dedicated Transportation Solutions
Goodwill [Roll Forward]
Goodwill			40,808	40,808	40,808
Accumulated impairment losses				0	0	0
Goodwill				40,808	40,808	40,808
Foreign currency translation adjustment				0	0
Acquisitions				0	0
Goodwill				40,808	40,808	40,808
Supply Chain Solutions
Goodwill [Roll Forward]
Goodwill			$ 146,741	146,741	146,353
Accumulated impairment losses				(18,899)	(18,899)	(18,899)
Goodwill				190,792	127,842	127,454
Foreign currency translation adjustment				(474)	388
Acquisitions				63,424	0
Goodwill				$ 209,691	$ 146,741	$ 146,353