Goodwill (Details)			12 Months Ended
	Oct. 01, 2017 segment	Apr. 01, 2017 segment	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Goodwill [Line Items]
Goodwill			$ 424,725,000	$ 415,993,000	$ 418,356,000
Accumulated impairment losses			(29,221,000)	(29,221,000)	(29,221,000)
Goodwill, net			395,504,000	386,772,000	389,135,000
Foreign currency translation adjustment			2,226,000	(2,363,000)
Acquisitions			$ 6,506,000
Number of reporting units, used for quantitative assessment | segment	1	2	3
Goodwill impairment loss, quantitative assessment			$ 0
Number of reporting units, used for qualitative assessment | segment	4	3
Fleet Management Solutions
Goodwill [Line Items]
Goodwill			237,176,000	228,832,000	231,358,000
Accumulated impairment losses			(10,322,000)	(10,322,000)	(10,322,000)
Goodwill, net			226,854,000	218,510,000	221,036,000
Foreign currency translation adjustment			1,838,000	(2,526,000)
Acquisitions			6,506,000
Dedicated Transportation Solutions
Goodwill [Line Items]
Goodwill			40,808,000	40,808,000	40,808,000
Accumulated impairment losses			0	0	0
Goodwill, net			40,808,000	40,808,000	40,808,000
Foreign currency translation adjustment				0
Acquisitions			0
Supply Chain Solutions
Goodwill [Line Items]
Goodwill			146,741,000	146,353,000	146,190,000
Accumulated impairment losses			(18,899,000)	(18,899,000)	(18,899,000)
Goodwill, net			127,842,000	127,454,000	$ 127,291,000
Foreign currency translation adjustment			388,000	$ 163,000
Acquisitions			$ 0