Revenue (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) customerTypes	Sep. 30, 2019 USD ($)
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Number of Different Client Types | customerTypes			2
Revenue	$ 691,495	$ 561,441	$ 1,757,262	$ 1,653,300
Truckload
Disaggregation of Revenue [Line Items]
Revenue	488,158	368,859	1,208,131	1,085,431
Less than truckload
Disaggregation of Revenue [Line Items]
Revenue	175,460	167,604	474,962	487,590
Other revenue
Disaggregation of Revenue [Line Items]
Revenue	27,876	24,978	74,170	80,279
Transactional
Disaggregation of Revenue [Line Items]
Revenue	533,853	433,319	1,359,021	1,273,687
Managed Transportation
Disaggregation of Revenue [Line Items]
Revenue	$ 157,641	$ 128,123	$ 398,241	$ 379,613