Revenue (Disaggregation of Revenue by Revenue Source) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of revenue
Revenues	$ 629,735	$ 528,643	$ 1,811,549	$ 1,549,372
Truckload Transportation Services
Disaggregation of revenue
Revenues	484,782	407,566	1,386,615	1,196,071
Werner Logistics
Disaggregation of revenue
Revenues	129,422	104,568	380,854	305,225
Inter-segment eliminations
Disaggregation of revenue
Revenues	(208)	(104)	(878)	(720)
Transportation Services
Disaggregation of revenue
Revenues	613,996	512,030	1,766,591	1,500,576
Other revenues
Disaggregation of revenue
Revenues	$ 15,739	$ 16,613	$ 44,958	$ 48,796