Revenue (Disaggregation of Revenue by Revenue Source) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of revenue
Revenues	$ 627,533	$ 619,130	$ 1,223,650	$ 1,181,814
Truckload Transportation Services
Disaggregation of revenue
Revenues	479,959	470,277	942,850	901,833
Werner Logistics
Disaggregation of revenue
Revenues	130,883	134,012	248,253	251,432
Inter-segment eliminations
Disaggregation of revenue
Revenues	(34)	(212)	(239)	(670)
Transportation Services
Disaggregation of revenue
Revenues	610,808	604,077	1,190,864	1,152,595
Other revenues
Disaggregation of revenue
Revenues	$ 16,725	$ 15,053	$ 32,786	$ 29,219