Segment Information (Summary Of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 562,684	$ 501,221
Operating Income	35,115	25,972
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues	431,556	385,003
Operating Income	33,422	23,466
Werner Logistics
Segment Reporting Information [Line Items]
Revenues	117,420	99,853
Operating Income	2,757	3,049
Other
Segment Reporting Information [Line Items]
Revenues	13,259	16,110
Operating Income	(386)	145
Corporate
Segment Reporting Information [Line Items]
Revenues	907	422
Operating Income	(678)	(688)
Subtotal
Segment Reporting Information [Line Items]
Revenues	563,142	501,388
Inter-segment eliminations
Segment Reporting Information [Line Items]
Revenues	$ (458)	$ (167)