Segment Information (Summary Of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 629,735	$ 528,643	$ 1,811,549	$ 1,549,372
Operating Income	63,386	35,874	149,284	98,759
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues	484,782	407,566	1,386,615	1,196,071
Operating Income	58,894	34,009	135,748	93,511
Werner Logistics
Segment Reporting Information [Line Items]
Revenues	129,422	104,568	380,854	305,225
Operating Income	4,776	1,318	13,135	6,652
Other
Segment Reporting Information [Line Items]
Revenues	15,107	16,020	42,788	47,257
Operating Income	576	1,001	433	605
Corporate
Segment Reporting Information [Line Items]
Revenues	632	593	2,170	1,539
Operating Income	(860)	(454)	(32)	(2,009)
Subtotal
Segment Reporting Information [Line Items]
Revenues	629,943	528,747	1,812,427	1,550,092
Inter-segment eliminations
Segment Reporting Information [Line Items]
Revenues	$ (208)	$ (104)	$ (878)	$ (720)