Segment Information (Summary Of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 619,130	$ 519,508	$ 1,181,814	$ 1,020,729
Operating Income	50,783	36,913	85,898	62,885
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues	470,277	403,502	901,833	788,505
Operating Income	43,432	36,036	76,854	59,502
Werner Logistics
Segment Reporting Information [Line Items]
Revenues	134,012	100,804	251,432	200,657
Operating Income	5,602	2,285	8,359	5,334
Other
Segment Reporting Information [Line Items]
Revenues	14,422	15,127	27,681	31,237
Operating Income	243	(541)	(143)	(396)
Corporate
Segment Reporting Information [Line Items]
Revenues	631	524	1,538	946
Operating Income	1,506	(867)	828	(1,555)
Subtotal
Segment Reporting Information [Line Items]
Revenues	619,342	519,957	1,182,484	1,021,345
Inter-segment eliminations
Segment Reporting Information [Line Items]
Revenues	$ (212)	$ (449)	$ (670)	$ (616)