Segment Information (Summary Of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 592,703	$ 596,117
Operating Income	31,066	48,019
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues	464,863	462,891
Operating Income	29,089	42,953
Werner Logistics
Segment Reporting Information [Line Items]
Revenues	112,164	117,370
Operating Income	1,085	4,711
Other
Segment Reporting Information [Line Items]
Revenues	15,068	15,472
Operating Income	2,900	1,179
Corporate
Segment Reporting Information [Line Items]
Revenues	619	589
Operating Income	(2,008)	(824)
Subtotal
Segment Reporting Information [Line Items]
Revenues	592,714	596,322
Inter-segment eliminations
Segment Reporting Information [Line Items]
Revenues	$ (11)	$ (205)