Segment Information (Summary Of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 596,117	$ 562,684
Operating Income	48,019	35,115
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues	462,891	431,556
Operating Income	42,953	33,422
Werner Logistics
Segment Reporting Information [Line Items]
Revenues	117,370	117,420
Operating Income	4,711	2,757
Other
Segment Reporting Information [Line Items]
Revenues	15,472	13,259
Operating Income	1,179	(386)
Corporate
Segment Reporting Information [Line Items]
Revenues	589	907
Operating Income	(824)	(678)
Subtotal
Segment Reporting Information [Line Items]
Revenues	596,322	563,142
Inter-segment eliminations
Segment Reporting Information [Line Items]
Revenues	$ (205)	$ (458)