Segment Information (Summary Of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 528,643	$ 508,676	$ 1,549,372	$ 1,490,159
Operating Income	35,874	29,074	98,759	91,114
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues	407,566	384,312	1,196,071	1,136,478
Operating Income	34,009	19,846	93,511	74,971
Werner Logistics
Segment Reporting Information [Line Items]
Revenues	104,568	109,459	305,225	310,001
Operating Income	1,318	4,894	6,652	16,502
Other Segment
Segment Reporting Information [Line Items]
Revenues	16,020	14,804	47,257	43,148
Operating Income	1,001	(1,191)	605	(4,964)
Corporate Segment
Segment Reporting Information [Line Items]
Revenues	593	313	1,539	1,300
Operating Income	(454)	5,525	(2,009)	4,605
Subtotal
Segment Reporting Information [Line Items]
Revenues	528,747	508,888	1,550,092	1,490,927
Intersegment Elimination
Segment Reporting Information [Line Items]
Revenues	$ (104)	$ (212)	$ (720)	$ (768)