Segment Information (Summary Of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 518,832	$ 508,676	$ 498,681	$ 482,802	$ 528,783	$ 534,448	$ 534,644	$ 495,654	$ 2,008,991	$ 2,093,529	$ 2,139,289
Operating income	$ 34,956	$ 29,074	$ 29,553	$ 32,487	$ 57,261	$ 52,800	$ 52,210	$ 38,185	126,070	200,456	160,088
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues									1,533,981	1,644,874	1,702,137
Operating income									107,713	189,850	152,992
Werner Logistics
Segment Reporting Information [Line Items]
Revenues									417,172	393,174	390,645
Operating income									20,734	16,898	7,535
Other
Segment Reporting Information [Line Items]
Revenues									57,062	54,512	46,588
Operating income									(6,177)	(7,513)	(3,991)
Corporate
Segment Reporting Information [Line Items]
Revenues									1,749	2,297	2,803
Operating income									3,800	1,221	3,552
Subtotal
Segment Reporting Information [Line Items]
Revenues									2,009,964	2,094,857	2,142,173
Inter-segment eliminations
Segment Reporting Information [Line Items]
Revenues									$ (973)	$ (1,328)	$ (2,884)