Earnings Per Share (Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net Income attributable to Werner	$ 63,761	$ 72,032	$ 46,492	$ 46,332	$ 39,132	$ 23,058	$ 182,285	$ 108,522
Weighted average common shares outstanding	67,475			69,097			67,776	69,148
Dilutive effect of stock-based awards	359			352			360	352
Shares used in computing diluted earnings per share	67,834			69,449			68,136	69,500
Basic earnings per share	$ 0.94			$ 0.67			$ 2.69	$ 1.57
Diluted earnings per share	$ 0.94			$ 0.67			$ 2.68	$ 1.56