Revenue (Disaggregation of Revenue by Revenue Source) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Disaggregation of revenue
Revenues	$ 562,684	$ 501,221
Truckload Transportation Services
Disaggregation of revenue
Revenues	431,556	385,003
Werner Logistics
Disaggregation of revenue
Revenues	117,420	99,853
Inter-segment eliminations
Disaggregation of revenue
Revenues	(458)	(167)
Transportation Services
Disaggregation of revenue
Revenues	548,518	484,689
Other revenues
Disaggregation of revenue
Revenues	$ 14,166	$ 16,532

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration