Accounting Policies Summary of Significant Accounting Policies (Details)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Percentage of customer revenue	45.00%	43.00%	43.00%
Accounts receivable recorded investment past due days	90

The disclosure indicates the percentage of revenue generated by the largest customers.

No definition available.

Name:	wern_RevenueFromMajorCustomersPercentage
Namespace Prefix:	wern_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration