Related Party Transactions (Details) - Principal Stockholder [Member] - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Lease annual rent payments	$ 1.00
Leasehold improvements to land total	6,600,000
Related party expense	$ 72,000	$ 50,000	$ 52,000

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of annual payment for rental of land from related party.

+ References

No definition available.

+ Details

Name:	wern_LeaseAnnualRentPayments
Namespace Prefix:	wern_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Gross amount, at the balance sheet date, of long-lived, depreciable assets that are an addition or improvement to assets held under lease arrangement with related party.

+ References

No definition available.

+ Details

Name:	wern_LeaseholdImprovementsToLandTotal
Namespace Prefix:	wern_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_PrincipalOwnerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: