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

The number of performance shares granted to participants.

No definition available.

Name:	wern_EquityCompensationArrangementbySharebasedPaymentAwardPerformanceAwardGranted
Namespace Prefix:	wern_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

The number of performance shares that were forfeited during the reporting period.

No definition available.

Name:	wern_EquityCompensationArrangementbySharebasedPaymentAwardPerformanceAwardsForfeitedinPeriod
Namespace Prefix:	wern_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Weighted average fair value as of the grant date of performance shares that were not exercised or put into effect as a result of the occurrence of a terminating event.

No definition available.

Name:	wern_EquityCompensationArrangementbySharebasedPaymentAwardPerformanceAwardsForfeituresWeightedAverageGrantDateFairValue
Namespace Prefix:	wern_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on performance shares.

No definition available.

Name:	wern_EquityCompensationArrangementbySharebasedPaymentAwardPerformanceAwardsGrantsinPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	wern_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

The number of non-vested equity based performance shares that validly exist and are outstanding as of the beginning of the period.

No definition available.

Name:	wern_EquityCompensationArrangementbySharebasedPaymentAwardPerformanceAwardsNonvestedNumberBeginningBalance
Namespace Prefix:	wern_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

The number of non-vested equity based performance shares that validly exist and are outstanding as of the end of the period.

No definition available.

Name:	wern_EquityCompensationArrangementbySharebasedPaymentAwardPerformanceAwardsNonvestedNumberEndingBalance
Namespace Prefix:	wern_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

The weighted average fair value of nonvested awards on performance shares for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units, beginning of period.

No definition available.

Name:	wern_EquityCompensationArrangementbySharebasedPaymentAwardPerformanceAwardsNonvestedWeightedAverageGrantDateFairValueBeginningBalance
Namespace Prefix:	wern_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

No definition available.

Name:	wern_EquityCompensationArrangementbySharebasedPaymentAwardPerformanceAwardsNonvestedWeightedAverageGrantDateFairValueEndingBalance
Namespace Prefix:	wern_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

The number of performance awards that vested during the reporting period.

No definition available.

Name:	wern_EquityCompensationArrangementbySharebasedPaymentAwardPerformanceAwardsVestedinPeriod
Namespace Prefix:	wern_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

The weighted average fair value as of grant date pertaining to performance shares for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

No definition available.