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Summary of Significant Accounting Policies (Self Insurance Retention Liability) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Self insurance Retention Liability [Line Items] |  |  |
Self insurance retention liability | $ 10,000 | $ 10,000 | $ 3,000
Annual aggregate limit | 10,000 |  |
Self insurance retention liability additional deductible |  |  | 5,000
Liability insurance coverage in excess of SIR policy | 10,000 | 10,000 | 10,000
Self insurance retention Workers' compensation | 2,000 | $ 2,000 | 1,000
Letters of credit outstanding, amount | 54,900 |  |
Minimum |  |  |
Self insurance Retention Liability [Line Items] |  |  |
Per claim range for the annual aggregate limit | 10,000 |  |
Self insurance retention liability additional deductible applicable range - with SIR additional deductible |  |  | 5,000
Maximum |  |  |
Self insurance Retention Liability [Line Items] |  |  |
Per claim range for the annual aggregate limit | 15,000 |  |
Self insurance retention liability additional deductible applicable range - with SIR additional deductible |  |  | $ 10,000
State of Nebraska [Member] |  |  |
Self insurance Retention Liability [Line Items] |  |  |
Workers' compensation insurance bonds | 25,600 |  |
Workers compensation insurance carrier [Member] |  |  |
Self insurance Retention Liability [Line Items] |  |  |
Workers' compensation insurance bonds | 13,400 |  |
Insurance carrier [Member] |  |  |
Self insurance Retention Liability [Line Items] |  |  |
Letters of credit outstanding, amount | $ 43,000 |  |

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- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Represents annual aggregate limit for claims between $10M and $15M. + References No definition available. + Details
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Namespace Prefix: | wern_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Liability Insurance Coverage in Excess of SIR Policy + References No definition available. + Details
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Namespace Prefix: | wern_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Represents the per claim range for the annual aggregate limit. + References No definition available. + Details
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Namespace Prefix: | wern_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Represents the per claim range when an additional deductible is required. + References No definition available. + Details
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Namespace Prefix: | wern_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition The disclosure indicates the amount of liability retained by the company (self-insured retention and deductible) for each bodily injury or property damage occurrence. + References No definition available. + Details
Name: | wern_SelfInsuranceRetentionLiability
Namespace Prefix: | wern_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The disclosure indicates the amount of additional liability retained by the company (self-insured retention and deductible) for each bodily injury or property damage occurrence between $5.0 million and $10.0 million. + References No definition available. + Details
Name: | wern_SelfInsuranceRetentionLiabilityAdditionalDeductible
Namespace Prefix: | wern_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The disclosure indicates the amount of liability retained by the company (self-insured retention) for each workers' compensation occurrence. + References No definition available. + Details
Name: | wern_SelfInsuranceRetentionWorkersCompensation
Namespace Prefix: | wern_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition [Line Items] for Self insurance Retention Liability [Table] + References No definition available. + Details
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Namespace Prefix: | wern_
Data Type: | xbrli:stringItemType
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- Definition The disclosure indicates the amount of the bonds carried for workers' compensation insurance. + References No definition available. + Details
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Namespace Prefix: | wern_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | wern_EmployeeBenefitsAxis=wern_StateOfNebraskaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | wern_EmployeeBenefitsAxis=wern_WorkersCompensationInsuranceCarrierMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |