Stock-Based Compensation And Employee Benefit Plans (Narrative) (Details) (USD $)	12 Months Ended
Dec. 31, 2011 years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum shares of common stock	20,000,000
Maximum aggregate shares awarded to employee	2,562,500
Shares available for granting additional awards	7,917,632
Unrecognized compensation cost of non-vested stock-based compensation awards	$ 9,767,000
Unrecognized compensation cost of non-vested stock-based compensation awards expected to be recognized over a period (years)	3.2
Maximum amount of annual contribution under employee stock purchase plan	$ 20,000
Percentage of contribution to employee stock purchase plan	15.00%
Percentage of interest accrues on Purchase Plan contributions	5.25%
Number of participants in Executive Nonqualified Excess Plan (the "Excess Plan")	61
Matching contribution description under 401K retirement savings plan	Effective January 1, 2011, we restored our matching contribution percentage to its previous level, one-half of the first three percent of pay contributed by the participant.
Annual contribution for employees under 401(k) Retirement Savings Plan, percent of net income	2.50%
Stock Options [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (months)	24
Stock Options [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (months)	72
Restricted Stock [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (months)	12
Restricted Stock [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (months)	84

As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph h

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, using a decimal to express in number of years.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod
Namespace Prefix:	us-gaap_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum annual discretionary contribution for employees under 401(k) retirement savings plan, expressed as a percentage of net income.

+ References

No definition available.

+ Details

Name:	wern_DiscretionaryProfitMatchDescriptionUnder401kRetirementSavingsPlan
Namespace Prefix:	wern_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Matching contribution description under 401K retirement savings plan.

+ References

No definition available.

+ Details

Name:	wern_MatchingContributionDescriptionUnder401kRetirementSavingsPlan
Namespace Prefix:	wern_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum annual amount of contributions to employee stock purchase plan made by plan participants.

+ References

No definition available.

+ Details

Name:	wern_MaximumAnnualStockPurchasePlanContributionsByPlanParticipants
Namespace Prefix:	wern_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of participants in executive nonqualified excess plan (the "excess plan")

+ References

No definition available.

+ Details

Name:	wern_NumberOfParticipantsInExecutiveNonqualifiedExcessPlan
Namespace Prefix:	wern_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of company matching contribution to employee stock purchase plan.

+ References

No definition available.

+ Details

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

- Definition

Percentage of interest paid by the company on participant purchase plan contributions until purchase is made.

+ References

No definition available.

+ Details

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

- Definition

The maximum number of shares that can be awarded per participant under an employee share-based payment plan.

+ References

No definition available.

+ Details

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