No definition available.

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

- Definition

Date when the business acquisition agreement was executed, in YYYY-MM-DD format.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionDateOfAcquisitionAgreement1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the acquirer obtains control of the acquiree, in YYYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 25
-Paragraph 7
-SubTopic 10
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479405/805-10-25-7

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-SubTopic 10
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-2

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 25
-Paragraph 6
-SubTopic 10
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479405/805-10-25-6

+ Details

Name:	us-gaap_BusinessAcquisitionEffectiveDateOfAcquisition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Name of the acquired entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-2

+ Details

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

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 30
-Paragraph 8
-SubTopic 30
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479637/805-30-30-8

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-SubTopic 30
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479581/805-30-50-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 30
-Paragraph 7
-SubTopic 30
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479637/805-30-30-7

+ Details

Name:	us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.

+ References

+ Details

Name:	us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of liabilities incurred by the acquirer as part of consideration transferred in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479581/805-30-50-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479668/805-30-25-5

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 30
-Paragraph 8
-SubTopic 30
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479637/805-30-30-8

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 30
-Paragraph 7
-SubTopic 30
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479637/805-30-30-7

+ Details

Name:	us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-13

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Business Combination, Consideration Transferred, Equity Interests Issued and Issuable, Closing Average Price Per Share, Trading Days Preceding Closing

+ References

No definition available.

+ Details

Name:	wldn_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuableClosingAveragePricePerShareTradingDaysPrecedingClosing
Namespace Prefix:	wldn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Business Combination, Contingent Consideration Arrangements, Earnout Payments, Earnout Period

+ References

No definition available.

+ Details

Name:	wldn_BusinessCombinationContingentConsiderationArrangementsEarnoutPaymentsEarnoutPeriod
Namespace Prefix:	wldn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Business Combination, Contingent Consideration Arrangements, Earnout Payments, Maximum Payout

+ References

No definition available.

+ Details

Name:	wldn_BusinessCombinationContingentConsiderationArrangementsEarnoutPaymentsMaximumPayout
Namespace Prefix:	wldn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=wldn_AlphaInspectionsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=wldn_AlternativePowerGenerationIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

SUBSEQUENT EVENTS (Details) $ in Thousands			12 Months Ended
SUBSEQUENT EVENTS (Details) $ in Thousands	Mar. 03, 2025 USD ($) D	Jan. 31, 2025 USD ($)	Dec. 27, 2024 USD ($)	Dec. 29, 2023 USD ($)
Business Combination, Consideration Transferred
Cash consideration			$ 7,364	$ 1,600
Subsequent Event \| Alpha Inspections, Inc.
Business Combination, Description
Business acquisition, name of acquired entity		Alpha Inspections, Inc.
Business Acquisition, Date of Acquisition
Business acquisition, effective date of acquisition		Jan. 31, 2025
Business acquisition, date of acquisition agreement		Jan. 31, 2025
Business Combination, Consideration Transferred
Business combination, consideration transferred		$ 12,000
Subsequent Event \| Alternative Power Generation, Inc.
Business Combination, Description
Business acquisition, name of acquired entity	Alternative Power Generation, Inc.
Business Acquisition, Date of Acquisition
Business acquisition, effective date of acquisition	Mar. 03, 2025
Business acquisition, date of acquisition agreement	Mar. 03, 2025
Business Combination, Consideration Transferred
Cash consideration	$ 19,500
Shares of common stock	$ 6,000
Shares of common stock, closing average price per share of common stock, trading day period preceding closing date \| D	20
Contingent consideration	$ 18,000
Business combination, consideration transferred	$ 43,500
Business Combination, Contingent Consideration Arrangements
Business combination, contingent consideration arrangements, earnout payments, earnout period	3 years
Business combination, contingent consideration arrangements, earnout payments, maximum payout	$ 18,000