v3.26.1
Document and Entity Information - $ / shares
6 Months Ended
Jul. 03, 2026
Aug. 06, 2026
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jul. 03, 2026  
Document Transition Report false  
Securities Act File Number 001-33076  
Entity Registrant Name WILLDAN GROUP, INC.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 14-1951112  
Entity Address, Address Line One 2401 East Katella Avenue  
Entity Address, Address Line Two Suite 300  
Entity Address, City or Town Anaheim  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 92806  
City Area Code 800  
Local Phone Number 424-9144  
Title of 12(b) Security Common Stock, par value $0.01 per share  
Entity Listing, Par Value Per Share $ 0.01  
Trading Symbol WLDN  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   15,232,091
Entity Central Index Key 0001370450  
Document Fiscal Period Focus Q2  
Document Fiscal Year Focus 2026  
Amendment Flag false  
Current Fiscal Year End Date --01-01