v3.5.0.2
Document and Entity Information - shares
6 Months Ended
Jul. 01, 2016
Aug. 03, 2016
Document and Entity Information    
Entity Registrant Name Willdan Group, Inc.  
Entity Central Index Key 0001370450  
Document Type 10-Q  
Document Period End Date Jul. 01, 2016  
Amendment Flag false  
Current Fiscal Year End Date --12-30  
Entity Current Reporting Status Yes  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   8,298,866
Document Fiscal Year Focus 2016  
Document Fiscal Period Focus Q2