Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

Document and Entity Information - shares
6 Months Ended
Jun. 30, 2021
Aug. 06, 2021
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2021  
Document Transition Report false  
Entity File Number 001-16501  
Entity Registrant Name Williams Industrial Services Group Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 73-1541378  
Entity Address, Address Line One 100 Crescent Centre Parkway  
Entity Address, Address Line Two Suite 1240  
Entity Address, City or Town Tucker  
Entity Address, State or Province GA  
Entity Address, Postal Zip Code 30084  
City Area Code 770  
Local Phone Number 879-4400  
Title of 12(b) Security Common Stock, par value $0.01 per share  
Trading Symbol WLMS  
Security Exchange Name NYSEAMER  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   25,915,502
Entity Central Index Key 0001136294  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2021  
Document Fiscal Period Focus Q2  
Amendment Flag false