Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2021
Mar. 07, 2022
Jul. 02, 2021
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 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 200 Ashford Center North    
Entity Address, Address Line Two Suite 425    
Entity Address, City or Town Atlanta    
Entity Address, State or Province GA    
Entity Address, Postal Zip Code 30338    
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 NYSE    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Entity Shell Company false    
Entity Public Float     $ 105,800,364
Entity Common Stock, Shares Outstanding   26,231,515  
Entity Central Index Key 0001136294    
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2021    
Document Fiscal Period Focus FY    
Amendment Flag false    
Auditor Name Moss Adams LLP    
Auditor Firm ID 659    
Auditor Location Dallas, Texas