Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

v3.8.0.1
Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2017
Mar. 01, 2018
Jun. 30, 2017
Document And Entity Information [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2017    
Document Fiscal Year Focus 2017    
Document Fiscal Period Focus FY    
Trading Symbol BBSI    
Entity Registrant Name BARRETT BUSINESS SERVICES INC    
Entity Central Index Key 0000902791    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Accelerated Filer    
Entity Common Stock, Shares Outstanding   7,304,085  
Entity Public Float     $ 402,103,034