v3.8.0.1
Document and Entity Information - USD ($)
12 Months Ended
Dec. 30, 2017
Feb. 16, 2018
Jul. 01, 2017
Document Information [Line Items]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 30, 2017    
Document Fiscal Year Focus 2017    
Document Fiscal Period Focus FY    
Trading Symbol SAM    
Entity Registrant Name BOSTON BEER CO INC    
Entity Central Index Key 0000949870    
Current Fiscal Year End Date --12-30    
Entity Well-known Seasoned Issuer No    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Large Accelerated Filer    
Entity Public Float     $ 1,163,800,000
Common Class A      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   8,814,850  
Common Class B      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   3,017,983