XML 23 R1.htm IDEA: XBRL DOCUMENT v3.10.0.1
Document and Entity Information - USD ($)
12 Months Ended
Dec. 29, 2018
Jan. 30, 2019
Jun. 30, 2018
Jul. 01, 2017
Document Information [Line Items]        
Entity Registrant Name Summit Materials, Inc.      
Entity Central Index Key 0001621563      
Document Type 10-K      
Document Period End Date Dec. 29, 2018      
Amendment Flag false      
Current Fiscal Year End Date --12-29      
Entity Current Reporting Status Yes      
Entity Filer Category Large Accelerated Filer      
Document Fiscal Year Focus 2018      
Document Fiscal Period Focus FY      
Entity Well-known Seasoned Issuer Yes      
Entity Voluntary Filers No      
Entity Public Float       $ 3,100,000,000
Common Class A        
Document Information [Line Items]        
Entity Common Stock, Shares Outstanding   111,671,837    
Common Class B        
Document Information [Line Items]        
Entity Common Stock, Shares Outstanding   99    
Summit Materials, LLC        
Document Information [Line Items]        
Entity Registrant Name Summit Materials, LLC      
Entity Central Index Key 0001571371      
Document Type 10-K      
Document Period End Date Dec. 29, 2018      
Amendment Flag false      
Current Fiscal Year End Date --12-29      
Entity Current Reporting Status Yes      
Entity Filer Category Non-accelerated Filer      
Document Fiscal Year Focus 2018      
Document Fiscal Period Focus FY      
Entity Well-known Seasoned Issuer No      
Entity Voluntary Filers No      
Entity Public Float     $ 0