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Summary of Organization and Significant Accounting Policies - General Information and Equity Offerings (Details)
$ / shares in Units, $ in Thousands
3 Months Ended
Jan. 10, 2017
USD ($)
item
$ / shares
shares
Apr. 01, 2017
USD ($)
segment
facility
shares
Dec. 31, 2016
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements      
Number of operating segments | segment   3  
Equity Offering      
Proceeds from sale of common stock, net of underwriting discounts   $ 237,600  
Number of Summit LP units purchased by Company, newly issued units (in shares) | shares   236,095  
Cement plant      
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements      
Number of plants | facility   2  
Ohio Valley Asphalt      
Principles of Consolidation      
Noncontrolling interest elimination (as a percent)   20.00%  
Summit Materials, LLC      
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements      
Number of operating segments | segment   3  
Summit Materials, LLC | Ohio Valley Asphalt      
Principles of Consolidation      
Noncontrolling interest elimination (as a percent)   20.00%  
Summit Holdings LP      
Principles of Consolidation      
Voting power (as a percent)   100.00%  
Noncontrolling interest elimination (as a percent)   4.40% 5.10%
Follow on Public Offering      
Equity Offering      
Proceeds from sale of common stock, net of underwriting discounts $ 237,600    
Common stock issued (in shares) | shares 10,000,000    
Offering price (in dollars per share) | $ / shares $ 24.05    
Cash paid for acquisitions $ 110,000    
Number of companies acquired | item 2