Acquisitions - Completed Acquisitions Information (Details) - item	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
West
Business Acquisition [Line Items]
Number of business acquisitions	6	3	3
East
Business Acquisition [Line Items]
Number of business acquisitions	8	5
Cement
Business Acquisition [Line Items]
Number of business acquisitions		1	1
Summit Materials, LLC | West
Business Acquisition [Line Items]
Number of business acquisitions	6	3	3
Summit Materials, LLC | East
Business Acquisition [Line Items]
Number of business acquisitions	8	5
Summit Materials, LLC | Cement
Business Acquisition [Line Items]
Number of business acquisitions		1	1