SUMMARY OF ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES - Business and Credit Concentration (Details)	3 Months Ended
	Mar. 28, 2020 state
Summit Materials, LLC
Business and Credit Concentrations
Number of states in which the entity operates	23
Tax Receivable Agreement | Summit Holdings LP
Business and Credit Concentrations
Percentage of benefits to be paid on tax receivable agreement	85.00%
Percentage of the tax receivable agreement allocated to additional paid-in capital	15.00%