ACCRUED EXPENSES - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 28, 2020	Dec. 28, 2019
Schedule Of Accrued Expenses [Line Items]
Interest	$ 15,852	$ 26,892
Payroll and benefits	18,797	29,356
Finance lease obligations	20,724	16,007
Insurance	13,870	14,968
Non-income taxes	10,377	7,666
Professional fees	1,189	902
Other	21,651	24,214
Total	102,460	120,005
Summit Materials, LLC
Schedule Of Accrued Expenses [Line Items]
Interest	15,852	26,892
Payroll and benefits	18,797	29,356
Finance lease obligations	20,724	16,007
Insurance	13,870	14,968
Non-income taxes	10,608	7,898
Professional fees	1,189	902
Other	21,651	24,214
Total	$ 102,691	$ 120,237