ACCRUED EXPENSES - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Oct. 02, 2021	Jan. 02, 2021
Schedule Of Accrued Expenses [Line Items]
Interest	$ 8,891	$ 21,860
Payroll and benefits	37,906	46,026
Finance lease obligations	17,424	24,601
Insurance	19,676	18,355
Non-income taxes	23,834	15,669
Deferred asset purchase payments	4,538	9,749
Professional fees	1,152	828
Other	23,957	23,482
Accrued expenses	137,378	160,570
Summit Materials, LLC
Schedule Of Accrued Expenses [Line Items]
Interest	8,891	21,860
Payroll and benefits	37,906	46,026
Finance lease obligations	17,424	24,601
Insurance	19,676	18,355
Non-income taxes	24,065	15,900
Deferred asset purchase payments	4,538	9,749
Professional fees	1,152	828
Other	23,957	23,482
Accrued expenses	$ 137,609	$ 160,801