DEBT - Summary of Activity for Deferred Financing Fees (Details) - USD ($) $ in Thousands	9 Months Ended
	Oct. 02, 2021	Sep. 26, 2020
Deferred Finance Costs, Own-share Lending Arrangement, Issuance Costs, Accumulated Amortization [Roll Forward]
Beginning balance	$ 18,367	$ 15,436
Loan origination fees		9,565
Amortization	(2,510)	(2,499)
Write off of deferred financing fees	(2,116)	(3,338)
Ending balance	13,741	19,164
Summit Materials, LLC
Deferred Finance Costs, Own-share Lending Arrangement, Issuance Costs, Accumulated Amortization [Roll Forward]
Beginning balance	18,367	15,436
Loan origination fees		9,565
Amortization	(2,510)	(2,499)
Write off of deferred financing fees	(2,116)	(3,338)
Ending balance	$ 13,741	$ 19,164