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ACQUISITIONS, DISPOSTIONS, GOODWILL AND INTANGIBLES - Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 02, 2021	Sep. 26, 2020	Oct. 02, 2021	Sep. 26, 2020	Jan. 02, 2021
Business Acquisition [Line Items]
Amortization expense	$ 900	$ 700	$ 2,800	$ 2,300
Estimated amortization expense
2021 (three months)	1,034		1,034
2022	4,141		4,141
2023	4,008		4,008
2024	3,913		3,913
2025	3,868		3,868
2026	3,724		3,724
Thereafter	49,650		49,650
Intangible assets, net	70,338		70,338		$ 47,852
Summit Materials, LLC
Business Acquisition [Line Items]
Amortization expense	900	$ 700	2,800	$ 2,300
Estimated amortization expense
2021 (three months)	1,034		1,034
2022	4,141		4,141
2023	4,008		4,008
2024	3,913		3,913
2025	3,868		3,868
2026	3,724		3,724
Thereafter	49,650		49,650
Intangible assets, net	$ 70,338		$ 70,338		$ 47,852