FAIR VALUE - Fair Value Measurements (Details) - Level 3 $ in Thousands	9 Months Ended
	Oct. 02, 2021 USD ($)	Sep. 26, 2020 USD ($)	Jan. 02, 2021 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current portion of acquisition-related liabilities and accrued expenses - contingent consideration	$ 554		$ 654
Acquisition-related liabilities and other noncurrent liabilities - contingent consideration	1,199		1,209
Adjustment to contingent consideration	0	$ 0
Summit Materials, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current portion of acquisition-related liabilities and accrued expenses - contingent consideration	554		654
Acquisition-related liabilities and other noncurrent liabilities - contingent consideration	1,199		$ 1,209
Adjustment to contingent consideration	$ 0	$ 0
Discount Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration fair value measurement input	0.095
Discount Rate | Summit Materials, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration fair value measurement input	0.095