REVENUE RECOGNITION - By Product (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 02, 2021	Sep. 26, 2020	Oct. 02, 2021	Sep. 26, 2020
Revenue from External Customer [Line Items]
Total revenue	$ 717,240	$ 709,619	$ 1,813,001	$ 1,707,818
Aggregates
Revenue from External Customer [Line Items]
Total revenue	160,317	136,396	431,201	362,546
Cement
Revenue from External Customer [Line Items]
Total revenue	87,645	82,698	207,953	188,854
Ready-mix concrete
Revenue from External Customer [Line Items]
Total revenue	183,114	179,124	525,208	488,710
Asphalt
Revenue from External Customer [Line Items]
Total revenue	116,364	128,125	238,674	255,992
Paving and related services
Revenue from External Customer [Line Items]
Total revenue	112,671	136,191	257,966	280,446
Other
Revenue from External Customer [Line Items]
Total revenue	57,129	47,085	151,999	131,270
Summit Materials, LLC
Revenue from External Customer [Line Items]
Total revenue	717,240	709,619	1,813,001	1,707,818
Summit Materials, LLC | Aggregates
Revenue from External Customer [Line Items]
Total revenue	160,317	136,396	431,201	362,546
Summit Materials, LLC | Cement
Revenue from External Customer [Line Items]
Total revenue	87,645	82,698	207,953	188,854
Summit Materials, LLC | Ready-mix concrete
Revenue from External Customer [Line Items]
Total revenue	183,114	179,124	525,208	488,710
Summit Materials, LLC | Asphalt
Revenue from External Customer [Line Items]
Total revenue	116,364	128,125	238,674	255,992
Summit Materials, LLC | Paving and related services
Revenue from External Customer [Line Items]
Total revenue	112,671	136,191	257,966	280,446
Summit Materials, LLC | Other
Revenue from External Customer [Line Items]
Total revenue	$ 57,129	$ 47,085	$ 151,999	$ 131,270