REVENUE RECOGNITION - By Product (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019
Revenue from External Customer [Line Items]
Total revenue	$ 367,190	$ 332,639
Aggregates
Revenue from External Customer [Line Items]
Total revenue	96,161	87,872
Cement
Revenue from External Customer [Line Items]
Total revenue	32,863	32,499
Ready-mix concrete
Revenue from External Customer [Line Items]
Total revenue	141,704	117,320
Asphalt
Revenue from External Customer [Line Items]
Total revenue	23,206	23,038
Paving and related services
Revenue from External Customer [Line Items]
Total revenue	33,426	34,345
Other
Revenue from External Customer [Line Items]
Total revenue	39,830	37,565
Summit Materials, LLC
Revenue from External Customer [Line Items]
Total revenue	367,190	332,639
Summit Materials, LLC | Aggregates
Revenue from External Customer [Line Items]
Total revenue	96,161	87,872
Summit Materials, LLC | Cement
Revenue from External Customer [Line Items]
Total revenue	32,863	32,499
Summit Materials, LLC | Ready-mix concrete
Revenue from External Customer [Line Items]
Total revenue	141,704	117,320
Summit Materials, LLC | Asphalt
Revenue from External Customer [Line Items]
Total revenue	23,206	23,038
Summit Materials, LLC | Paving and related services
Revenue from External Customer [Line Items]
Total revenue	33,426	34,345
Summit Materials, LLC | Other
Revenue from External Customer [Line Items]
Total revenue	$ 39,830	$ 37,565