SUPPLEMENTAL CASH FLOW INFORMATION - Schedule of Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019
Cash payments:
Interest	$ 36,310	$ 21,126
Refunds for income taxes, net	(298)	(20)
Operating cash payments on operating leases	2,948	2,837
Operating cash payments on finance leases	794	699
Finance cash payments on finance leases	3,883	2,580
Non cash financing activities:
Right of use assets obtained in exchange for operating lease obligations	577	1,608
Right of use assets obtained in exchange for finance leases obligations	6,267	9,442
Exchange of LP Units to shares of Class A common stock	4,648	277
Summit Materials, LLC
Cash payments:
Interest	36,310	21,126
Refunds for income taxes, net	(298)	(20)
Operating cash payments on operating leases	2,948	2,837
Operating cash payments on finance leases	794	699
Finance cash payments on finance leases	3,883	2,580
Non cash financing activities:
Right of use assets obtained in exchange for operating lease obligations	577	1,608
Right of use assets obtained in exchange for finance leases obligations	$ 6,267	$ 9,442