SUPPLEMENTAL CASH FLOW INFORMATION - Schedule of Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018
Cash payments:
Interest	$ 89,759	$ 79,367
(Refund) payments for income taxes, net	(912)	3,362
Operating cash payments on operating leases	8,188
Operating cash payments on finance leases	2,322
Non cash financing activities:	9,806
Right of use assets obtained in exchange for finance leases obligations
Right of use assets obtained in exchange for operating lease obligations	4,387
Right of use assets obtained in exchange for finance leases obligations	18,586
Exchange of LP Units to shares of Class A common stock	1,995	7,499
Summit Materials, LLC
Cash payments:
Interest	89,759	79,367
(Refund) payments for income taxes, net	(912)	$ 3,362
Operating cash payments on operating leases	8,188
Operating cash payments on finance leases	2,322
Non cash financing activities:	9,806
Right of use assets obtained in exchange for finance leases obligations
Right of use assets obtained in exchange for operating lease obligations	4,387
Right of use assets obtained in exchange for finance leases obligations	$ 18,586