Supplemental Cash Flow Information - Schedule of Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Cash payments:
Interest	$ 99,551	$ 104,614	$ 103,250
Payments (refunds) for income taxes, net	1,754	(919)	3,340
Operating cash payments on operating leases	10,452	10,618
Operating cash payments on finance leases	3,132	3,051
Finance cash payments on finance leases	14,408	13,164
Non cash financing activities:
Right of use assets obtained in exchange for operating lease obligations	4,849	5,842
Right of use assets obtained in exchange for finance leases obligations	18,016	23,965
Exchange of LP Units to shares of Class A common stock	8,227	3,847	7,499
Summit Materials, LLC
Cash payments:
Interest	99,551	104,614	103,250
Payments (refunds) for income taxes, net	1,754	(919)	$ 3,340
Operating cash payments on operating leases	10,452	10,618
Operating cash payments on finance leases	3,132	3,051
Finance cash payments on finance leases	14,408	13,164
Non cash financing activities:
Right of use assets obtained in exchange for operating lease obligations	4,849	5,842
Right of use assets obtained in exchange for finance leases obligations	$ 18,016	$ 23,965