ACCRUED EXPENSES - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 29, 2019	Dec. 29, 2018
Schedule Of Accrued Expenses [Line Items]
Interest	$ 25,326	$ 26,223
Payroll and benefits	22,482	15,952
Finance lease obligations	17,805
Finance lease obligations		15,557
Insurance	15,807	13,625
Non-income taxes	13,075	7,442
Professional fees	1,482	1,408
Other	18,019	20,284
Total	113,996	100,491
Summit Materials, LLC
Schedule Of Accrued Expenses [Line Items]
Interest	25,326	26,223
Payroll and benefits	22,482	15,952
Finance lease obligations	17,805
Finance lease obligations		15,557
Insurance	15,807	13,625
Non-income taxes	13,307	7,674
Professional fees	1,482	1,408
Other	18,019	19,590
Total	$ 114,228	$ 100,029