Income Taxes - Schedule of Income Tax Benefit (Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]
Income tax expense (benefit) at federal statutory tax rate	$ 16,427	$ 20,177	$ (55,365)
Less: Income tax benefit at federal statutory tax rate for LLC entities	(658)	(561)	(2,123)
State and local income taxes	3,792	4,894	(5,209)
Permanent differences	(6,272)	(5,537)	(4,410)
Effective tax rate change	(2,006)	4,034	216,904
Unrecognized tax benefits	18,885	22,663	0
Tax receivable agreement (benefit) expense	2,436	(8,282)	104,804
Change in valuation allowance	(17,691)	17,592	(500,162)
Impact of LP Unit ownership change	0	0	(31,790)
Other	2,188	4,767	(6,626)
Income tax expense (benefit)	17,101	59,747	(283,977)
Summit Materials, LLC
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]
Income tax expense (benefit) at federal statutory tax rate	19,947	15,563	39,797
Less: Income tax benefit at federal statutory tax rate for LLC entities	(15,387)	(13,863)	(36,171)
State and local income taxes	1,680	1,614	1,751
Permanent differences	13	(1,194)	(630)
Effective tax rate change	(725)	(1,148)	(24,243)
Unrecognized tax benefits	5,038	6,487	0
Change in valuation allowance	(2,478)	2,586	0
Other	(1,703)	228	(849)
Income tax expense (benefit)	$ 6,385	$ 10,273	$ (20,345)