Income Taxes - Schedule of Income Tax Benefit (Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]
Income tax expense (benefit) at federal statutory tax rate	$ 20,177	$ (55,365)	$ 14,290
Less: Income tax benefit at federal statutory tax rate for LLC entities	(561)	(2,123)	(10,608)
State and local income taxes	4,894	(5,209)	2,490
Permanent differences	(5,537)	(4,410)	(5,902)
Effective tax rate change	4,034	216,904	(1,432)
Unrecognized tax benefits	22,663	0	0
Tax receivable agreement (benefit) expense	(8,282)	104,804	5,228
Change in valuation allowance	17,592	(500,162)	239,008
Impact of LP Unit ownership change	0	(31,790)	(252,456)
Other	4,767	(6,626)	4,083
Income tax expense (benefit)	59,747	(283,977)	(5,299)
Summit Materials, LLC
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Line Items]
Income tax expense (benefit) at federal statutory tax rate	15,563	39,797	19,882
Less: Income tax benefit at federal statutory tax rate for LLC entities	(13,863)	(36,171)	(21,042)
State and local income taxes	1,614	1,751	1,279
Permanent differences	(1,194)	(630)	(1,726)
Effective tax rate change	(1,148)	(24,243)	(1,432)
Unrecognized tax benefits	6,487	0	0
Change in valuation allowance	2,586	0	148
Other	228	(849)	(2,391)
Income tax expense (benefit)	$ 10,273	$ (20,345)	$ (5,282)