Acquisitions - Intangible Assets By Type (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 23,371	$ 25,843
Accumulated Amortization	(6,376)	(7,854)
Net Carrying Amount	16,995	17,989
Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	23,371	25,843
Accumulated Amortization	(6,376)	(7,854)
Net Carrying Amount	16,995	17,989
Leases
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	15,888	15,888
Accumulated Amortization	(3,963)	(3,382)
Net Carrying Amount	11,925	12,506
Leases | Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	15,888	15,888
Accumulated Amortization	(3,963)	(3,382)
Net Carrying Amount	11,925	12,506
Reserve Rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,234	8,706
Accumulated Amortization	(1,550)	(3,710)
Net Carrying Amount	4,684	4,996
Reserve Rights | Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,234	8,706
Accumulated Amortization	(1,550)	(3,710)
Net Carrying Amount	4,684	4,996
Trade Names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,000	1,000
Accumulated Amortization	(733)	(658)
Net Carrying Amount	267	342
Trade Names | Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,000	1,000
Accumulated Amortization	(733)	(658)
Net Carrying Amount	267	342
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	249	249
Accumulated Amortization	(130)	(104)
Net Carrying Amount	119	145
Other | Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	249	249
Accumulated Amortization	(130)	(104)
Net Carrying Amount	$ 119	$ 145