Acquisitions - Summary of Assets Acquired and Liabilities Assumed (Detail) $ in Thousands			3 Months Ended	9 Months Ended		12 Months Ended
	Jan. 10, 2017 USD ($)	Aug. 30, 2016 facility item	Apr. 01, 2017 USD ($)	Sep. 30, 2017 USD ($) facility	Oct. 01, 2016 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Net gain on asset disposals				$ 6,063	$ 5,844
Goodwill				$ 1,012,771		$ 782,212
Cement plant
Business Acquisition [Line Items]
Number of Plants Owned and Operated | facility				2
Follow on Public Offering
Business Acquisition [Line Items]
Cash paid for acquisitions	$ 110,000
Cement
Business Acquisition [Line Items]
Goodwill				$ 204,656		204,538
Cement | Cement terminal
Business Acquisition [Line Items]
Number of plants acquired | facility		2
Summit Materials, LLC
Business Acquisition [Line Items]
Net gain on asset disposals				6,063	$ 5,844
Goodwill				1,012,771		782,212
Summit Materials, LLC | Cement
Business Acquisition [Line Items]
Goodwill				204,656		204,538
Summit Materials, LLC | Cement | Cement terminal
Business Acquisition [Line Items]
Number of plants acquired | item		2
2016 Acquisitions
Business Acquisition [Line Items]
Financial assets						22,204
Inventories						17,215
Property, plant and equipment						180,321
Intangible assets						5,531
Other assets						6,757
Financial liabilities						(20,248)
Other long-term liabilities						(36,074)
Net assets acquired						175,706
Goodwill						176,319
Purchase price						352,025
Acquisition related liabilities						(17,034)
Other						1,967
Net cash paid for acquisitions						336,958
Amount reclassified from financial assets to liabilities			$ 1,200
2016 Acquisitions | Summit Materials, LLC
Business Acquisition [Line Items]
Financial assets						22,204
Inventories						17,215
Property, plant and equipment						180,321
Intangible assets						5,531
Other assets						6,757
Financial liabilities						(20,248)
Other long-term liabilities						(36,074)
Net assets acquired						175,706
Goodwill						176,319
Purchase price						352,025
Acquisition related liabilities						(17,034)
Other						1,967
Net cash paid for acquisitions						$ 336,958
Amount reclassified from financial assets to liabilities			$ 1,200
2017 Acquisitions
Business Acquisition [Line Items]
Financial assets				31,895
Inventories				11,315
Property, plant and equipment				159,154
Other assets				5,321
Financial liabilities				(16,422)
Other long-term liabilities				(17,806)
Net assets acquired				173,457
Goodwill				222,451
Purchase price				395,908
Acquisition related liabilities				(23,238)
Other				(1,191)
Net cash paid for acquisitions				371,479
2017 Acquisitions | Summit Materials, LLC
Business Acquisition [Line Items]
Financial assets				31,895
Inventories				11,315
Property, plant and equipment				159,154
Other assets				5,321
Financial liabilities				(16,422)
Other long-term liabilities				(17,806)
Net assets acquired				173,457
Goodwill				222,451
Purchase price				395,908
Acquisition related liabilities				(23,238)
Other				(1,191)
Net cash paid for acquisitions				$ 371,479