Acquisitions - Summary of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Business Acquisition [Line Items]
Goodwill	$ 1,199,699	$ 1,192,028	$ 1,036,320
Summit Materials, LLC
Business Acquisition [Line Items]
Goodwill	1,200,699	1,193,028	$ 1,037,320
Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Financial assets	0	14,769
Inventories	52	18,313
Property, plant and equipment	3,542	124,957
Intangible assets	0	3,175
Other assets	0	1,539
Financial liabilities	(36)	(13,529)
Other long-term liabilities	0	(8,125)
Net assets acquired	3,558	141,099
Goodwill	1,834	154,120
Purchase price	5,392	295,219
Acquisition-related liabilities	0	(49,202)
Net cash paid for acquisitions	5,392	246,017
Series of Individually Immaterial Business Acquisitions \| Summit Materials, LLC
Business Acquisition [Line Items]
Financial assets	0	14,769
Inventories	52	18,313
Property, plant and equipment	3,542	124,957
Intangible assets	0	3,175
Other assets	0	1,539
Financial liabilities	(36)	(13,529)
Other long-term liabilities	0	(8,125)
Net assets acquired	3,558	141,099
Goodwill	1,834	154,120
Purchase price	5,392	295,219
Acquisition-related liabilities	0	(49,202)
Net cash paid for acquisitions	$ 5,392	$ 246,017

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