Property, Plant and Equipment, net and Intangibles, net - Components of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Jan. 02, 2021	Dec. 28, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 2,983,094	$ 2,703,264
Less accumulated depreciation, depletion and amortization	(1,132,925)	(955,815)
Property, plant and equipment including finance lease right-of-use asset, net	1,850,169	1,747,449
Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	2,983,094	2,703,264
Less accumulated depreciation, depletion and amortization	(1,132,925)	(955,815)
Property, plant and equipment including finance lease right-of-use asset, net	1,850,169	1,747,449
Mineral bearing land and leased interests
Property, Plant and Equipment [Line Items]
Property, plant and equipment	468,966	333,024
Mineral bearing land and leased interests \| Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	468,966	333,024
Land (non-mineral bearing)
Property, Plant and Equipment [Line Items]
Property, plant and equipment	197,432	182,065
Land (non-mineral bearing) \| Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	197,432	182,065
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 181,198	178,088
Buildings and improvements \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Buildings and improvements \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	30 years
Buildings and improvements \| Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 181,198	178,088
Buildings and improvements \| Summit Materials, LLC \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Buildings and improvements \| Summit Materials, LLC \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	30 years
Plants, machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 1,397,410	1,318,512
Plants, machinery and equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Plants, machinery and equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Plants, machinery and equipment \| Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 1,397,410	1,318,512
Plants, machinery and equipment \| Summit Materials, LLC \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Plants, machinery and equipment \| Summit Materials, LLC \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Mobile equipment and barges
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 543,133	501,809
Mobile equipment and barges \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	6 years
Mobile equipment and barges \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	8 years
Mobile equipment and barges \| Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 543,133	501,809
Mobile equipment and barges \| Summit Materials, LLC \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	6 years
Mobile equipment and barges \| Summit Materials, LLC \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	8 years
Truck and auto fleet
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 56,163	54,838
Truck and auto fleet \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Truck and auto fleet \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	8 years
Truck and auto fleet \| Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 56,163	54,838
Truck and auto fleet \| Summit Materials, LLC \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Truck and auto fleet \| Summit Materials, LLC \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	8 years
Landfill airspace and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 52,202	49,766
Landfill airspace and improvements \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Landfill airspace and improvements \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	30 years
Landfill airspace and improvements \| Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 52,202	49,766
Landfill airspace and improvements \| Summit Materials, LLC \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Landfill airspace and improvements \| Summit Materials, LLC \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	30 years
Office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 45,942	43,155
Office equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Office equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Office equipment \| Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment including finance lease right-of-use asset, gross	$ 45,942	43,155
Office equipment \| Summit Materials, LLC \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Office equipment \| Summit Materials, LLC \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 40,648	42,007
Construction in progress \| Summit Materials, LLC
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 40,648	$ 42,007
Other \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	4 years
Other \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Other \| Summit Materials, LLC \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	4 years
Other \| Summit Materials, LLC \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years

Amount of accumulated depreciation and amortization from plant, property, and equipment and right-of-use asset from finance lease.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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