Commitments and Contingencies - Narrative (Details)	12 Months Ended
Jan. 02, 2021
Loss Contingencies [Line Items]
Term of purchase commitments	1 year
Summit Materials, LLC
Loss Contingencies [Line Items]
Term of purchase commitments	1 year

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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