Income Taxes [Line Items]

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Percentage of benefits related to tax receivable agreement paid by entity.

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Represents the liability due to former holders of LP Units related to the Tax Receivable Agreement.

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- Definition

Unrecognized Tax Benefits, Decrease Due To Coronavirus Aid, Relief And Economic Stability (CARES) Act

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Unrecognized Tax Benefits, Decrease Due To Tax Cuts And Jobs Act (TCJA) Of Two Thousand Seventeen

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- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from investments (excludes investments in subsidiaries and equity method investments).

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No definition available.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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The sum of the amounts of estimated penalties and interest recognized in the period arising from income tax examinations.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The total amount of distributions to limited partners.

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The number of shares issued during the period upon the conversion of units. An example of a convertible unit is an umbrella partnership real estate investment trust unit (UPREIT unit).

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INCOME TAXES - Narrative (Details) - USD ($)	3 Months Ended			9 Months Ended
INCOME TAXES - Narrative (Details) - USD ($)	Sep. 26, 2020	Mar. 28, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019	Dec. 28, 2019
Income Taxes [Line Items]
Income tax (benefit) expense	$ (19,613,000)		$ 45,602,000	$ (25,333,000)	$ 34,272,000
Unrecognized tax benefits, decrease due to CARES Act		$ 9,500,000
Unrecognized tax benefits, decrease due to Tax Cuts and Jobs Act of 2017	32,900,000
Valuation allowance	1,675,000			1,675,000		$ 1,675,000
Income tax provision, interest or penalties recognized	0		0	0	0
Deferred tax asset, Investment in limited partnership	1,200,000			1,200,000
Tax receivable agreement liability	327,957,000			327,957,000		326,965,000
Tax Receivable Agreement
Income Taxes [Line Items]
Tax receivable agreement liability	328,000,000.0			328,000,000.0		$ 327,000,000.0
Summit Holdings LP
Income Taxes [Line Items]
Distributions to LP Unitholders				$ 0	0
Summit Holdings LP \| Tax Receivable Agreement
Income Taxes [Line Items]
Percentage of benefits to be paid on tax receivable agreement				85.00%
Summit Materials, LLC
Income Taxes [Line Items]
Income tax (benefit) expense	(5,106,000)		18,757,000	$ (4,877,000)	12,265,000
Income tax provision, interest or penalties recognized	$ 0		$ 0	$ 0	$ 0
Common Class A
Income Taxes [Line Items]
Exchanges during period (in shares)				196,542	107,336