GOODWILL AND INTANGIBLES - Summary of Goodwill by Reportable Segments (Details) $ in Thousands	3 Months Ended
Mar. 28, 2020 USD ($)
Goodwill [Roll Forward]
Balance, December 28, 2019	$ 1,199,699
Foreign currency translation adjustments	(4,142)
Balance, March 28, 2020	1,195,557
West
Goodwill [Roll Forward]
Balance, December 28, 2019	584,617
Foreign currency translation adjustments	(4,142)
Balance, March 28, 2020	580,475
East
Goodwill [Roll Forward]
Balance, December 28, 2019	410,426
Foreign currency translation adjustments	0
Balance, March 28, 2020	410,426
Cement
Goodwill [Roll Forward]
Balance, December 28, 2019	204,656
Foreign currency translation adjustments	0
Balance, March 28, 2020	204,656
Summit Materials, LLC
Goodwill [Roll Forward]
Balance, December 28, 2019	1,200,699
Foreign currency translation adjustments	(4,142)
Balance, March 28, 2020	1,196,557
Summit Materials, LLC \| West
Goodwill [Roll Forward]
Balance, December 28, 2019	585,617
Foreign currency translation adjustments	(4,142)
Balance, March 28, 2020	581,475
Summit Materials, LLC \| East
Goodwill [Roll Forward]
Balance, December 28, 2019	410,426
Foreign currency translation adjustments	0
Balance, March 28, 2020	410,426
Summit Materials, LLC \| Cement
Goodwill [Roll Forward]
Balance, December 28, 2019	204,656
Foreign currency translation adjustments	0
Balance, March 28, 2020	$ 204,656

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

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- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

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