Acquisitions - Summary of Goodwill by Reportable Segments (Details) $ in Thousands	6 Months Ended
Jul. 01, 2017 USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 782,212
Acquisitions	134,127
Foreign currency translation adjustments	2,172
Ending balance	918,511
Accumulated impairment losses	(68,202)
Summit Materials, LLC
Goodwill [Roll Forward]
Beginning balance	782,212
Acquisitions	134,127
Foreign currency translation adjustments	2,172
Ending balance	918,511
Accumulated impairment losses	(68,202)
West
Goodwill [Roll Forward]
Beginning balance	334,257
Acquisitions	95,000
Foreign currency translation adjustments	2,172
Ending balance	431,429
Accumulated impairment losses	(53,264)
West \| Summit Materials, LLC
Goodwill [Roll Forward]
Beginning balance	334,257
Acquisitions	95,000
Foreign currency translation adjustments	2,172
Ending balance	431,429
Accumulated impairment losses	(53,264)
East
Goodwill [Roll Forward]
Beginning balance	243,417
Acquisitions	39,009
Ending balance	282,426
Accumulated impairment losses	(14,938)
East \| Summit Materials, LLC
Goodwill [Roll Forward]
Beginning balance	243,417
Acquisitions	39,009
Ending balance	282,426
Accumulated impairment losses	(14,938)
Cement
Goodwill [Roll Forward]
Beginning balance	204,538
Acquisitions	118
Ending balance	204,656
Cement \| Summit Materials, LLC
Goodwill [Roll Forward]
Beginning balance	204,538
Acquisitions	118
Ending balance	$ 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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=64834752&loc=SL49117168-202975

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