Acquisitions - Summary of Assets Acquired and Liabilities Assumed (Detail) $ in Thousands				1 Months Ended	3 Months Ended	12 Months Ended
	Aug. 13, 2015 USD ($)	Aug. 11, 2015 USD ($)	Jul. 17, 2015 USD ($)	Aug. 13, 2015 USD ($)	Apr. 01, 2017 USD ($)	Dec. 30, 2017 USD ($) facility	Dec. 31, 2016 USD ($)	Jan. 02, 2016 USD ($)
Business Acquisition [Line Items]
Net gain on asset disposals						$ 7,638	$ 3,102	$ 23,087
Number of Plants Owned and Operated | facility						2
Goodwill						$ 1,036,320	782,212	596,397
Amount reclassified from financial assets to liabilities					$ 1,200
Cement
Business Acquisition [Line Items]
Goodwill						204,656	204,538	194,163
Summit Materials, LLC
Business Acquisition [Line Items]
Net gain on asset disposals						$ (3,856)		9,877
Number of Plants Owned and Operated | facility						2
Goodwill						$ 1,037,320	782,212	596,397
Amount reclassified from financial assets to liabilities					$ 1,200
Summit Materials, LLC | Cement
Business Acquisition [Line Items]
Goodwill						204,656	204,538	$ 194,163
Davenport Assets
Business Acquisition [Line Items]
Cash paid for acquisitions	$ 80,000		$ 370,000	$ 450,000
Davenport Assets | Follow on Public Offering
Business Acquisition [Line Items]
Cash paid for acquisitions		$ 80,000
Davenport Assets | Summit Materials, LLC
Business Acquisition [Line Items]
Cash paid for acquisitions	450,000		370,000
Davenport Assets | Summit Materials, LLC | Follow on Public Offering
Business Acquisition [Line Items]
Cash paid for acquisitions	$ 80,000
2016 Acquisitions
Business Acquisition [Line Items]
Financial assets							22,204
Inventories							17,215
Property, plant and equipment							180,321
Intangible assets							5,531
Other assets							6,757
Financial liabilities							(20,248)
Other long-term liabilities							(36,074)
Net assets acquired							175,706
Goodwill							176,319
Purchase price							352,025
Acquisition related liabilities							(17,034)
Other							1,967
Net cash paid for acquisitions							$ 336,958
2016 Acquisitions | Summit Materials, LLC
Business Acquisition [Line Items]
Financial assets			22,204
Inventories			17,215
Property, plant and equipment			180,321
Intangible assets			5,531
Other assets			6,757
Financial liabilities			(20,248)
Other long-term liabilities			(36,074)
Net assets acquired			175,706
Goodwill			176,319
Purchase price			352,025
Acquisition related liabilities			(17,034)
Other			1,967
Net cash paid for acquisitions			$ 336,958
2017 Acquisitions
Business Acquisition [Line Items]
Financial assets						31,615
Inventories						8,300
Property, plant and equipment						160,975
Intangible assets						161
Other assets						4,200
Financial liabilities						(15,501)
Other long-term liabilities						(17,610)
Net assets acquired						172,140
Goodwill						247,536
Purchase price						419,676
Acquisition related liabilities						(43,452)
Other						(1,294)
Net cash paid for acquisitions						374,930
2017 Acquisitions | Summit Materials, LLC
Business Acquisition [Line Items]
Financial assets						31,615
Inventories						8,300
Property, plant and equipment						160,975
Intangible assets						161
Other assets						4,200
Financial liabilities						(15,501)
Other long-term liabilities						(17,610)
Net assets acquired						172,140
Goodwill						247,536
Purchase price						419,676
Acquisition related liabilities						(43,452)
Other						(1,294)
Net cash paid for acquisitions						$ 374,930