Summary of Organization and Significant Accounting Policies - New Accounting Standards (Details) - USD ($)	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016	Jan. 03, 2016
New Accounting Standards
Cost of Goods Sold	$ 898,281,000	$ 751,419,000	$ 676,074,000
Other (income) expense, net	(5,303,000)	1,361,000	(2,042,000)
General and administrative expenses	242,670,000	243,512,000	177,769,000
Accounting Standards Update 2016-09 | Adjustments for New Accounting Principle, Early Adoption
New Accounting Standards
Cumulative effect adjustment				$ 1,700,000
Accounting Standards Update 2017-07 | Adjustments for New Accounting Principle, Early Adoption
New Accounting Standards
Cost of Goods Sold		(278,000)	(383,000)
Other (income) expense, net		278,000	383,000
General and administrative expenses		350,000
Summit Materials, LLC
New Accounting Standards
Cost of Goods Sold	898,281,000	751,419,000	676,074,000
Other (income) expense, net	(5,289,000)	1,374,000	(2,042,000)
General and administrative expenses	$ 242,670,000	243,512,000	177,769,000
Summit Materials, LLC | Accounting Standards Update 2016-09 | Adjustments for New Accounting Principle, Early Adoption
New Accounting Standards
Cumulative effect adjustment				$ 1,700,000
Summit Materials, LLC | Accounting Standards Update 2017-07 | Adjustments for New Accounting Principle, Early Adoption
New Accounting Standards
Cost of Goods Sold		(278,000)	$ (383,000)
General and administrative expenses		$ (350,000)