Income Taxes - Components of Income Tax Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Jan. 02, 2016	Dec. 27, 2014
Provision for income taxes:
Current	$ 2,835	$ 1,605	$ (905)
Deferred	(8,134)	(19,868)	(6,078)
Income tax benefit	(5,299)	(18,263)	(6,983)
Valuation allowance	502,839	263,825	2,523
Summit Materials, LLC
Provision for income taxes:
Current	2,835	1,605	(905)
Deferred	(8,117)	(19,868)	(6,078)
Income tax benefit	(5,282)	(18,263)	$ (6,983)
Valuation allowance	$ 2,677	$ 2,523