Income Taxes - Components of Income Tax Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Provision for income taxes:
Current	$ 2,530	$ 2,835	$ 1,605
Deferred	(286,507)	(8,134)	(19,868)
Income tax expense (benefit)	(283,977)	(5,299)	(18,263)
Valuation allowance	1,675	502,839	263,825
Summit Materials, LLC
Provision for income taxes:
Current	2,762	2,835	1,605
Deferred	(23,107)	(8,134)	(19,868)
Income tax expense (benefit)	(20,345)	(5,282)	$ (18,263)
Valuation allowance	$ 1,675	$ 2,677