Employee Benefit Plans - Target Allocaiton of Company's Pension Plans' Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss (credit) expected to be amortized from AOCI	$ 300
Pension Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of investments	$ 0	$ 0
Pension Benefits | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation	30.00%
Pension Benefits | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation	63.00%
Pension Benefits | Cash
Defined Benefit Plan Disclosure [Line Items]
Target allocation	5.00%
Pension Benefits | Precious Metals
Defined Benefit Plan Disclosure [Line Items]
Target allocation	2.00%
Summit Materials, LLC | Pension Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of investments	$ 0	$ 0
Summit Materials, LLC | Pension Benefits | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation	30.00%
Summit Materials, LLC | Pension Benefits | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation	63.00%
Summit Materials, LLC | Pension Benefits | Cash
Defined Benefit Plan Disclosure [Line Items]
Target allocation	5.00%
Summit Materials, LLC | Pension Benefits | Precious Metals
Defined Benefit Plan Disclosure [Line Items]
Target allocation	2.00%