Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 28, 2020	Dec. 28, 2019
Accumulated depreciation, depletion and amortization	$ 1,000,745	$ 955,815
Accumulated amortization	11,071	10,366
Valuation allowance	1,675	1,675
Summit Materials, LLC
Accumulated depreciation, depletion and amortization	1,000,745	955,815
Accumulated amortization	$ 11,071	$ 10,366
Class A Common Stock
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, shares issued (in shares)	114,110,597	113,309,385
Common stock, shares outstanding (in shares)	114,110,597	113,309,385
Class B Common Stock
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, shares issued (in shares)	99	99
Common stock, shares outstanding (in shares)	99	99