Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 26, 2020	Dec. 28, 2019
Accumulated depreciation, depletion and amortization	$ 1,088,710	$ 955,815
Accumulated amortization	12,467	10,366
Valuation allowance	1,675	1,675
Summit Materials, LLC
Accumulated depreciation, depletion and amortization	1,088,710	955,815
Accumulated amortization	$ 12,467	$ 10,366
Common Class A
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)	114,123,911	113,309,385
Common stock, shares outstanding (in shares)	114,123,911	113,309,385
Common Class B
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