Unaudited Consolidated Statements of Changes in Stockholders' Equity / Members' Interest - USD ($) $ in Thousands	Total	Summit Materials, LLC	Common Class A	Common Class B	Members' equity Summit Materials, LLC	Accumulated Earnings (Deficit)	Accumulated Earnings (Deficit) Summit Materials, LLC	Accumulated other comprehensive income (loss)	Accumulated other comprehensive income (loss) Summit Materials, LLC	Common Stock	Common Stock Common Class A	Common Stock Common Class B	Additional Paid-in Capital	Noncontrolling Interest In Summit Holdings
Beginning balance at Jan. 02, 2021	$ 1,616,268					$ 326,772		$ 5,203	$ (18,583)		$ 1,145	$ 0	$ 1,264,681	$ 18,467
Beginning balance at Jan. 02, 2021		$ 1,662,768			$ 1,459,211		$ 222,140		(18,583)
Beginning balance (in shares) at Jan. 02, 2021			114,390,595								114,390,595	99
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net contributed capital		15,920			15,920
Net loss	(23,245)	(27,790)				(22,517)	(27,790)							(728)
LP Unit exchanges (in shares)			711,794								711,794
LP Unit exchanges	0										$ 7		4,744	(4,751)
Other comprehensive income (loss), net of tax	1,680	2,126						1,635	2,126					45
Distributions		(2,500)			(2,500)
Stock option exercises (in shares)			863,338								863,338
Stock option exercises	15,920										$ 9		15,911
Share-based compensation	5,363	5,363			5,363								5,363
Shares redeemed to settle taxes and other (in shares)			678,605								678,605
Shares redeemed to settle taxes and other	(1,426)	(416)			(416)						$ 6		(1,432)
Ending balance at Apr. 03, 2021	1,614,560					304,255		6,838	(16,457)		$ 1,167	$ 0	1,289,267	13,033
Ending balance at Apr. 03, 2021		1,655,471			1,477,578		194,350		(16,457)
Ending balance (in shares) at Apr. 03, 2021			116,644,332								116,644,332	99
Beginning balance at Jan. 01, 2022	1,823,212					478,956		7,083	(16,026)		$ 1,188	$ 0	1,326,340	9,645
Beginning balance at Jan. 01, 2022		1,884,944			1,507,859		393,111		(16,026)
Beginning balance (in shares) at Jan. 01, 2022			118,705,108	99							118,705,108	99
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net contributed capital		(47,482)			(47,482)
Net loss	(34,800)	(46,387)				(34,292)	(46,387)							(508)
Other comprehensive income (loss), net of tax	1,325	1,744						1,306	1,744					19
Stock option exercises (in shares)			1,589								1,589
Stock option exercises	27										$ 0		27
Share-based compensation	5,422	5,422			5,422								5,422
Repurchases of common stock (in shares)			(1,506,878)							(1,506,878)
Repurchases of common stock	(47,509)		$ (47,500)			(47,494)				$ (15)			(121)	121
Shares redeemed to settle taxes and other (in shares)			842,029								842,029
Shares redeemed to settle taxes and other	(1,180)	(1,180)			(1,180)						$ 8		(1,120)	(68)
Ending balance at Apr. 02, 2022	$ 1,746,497					$ 397,170		$ 8,389	(14,282)		$ 1,181	$ 0	$ 1,330,548	$ 9,209
Ending balance at Apr. 02, 2022		$ 1,797,061			$ 1,464,619		$ 346,724		$ (14,282)
Ending balance (in shares) at Apr. 02, 2022			118,041,848	99							118,041,848	99