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) income	(23,245)	(27,790)				(22,517)	(27,790)							(728)
LP Unit exchanges (in shares)											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
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
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			$ 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	99
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 (loss) income	109,891	130,900
LP Unit exchanges (in shares)			1,440,983
Other comprehensive income (loss), net of tax	506
Stock option exercises (in shares)			1,744,256
Shares redeemed to settle taxes and other (in shares)			989,116
Ending balance at Oct. 02, 2021	1,771,764					435,118		5,670	(17,901)		$ 1,186	$ 0	1,319,897	9,893
Ending balance at Oct. 02, 2021		1,838,190			1,503,051		353,040		(17,901)
Ending balance (in shares) at Oct. 02, 2021			118,564,950								118,564,950	99
Beginning balance at Apr. 03, 2021	1,614,560					304,255		6,838			$ 1,167	$ 0	1,289,267	13,033
Beginning balance at Apr. 03, 2021		1,655,471			1,477,578		194,350		(16,457)
Beginning balance (in shares) at Apr. 03, 2021											116,644,332	99
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net contributed capital		15,846			15,846
Net (loss) income	57,758	69,815				56,659	69,815							1,099
LP Unit exchanges (in shares)											445,540
LP Unit exchanges	0										$ 4		3,631	(3,635)
Other comprehensive income (loss), net of tax	2,079	2,632						2,028	2,632					51
Stock option exercises (in shares)											847,480
Stock option exercises	15,845										$ 8		15,837
Share-based compensation	4,827	4,827			4,827								4,827
Shares redeemed to settle taxes and other (in shares)											18,536
Shares redeemed to settle taxes and other	(147)	0			0						$ 1		(148)
Ending balance at Jul. 03, 2021	1,694,922					360,914		8,866			$ 1,180	$ 0	1,313,414	10,548
Ending balance at Jul. 03, 2021		1,748,591			1,498,251		264,165		(13,825)
Ending balance (in shares) at Jul. 03, 2021											117,955,888	99
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net contributed capital		650			650
Net (loss) income	75,378	88,875				74,204	88,875							1,174
LP Unit exchanges (in shares)											283,649
LP Unit exchanges	0										$ 3		1,769	(1,772)
Other comprehensive income (loss), net of tax	(3,253)	(4,076)						(3,196)	(4,076)					(57)
Stock option exercises (in shares)											33,438
Stock option exercises	651												651
Share-based compensation	4,685	4,685			4,685								4,685
Shares redeemed to settle taxes and other (in shares)											291,975
Shares redeemed to settle taxes and other	(619)	(535)			(535)						$ 3		(622)
Ending balance at Oct. 02, 2021	1,771,764					435,118		5,670	(17,901)		$ 1,186	$ 0	1,319,897	9,893
Ending balance at Oct. 02, 2021		1,838,190			1,503,051		353,040		(17,901)
Ending balance (in shares) at Oct. 02, 2021			118,564,950								118,564,950	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) income	(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
Stock option exercises	27												27
Share-based compensation	5,422	5,422			5,422								5,422
Repurchases of common stock (in shares)										(1,506,878)
Repurchases of common stock	(47,509)					(47,494)				$ (15)			(121)	121
Shares redeemed to settle taxes and other (in shares)											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			$ 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
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 (loss) income	245,617	301,047
LP Unit exchanges (in shares)			2,000
Other comprehensive income (loss), net of tax	(10,709)
Stock option exercises (in shares)			10,098
Repurchases of common stock (in shares)			(3,427,510)
Repurchases of common stock			$ (101,000)
Shares redeemed to settle taxes and other (in shares)			1,097,273
Ending balance at Oct. 01, 2022	1,971,224					620,320		(3,470)	(30,139)		$ 1,165	$ 0	1,340,602	12,607
Ending balance at Oct. 01, 2022		2,051,226			1,387,207		694,158		(30,139)
Ending balance (in shares) at Oct. 01, 2022			116,386,969	99							116,386,969	99
Beginning balance at Apr. 02, 2022	1,746,497					397,170		8,389			$ 1,181	$ 0	1,330,548	9,209
Beginning balance at Apr. 02, 2022		1,797,061			1,464,619		346,724		(14,282)
Beginning balance (in shares) at Apr. 02, 2022											118,041,848	99
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net contributed capital		96			96
Net (loss) income	192,766	242,101				190,113	242,101							2,653
Other comprehensive income (loss), net of tax	(4,257)	(5,610)						(4,196)	(5,610)					(61)
Distributions		(25)			(25)
Stock option exercises (in shares)											4,929
Stock option exercises	96												96
Share-based compensation	4,734	4,734			4,734								4,734
Distributions from partnership	(25)													(25)
Shares redeemed to settle taxes and other (in shares)											67,835
Shares redeemed to settle taxes and other	991	991			991						$ 1		997	(7)
Ending balance at Jul. 02, 2022	1,940,802					587,283		4,193			$ 1,182	$ 0	1,336,375	11,769
Ending balance at Jul. 02, 2022		2,039,348			1,470,415		588,825		(19,892)
Ending balance (in shares) at Jul. 02, 2022											118,114,612	99
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net contributed capital		(53,395)			(53,395)
Net (loss) income	87,651	105,333				86,489	105,333							1,162
LP Unit exchanges (in shares)											2,000
LP Unit exchanges	0												34	(34)
Other comprehensive income (loss), net of tax	(7,777)	(10,247)						(7,663)	(10,247)					(114)
Distributions		(34,130)			(34,130)
Stock option exercises (in shares)											3,580
Stock option exercises	76												76
Share-based compensation	4,902	4,902			4,902								4,902
Repurchases of common stock (in shares)										(1,920,632)
Repurchases of common stock	(53,471)					(53,452)				$ (19)			(198)	198
Distributions from partnership	(374)													(374)
Shares redeemed to settle taxes and other (in shares)											187,409
Shares redeemed to settle taxes and other	(585)	(585)			(585)						$ 2		(587)
Ending balance at Oct. 01, 2022	$ 1,971,224					$ 620,320		$ (3,470)	(30,139)		$ 1,165	$ 0	$ 1,340,602	$ 12,607
Ending balance at Oct. 01, 2022		$ 2,051,226			$ 1,387,207		$ 694,158		$ (30,139)
Ending balance (in shares) at Oct. 01, 2022			116,386,969	99							116,386,969	99