STOCKHOLDERS' EQUITY/MEMBERS' INTEREST - Equity Offerings (Details) - shares	6 Months Ended
	Jul. 01, 2023	Jul. 02, 2022	Dec. 31, 2022	Jan. 01, 2022
Common Class A
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	118,408,655	120,684,322
Exchanges during period (in shares)	2,000
Stock option exercises (in shares)	4,240	6,518
Repurchases of common stock, (in shares)		(1,506,878)
Other equity transactions (in shares)	471,379	909,864
Ending balance (in shares)	118,886,274	120,093,826
Summit Materials, Inc. and Summit Holdings, LP
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	119,720,659	121,998,328
Exchanges during period (in shares)	0
Stock option exercises (in shares)	4,240	6,518
Repurchases of common stock, (in shares)		(1,506,878)
Other equity transactions (in shares)	471,379	909,864
Ending balance (in shares)	120,196,278	121,407,832
LP Units | Summit Holdings LP
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Number of LP Units outstanding, beginning balance (in shares)	1,312,004	1,314,006
Number of LP Units exchanged (in shares)	(2,000)
Number of LP Units outstanding, ending balance (in shares)	1,310,004	1,314,006
Summit Materials Inc
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ownership percentage	98.90%	98.90%	98.90%	98.90%