GUARANTOR AND NON-GUARANTOR FINANCIAL INFORMATION - Schedule of Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 30, 2024	Apr. 01, 2023
Condensed Consolidating Statements of Operations
Net cash (used in) provided by operating activities	$ (40,245)	$ 335
Cash flows from investing activities:
Acquisitions, net of cash acquired	(1,100,919)	(55,477)
Purchase of property, plant and equipment	(58,519)	(63,584)
Proceeds from the sale of property, plant, and equipment	2,664	1,777
Proceeds from sale of businesses	75,993	0
Other	(1,240)	(1,045)
Net cash used in investing activities	(1,103,421)	(118,329)
Cash flows from financing activities:
Proceeds from debt issuances	1,007,475	0
Payments on long-term debt	(506,392)	(4,414)
Payments on acquisition-related liabilities	(6,124)	(11,374)
Debt issuance costs	(17,550)	(1,566)
Other	(9,260)	(5,719)
Net cash provided by (used in) financing activities	468,742	(23,058)
Impact of foreign currency on cash	(1,128)	58
Net decrease in cash and cash equivalents and restricted cash	(676,052)	(140,994)
Cash and cash equivalents and restricted cash—beginning of period	1,174,162	520,451
Cash and cash equivalents and restricted cash—end of period	498,110	379,457
Summit Materials, LLC
Condensed Consolidating Statements of Operations
Net cash (used in) provided by operating activities	(33,505)	335
Cash flows from investing activities:
Acquisitions, net of cash acquired	(1,100,919)	(55,477)
Purchase of property, plant and equipment	(58,519)	(63,584)
Proceeds from the sale of property, plant, and equipment	2,664	1,777
Proceeds from sale of businesses	75,993	0
Other	(22,640)
Other	(1,240)	(1,045)
Net cash used in investing activities	(1,103,421)	(118,329)
Cash flows from financing activities:
Capital distributions to member	593	15
Proceeds from debt issuances	1,007,475	0
Loans received from and payments made on loans from other Summit Companies	0	0
Payments on long-term debt	(506,392)	(4,414)
Payments on acquisition-related liabilities	(6,124)	(11,374)
Debt issuance costs	(17,550)	(1,566)
Other	(9,409)	(5,719)
Net cash provided by (used in) financing activities	468,593	(23,058)
Impact of foreign currency on cash	(1,128)	58
Net decrease in cash and cash equivalents and restricted cash	(669,461)	(140,994)
Cash and cash equivalents and restricted cash—beginning of period	1,155,669	520,451
Cash and cash equivalents and restricted cash—end of period	486,208	379,457
Summit Materials, LLC | Eliminations
Condensed Consolidating Statements of Operations
Net cash (used in) provided by operating activities	0	0
Cash flows from investing activities:
Acquisitions, net of cash acquired	0	0
Purchase of property, plant and equipment	0	0
Proceeds from the sale of property, plant, and equipment	0	0
Proceeds from sale of businesses	0
Other	0
Other		0
Net cash used in investing activities	0	0
Cash flows from financing activities:
Capital distributions to member	0	0
Proceeds from debt issuances	0
Loans received from and payments made on loans from other Summit Companies	(453)	3,548
Payments on long-term debt	0	0
Payments on acquisition-related liabilities	0	0
Debt issuance costs	0	0
Other	0	0
Net cash provided by (used in) financing activities	(453)	3,548
Impact of foreign currency on cash	0	0
Net decrease in cash and cash equivalents and restricted cash	(453)	3,548
Cash and cash equivalents and restricted cash—beginning of period	(2,755)	(7,018)
Cash and cash equivalents and restricted cash—end of period	(3,208)	(3,470)
Summit Materials, LLC | Issuers | Reportable Legal Entities
Condensed Consolidating Statements of Operations
Net cash (used in) provided by operating activities	(22,707)	(55,528)
Cash flows from investing activities:
Acquisitions, net of cash acquired	97,153	0
Purchase of property, plant and equipment	(4,415)	(2,895)
Proceeds from the sale of property, plant, and equipment	0	0
Proceeds from sale of businesses	0
Other	0
Other		0
Net cash used in investing activities	92,738	(2,895)
Cash flows from financing activities:
Capital distributions to member	(52,015)	(55,870)
Proceeds from debt issuances	1,007,475
Loans received from and payments made on loans from other Summit Companies	(1,161,406)	(25,853)
Payments on long-term debt	(504,464)	(1,274)
Payments on acquisition-related liabilities	0	0
Debt issuance costs	(17,550)	(1,566)
Other	(7,860)	(2,740)
Net cash provided by (used in) financing activities	(735,820)	(87,303)
Impact of foreign currency on cash	0	0
Net decrease in cash and cash equivalents and restricted cash	(665,789)	(145,726)
Cash and cash equivalents and restricted cash—beginning of period	1,110,410	498,307
Cash and cash equivalents and restricted cash—end of period	444,621	352,581
Summit Materials, LLC | Guarantors  | Reportable Legal Entities
Condensed Consolidating Statements of Operations
Net cash (used in) provided by operating activities	(14,571)	49,394
Cash flows from investing activities:
Acquisitions, net of cash acquired	(1,198,072)	(55,477)
Purchase of property, plant and equipment	(52,077)	(58,356)
Proceeds from the sale of property, plant, and equipment	2,662	1,777
Proceeds from sale of businesses	75,993
Other	(22,640)
Other		(1,045)
Net cash used in investing activities	(1,194,134)	(113,101)
Cash flows from financing activities:
Capital distributions to member	52,608	55,885
Proceeds from debt issuances	0
Loans received from and payments made on loans from other Summit Companies	1,165,362	24,951
Payments on long-term debt	(1,928)	(3,140)
Payments on acquisition-related liabilities	(6,124)	(11,374)
Debt issuance costs	0	0
Other	(1,293)	(2,766)
Net cash provided by (used in) financing activities	1,208,625	63,556
Impact of foreign currency on cash	0	0
Net decrease in cash and cash equivalents and restricted cash	(80)	(151)
Cash and cash equivalents and restricted cash—beginning of period	3,115	2,864
Cash and cash equivalents and restricted cash—end of period	3,035	2,713
Summit Materials, LLC | Non-Guarantors | Reportable Legal Entities
Condensed Consolidating Statements of Operations
Net cash (used in) provided by operating activities	3,773	6,469
Cash flows from investing activities:
Acquisitions, net of cash acquired	0	0
Purchase of property, plant and equipment	(2,027)	(2,333)
Proceeds from the sale of property, plant, and equipment	2	0
Proceeds from sale of businesses	0
Other	0
Other		0
Net cash used in investing activities	(2,025)	(2,333)
Cash flows from financing activities:
Capital distributions to member	0	0
Proceeds from debt issuances	0
Loans received from and payments made on loans from other Summit Companies	(3,503)	(2,646)
Payments on long-term debt	0	0
Payments on acquisition-related liabilities	0	0
Debt issuance costs	0	0
Other	(256)	(213)
Net cash provided by (used in) financing activities	(3,759)	(2,859)
Impact of foreign currency on cash	(1,128)	58
Net decrease in cash and cash equivalents and restricted cash	(3,139)	1,335
Cash and cash equivalents and restricted cash—beginning of period	44,899	26,298
Cash and cash equivalents and restricted cash—end of period	$ 41,760	$ 27,633