GUARANTOR AND NON-GUARANTOR FINANCIAL INFORMATION - Schedule of Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jul. 01, 2023	Jul. 02, 2022	Dec. 31, 2022
Condensed Consolidating Statements of Operations
Net cash (used in) provided by operating activities	$ 94,042	$ 16,254
Cash flows from investing activities:
Acquisitions, net of cash acquired	(237,666)	(1,933)
Purchase of property, plant and equipment	(126,893)	(129,580)
Proceeds from the sale of property, plant, and equipment	5,760	5,427
Proceeds from sale of businesses	0	341,741
Other	(1,852)	(1,098)
Net cash (used in) provided by financing activities	(360,651)	214,557
Cash flows from financing activities:
Payments on long-term debt	(6,720)	(86,821)
Payments on acquisition-related liabilities	(11,539)	(11,577)
Distributions from partnership	0	(25)
Debt issuance costs	(1,566)
Other	(4,838)	(187)
Net cash used in financing activities	(24,579)	(145,996)
Impact of foreign currency on cash	747	(461)
Net (decrease) increase in cash	(290,441)	84,354
Cash and cash equivalents – beginning of period	520,451	380,961	$ 380,961
Cash and cash equivalents – end of period	230,010	465,315	520,451
Summit Materials, LLC
Condensed Consolidating Statements of Operations
Net cash (used in) provided by operating activities	94,042	16,254
Cash flows from investing activities:
Acquisitions, net of cash acquired	(237,666)	(1,933)
Purchase of property, plant and equipment	(126,893)	(129,580)
Proceeds from the sale of property, plant, and equipment	5,760	5,427
Proceeds from sale of businesses	0	341,741
Other	(1,852)	(1,098)
Net cash (used in) provided by financing activities	(360,651)	214,557
Cash flows from financing activities:
Capital distributions to member	84	(47,386)
Loans received from and payments made on loans from other Summit Companies	0	0
Payments on long-term debt	(6,720)	(86,821)
Payments on acquisition-related liabilities	(11,539)	(11,577)
Distributions from partnership	0	(25)
Debt issuance costs	(1,566)
Other	(4,838)	(187)
Net cash used in financing activities	(24,579)	(145,996)
Impact of foreign currency on cash	747	(461)
Net (decrease) increase in cash	(290,441)	84,354
Cash and cash equivalents – beginning of period	520,451	380,961	380,961
Cash and cash equivalents – end of period	230,010	465,315	520,451
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	0
Net cash (used in) provided by financing activities	0	0
Cash flows from financing activities:
Capital distributions to member	0	0
Loans received from and payments made on loans from other Summit Companies	1,643	621
Payments on long-term debt	0	0
Payments on acquisition-related liabilities	0	0
Distributions from partnership		0
Debt issuance costs	0
Other	0	0
Net cash used in financing activities	1,643	621
Impact of foreign currency on cash	0	0
Net (decrease) increase in cash	1,643	621
Cash and cash equivalents – beginning of period	(7,018)	(4,684)	(4,684)
Cash and cash equivalents – end of period	(5,375)	(4,063)	(7,018)
Summit Materials, LLC | Issuers | Reportable Legal Entities
Condensed Consolidating Statements of Operations
Net cash (used in) provided by operating activities	(62,840)	(63,758)
Cash flows from investing activities:
Acquisitions, net of cash acquired	0	0
Purchase of property, plant and equipment	(6,350)	(5,657)
Proceeds from the sale of property, plant, and equipment	0	0
Proceeds from sale of businesses		0
Other	0	0
Net cash (used in) provided by financing activities	(6,350)	(5,657)
Cash flows from financing activities:
Capital distributions to member	(239,264)	(49,319)
Loans received from and payments made on loans from other Summit Companies	13,332	275,632
Payments on long-term debt	(2,548)	(75,553)
Payments on acquisition-related liabilities	0	0
Distributions from partnership		(25)
Debt issuance costs	(1,566)
Other	(1,590)	(187)
Net cash used in financing activities	(231,636)	150,548
Impact of foreign currency on cash	0	0
Net (decrease) increase in cash	(300,826)	81,133
Cash and cash equivalents – beginning of period	498,307	365,044	365,044
Cash and cash equivalents – end of period	197,481	446,177	498,307
Summit Materials, LLC | Guarantors  | Reportable Legal Entities
Condensed Consolidating Statements of Operations
Net cash (used in) provided by operating activities	146,620	73,145
Cash flows from investing activities:
Acquisitions, net of cash acquired	(237,666)	(1,933)
Purchase of property, plant and equipment	(117,310)	(121,589)
Proceeds from the sale of property, plant, and equipment	5,435	5,182
Proceeds from sale of businesses		341,741
Other	(1,852)	(1,098)
Net cash (used in) provided by financing activities	(351,393)	222,303
Cash flows from financing activities:
Capital distributions to member	239,348	1,933
Loans received from and payments made on loans from other Summit Companies	(12,997)	(273,262)
Payments on long-term debt	(4,172)	(11,268)
Payments on acquisition-related liabilities	(11,539)	(11,577)
Distributions from partnership		0
Debt issuance costs	0
Other	(3,033)	0
Net cash used in financing activities	207,607	(294,174)
Impact of foreign currency on cash	0	0
Net (decrease) increase in cash	2,834	1,274
Cash and cash equivalents – beginning of period	2,864	2,264	2,264
Cash and cash equivalents – end of period	5,698	3,538	2,864
Summit Materials, LLC | Non-Guarantors | Reportable Legal Entities
Condensed Consolidating Statements of Operations
Net cash (used in) provided by operating activities	10,262	6,867
Cash flows from investing activities:
Acquisitions, net of cash acquired	0	0
Purchase of property, plant and equipment	(3,233)	(2,334)
Proceeds from the sale of property, plant, and equipment	325	245
Proceeds from sale of businesses		0
Other	0	0
Net cash (used in) provided by financing activities	(2,908)	(2,089)
Cash flows from financing activities:
Capital distributions to member	0	0
Loans received from and payments made on loans from other Summit Companies	(1,978)	(2,991)
Payments on long-term debt	0	0
Payments on acquisition-related liabilities	0	0
Distributions from partnership		0
Debt issuance costs	0
Other	(215)	0
Net cash used in financing activities	(2,193)	(2,991)
Impact of foreign currency on cash	747	(461)
Net (decrease) increase in cash	5,908	1,326
Cash and cash equivalents – beginning of period	26,298	18,337	18,337
Cash and cash equivalents – end of period	$ 32,206	$ 19,663	$ 26,298