SEGMENT INFORMATION - Financial Data (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 01, 2022 USD ($)	Oct. 02, 2021 USD ($)	Oct. 01, 2022 USD ($) segment	Oct. 02, 2021 USD ($)	Jan. 01, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			3
Number of reportable segments | segment			3
Total revenue	$ 752,747	$ 717,240	$ 1,860,248	$ 1,813,001
Income from operations before taxes	112,480	95,891	319,650	143,369
Interest expense	21,980	24,134	62,728	72,536
Depreciation, depletion and amortization	51,439	58,381	148,373	171,474
Accretion	694	701	2,110	2,177
Loss on debt financings	0	6,016	0	6,016
Tax receivable agreement expense	0	0	954	0
(Gain) loss on sale of businesses	(4,115)	113	(174,373)	(15,319)
Non-cash compensation	4,902	4,685	15,058	14,875
Other	(2,492)	363	(2,315)	682
Total Adjusted EBITDA	184,888	190,284	372,185	395,810
Total purchases of property, plant and equipment			189,008	170,070
Total depreciation, depletion, amortization and accretion	52,133	59,082	150,483	173,651
Total assets	4,284,955		4,284,955		$ 4,239,125
Operating segment
Segment Reporting Information [Line Items]
Total purchases of property, plant and equipment			181,081	169,458
Total depreciation, depletion, amortization and accretion	51,312	58,014	148,143	170,378
Total assets	3,655,556		3,655,556		3,649,022
Corporate, non-segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	(4,109)	(11,463)	(26,400)	(36,306)
Total purchases of property, plant and equipment			7,927	612
Total depreciation, depletion, amortization and accretion	821	1,068	2,340	3,273
Total assets	629,399		629,399		590,103
West
Segment Reporting Information [Line Items]
Total revenue	439,411	369,250	1,075,393	958,351
West | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	98,281	92,303	215,617	211,722
Total purchases of property, plant and equipment			85,462	85,137
Total depreciation, depletion, amortization and accretion	24,908	24,796	71,495	75,287
Total assets	1,625,846		1,625,846		1,512,298
East
Segment Reporting Information [Line Items]
Total revenue	193,421	255,490	525,064	635,659
(Gain) loss on sale of businesses			(174,400)
East | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	44,119	69,084	98,949	138,113
Total purchases of property, plant and equipment			65,116	69,469
Total depreciation, depletion, amortization and accretion	15,445	22,809	48,655	66,306
Total assets	1,136,239		1,136,239		1,292,638
Cement
Segment Reporting Information [Line Items]
Total revenue	119,915	92,500	259,791	218,991
Cement | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	46,597	40,360	84,019	82,281
Total purchases of property, plant and equipment			30,503	14,852
Total depreciation, depletion, amortization and accretion	10,959	10,409	27,993	28,785
Total assets	893,471		$ 893,471		844,086
Summit Materials, LLC
Segment Reporting Information [Line Items]
Number of operating segments | segment			3
Number of reportable segments | segment			3
Total revenue	752,747	717,240	$ 1,860,248	1,813,001
Income from operations before taxes	112,480	95,891	320,604	143,431
Interest expense	21,980	24,134	62,728	72,474
Depreciation, depletion and amortization	51,439	58,381	148,373	171,474
Accretion	694	701	2,110	2,177
Loss on debt financings	0	6,016	0	6,016
(Gain) loss on sale of businesses	(4,115)	113	(174,373)	(15,319)
Non-cash compensation	4,902	4,685	15,058	14,875
Other	(2,492)	363	(2,315)	682
Total Adjusted EBITDA	184,888	190,284	372,185	395,810
Total purchases of property, plant and equipment			189,008	170,070
Total depreciation, depletion, amortization and accretion	52,133	59,082	150,483	173,651
Total assets	4,100,489		4,100,489		4,035,559
Summit Materials, LLC | Operating segment
Segment Reporting Information [Line Items]
Total purchases of property, plant and equipment			181,081	169,458
Total depreciation, depletion, amortization and accretion	51,312	58,014	148,143	170,378
Total assets	3,655,556		3,655,556		3,649,022
Summit Materials, LLC | Corporate, non-segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	(4,109)	(11,463)	(26,400)	(36,306)
Total purchases of property, plant and equipment			7,927	612
Total depreciation, depletion, amortization and accretion	821	1,068	2,340	3,273
Total assets	444,933		444,933		386,537
Summit Materials, LLC | West
Segment Reporting Information [Line Items]
Total revenue	439,411	369,250	1,075,393	958,351
Summit Materials, LLC | West | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	98,281	92,303	215,617	211,722
Total purchases of property, plant and equipment			85,462	85,137
Total depreciation, depletion, amortization and accretion	24,908	24,796	71,495	75,287
Total assets	1,625,846		1,625,846		1,512,298
Summit Materials, LLC | East
Segment Reporting Information [Line Items]
Total revenue	193,421	255,490	525,064	635,659
(Gain) loss on sale of businesses			(174,400)
Summit Materials, LLC | East | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	44,119	69,084	98,949	138,113
Total purchases of property, plant and equipment			65,116	69,469
Total depreciation, depletion, amortization and accretion	15,445	22,809	48,655	66,306
Total assets	1,136,239		1,136,239		1,292,638
Summit Materials, LLC | Cement
Segment Reporting Information [Line Items]
Total revenue	119,915	92,500	259,791	218,991
Summit Materials, LLC | Cement | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	46,597	40,360	84,019	82,281
Total purchases of property, plant and equipment			30,503	14,852
Total depreciation, depletion, amortization and accretion	10,959	$ 10,409	27,993	$ 28,785
Total assets	$ 893,471		$ 893,471		$ 844,086