SEGMENT INFORMATION - Financial Data (Details) $ in Thousands	3 Months Ended
	Apr. 02, 2022 USD ($) segment	Apr. 03, 2021 USD ($)	Jan. 01, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment	3
Number of reportable segments | segment	3
Total revenue	$ 420,947	$ 427,844
Loss from operations before taxes	(39,543)	(28,688)
Interest expense	20,149	24,186
Depreciation, depletion and amortization	50,479	55,570
Accretion	714	766
Gain on sale of businesses	(14,205)	(15,668)
Non-cash compensation	5,422	5,363
Other	247	205
Total Adjusted EBITDA	23,263	41,734
Total purchases of property, plant and equipment	57,774	69,757
Total depreciation, depletion, amortization and accretion	51,193	56,336
Total assets	4,143,245		$ 4,239,125
Operating segment
Segment Reporting Information [Line Items]
Total purchases of property, plant and equipment	57,315	69,543
Total depreciation, depletion, amortization and accretion	50,444	55,232
Total assets	3,639,103		3,649,022
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	(11,746)	(13,158)
Total purchases of property, plant and equipment	459	214
Total depreciation, depletion, amortization and accretion	749	1,104
Total assets	504,142		590,103
West
Segment Reporting Information [Line Items]
Total revenue	252,232	251,133
West | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	32,692	40,648
Total purchases of property, plant and equipment	26,874	34,068
Total depreciation, depletion, amortization and accretion	24,575	25,140
Total assets	1,527,170		1,512,298
East
Segment Reporting Information [Line Items]
Total revenue	122,490	136,042
East | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	8,136	11,745
Total purchases of property, plant and equipment	24,326	33,202
Total depreciation, depletion, amortization and accretion	18,295	21,943
Total assets	1,259,620		1,292,638
Cement
Segment Reporting Information [Line Items]
Total revenue	46,225	40,669
Cement | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	(5,819)	2,499
Total purchases of property, plant and equipment	6,115	2,273
Total depreciation, depletion, amortization and accretion	7,574	8,149
Total assets	$ 852,313		844,086
Summit Materials, LLC
Segment Reporting Information [Line Items]
Number of operating segments | segment	3
Number of reportable segments | segment	3
Total revenue	$ 420,947	427,844
Loss from operations before taxes	(39,543)	(28,626)
Interest expense	20,149	24,124
Depreciation, depletion and amortization	50,479	55,570
Accretion	714	766
Gain on sale of businesses	(14,205)	(15,668)
Non-cash compensation	5,422	5,363
Other	247	205
Total Adjusted EBITDA	23,263	41,734
Total purchases of property, plant and equipment	57,774	69,757
Total depreciation, depletion, amortization and accretion	51,193	56,336
Total assets	3,932,873		4,035,559
Summit Materials, LLC | Operating segment
Segment Reporting Information [Line Items]
Total purchases of property, plant and equipment	57,315	69,543
Total depreciation, depletion, amortization and accretion	50,444	55,232
Total assets	3,639,103		3,649,022
Summit Materials, LLC | Corporate, Non-Segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	(11,746)	(13,158)
Total purchases of property, plant and equipment	459	214
Total depreciation, depletion, amortization and accretion	749	1,104
Total assets	293,770		386,537
Summit Materials, LLC | West
Segment Reporting Information [Line Items]
Total revenue	252,232	251,133
Summit Materials, LLC | West | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	32,692	40,648
Total purchases of property, plant and equipment	26,874	34,068
Total depreciation, depletion, amortization and accretion	24,575	25,140
Total assets	1,527,170		1,512,298
Summit Materials, LLC | East
Segment Reporting Information [Line Items]
Total revenue	122,490	136,042
Summit Materials, LLC | East | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	8,136	11,745
Total purchases of property, plant and equipment	24,326	33,202
Total depreciation, depletion, amortization and accretion	18,295	21,943
Total assets	1,259,620		1,292,638
Summit Materials, LLC | Cement
Segment Reporting Information [Line Items]
Total revenue	46,225	40,669
Summit Materials, LLC | Cement | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	(5,819)	2,499
Total purchases of property, plant and equipment	6,115	2,273
Total depreciation, depletion, amortization and accretion	7,574	$ 8,149
Total assets	$ 852,313		$ 844,086