GUARANTOR AND NON-GUARANTOR FINANCIAL INFORMATION - Schedule of Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Thousands	Apr. 02, 2022	Jan. 01, 2022	Apr. 03, 2021	Jan. 02, 2021
Current assets:
Cash and cash equivalents	$ 287,392	$ 380,961
Accounts receivable, net	239,839	287,226
Cost and estimated earnings in excess of billings	12,723	7,600
Inventories	187,009	180,760
Total current assets	777,840	869,610
Property, plant and equipment, net	1,766,594	1,842,908
Goodwill	1,146,276	1,163,750
Intangible assets, net	67,015	69,396
Operating lease right-of-use assets	28,766	30,150
Total assets	4,143,245	4,239,125
Current liabilities:
Current portion of debt	6,354	6,354
Current portion of acquisition-related liabilities	13,078	13,110
Accounts payable	146,292	128,232
Accrued expenses	113,569	147,476
Current operating lease liabilities	5,934	6,497
Billings in excess of costs and estimated earnings	6,734	7,401
Total current liabilities	305,071	309,070
Long-term debt	1,590,050	1,591,019
Acquisition-related liabilities	22,928	33,369
Noncurrent operating lease liabilities	28,017	28,880
Total liabilities	2,396,748	2,415,913
Total liabilities and stockholders’ equity/member's interest	4,143,245	4,239,125
Summit Materials, LLC
Current assets:
Cash and cash equivalents	287,392	380,961
Accounts receivable, net	239,839	287,226
Intercompany receivables	0	0
Cost and estimated earnings in excess of billings	12,723	7,600
Inventories	187,009	180,760
Other current assets	50,877	13,063
Total current assets	777,840	869,610
Property, plant and equipment, net	1,766,594	1,842,908
Goodwill	1,147,276	1,164,750
Intangible assets, net	67,015	69,396
Operating lease right-of-use assets	28,766	30,150
Other assets	145,382	58,745
Total assets	3,932,873	4,035,559
Current liabilities:
Current portion of debt	6,354	6,354
Current portion of acquisition-related liabilities	13,078	13,110
Accounts payable	146,902	128,843
Accrued expenses	127,338	148,136
Accrued expenses	114,228	148,136
Current operating lease liabilities	5,934	6,497
Intercompany payables	0	0
Billings in excess of costs and estimated earnings	6,734	7,401
Total current liabilities	306,340	310,341
Long-term debt	1,590,050	1,591,019
Acquisition-related liabilities	22,928	33,369
Noncurrent operating lease liabilities	28,017	28,880
Other noncurrent liabilities	188,477	187,006
Total liabilities	2,135,812	2,150,615
Total member's interest	1,797,061	1,884,944	$ 1,655,471	$ 1,662,768
Total liabilities and stockholders’ equity/member's interest	3,932,873	4,035,559
Summit Materials, LLC | Eliminations
Current assets:
Cash and cash equivalents	(3,982)	(4,684)
Accounts receivable, net	(127)	59
Intercompany receivables	(2,128,441)	(2,113,528)
Cost and estimated earnings in excess of billings	0	0
Inventories	0	0
Other current assets	0	0
Total current assets	(2,132,550)	(2,118,153)
Property, plant and equipment, net	0	0
Goodwill	0	0
Intangible assets, net	0	0
Operating lease right-of-use assets	0	0
Other assets	(4,589,113)	(4,579,370)
Total assets	(6,721,663)	(6,697,523)
Current liabilities:
Current portion of debt	0	0
Current portion of acquisition-related liabilities	0	0
Accounts payable	(127)	59
Accrued expenses	(3,982)	(4,684)
Current operating lease liabilities	0	0
Intercompany payables	(2,128,441)	(2,113,528)
Billings in excess of costs and estimated earnings	0	0
Total current liabilities	(2,132,550)	(2,118,153)
Long-term debt	0	0
Acquisition-related liabilities	0	0
Noncurrent operating lease liabilities	0	0
Other noncurrent liabilities	(164,421)	(164,421)
Total liabilities	(2,296,971)	(2,282,574)
Total member's interest	(4,424,692)	(4,414,949)
Total liabilities and stockholders’ equity/member's interest	(6,721,663)	(6,697,523)
Summit Materials, LLC | Issuers | Reportable Legal Entities
Current assets:
Cash and cash equivalents	270,487	365,044
Accounts receivable, net	49	94
Intercompany receivables	357,196	366,619
Cost and estimated earnings in excess of billings	0	0
Inventories	0	0
Other current assets	3,519	3,036
Total current assets	631,251	734,793
Property, plant and equipment, net	11,384	10,013
Goodwill	0	0
Intangible assets, net	0	0
Operating lease right-of-use assets	5,376	5,612
Other assets	4,424,084	4,417,039
Total assets	5,072,095	5,167,457
Current liabilities:
Current portion of debt	6,354	6,354
Current portion of acquisition-related liabilities	0	0
Accounts payable	5,524	6,284
Accrued expenses	39,221	55,440
Current operating lease liabilities	798	780
Intercompany payables	1,618,099	1,607,816
Billings in excess of costs and estimated earnings	0	0
Total current liabilities	1,669,996	1,676,674
Long-term debt	1,590,050	1,591,019
Acquisition-related liabilities	0	0
Noncurrent operating lease liabilities	9,441	9,647
Other noncurrent liabilities	5,547	5,173
Total liabilities	3,275,034	3,282,513
Total member's interest	1,797,061	1,884,944
Total liabilities and stockholders’ equity/member's interest	5,072,095	5,167,457
Summit Materials, LLC | Guarantors  | Reportable Legal Entities
Current assets:
Cash and cash equivalents	1,475	2,264
Accounts receivable, net	217,943	264,888
Intercompany receivables	1,771,245	1,746,909
Cost and estimated earnings in excess of billings	11,947	6,942
Inventories	180,997	175,211
Other current assets	44,966	8,920
Total current assets	2,228,573	2,205,134
Property, plant and equipment, net	1,665,426	1,742,721
Goodwill	1,085,924	1,104,019
Intangible assets, net	62,093	64,466
Operating lease right-of-use assets	18,058	19,693
Other assets	309,795	220,500
Total assets	5,369,869	5,356,533
Current liabilities:
Current portion of debt	0	0
Current portion of acquisition-related liabilities	13,078	13,110
Accounts payable	130,424	114,405
Accrued expenses	89,979	94,858
Current operating lease liabilities	4,387	5,053
Intercompany payables	508,948	502,334
Billings in excess of costs and estimated earnings	6,210	6,960
Total current liabilities	753,026	736,720
Long-term debt	0	0
Acquisition-related liabilities	22,928	33,369
Noncurrent operating lease liabilities	14,199	15,101
Other noncurrent liabilities	228,195	227,348
Total liabilities	1,018,348	1,012,538
Total member's interest	4,351,521	4,343,995
Total liabilities and stockholders’ equity/member's interest	5,369,869	5,356,533
Summit Materials, LLC | Non-Guarantors | Reportable Legal Entities
Current assets:
Cash and cash equivalents	19,412	18,337
Accounts receivable, net	21,974	22,185
Intercompany receivables	0	0
Cost and estimated earnings in excess of billings	776	658
Inventories	6,012	5,549
Other current assets	2,392	1,107
Total current assets	50,566	47,836
Property, plant and equipment, net	89,784	90,174
Goodwill	61,352	60,731
Intangible assets, net	4,922	4,930
Operating lease right-of-use assets	5,332	4,845
Other assets	616	576
Total assets	212,572	209,092
Current liabilities:
Current portion of debt	0	0
Current portion of acquisition-related liabilities	0	0
Accounts payable	11,081	8,095
Accrued expenses	2,120	2,522
Current operating lease liabilities	749	664
Intercompany payables	1,394	3,378
Billings in excess of costs and estimated earnings	524	441
Total current liabilities	15,868	15,100
Long-term debt	0	0
Acquisition-related liabilities	0	0
Noncurrent operating lease liabilities	4,377	4,132
Other noncurrent liabilities	119,156	118,906
Total liabilities	139,401	138,138
Total member's interest	73,171	70,954
Total liabilities and stockholders’ equity/member's interest	$ 212,572	$ 209,092