Guarantor and Non-Guarantor Financial Information - Schedule of Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Oct. 01, 2016	Jan. 02, 2016
Current assets:
Cash and cash equivalents	$ 287,082	$ 143,392	$ 31,643	$ 186,405
Accounts receivable, net	295,491	162,377
Cost and estimated earnings in excess of billings	39,316	7,450
Inventories	181,784	157,679
Other current assets	11,669	12,800
Total current assets	815,342	483,698
Property, plant and equipment, net	1,620,123	1,446,452
Goodwill	1,012,771	782,212
Intangible assets, net	16,995	17,989
Other assets	50,068	46,789
Total assets	3,992,792	2,781,466
Current liabilities:
Current portion of debt	6,500	6,500
Current portion of acquisition-related liabilities	25,153	24,162
Accounts payable	134,925	81,565
Accrued expenses	130,502	111,605
Billings in excess of costs and estimated earnings	18,043	15,456
Total current liabilities	315,123	239,288
Long-term debt	1,807,064	1,514,456
Acquisition-related liabilities	36,326	32,664
Other noncurrent liabilities	68,030	76,874
Total liabilities	2,775,428	1,921,427
Total liabilities and stockholders' equity / member's interest	3,992,792	2,781,466
Summit Materials, LLC
Current assets:
Cash and cash equivalents	287,082	142,672	14,182	185,388
Accounts receivable, net	295,491	162,377
Cost and estimated earnings in excess of billings	39,316	7,450
Inventories	181,784	157,679
Other current assets	11,669	12,800
Total current assets	815,342	482,978
Property, plant and equipment, net	1,620,123	1,446,452
Goodwill	1,012,771	782,212
Intangible assets, net	16,995	17,989
Other assets	50,068	46,789
Total assets	3,515,299	2,776,420
Current liabilities:
Current portion of debt	6,500	6,500
Current portion of acquisition-related liabilities	22,653	21,663
Accounts payable	134,318	81,610
Accrued expenses	130,502	110,473
Billings in excess of costs and estimated earnings	18,043	15,456
Total current liabilities	312,016	235,702
Long-term debt	1,807,064	1,514,456
Acquisition-related liabilities	30,644	25,161
Other noncurrent liabilities	131,547	124,708
Total liabilities	2,281,271	1,900,027
Total member's interest	1,234,028	876,393
Total liabilities and stockholders' equity / member's interest	3,515,299	2,776,420
Summit Materials, LLC | Eliminations
Current assets:
Cash and cash equivalents	(14,572)	(10,666)	(17,648)	(11,600)
Accounts receivable, net	(130)	(102)
Intercompany receivables	(955,999)	(843,434)
Total current assets	(970,701)	(854,202)
Other assets	(3,875,482)	(3,283,133)
Total assets	(4,846,183)	(4,137,335)
Current liabilities:
Accounts payable	(130)	(102)
Accrued expenses	(14,572)	(10,666)
Intercompany payables	(955,999)	(843,434)
Total current liabilities	(970,701)	(854,202)
Other noncurrent liabilities	(171,318)	(165,242)
Total liabilities	(1,142,019)	(1,019,444)
Total member's interest	(3,704,164)	(3,117,891)
Total liabilities and stockholders' equity / member's interest	(4,846,183)	(4,137,335)
Summit Materials, LLC | Issuers
Current assets:
Cash and cash equivalents	283,331	133,862	14,329	180,712
Intercompany receivables	592,870	521,658
Other current assets	1,927	1,259
Total current assets	878,128	656,779
Property, plant and equipment, net	8,938	7,033
Other assets	3,756,415	3,202,706
Total assets	4,643,481	3,866,518
Current liabilities:
Current portion of debt	6,500	6,500
Current portion of acquisition-related liabilities		1,000
Accounts payable	2,295	1,497
Accrued expenses	44,464	46,460
Intercompany payables	571,155	509,503
Total current liabilities	624,414	564,960
Long-term debt	1,807,064	1,514,456
Other noncurrent liabilities	3,344	2,395
Total liabilities	2,434,822	2,081,811
Total member's interest	2,208,659	1,784,707
Total liabilities and stockholders' equity / member's interest	4,643,481	3,866,518
Summit Materials, LLC | Guarantors
Current assets:
Cash and cash equivalents	2,199	4,820	4,783	4,068
Accounts receivable, net	275,490	155,389
Intercompany receivables	363,129	321,776
Cost and estimated earnings in excess of billings	36,998	6,830
Inventories	176,310	153,374
Other current assets	9,006	11,012
Total current assets	863,132	653,201
Property, plant and equipment, net	1,572,349	1,418,902
Goodwill	951,482	735,490
Intangible assets, net	16,995	17,989
Other assets	166,889	125,270
Total assets	3,570,847	2,950,852
Current liabilities:
Current portion of acquisition-related liabilities	22,653	20,663
Accounts payable	120,086	76,886
Accrued expenses	97,815	73,807
Intercompany payables	381,373	327,405
Billings in excess of costs and estimated earnings	16,740	15,242
Total current liabilities	638,667	514,003
Acquisition-related liabilities	30,644	25,161
Other noncurrent liabilities	224,157	231,199
Total liabilities	893,468	770,363
Total member's interest	2,677,379	2,180,489
Total liabilities and stockholders' equity / member's interest	3,570,847	2,950,852
Summit Materials, LLC | Non Guarantors
Current assets:
Cash and cash equivalents	16,124	14,656	$ 12,718	$ 12,208
Accounts receivable, net	20,131	7,090
Cost and estimated earnings in excess of billings	2,318	620
Inventories	5,474	4,305
Other current assets	736	529
Total current assets	44,783	27,200
Property, plant and equipment, net	38,836	20,517
Goodwill	61,289	46,722
Other assets	2,246	1,946
Total assets	147,154	96,385
Current liabilities:
Accounts payable	12,067	3,329
Accrued expenses	2,795	872
Intercompany payables	3,471	6,526
Billings in excess of costs and estimated earnings	1,303	214
Total current liabilities	19,636	10,941
Other noncurrent liabilities	75,364	56,356
Total liabilities	95,000	67,297
Total member's interest	52,154	29,088
Total liabilities and stockholders' equity / member's interest	$ 147,154	$ 96,385