Segment Information - Financial Data (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 29, 2018 USD ($) segment	Sep. 30, 2017 USD ($)	Dec. 30, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			3
Number of reportable segments | segment			3
Total revenue	$ 694,661	$ 634,181	$ 1,609,972	$ 1,442,551
Income (loss) from operations before taxes	94,757	(414,046)	71,206	(415,809)
Interest expense	28,889	28,921	86,616	79,876
Depreciation, depletion and amortization	53,494	48,483	149,439	132,374
Accretion	480	486	1,224	1,382
Loss on debt financings	0	0	149	190
Tax receivable agreement expense	0	501,752	0	503,277
Gain on sale of business	(12,108)	0	(12,108)	0
Transaction costs	1,260	2,581	3,817	6,474
Non-cash compensation	5,643	4,724	19,833	14,148
Other	(409)	(200)	(7,316)	(346)
Total Adjusted EBITDA	172,006	172,701	312,860	321,566
Total purchases of property, plant and equipment			183,752	147,478
Total depreciation, depletion, amortization and accretion	53,974	48,969	150,663	133,756
Total assets	3,896,334		3,896,334		$ 3,787,333
West
Segment Reporting Information [Line Items]
Total revenue	367,912	327,917	871,338	746,991
Gain on sale of business	(12,108)
East
Segment Reporting Information [Line Items]
Total revenue	232,777	204,990	525,270	466,222
Cement
Segment Reporting Information [Line Items]
Total revenue	93,972	101,274	213,364	229,338
Operating segment
Segment Reporting Information [Line Items]
Total purchases of property, plant and equipment			177,806	142,483
Total depreciation, depletion, amortization and accretion	53,400	48,350	148,744	131,816
Total assets	3,551,610		3,551,610		3,131,724
Operating segment | West
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	73,916	76,637	151,316	152,856
Total purchases of property, plant and equipment			104,217	64,257
Total depreciation, depletion, amortization and accretion	23,289	18,907	68,029	51,989
Total assets	1,422,966		1,422,966		1,225,463
Operating segment | East
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	58,305	56,397	100,497	99,511
Total purchases of property, plant and equipment			51,968	52,920
Total depreciation, depletion, amortization and accretion	19,429	17,628	54,982	49,939
Total assets	1,229,567		1,229,567		1,035,609
Operating segment | Cement
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	44,299	46,860	82,626	93,328
Total purchases of property, plant and equipment			21,621	25,306
Total depreciation, depletion, amortization and accretion	10,682	11,815	25,733	29,888
Total assets	899,077		899,077		870,652
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	(4,514)	(7,193)	(21,579)	(24,129)
Total purchases of property, plant and equipment			5,946	4,995
Total depreciation, depletion, amortization and accretion	574	619	1,919	1,940
Total assets	344,724		$ 344,724		655,609
Summit Materials, LLC
Segment Reporting Information [Line Items]
Number of operating segments | segment			3
Total revenue	694,661	634,181	$ 1,609,972	1,442,551
Income (loss) from operations before taxes	94,926	87,919	71,756	88,149
Interest expense	28,720	28,708	86,066	79,195
Depreciation, depletion and amortization	53,494	48,483	149,439	132,374
Accretion	480	486	1,224	1,382
Loss on debt financings	0	0	149	190
Gain on sale of business	(12,108)	0	(12,108)	0
Transaction costs	1,260	2,581	3,817	6,474
Non-cash compensation	5,643	4,724	19,833	14,148
Other	(409)	(200)	(7,316)	(346)
Total Adjusted EBITDA	172,006	172,701	312,860	321,566
Total purchases of property, plant and equipment			183,752	147,478
Total depreciation, depletion, amortization and accretion	53,974	48,969	150,663	133,756
Total assets	3,629,802		3,629,802		3,504,241
Summit Materials, LLC | West
Segment Reporting Information [Line Items]
Total revenue	367,912	327,917	871,338	746,991
Gain on sale of business			(12,100)
Summit Materials, LLC | East
Segment Reporting Information [Line Items]
Total revenue	232,777	204,990	525,270	466,222
Summit Materials, LLC | Cement
Segment Reporting Information [Line Items]
Total revenue	93,972	101,274	213,364	229,338
Summit Materials, LLC | Operating segment
Segment Reporting Information [Line Items]
Total purchases of property, plant and equipment			177,806	142,483
Total depreciation, depletion, amortization and accretion	53,400	48,350	148,744	131,816
Total assets	3,551,610		3,551,610		3,131,724
Summit Materials, LLC | Operating segment | West
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	73,916	76,637	151,316	152,856
Total purchases of property, plant and equipment			104,217	64,257
Total depreciation, depletion, amortization and accretion	23,289	18,907	68,029	51,989
Total assets	1,422,966		1,422,966		1,225,463
Summit Materials, LLC | Operating segment | East
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	58,305	56,397	100,497	99,511
Total purchases of property, plant and equipment			51,968	52,920
Total depreciation, depletion, amortization and accretion	19,429	17,628	54,982	49,939
Total assets	1,229,567		1,229,567		1,035,609
Summit Materials, LLC | Operating segment | Cement
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	44,299	46,860	82,626	93,328
Total purchases of property, plant and equipment			21,621	25,306
Total depreciation, depletion, amortization and accretion	10,682	11,815	25,733	29,888
Total assets	899,077		899,077		870,652
Summit Materials, LLC | Corporate, Non-Segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	(4,514)	(7,193)	(21,579)	(24,129)
Total purchases of property, plant and equipment			5,946	4,995
Total depreciation, depletion, amortization and accretion	574	$ 619	1,919	$ 1,940
Total assets	$ 78,192		$ 78,192		$ 372,517