Guarantor and Non-Guarantor Financial Information - Schedule of Condensed Consolidating Statements of Operations and Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended								10 Months Ended	12 Months Ended
	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Oct. 01, 2016	Jul. 02, 2016	Apr. 02, 2016	Jan. 02, 2016	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Condensed Consolidating Statements of Operations
Revenue										$ 1,932,575	$ 1,626,063	$ 1,432,297
Cost of revenue (excluding items shown separately below)										1,281,777	1,071,792	990,262
Depreciation, depletion, amortization and accretion										179,518	149,300	119,723
Operating income	$ 57,306	$ 113,911	$ 82,444	$ (32,784)	$ 48,761	$ 88,410	$ 46,948	$ (29,457)		220,877	154,662	135,024
(Loss) income from operations before taxes										(158,200)	40,827	(19,194)
Income tax expense (benefit)										(283,977)	(5,299)	(18,263)
Income (loss) from continuing operations										125,777	46,126	(931)
Income from discontinued operations												(2,415)
Net income (loss)	44,510	84,287	52,088	(55,108)	6,049	61,106	21,505	(42,534)	$ 44,789	125,777	46,126	1,484
Net income (loss) attributable to member of Summit Materials, LLC	43,010	81,264	50,000	(52,444)	(290)	44,820	13,371	(21,118)		121,830	36,783	27,718
Comprehensive income (loss) income attributable to member of Summit Materials, LLC										131,465	37,329	24,923
Summit Materials, LLC
Condensed Consolidating Statements of Operations
Revenue										1,932,575	1,626,063	1,432,297
Cost of revenue (excluding items shown separately below)										1,281,777	1,071,792	990,262
General and administrative expenses										250,403	250,309	187,288
Depreciation, depletion, amortization and accretion										179,518	149,300	119,723
Operating income	57,306	113,911	82,444	(32,784)	48,761	88,410	46,948	(29,457)		220,877	154,662	135,024
Other (income) expense, net										(474)	1,374	69,589
Interest expense (income)										107,655	96,483	83,757
(Loss) income from operations before taxes										113,696	56,805	(18,322)
Income tax expense (benefit)										(20,345)	(5,282)	(18,263)
Income (loss) from continuing operations										134,041	62,087	(59)
Income from discontinued operations												(2,415)
Net income (loss)	$ 52,435	$ 82,633	$ 53,827	$ (54,854)	$ 21,211	$ 61,360	$ 21,759	$ (42,243)		134,041	62,087	2,356
Net income (loss) attributable to noncontrolling interest										(27)	16	(1,826)
Net income (loss) attributable to member of Summit Materials, LLC										134,068	62,071	4,182
Comprehensive income (loss) income attributable to member of Summit Materials, LLC										144,377	63,093	(8,738)
Summit Materials, LLC | Eliminations
Condensed Consolidating Statements of Operations
Revenue										(5,879)	(7,859)	(32,685)
Cost of revenue (excluding items shown separately below)										(5,879)	(7,859)	(32,685)
Other (income) expense, net										309,860	238,874	166,632
(Loss) income from operations before taxes										(309,860)	(238,874)	(166,632)
Income (loss) from continuing operations												(166,632)
Net income (loss)										(309,860)	(238,874)	(166,632)
Net income (loss) attributable to noncontrolling interest										(27)	16	(1,826)
Net income (loss) attributable to member of Summit Materials, LLC										(309,833)	(238,890)	(164,806)
Comprehensive income (loss) income attributable to member of Summit Materials, LLC										(299,524)	(237,868)	(151,886)
Summit Materials, LLC | Issuers
Condensed Consolidating Statements of Operations
General and administrative expenses										63,954	91,533	73,555
Depreciation, depletion, amortization and accretion										2,601	2,410	2,316
Operating income										(66,555)	(93,943)	(75,871)
Other (income) expense, net										(307,876)	(239,082)	(107,275)
Interest expense (income)										105,735	83,068	27,222
(Loss) income from operations before taxes										135,586	62,071	4,182
Income tax expense (benefit)										1,518
Income (loss) from continuing operations												4,182
Net income (loss)										134,068	62,071	4,182
Net income (loss) attributable to member of Summit Materials, LLC										134,068	62,071	4,182
Comprehensive income (loss) income attributable to member of Summit Materials, LLC										144,377	63,093	(8,738)
Summit Materials, LLC | Guarantors
Condensed Consolidating Statements of Operations
Revenue										1,854,434	1,586,858	1,364,622
Cost of revenue (excluding items shown separately below)										1,227,037	1,047,120	958,144
General and administrative expenses										178,023	152,402	107,282
Depreciation, depletion, amortization and accretion										172,738	142,773	112,166
Operating income										276,636	244,563	187,030
Other (income) expense, net										(1,925)	1,908	9,938
Interest expense (income)										(2,415)	9,956	52,970
(Loss) income from operations before taxes										280,976	232,699	124,122
Income tax expense (benefit)										(23,774)	(5,551)	(18,664)
Income (loss) from continuing operations												142,786
Income from discontinued operations												(2,415)
Net income (loss)										304,750	238,250	145,201
Net income (loss) attributable to member of Summit Materials, LLC										304,750	238,250	145,201
Comprehensive income (loss) income attributable to member of Summit Materials, LLC										302,209	239,353	146,380
Summit Materials, LLC | Non Guarantors
Condensed Consolidating Statements of Operations
Revenue										84,020	47,064	100,360
Cost of revenue (excluding items shown separately below)										60,619	32,531	64,803
General and administrative expenses										8,426	6,374	6,451
Depreciation, depletion, amortization and accretion										4,179	4,117	5,241
Operating income										10,796	4,042	23,865
Other (income) expense, net										(533)	(326)	294
Interest expense (income)										4,335	3,459	3,565
(Loss) income from operations before taxes										6,994	909	20,006
Income tax expense (benefit)										1,911	269	401
Income (loss) from continuing operations												19,605
Net income (loss)										5,083	640	19,605
Net income (loss) attributable to member of Summit Materials, LLC										5,083	640	19,605
Comprehensive income (loss) income attributable to member of Summit Materials, LLC										$ (2,685)	$ (1,485)	$ 5,506