Guarantor and Non-Guarantor Financial Information - Schedule of Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Condensed Consolidating Statements of Operations
Net cash provided by operating activities	$ 292,183	$ 244,863	$ 98,203
Cash flow from investing activities:
Acquisitions, net of cash acquired	(374,930)	(336,958)	(510,017)
Purchase of property, plant and equipment	(194,146)	(153,483)	(88,950)
Proceeds from the sale of property, plant, and equipment	17,072	16,868	13,110
Other	(471)	2,921	1,510
Net cash used for investing activities	(552,475)	(470,652)	(584,347)
Cash flow from financing activities:
Capital issuance costs	(627)	(136)	(61,609)
Net proceeds from debt issuance	302,000	354,000	1,748,875
Payments on long-term debt	(16,438)	(120,702)	(1,505,486)
Purchase of noncontrolling interests	(532)		(497,848)
Payments on acquisition-related liabilities	(34,650)	(32,040)	(18,056)
Financing costs	(6,416)	(5,801)	(14,246)
Distributions from partnership	(1,974)	(13,034)	(28,736)
Other	(869)	(20)	(1)
Net cash provided by financing activities	499,755	182,707	660,337
Impact of cash on foreign currency	701	69	(1,003)
Net increase (decrease) in cash	240,164	(43,013)	173,190
Cash and cash equivalents-beginning of period	143,392	186,405	13,215
Cash and cash equivalents-end of period	383,556	143,392	186,405
Summit Materials, LLC
Condensed Consolidating Statements of Operations
Net cash provided by operating activities	295,132	244,877	98,203
Cash flow from investing activities:
Acquisitions, net of cash acquired	(374,930)	(336,958)	(510,017)
Purchase of property, plant and equipment	(194,146)	(153,483)	(88,950)
Proceeds from the sale of property, plant, and equipment	17,072	16,868	13,110
Other	(471)	2,921	1,510
Net cash used for investing activities	(552,475)	(470,652)	(584,347)
Cash flow from financing activities:
Proceeds from investment by member	304,541	27,377	507,766
Capital issuance costs	(627)	(136)	(12,930)
Net proceeds from debt issuance	302,000	354,000	1,748,875
Payments on long-term debt	(16,438)	(120,702)	(1,505,486)
Purchase of noncontrolling interests	(532)
Payments on acquisition-related liabilities	(32,150)	(29,540)	(18,056)
Financing costs	(6,416)	(5,801)	(14,246)
Distributions from partnership	(51,986)	(42,192)	(46,603)
Other	(866)	(16)
Net cash provided by financing activities	497,526	182,990	659,320
Impact of cash on foreign currency	701	69	(1,003)
Net increase (decrease) in cash	240,884	(42,716)	172,173
Cash and cash equivalents-beginning of period	142,672	185,388	13,215
Cash and cash equivalents-end of period	383,556	142,672	185,388
Summit Materials, LLC | Eliminations
Condensed Consolidating Statements of Operations
Net cash provided by operating activities			(167)
Cash flow from financing activities:
Loans received from and payments made on loans from other Summit Companies	(1,706)	934	(5,544)
Payments on long-term debt			1,056
Other			167
Net cash provided by financing activities	(1,706)	934	(4,321)
Net increase (decrease) in cash	(1,706)	934	(4,488)
Cash and cash equivalents-beginning of period	(10,666)	(11,600)	(7,112)
Cash and cash equivalents-end of period	(12,372)	(10,666)	(11,600)
Summit Materials, LLC | Issuers
Condensed Consolidating Statements of Operations
Net cash provided by operating activities	(127,102)	(132,328)	(276,104)
Cash flow from investing activities:
Acquisitions, net of cash acquired	(24,538)	(42,844)
Purchase of property, plant and equipment	(6,196)	(5,247)	(5,636)
Net cash used for investing activities	(30,734)	(48,091)	(5,636)
Cash flow from financing activities:
Proceeds from investment by member	40,913	(502,140)	(155,060)
Capital issuance costs	(627)	(136)	(12,930)
Net proceeds from debt issuance	302,000	354,000	1,748,875
Loans received from and payments made on loans from other Summit Companies	119,858	440,738	(208,459)
Payments on long-term debt	(8,463)	(110,500)	(859,796)
Payments on acquisition-related liabilities		(400)	(166)
Financing costs	(6,416)	(5,801)	(14,246)
Distributions from partnership	(51,986)	(42,192)	(46,603)
Other	(564)
Net cash provided by financing activities	394,715	133,569	451,615
Net increase (decrease) in cash	236,879	(46,850)	169,875
Cash and cash equivalents-beginning of period	133,862	180,712	10,837
Cash and cash equivalents-end of period	370,741	133,862	180,712
Summit Materials, LLC | Guarantors
Condensed Consolidating Statements of Operations
Net cash provided by operating activities	392,316	373,588	356,187
Cash flow from investing activities:
Acquisitions, net of cash acquired	(324,892)	(294,114)	(510,017)
Purchase of property, plant and equipment	(182,295)	(146,336)	(81,980)
Proceeds from the sale of property, plant, and equipment	16,822	16,606	12,945
Other	(471)	2,921	1,510
Net cash used for investing activities	(490,836)	(420,923)	(577,542)
Cash flow from financing activities:
Proceeds from investment by member	252,911	529,517	662,826
Loans received from and payments made on loans from other Summit Companies	(108,026)	(442,072)	226,703
Payments on long-term debt	(7,967)	(10,202)	(646,746)
Purchase of noncontrolling interests	(532)
Payments on acquisition-related liabilities	(32,150)	(29,140)	(17,890)
Other	(282)	(16)	(167)
Net cash provided by financing activities	103,954	48,087	224,726
Net increase (decrease) in cash	5,434	752	3,371
Cash and cash equivalents-beginning of period	4,820	4,068	697
Cash and cash equivalents-end of period	10,254	4,820	4,068
Summit Materials, LLC | Non Guarantors
Condensed Consolidating Statements of Operations
Net cash provided by operating activities	29,918	3,617	18,287
Cash flow from investing activities:
Acquisitions, net of cash acquired	(25,500)
Purchase of property, plant and equipment	(5,655)	(1,900)	(1,334)
Proceeds from the sale of property, plant, and equipment	250	262	165
Net cash used for investing activities	(30,905)	(1,638)	(1,169)
Cash flow from financing activities:
Proceeds from investment by member	10,717
Loans received from and payments made on loans from other Summit Companies	(10,126)	400	(12,700)
Payments on long-term debt	(8)
Other	(20)
Net cash provided by financing activities	563	400	(12,700)
Impact of cash on foreign currency	701	69	(1,003)
Net increase (decrease) in cash	277	2,448	3,415
Cash and cash equivalents-beginning of period	14,656	12,208	8,793
Cash and cash equivalents-end of period	$ 14,933	$ 14,656	$ 12,208