Consolidated Statements of Changes in Stockholders' Equity / Member's Interest and Redeemable Noncontrolling Interest - USD ($)	Summit Materials, LLC Members' equity	Summit Materials, LLC Total Member's Interest	Summit Materials, LLC Noncontrolling Interest in subsidiaries	Summit Materials, LLC Accumulated Earnings/Deficit	Summit Materials, LLC Accumulated Other Comprehensive Operations	Summit Materials, LLC	Noncontrolling Interest in subsidiaries	Accumulated Earnings/Deficit	Accumulated Other Comprehensive Operations	Common Stock Common Class A	Common Stock Common Class B	Additional Paid-in Capital	Noncontrolling Interest in Summit Inc.	Common Class A	Common Class B	Total
Beginning Balance (in shares) at Jan. 02, 2016														49,745,944
Increase (decrease) in stockholders' equity / members' interest and redeemable noncontrolling interest
Issuance of Shares (in shares)														1,038
Dividend (in shares)														1,135,692
Ending Balance (in shares) at Apr. 02, 2016														50,882,674
Beginning Balance (in shares) at Jan. 02, 2016														49,745,944
Increase (decrease) in stockholders' equity / members' interest and redeemable noncontrolling interest
Net income (loss)						$ (20,484,000)										$ (21,029,000)
Other comprehensive income (loss)						1,985,000										1,985,000
Ending Balance (in shares) at Jul. 02, 2016														64,066,678
Beginning Balance (in shares) at Apr. 02, 2016														50,882,674
Increase (decrease) in stockholders' equity / members' interest and redeemable noncontrolling interest
Net income (loss)						21,759,000										21,505,000
LP Unit exchanges (in shares)														13,177,754
Other comprehensive income (loss)						(423,000)										(423,000)
Other (in shares)														6,250
Ending Balance (in shares) at Jul. 02, 2016														64,066,678
Beginning Balance at Dec. 31, 2016							$ 1,378,000
Beginning Balance at Dec. 31, 2016								$ 19,028,000	$ (2,249,000)	$ 961,000	$ 100	$ 824,304,000	$ 16,617,000			860,039,000
Beginning Balance at Dec. 31, 2016	$ 1,087,558,000	$ 876,393,000	$ 1,378,000	$ (185,099,000)	$ (27,444,000)	876,393,000
Beginning Balance (in shares) at Dec. 31, 2016										96,033,222				96,033,222	100
Increase (decrease) in stockholders' equity / members' interest and redeemable noncontrolling interest
Issuance of Shares (in shares)														10,000,000
LP Unit exchanges (in shares)														236,095
Other (in shares)														134,423
Ending Balance (in shares) at Apr. 01, 2017														106,403,740
Beginning Balance at Dec. 31, 2016							1,378,000
Beginning Balance at Dec. 31, 2016								19,028,000	(2,249,000)	$ 961,000	$ 100	824,304,000	16,617,000			860,039,000
Beginning Balance at Dec. 31, 2016	1,087,558,000	876,393,000	1,378,000	(185,099,000)	(27,444,000)	876,393,000
Beginning Balance (in shares) at Dec. 31, 2016										96,033,222				96,033,222	100
Increase (decrease) in stockholders' equity / members' interest and redeemable noncontrolling interest
Net contributed capital	242,966,000	242,966,000
Net income (loss)		(1,027,000)	(86,000)	(941,000)		(1,027,000)		(2,444,000)					(490,000)			(3,020,000)
Net loss							(86,000)
Issuance of Shares										$ 100,000		238,367,000	(1,496,000)			236,971,000
Issuance of Shares (in shares)										10,000,000
LP Unit exchanges										$ 10,000		2,600,000	(2,610,000)
LP Unit exchanges (in shares)										1,014,159
Other comprehensive income (loss)		4,709,000			4,709,000	4,709,000			4,522,000				187,000			4,709,000
Share-based compensation	9,424,000	9,424,000										9,424,000				9,424,000
Distributions	(2,579,000)	(2,579,000)
Distributions from partnership													(79,000)			(79,000)
Other										$ 5,000		4,900,000				4,905,000
Other (in shares)										444,598
Other	(832,000)	(832,000)
Ending Balance at Jul. 01, 2017								16,584,000	2,273,000	$ 1,076,000		1,079,595,000	12,129,000			1,112,949,000
Ending Balance at Jul. 01, 2017	1,336,537,000	1,129,054,000	1,292,000	(186,040,000)	(22,735,000)	1,129,054,000
Ending Balance at Jul. 01, 2017							1,292,000
Ending Balance (in shares) at Jul. 01, 2017										107,491,979	100			107,491,979	100
Beginning Balance (in shares) at Apr. 01, 2017														106,403,740
Increase (decrease) in stockholders' equity / members' interest and redeemable noncontrolling interest
Net income (loss)						53,827,000										52,088,000
LP Unit exchanges (in shares)														778,064
Other comprehensive income (loss)						3,591,000										3,591,000
Other (in shares)														310,175
Ending Balance at Jul. 01, 2017								$ 16,584,000	$ 2,273,000	$ 1,076,000		$ 1,079,595,000	$ 12,129,000			$ 1,112,949,000
Ending Balance at Jul. 01, 2017	$ 1,336,537,000	$ 1,129,054,000	$ 1,292,000	$ (186,040,000)	$ (22,735,000)	$ 1,129,054,000
Ending Balance at Jul. 01, 2017							$ 1,292,000
Ending Balance (in shares) at Jul. 01, 2017										107,491,979	100			107,491,979	100