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 Common Class A	Additional Paid-in Capital	Noncontrolling Interest in Summit Inc.	Common Class A	Common Class B	Total
Beginning Balance at Jan. 02, 2016							$ 1,362,000
Beginning Balance at Jan. 02, 2016								$ 10,870,000	$ (2,795,000)	$ 497,000	$ 690,000		$ 619,003,000	$ 138,233,000			$ 767,860,000
Beginning Balance at Jan. 02, 2016	$ 1,050,882,000	$ 778,292,000	$ 1,362,000	$ (245,486,000)	$ (28,466,000)
Beginning Balance (in shares) at Jan. 02, 2016										49,745,944	69,007,297
Increase (decrease) in stockholders' equity / members' interest and redeemable noncontrolling interest
Net contributed capital	(115,000)	(115,000)
Net income (loss)		(42,243,000)	(79,000)	(42,164,000)		$ (42,243,000)		(21,118,000)						(21,337,000)			(42,534,000)
Net loss							(79,000)
Issuance of Shares										$ 1,000		$ (115,000)					(114,000)
Issuance of Shares (in shares)										1,038
Other comprehensive income (loss)		2,408,000			2,408,000	2,408,000			1,198,000					1,210,000			2,408,000
Share-based compensation	3,720,000	2,036,000		(1,684,000)				(1,684,000)					3,720,000				2,036,000
Distributions	(2,500,000)	(2,500,000)
Ending Balance at Apr. 02, 2016								(11,932,000)	(1,597,000)	$ 498,000	$ 690,000		622,608,000	118,106,000			729,656,000
Ending Balance at Apr. 02, 2016	1,051,987,000	737,878,000	1,283,000	(289,334,000)	(26,058,000)
Ending Balance at Apr. 02, 2016							1,283,000
Ending Balance (in shares) at Apr. 02, 2016										49,746,982	69,007,297
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	237,991,000	237,991,000
Net income (loss)		(54,854,000)	(98,000)	(54,756,000)		(54,854,000)		(52,444,000)						(2,566,000)			(55,108,000)
Net loss							(98,000)
Issuance of Shares										$ 100,000			238,357,000	(1,496,000)			236,961,000
Issuance of Shares (in shares)										10,000,000
LP Unit exchanges										$ 2,000			708,000	(710,000)
LP Unit exchanges (in shares)										236,095
Other comprehensive income (loss)		1,118,000			1,118,000	1,118,000			1,063,000					55,000			1,118,000
Share-based compensation	4,748,000	4,748,000											4,748,000				4,748,000
Distributions	(2,579,000)	(2,579,000)
Distributions from partnership														(79,000)			(79,000)
Other										$ 2,000			39,000				41,000
Other (in shares)										134,423
Other	(732,000)	(732,000)
Ending Balance at Apr. 01, 2017								$ (33,416,000)	$ (1,186,000)	$ 1,065,000			$ 1,068,156,000	$ 11,821,000			$ 1,047,720,000
Ending Balance at Apr. 01, 2017	$ 1,326,986,000	$ 1,062,085,000	$ 1,280,000	$ (239,855,000)	$ (26,326,000)	$ 1,062,085,000
Ending Balance at Apr. 01, 2017							$ 1,280,000
Ending Balance (in shares) at Apr. 01, 2017										106,403,740	100				106,403,740	100