Consolidated Statements of Changes in Stockholders' Equity / Member's Interest and Redeemable Noncontrolling Interest - USD ($) $ in Thousands	Summit Materials, LLC Redeemable Noncontrolling Interest	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	Redeemable Noncontrolling Interest	Partners' Interest	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 at Dec. 27, 2014	$ 33,740
Increase (decrease) in redeemable noncontrolling interest
Accretion/ redemption value adjustment								$ 32,252
Net income (loss)								(1,890)
Ending Balance at Mar. 11, 2015								64,102
Beginning Balance at Dec. 27, 2014								33,740	$ 285,685	$ 1,298									$ 286,983
Beginning Balance at Dec. 27, 2014		$ 518,647	$ 286,983	$ 1,298	$ (217,416)	$ (15,546)
Increase (decrease) in stockholders' equity / members' interest and redeemable noncontrolling interest
Accretion/ redemption value adjustment									(32,252)										(32,252)
Net income (loss)									(41,338)	(77)									(41,415)
Other comprehensive income (loss)									(5,249)										(5,249)
Share-based compensation									424										424
Ending Balance at Mar. 11, 2015									207,270	1,221									208,491
Beginning Balance at Dec. 27, 2014	33,740
Increase (decrease) in redeemable noncontrolling interest
Accretion/ redemption value adjustment	(31,850)
Net income (loss)	$ (1,890)
Beginning Balance at Dec. 27, 2014								33,740	285,685	1,298									286,983
Beginning Balance at Dec. 27, 2014		518,647	286,983	1,298	(217,416)	(15,546)
Increase (decrease) in stockholders' equity / members' interest and redeemable noncontrolling interest
Net contributed capital		558,939	558,939
Accretion/ redemption value adjustment			(32,252)		(32,252)
Net income (loss)			4,246	64	4,182		$ 2,356												1,484
Other comprehensive income (loss)			(12,920)			(12,920)	(12,920)												(12,920)
Share-based compensation		19,899	19,899
Distributions		(46,603)	(46,603)
Ending Balance at Jan. 02, 2016										1,362	$ 10,870	$ (2,795)	$ 497	$ 690	$ 619,003	$ 138,233			767,860
Ending Balance at Jan. 02, 2016		1,050,882	778,292	1,362	(245,486)	(28,466)
Ending Balance (in shares) at Jan. 02, 2016													49,745,944	69,007,297
Beginning Balance at Mar. 11, 2015								64,102
Increase (decrease) in redeemable noncontrolling interest
Purchase of redeemable noncontrolling interest								$ (64,102)
Beginning Balance at Mar. 11, 2015									207,270	1,221									208,491
Increase (decrease) in stockholders' equity / members' interest and redeemable noncontrolling interest
Recording of noncontrolling interest upon reorganization									$ (207,270)							207,270
Net income (loss)										141	27,718					16,930			44,789
Issuance of Shares													$ 480	$ 690	(690)				975,835
Issuance of Shares (in shares)													47,981,653	69,007,397
Other comprehensive income (loss)												(2,795)				(4,876)			(7,671)
Share-based compensation															19,475				19,475
Share repurchase (in shares)														(100)
Purchase of noncontrolling interests															$ 18,515
Purchase of redeemable noncontrolling interests (in shares)													1,029,183
Purchase of redeemable noncontrolling interests													$ 10						18,525
Other (in shares)															975,355,000
Purchase of LP Units															$ (411,532)	(51,315)			(462,847)
Dividend											(16,848)		$ 7		17,880	(1,040)			(1)
Dividend (in shares)													735,108
Distributions from partnership																(28,736)			(28,736)
Ending Balance at Jan. 02, 2016										1,362	10,870	(2,795)	$ 497	$ 690	619,003	138,233			767,860
Ending Balance at Jan. 02, 2016		1,050,882	778,292	1,362	(245,486)	(28,466)
Ending 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		27,260	27,260
Net income (loss)			62,087	16	62,071		62,087			16	36,783					9,327			46,126
LP Unit exchanges													$ 451		117,813	(118,264)
LP Unit exchanges (in shares)													45,124,528
Other comprehensive income (loss)			1,022			1,022	1,022					546				476			1,022
Share-based compensation		51,624	49,940		(1,684)						(1,684)				51,624				49,940
Stock Option Exercises													$ 2		438				440
Options, Exercised (in shares)													24,354
Class B share cancellation														$ (690)	690
Class B share cancellation (in shares)														(69,007,197)
Distributions		(42,192)	(42,192)
Other		(16)	(16)												7,689				7,689
Other (in shares)													2,704
Dividend											(26,941)		$ 11		27,047	(121)			(4)
Dividend (in shares)													1,135,692
Distributions from partnership																(13,034)			(13,034)
Ending Balance at Dec. 31, 2016										1,378	19,028	(2,249)	$ 961		824,304	16,617			860,039
Ending Balance at Dec. 31, 2016		1,087,558	876,393	1,378	(185,099)	(27,444)	876,393
Ending Balance (in shares) at Dec. 31, 2016													96,033,222	100			96,033,222	100
Increase (decrease) in stockholders' equity / members' interest and redeemable noncontrolling interest
Net contributed capital		303,914	303,914
Net income (loss)			134,041	(27)	134,068		134,041			(27)	121,830					3,974			125,777
Issuance of Shares													$ 100		238,367	(1,496)			236,971
Issuance of Shares (in shares)													10,000,000
LP Unit exchanges													$ 15		4,159	(4,174)
LP Unit exchanges (in shares)													1,461,677
Other comprehensive income (loss)			10,309			10,309	10,309					9,635				386			10,021
Share-based compensation		21,140	21,140												21,140				21,140
Stock Option Exercises													$ 12		21,649				21,661
Options, Exercised (in shares)													1,203,121
Purchase of noncontrolling interests										(1,148)									(1,148)
Purchase of redeemable noncontrolling interests			(1,148)	(1,148)
Distributions		(51,986)	(51,986)
Other										$ (203)			$ 1		(562)				(764)
Other (in shares)													131,518
Other		(866)	(1,069)	$ (203)
Dividend											(45,025)		$ 15		45,163	(155)			(2)
Dividend (in shares)													1,521,056
Distributions from partnership																(1,974)			(1,974)
Ending Balance at Dec. 30, 2017											$ 95,833	$ 7,386	$ 1,104		$ 1,154,220	$ 13,178			$ 1,271,721
Ending Balance at Dec. 30, 2017		$ 1,359,760	$ 1,291,594		$ (51,031)	$ (17,135)	$ 1,291,594
Ending Balance (in shares) at Dec. 30, 2017													110,350,594	100			110,350,594	100