Stockholders' Equity - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 30, 2017	Dec. 31, 2016
Changes in each component of accumulated other comprehensive loss
Beginning balance	$ 842,044
Ending balance	1,258,543	$ 842,044
Accumulated Other Comprehensive Operations
Changes in each component of accumulated other comprehensive loss
Beginning balance	(2,249)	(2,795)
Curtailment adjustment	309
Liability adjustment	605	401
Foreign currency translation adjustment	7,743	273
Income (loss) on cash flow hedges	978	(128)
Ending balance	7,386	(2,249)
Change in retirement plans
Changes in each component of accumulated other comprehensive loss
Beginning balance	1,450	1,049
Curtailment adjustment	309
Liability adjustment	605	401
Ending balance	2,364	1,450
Foreign currency translation adjustment
Changes in each component of accumulated other comprehensive loss
Beginning balance	(3,106)	(3,379)
Foreign currency translation adjustment	7,743	273
Ending balance	4,637	(3,106)
Cash flow hedge adjustments
Changes in each component of accumulated other comprehensive loss
Beginning balance	(593)	(465)
Income (loss) on cash flow hedges	978	(128)
Ending balance	385	(593)
Summit Materials, LLC \| Accumulated Other Comprehensive Operations
Changes in each component of accumulated other comprehensive loss
Beginning balance	(27,444)	(28,466)
Curtailment adjustment	429
Liability adjustment	(699)	426
Foreign currency translation adjustment	7,768	2,125
Income (loss) on cash flow hedges	1,413	(1,529)
Ending balance	(17,135)	(27,444)
Summit Materials, LLC \| Change in retirement plans
Changes in each component of accumulated other comprehensive loss
Beginning balance	(7,181)	(7,607)
Curtailment adjustment	429
Liability adjustment	(699)	426
Ending balance	(6,053)	(7,181)
Summit Materials, LLC \| Foreign currency translation adjustment
Changes in each component of accumulated other comprehensive loss
Beginning balance	(17,790)	(19,915)
Foreign currency translation adjustment	7,768	2,125
Ending balance	(10,022)	(17,790)
Summit Materials, LLC \| Cash flow hedge adjustments
Changes in each component of accumulated other comprehensive loss
Beginning balance	(2,473)	(944)
Income (loss) on cash flow hedges	1,413	(1,529)
Ending balance	$ (1,060)	$ (2,473)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax of (increase) decrease in the value of the projected benefit obligation related to a change in an actuarial assumption and increase (decrease) in the value of the plan assets resulting from experience different from that assumed, that has not been recognized in net periodic benefit (cost) credit.

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Amount after tax and reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss), attributable to parent entity.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature, attributable to parent entity.

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Amount after tax of gain (loss) adjustment to other comprehensive income (loss) resulting from settlement or curtailment of defined benefit pension and other postretirement defined benefit plans.

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- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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