Employee Benefit Plans - Estimated Benefit Payments (Detail) $ in Thousands	12 Months Ended
Dec. 30, 2017 USD ($)
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Expected contribution to plans in 2018	$ 1,400
Summit Materials, LLC
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Expected contribution to plans in 2018	1,400
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
2018	1,835
2019	1,830
2020	1,804
2021	1,771
2022	1,768
2023 - 2027	8,457
Pension Benefits \| Summit Materials, LLC
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
2018	1,835
2019	1,830
2020	1,804
2021	1,771
2022	1,768
2023 - 2027	8,457
Healthcare & Life Ins
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
2018	702
2019	667
2020	675
2021	655
2022	649
2023 - 2027	3,250
Healthcare & Life Ins \| Summit Materials, LLC
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
2018	702
2019	667
2020	675
2021	655
2022	649
2023 - 2027	$ 3,250

Pension Plans, Postretirement and Other Employee Benefits [Line Items]

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- Definition

Amount of benefits from a defined benefit plan expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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- Definition

Amount of benefits from a defined benefit plan expected to be paid in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

Amount of benefits from a defined benefit plan expected to be paid in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

Amount of benefits from a defined benefit plan expected to be paid in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

Amount of benefits from a defined benefit plan expected to be paid in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

Amount of benefits from a defined benefit plan expected to be paid in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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