Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Jan. 19, 2017	Dec. 31, 2016
Debt
Total debt	$ 1,831,754		$ 1,536,065
Current portion of long-term debt	6,500		6,500
Long-term debt	1,825,254		1,529,565
Gross amount	1,835,375
Debt discount	3,621
Summit Materials, LLC
Debt
Total debt	1,831,754		1,536,065
Current portion of long-term debt	6,500		6,500
Long-term debt	1,825,254		1,529,565
Gross amount	1,835,375
Debt discount	3,621
Term Loan, due 2022
Debt
Total debt	633,165		637,658
Gross amount	635,400	$ 640,300	640,300
Debt discount	2,200		2,600
Term Loan, due 2022 \| Summit Materials, LLC
Debt
Total debt	633,165		637,658
Gross amount	635,400		640,300
Debt discount	2,200		2,600
8 1/2% Senior Notes, due 2022
Debt
Total debt	$ 250,000		$ 250,000
Debt instrument interest rate (as a percent)	8.50%		8.50%
8 1/2% Senior Notes, due 2022 \| Summit Materials, LLC
Debt
Total debt	$ 250,000		$ 250,000
Debt instrument interest rate (as a percent)	8.50%		8.50%
6 1/8% Senior Notes, due 2023
Debt
Total debt	$ 648,589		$ 648,407
Gross amount	650,000		650,000
Debt discount	$ 1,400		$ 1,600
Debt instrument interest rate (as a percent)	6.125%		6.125%
6 1/8% Senior Notes, due 2023 \| Summit Materials, LLC
Debt
Total debt	$ 648,589		$ 648,407
Gross amount	650,000		650,000
Debt discount	$ 1,400		$ 1,600
Debt instrument interest rate (as a percent)	6.125%		6.125%
5 1/8% Senior Notes, due 2025
Debt
Total debt	$ 300,000
Debt instrument interest rate (as a percent)	5.125%
5 1/8% Senior Notes, due 2025 \| Summit Materials, LLC
Debt
Long-term debt	$ 300,000
Debt instrument interest rate (as a percent)	5.125%

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount, after accumulated amortization, of debt discount.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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