Related Party Transactions - Additional Information (Details) - USD ($) $ in Millions								1 Months Ended		12 Months Ended
	Jan. 10, 2017	Aug. 13, 2015	Aug. 11, 2015	Jul. 17, 2015	Apr. 16, 2015	Mar. 17, 2015	Mar. 11, 2015	Aug. 31, 2015	Aug. 13, 2015	Dec. 31, 2016	Mar. 31, 2016	Nov. 30, 2015	Jul. 31, 2015
IPO | Common Class A
Related Party Transactions
Issuance of Shares (in shares)							25,555,555
Follow on Public Offering | Common Class A
Related Party Transactions
Issuance of Shares (in shares)	10,000,000		22,425,000
Davenport Assets
Related Party Transactions
Cash paid for acquisitions		$ 80.0		$ 370.0					$ 450.0
Davenport Assets | Follow on Public Offering
Related Party Transactions
Cash paid for acquisitions			$ 80.0
Summit Materials, LLC | Davenport Assets
Related Party Transactions
Cash paid for acquisitions		450.0		370.0
Summit Materials, LLC | Davenport Assets | Follow on Public Offering
Related Party Transactions
Cash paid for acquisitions		$ 80.0
Affiliates of the Sponsors Blackstone Management Partners and Silverhawk Summit | Termination fee paid to related parties | IPO
Related Party Transactions
Related party expense						$ 13.8
Affiliates of the Sponsors Blackstone Management Partners and Silverhawk Summit | Termination fee paid to related parties | Summit Materials, LLC | IPO
Related Party Transactions
Related party expense						13.8
Affiliates of BMP | Termination fee paid to related parties | IPO
Related Party Transactions
Related party expense						13.4
Affiliates of BMP | Termination fee paid to related parties | Summit Materials, LLC | IPO
Related Party Transactions
Related party expense						13.4
Affiliates of Silverhawk Summit LP | Termination fee paid to related parties | IPO
Related Party Transactions
Related party expense						0.4
Affiliates of Silverhawk Summit LP | Termination fee paid to related parties | Summit Materials, LLC | IPO
Related Party Transactions
Related party expense						$ 0.4
Blackstone Advisory Partners LP | Follow on Public Offering | Common Class A
Related Party Transactions
Issuance of Shares (in shares)								1,681,875
Blackstone Advisory Partners LP | Summit Materials, LLC | Follow on Public Offering | Common Class A
Related Party Transactions
Issuance of Shares (in shares)								1,681,875
Blackstone Advisory Partners LP | Issuance of notes | Term Loan, due 2022
Related Party Transactions
Notes issued to related party											$ 18.8
Blackstone Advisory Partners LP | Issuance of notes | 6 1/8% Senior Notes, due 2023
Related Party Transactions
Notes issued to related party												$ 22.5	$ 26.3
Blackstone Advisory Partners LP | Issuance of notes | Summit Materials, LLC | Term Loan, due 2022
Related Party Transactions
Notes issued to related party											$ 18.8
Blackstone Advisory Partners LP | Issuance of notes | Summit Materials, LLC | 6 1/8% Senior Notes, due 2023
Related Party Transactions
Notes issued to related party												$ 22.5	$ 26.3
Blackstone Capital Partners V LP | Equity commitment financing | Davenport Assets
Related Party Transactions
Equity commitment financing				$ 90.0
Commitment fee paid										$ 1.8
Blackstone Capital Partners V LP | Equity commitment financing | Summit Materials, LLC
Related Party Transactions
Commitment fee paid										$ 1.8
Blackstone Capital Partners V LP | Equity commitment financing | Summit Materials, LLC | Davenport Assets
Related Party Transactions
Equity commitment financing					$ 90.0