Debt - Other - Additional Information (Details) - CAD CAD in Millions	Jan. 15, 2015	Sep. 30, 2017	Dec. 31, 2016
Canadian subsidiary credit agreement
Debt
Amount outstanding		CAD 0.0	CAD 0.0
Canadian subsidiary credit agreement | Summit Materials, LLC
Debt
Amount outstanding		CAD 0.0	CAD 0.0
Canadian subsidiary credit agreement, Operating activities
Debt
Revolving credit commitment	CAD 6.0
Canadian subsidiary credit agreement, Operating activities | Summit Materials, LLC
Debt
Revolving credit commitment	6.0
Canadian subsidiary credit agreement, Capital equipment
Debt
Revolving credit commitment	CAD 0.5
Basis spread on variable rate	0.90%
Canadian subsidiary credit agreement, Capital equipment | Summit Materials, LLC
Debt
Revolving credit commitment	CAD 0.5
Basis spread on variable rate	0.90%
Canadian subsidiary credit agreement, Guarantees
Debt
Revolving credit commitment	CAD 0.4
Canadian subsidiary credit agreement, Guarantees | Summit Materials, LLC
Debt
Revolving credit commitment	CAD 0.4
Prime rate | Canadian subsidiary credit agreement, Operating activities
Debt
Basis spread on variable rate	0.20%
Prime rate | Canadian subsidiary credit agreement, Operating activities | Summit Materials, LLC
Debt
Basis spread on variable rate	0.20%