Revenue and segmented information - Revenue from significant customers (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Major customers disclosures
Revenues	$ 1,631.2	$ 1,557.5
Commercial Customer 1
Major customers disclosures
Revenues	119.9	197.1
Canadian Federal Government and agencies
Major customers disclosures
Revenues	194.3	212.3
U.S. Federal Government and agencies
Major customers disclosures
Revenues	$ 293.8	$ 97.5

The income arising in the course of an entity's ordinary activities. Income is increases in economic benefits during the accounting period in the form of inflows or enhancements of assets or decreases of liabilities that result in an increase in equity, other than those relating to contributions from equity participants.

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+ Details