Capital management (Details) $ in Millions	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2016 USD ($)
Capital management
Share capital	$ 1,550.3	$ 466.9	$ 455.8
Contributed surplus	50.6	31.0	30.7
Retained earnings	261.8	208.8	$ 144.2
Total	$ 1,862.7	$ 706.7
Maximum debt to EBITDA	5.5

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The nominal value of capital issued.

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A component of equity resulting from share-based payments.

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A component of equity representing the entity's cumulative undistributed earnings or deficit.

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The amount of total equity, excluding accumulated other comprehensive income.

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The maximum ratio of debt to earnings before interest, taxes, depreciation and amortization, (EBITDA) ratio as defined in the agreement covenant.

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No definition available.

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