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Management of Capital (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
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Disclosure of objectives, policies and processes for managing capital [abstract] |  |
Shareholder's equity | $ 2,681.2 | $ 1,759.4
Current portion of financing obligations (note 10) | 4.2 | 3.6
Non-current portion of non-current borrowings | 3.3 | 301.3
Managed capital | $ 2,688.7 | $ 2,064.3

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