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Share Capital (Antidilutive Securities) (Details) shares in Thousands |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Feb. 09, 2017 $ / shares | Dec. 31, 2017 CAD / shares | Dec. 31, 2017 shares | Dec. 31, 2016 CAD / shares shares
Earnings per share [line items] |  |  |  |
Share price of company (in CAD per share) | (per share) | $ 7.95 | CAD 9.40 |  | CAD 8.78
Antidilutive securities |  |  | 15,152 | 21,191
Employee Stock Option1 [Member] |  |  |  |
Earnings per share [line items] |  |  |  |
Antidilutive securities |  |  | 2,920 | 9,512
Equity Settled LTI [Member] |  |  |  |
Earnings per share [line items] |  |  |  |
Antidilutive securities |  |  | 0 | 369
Warrants [Member] |  |  |  |
Earnings per share [line items] |  |  |  |
Antidilutive securities |  |  | 12,232 | 11,310

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