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Share Capital (Schedule of Stock Options Range for Outstanding and Exercisable Shares) (Details) | Dec. 31, 2017 CAD shares year | Dec. 31, 2017 USD ($) shares year | Dec. 31, 2016 CAD shares | Dec. 31, 2015 CAD shares
--- | --- | --- | --- | ---
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] |  |  |  |
Number of options outstanding (in shares) | shares | 10,429,345 | 10,429,345 | 9,511,636 | 10,237,362
Outstanding weighted average exercise price (CAD per share) | CAD | CAD 7.94 |  | CAD 10.87 | CAD 12.15
Weighted average remaining contractual life of options outstanding (years) | year | 2.02 | 2.02 |  |
Number of options exercisable (in shares) | shares | 8,490,190 | 8,490,190 |  |
Exercisable weighted average exercise price (CAD per share)) | CAD | CAD 8.53 |  |  |
$0.82 - $3.00 |  |  |  |
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] |  |  |  |
Number of options outstanding (in shares) | shares | 1,770,508 | 1,770,508 |  |
Outstanding weighted average exercise price (CAD per share) | CAD | CAD 2.04 |  |  |
Weighted average remaining contractual life of options outstanding (years) | year | 0.90 | 0.90 |  |
Number of options exercisable (in shares) | shares | 1,770,508 | 1,770,508 |  |
Exercisable weighted average exercise price (CAD per share)) | CAD | CAD 2.04 |  |  |
$3.01 - $7.00 |  |  |  |
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] |  |  |  |
Number of options outstanding (in shares) | shares | 2,119,866 | 2,119,866 |  |
Outstanding weighted average exercise price (CAD per share) | CAD | CAD 3.91 |  |  |
Weighted average remaining contractual life of options outstanding (years) | year | 3.97 | 3.97 |  |
Number of options exercisable (in shares) | shares | 1,039,866 | 1,039,866 |  |
Exercisable weighted average exercise price (CAD per share)) | CAD | CAD 4.07 |  |  |
$7.01 - $11.00 |  |  |  |
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] |  |  |  |
Number of options outstanding (in shares) | shares | 4,234,349 | 4,234,349 |  |
Outstanding weighted average exercise price (CAD per share) | CAD | CAD 8.07 |  |  |
Weighted average remaining contractual life of options outstanding (years) | year | 2.21 | 2.21 |  |
Number of options exercisable (in shares) | shares | 3,375,194 | 3,375,194 |  |
Exercisable weighted average exercise price (CAD per share)) | CAD | CAD 7.88 |  |  |
$11.01 - $15.00 |  |  |  |
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] |  |  |  |
Number of options outstanding (in shares) | shares | 985,311 | 985,311 |  |
Outstanding weighted average exercise price (CAD per share) | CAD | CAD 14.11 |  |  |
Weighted average remaining contractual life of options outstanding (years) | year | 0.65 | 0.65 |  |
Number of options exercisable (in shares) | shares | 985,311 | 985,311 |  |
Exercisable weighted average exercise price (CAD per share)) | CAD | CAD 14.11 |  |  |
$15.01 - $19.00 |  |  |  |
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] |  |  |  |
Number of options outstanding (in shares) | shares | 1,112,425 | 1,112,425 |  |
Outstanding weighted average exercise price (CAD per share) | CAD | CAD 16.59 |  |  |
Weighted average remaining contractual life of options outstanding (years) | year | 0.81 | 0.81 |  |
Number of options exercisable (in shares) | shares | 1,112,425 | 1,112,425 |  |
Exercisable weighted average exercise price (CAD per share)) | CAD | CAD 16.59 |  |  |
$19.01 - $23.00 |  |  |  |
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] |  |  |  |
Number of options outstanding (in shares) | shares | 206,886 | 206,886 |  |
Outstanding weighted average exercise price (CAD per share) | CAD | CAD 20.88 |  |  |
Weighted average remaining contractual life of options outstanding (years) | year | 0.66 | 0.66 |  |
Number of options exercisable (in shares) | shares | 206,886 | 206,886 |  |
Exercisable weighted average exercise price (CAD per share)) | CAD | CAD 20.88 |  |  |
Bottom of range [member] | $0.82 - $3.00 |  |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |  |
Exercise price of outstanding share options | $ |  | $ 0.82 |  |
Bottom of range [member] | $3.01 - $7.00 |  |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |  |
Exercise price of outstanding share options | $ |  | 3.01 |  |
Bottom of range [member] | $7.01 - $11.00 |  |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |  |
Exercise price of outstanding share options | $ |  | 7.011 |  |
Bottom of range [member] | $11.01 - $15.00 |  |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |  |
Exercise price of outstanding share options | $ |  | 11.01 |  |
Bottom of range [member] | $15.01 - $19.00 |  |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |  |
Exercise price of outstanding share options | $ |  | 15.01 |  |
Bottom of range [member] | $19.01 - $23.00 |  |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |  |
Exercise price of outstanding share options | $ |  | 19.01 |  |
Top of range [member] | $0.82 - $3.00 |  |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |  |
Exercise price of outstanding share options | $ |  | 3.00 |  |
Top of range [member] | $3.01 - $7.00 |  |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |  |
Exercise price of outstanding share options | $ |  | 7.00 |  |
Top of range [member] | $7.01 - $11.00 |  |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |  |
Exercise price of outstanding share options | $ |  | 11.00 |  |
Top of range [member] | $11.01 - $15.00 |  |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |  |
Exercise price of outstanding share options | $ |  | 15.00 |  |
Top of range [member] | $15.01 - $19.00 |  |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |  |
Exercise price of outstanding share options | $ |  | 19.00 |  |
Top of range [member] | $19.01 - $23.00 |  |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |  |
Exercise price of outstanding share options | $ |  | $ 23.00 |  |

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