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Share capital - Stock Option Range of Exercise Prices and Weighted Average Years to Expiration (Details) shares in Thousands | Dec. 31, 2018 CAD ($) shares year | Dec. 31, 2017 CAD ($) shares | Dec. 31, 2016 CAD ($) shares
--- | --- | --- | ---
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] |  |  |
Number of outstanding options (in shares) | shares | 67,632 | 57,602 | 50,410
Weighted- average years to expiry (in years) | year | 3.28 |  |
Weighted-average exercise price (in Cdn.$per share) | $ 2.96 | $ 2.70 | $ 2.24
Number of exercisable options (in shares) | shares | 37,372 |  |
Weighted-average exercise price (in Cdn.$per share) | $ 2.63 |  |
1.12 – 1.99 |  |  |
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] |  |  |
Number of outstanding options (in shares) | shares | 8,513 |  |
Weighted- average years to expiry (in years) | year | 2.09 |  |
Weighted-average exercise price (in Cdn.$per share) | $ 1.12 |  |
Number of exercisable options (in shares) | shares | 7,558 |  |
Weighted-average exercise price (in Cdn.$per share) | $ 1.12 |  |
2.00 – 2.99 |  |  |
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] |  |  |
Number of outstanding options (in shares) | shares | 10,610 |  |
Weighted- average years to expiry (in years) | year | 1.35 |  |
Weighted-average exercise price (in Cdn.$per share) | $ 2.08 |  |
Number of exercisable options (in shares) | shares | 10,174 |  |
Weighted-average exercise price (in Cdn.$per share) | $ 2.05 |  |
3.00 – 3.99 |  |  |
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] |  |  |
Number of outstanding options (in shares) | shares | 48,434 |  |
Weighted- average years to expiry (in years) | year | 3.91 |  |
Weighted-average exercise price (in Cdn.$per share) | $ 3.47 |  |
Number of exercisable options (in shares) | shares | 19,590 |  |
Weighted-average exercise price (in Cdn.$per share) | $ 3.50 |  |
4.00 – 4.99 |  |  |
Disclosure of number and weighted average remaining contractual life of outstanding share options [line items] |  |  |
Number of outstanding options (in shares) | shares | 75 |  |
Weighted- average years to expiry (in years) | year | 3.10 |  |
Weighted-average exercise price (in Cdn.$per share) | $ 4.05 |  |
Number of exercisable options (in shares) | shares | 50 |  |
Weighted-average exercise price (in Cdn.$per share) | $ 4.05 |  |
Bottom of range | 1.12 – 1.99 |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |
Exercise price of outstanding options (in Cdn.$per share) | 1.12 |  |
Bottom of range | 2.00 – 2.99 |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |
Exercise price of outstanding options (in Cdn.$per share) | 2.00 |  |
Bottom of range | 3.00 – 3.99 |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |
Exercise price of outstanding options (in Cdn.$per share) | 3.00 |  |
Bottom of range | 4.00 – 4.99 |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |
Exercise price of outstanding options (in Cdn.$per share) | 4.00 |  |
Top of range | 1.12 – 1.99 |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |
Exercise price of outstanding options (in Cdn.$per share) | 1.99 |  |
Top of range | 2.00 – 2.99 |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |
Exercise price of outstanding options (in Cdn.$per share) | 2.99 |  |
Top of range | 3.00 – 3.99 |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |
Exercise price of outstanding options (in Cdn.$per share) | 3.99 |  |
Top of range | 4.00 – 4.99 |  |  |
Disclosure of range of exercise prices of outstanding share options [line items] |  |  |
Exercise price of outstanding options (in Cdn.$per share) | $ 4.99 |  |

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