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Share Capital (Stock Options) (Details) | 12 Months Ended
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Dec. 31, 2018 CAD ($) shares | Dec. 31, 2018 USD ($) shares | Dec. 31, 2017 CAD ($) shares | Dec. 31, 2017 USD ($) shares
Disclosure of share capital, reserves and other equity interest [Abstract] |  |  |  |
Number of options outstanding | shares | 10,429,345 | 10,429,345 | 9,511,636 | 9,511,636
Granted | shares | 1,009,100 | 1,009,100 | 578,490 | 578,490
Conversion shares | shares |  |  | 2,863,146 | 2,863,146
Exercised | shares | (1,984,698) | (1,984,698) | (510,673) | (510,673)
Expired | shares | (2,798,292) | (2,798,292) | (2,013,254) | (2,013,254)
Number of options outstanding | shares | 6,655,455 | 6,655,455 | 10,429,345 | 10,429,345
Weighted average exercise price of share options outstanding (CAD$) | $ 7.94 |  | $ 10.87 |
Weighted average exercise price of share options granted (CAD$) |  | $ 6.56 |  | $ 9.62
Weighted average exercise price of share options conversion of Carlisle options to Alamos (CAD$) |  |  |  | 3.53
Weighted average exercise price of share options exercised (CAD$) |  | $ 2.40 |  | $ 6.23
Weighted average exercise price of share options expired (CAD$) | 12.70 |  | 16.42 |
Weighted average exercise price of share options outstanding (CAD$) | 7.38 |  | 7.94 |
Weighted average share price for share options in share-based payment arrangement exercised during period at date of exercise (CAD$) | $ 5.89 |  | $ 9.99 |

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