The quantity of stock options that are exercisable and the weighted average remaining life were as follows:
| As at December 31, | 2017 | 2016 | ||||||
| Time vesting option plans | 2,612,679 | 1,779,707 | ||||||
| Performance vesting option plans | 476,413 | 582,854 | ||||||
| Weighted average remaining life | 4 years | 6 years | ||||||