The movement in the number of stock options outstanding and their weighted average exercise price were as follows:
| Time vesting option plans | Performance
vesting option plans |
|||||||||||||||
| Number
of options |
Weighted- average exercise price |
Number
of options |
Weighted- average exercise price |
|||||||||||||
| Outstanding at December 31, 2015 and January 1, 2016 | 3,763,671 | $ | 23.65 | 1,825,324 | $ | 19.38 | ||||||||||
| Granted | — | — | ||||||||||||||
| Forfeited | (143,440 | ) | (32,684 | ) | ||||||||||||
| Exercised (Note 25) | (86,116 | ) | (92,526 | ) | ||||||||||||
| Repurchased | (857,096 | ) | (396,381 | ) | ||||||||||||
| Expired | — | — | ||||||||||||||
| Outstanding at December 31, 2016 and January 1, 2017 | 2,677,019 | $ | 24.54 | 1,303,733 | $ | 20.16 | ||||||||||
| Granted | — | — | ||||||||||||||
| Forfeited | (15,507 | ) | (17,638 | ) | ||||||||||||
| Exercised (Note 25) | (3,150 | ) | (3,850 | ) | ||||||||||||
| Exchanged | 805,835 | (805,835 | ) | |||||||||||||
| Expired | — | — | ||||||||||||||
| Outstanding at December 31, 2017 | 3,464,197 | $ | 24.85 | 476,410 | $ | 11.07 | ||||||||||