21. OTHER CURRENT LIABILITIES
| As at December 31, | 2017 | 2016 | ||||||
| Deferred revenue | $ | 66,449 | $ | 73,900 | ||||
| Decommissioning liabilities (Note 23) | 1,205 | 114 | ||||||
| Uncertain tax positions | 1,315 | 1,315 | ||||||
| Income taxes payable | 4,121 | 2,135 | ||||||
| Other | 4,234 | 2,984 | ||||||
| Other current liabilities | $ | 77,324 | $ | 80,448 | ||||