| | | December 31, 2017 | | December 31, 2016 | | December 31, 2015 | | |||
| Within 1 year | | | 300 | | | 289 | | | 455 | |
| After 1 year but not more than 5 years | | | 243 | | | 646 | | | 822 | |
| Total | | | 543 | | | 935 | | | 1,277 | |