| The fair value of the plan assets by major categories at each balance sheet date was as follows: |
| December 31 | ||||||||||||
| 2016 | 2017 | |||||||||||
| NT$ | NT$ | US$ (Note 4) | ||||||||||
| Cash | $ | 2,232,367 | $ | 2,317,764 | $ | 78,197 | ||||||
| Debt instruments | 1,030,384 | 691,619 | 23,334 | |||||||||
| Equity instruments | 1,071,777 | 1,254,109 | 42,311 | |||||||||
| Others | 82,839 | 77,881 | 2,628 | |||||||||
| Total | $ | 4,417,367 | $ | 4,341,373 | $ | 146,470 | ||||||