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Share-based Payments Arrangement - CHIEF's Employee Stock Options Outstanding (Detail) - CHIEF Telecom Inc. (CHIEF) [Member] | Dec. 31, 2017 TWD ($) yr | Dec. 19, 2017 TWD ($) | Dec. 31, 2016 TWD ($) yr | Jul. 31, 2016 TWD ($) | Jun. 30, 2016 TWD ($) | Dec. 31, 2015 TWD ($) | Oct. 22, 2015 TWD ($) | Dec. 31, 2014 TWD ($)
--- | --- | --- | --- | --- | --- | --- | --- | ---
Disclosure of range of exercise prices of outstanding share options [Line Items] |  |  |  |  |  |  |  |
Range of Exercise Price |  | $ 147.00 |  | $ 34.40 | $ 43.00 |  | $ 43.00 |
Granted on October 22, 2015 [Member] |  |  |  |  |  |  |  |
Disclosure of range of exercise prices of outstanding share options [Line Items] |  |  |  |  |  |  |  |
Range of Exercise Price | $ 34.40 |  | $ 34.40 |  |  |  |  |
Number of Options Outstanding | 1,936 |  | 1,948 |  |  | 2,000 |  | 0
Weighted-average Remaining Contractual Life (Years) | yr | 2.81 |  | 3.81 |  |  |  |  |
Weighted-average Exercise Price | $ 34.40 |  | $ 34.40 |  |  | $ 43.00 |  | $ 0
Options Exercisable Number of Options | 968 |  | 0 |  |  | 0 |  |
Option Exercisable Weighted-average Exercise Price | $ 34.40 |  | $ 0 |  |  | $ 0 |  |
Granted on December 19, 2017 [Member] |  |  |  |  |  |  |  |
Disclosure of range of exercise prices of outstanding share options [Line Items] |  |  |  |  |  |  |  |
Range of Exercise Price | $ 147.00 |  |  |  |  |  |  |
Number of Options Outstanding | 950 |  |  |  |  |  |  |
Weighted-average Remaining Contractual Life (Years) | yr | 4.96 |  |  |  |  |  |  |
Weighted-average Exercise Price | $ 147.00 |  |  |  |  |  |  |
Options Exercisable Number of Options | 0 |  |  |  |  |  |  |
Option Exercisable Weighted-average Exercise Price | $ 0 |  |  |  |  |  |  |

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