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Share-based Payments Arrangement - SENAO's Employee Stock Options Outstanding (Detail) - Senao International Co., Ltd. (SENAO) [Member] | Dec. 31, 2017 TWD ($) yr | Jul. 31, 2017 TWD ($) | Jun. 30, 2017 TWD ($) | Dec. 31, 2016 TWD ($) yr | Jul. 31, 2016 TWD ($) | Jun. 30, 2016 TWD ($) | Dec. 31, 2015 TWD ($) | Jul. 31, 2015 TWD ($) | Dec. 31, 2014 TWD ($)
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Disclosure of range of exercise prices of outstanding share options [Line Items] |  |  |  |  |  |  |  |  |
Range of Exercise Price | $ 70.70 | $ 70.70 | $ 76.10 | $ 76.10 | $ 76.10 | $ 81.40 | $ 81.40 | $ 84.30 |
Number of Options Outstanding | 5,926,000 |  |  | 6,587,000 |  |  | 7,787,000 |  | 9,027,000
Weighted-average Remaining Contractual Life (Years) | yr | 1.35 |  |  | 2.35 |  |  |  |  |
Weighted-average Exercise Price | $ 70.70 |  |  | $ 76.10 |  |  | $ 81.40 |  | $ 84.30
Options Exercisable Number of Options | 5,926,000 |  |  | 4,947,000 |  |  | 4,049,000 |  |
Option Exercisable Weighted-average Exercise Price | $ 70.70 |  |  | $ 76.10 |  |  | $ 81.40 |  |

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- Definition The exercise price of outstanding share options. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 2 -IssueDate 2016-01-13 -Paragraph 45 -Subparagraph d -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2016-03-30&anchor=para_45_d&doctype=Standard -URIDate 2016-03-31 + Details
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