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Share-based Payments Arrangement - CHIEF's Outstanding Stock Options (Detail) - CHIEF Telecom Inc. (CHIEF) [Member] | 12 Months Ended
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Dec. 31, 2018 TWD ($) | Dec. 31, 2017 TWD ($) | Dec. 31, 2016 TWD ($)
Granted on October 22, 2015 [Member] |  |  |
Disclosure of terms and conditions of share-based payment arrangement [Line Items] |  |  |
Number of options, Options outstanding at beginning of the year | 1,936.00 | 1,948.00 | 2,000.00
Number of options, Options granted | 0 | 0 | 0
Number of options, Options forfeited | (26.00) | (12.00) | (52.00)
Number of options, Options outstanding at end of the year | 882.75 | 1,936.00 | 1,948.00
Number of options, Options exercisable at end of the year | 416.50 | 968.00 | 0
Weighted-average exercise price, Options outstanding at beginning of the year | $ 34.40 | $ 34.40 | $ 43.00
Weighted average exercise price, Options granted | 0 | 0 | 0
Weighted average exercise price, Options forfeited | 0 | 0 | 0
Weighted-average exercise price, Options outstanding at end of the year | 34.40 | 34.40 | 34.40
Weighted average exercise price, Option exercisable at end of the year | $ 34.40 | $ 34.40 | $ 0
Number of options, Options excercised | (1,027.25) |  |
Weighted average exercise price, Options exercised | $ 34.40 |  |
Granted on December 19, 2017 [Member] |  |  |
Disclosure of terms and conditions of share-based payment arrangement [Line Items] |  |  |
Number of options, Options outstanding at beginning of the year | 950.00 | 0 |
Number of options, Options granted | 0 | 950.00 |
Number of options, Options forfeited | (25.00) | 0 |
Number of options, Options outstanding at end of the year | 925.00 | 950.00 | 0
Number of options, Options exercisable at end of the year | 0 | 0 |
Weighted-average exercise price, Options outstanding at beginning of the year | $ 147.00 | $ 0 |
Weighted average exercise price, Options granted | 0 | 147.00 |
Weighted average exercise price, Options forfeited | 0 | 0 |
Weighted-average exercise price, Options outstanding at end of the year | 140.60 | 147.00 | $ 0
Weighted average exercise price, Option exercisable at end of the year | $ 0 | $ 0 |
Number of options, Options excercised | 0 |  |
Weighted average exercise price, Options exercised | $ 0 |  |
Granted on October 31, 2018 [Member] |  |  |
Disclosure of terms and conditions of share-based payment arrangement [Line Items] |  |  |
Number of options, Options outstanding at beginning of the year | 0 |  |
Number of options, Options granted | 50.00 |  |
Number of options, Options forfeited | 0 |  |
Number of options, Options outstanding at end of the year | 50.00 | 0 |
Number of options, Options exercisable at end of the year | 0 |  |
Weighted-average exercise price, Options outstanding at beginning of the year | $ 0 |  |
Weighted average exercise price, Options granted | 147.00 |  |
Weighted average exercise price, Options forfeited | 0 |  |
Weighted-average exercise price, Options outstanding at end of the year | 147.00 | $ 0 |
Weighted average exercise price, Option exercisable at end of the year | $ 0 |  |
Number of options, Options excercised | 0 |  |
Weighted average exercise price, Options exercised | $ 0 |  |

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- Definition The number of share options outstanding in a share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 2 -IssueDate 2018-01-01 -Paragraph 45 -Subparagraph d -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2018-03-01&anchor=para_45_d&doctype=Standard -URIDate 2018-03-16 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 2 -IssueDate 2018-01-01 -Paragraph 45 -Subparagraph b -Clause i -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2018-03-01&anchor=para_45_b_i&doctype=Standard -URIDate 2018-03-16 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 2 -IssueDate 2018-01-01 -Paragraph 45 -Subparagraph b -Clause vi -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2018-03-01&anchor=para_45_b_vi&doctype=Standard -URIDate 2018-03-16 + Details
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