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Investments Accounted For Using Equity Method - Additional Information (Detail) $ in Millions | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Jun. 30, 2018 TWD ($) | Jan. 31, 2018 TWD ($) | Dec. 31, 2016 TWD ($) | Sep. 30, 2016 TWD ($) | Dec. 31, 2018 NumberofSeat | Oct. 31, 2018 | Dec. 31, 2017
Huada Digital Corporation ("HDD") [Member] |  |  |  |  |  |  |
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items] |  |  |  |  |  |  |
Losses on disposals recognized |  |  |  | $ 0.4 |  |  |
KingwayTek Technology Co., Ltd. ("KWT") [Member] |  |  |  |  |  |  |
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items] |  |  |  |  |  |  |
Percentage of ownership in associates |  |  |  |  | 26.00% |  | 26.00%
Taiwan International Ports Logistics Corporation ("TIPL") [Member] |  |  |  |  |  |  |
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items] |  |  |  |  |  |  |
Percentage of ownership in associates |  |  |  |  | 27.00% |  | 27.00%
Click Force Co., Ltd. ("CF") [Member] |  |  |  |  |  |  |
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items] |  |  |  |  |  |  |
Percentage of ownership in associates |  |  |  |  | 49.00% |  | 49.00%
Alliance Digital Tech Co., Ltd. ("ADT") [Member] |  |  |  |  |  |  |
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items] |  |  |  |  |  |  |
Ownership interest in associates |  |  | 14.00% |  |  |  |
Investments in cash in associates |  |  | $ 30.0 |  |  |  |
Percentage of ownership in associates |  |  |  |  | 14.00% |  | 14.00%
MeWorks LIMITED (HK) ("MeWorks") [Member] |  |  |  |  |  |  |
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items] |  |  |  |  |  |  |
Percentage of ownership in associates |  |  |  |  | 20.00% |  | 20.00%
UUPON Inc [member] |  |  |  |  |  |  |
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items] |  |  |  |  |  |  |
Ownership interest in associates |  |  |  |  | 22.00% |  |
Percentage of ownership in associates |  |  |  |  | 22.00% |  | 22.00%
HopeTech Technologies Limited [Member] |  |  |  |  |  |  |
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items] |  |  |  |  |  |  |
Proceeds From Capital Reduction |  | $ 19.0 |  |  |  |  |
Proceeds from disposal of shares | $ 3.0 |  |  |  |  |  |
Losses on disposals recognized | $ 0.1 |  |  |  |  |  |
Chunghwa PChome Fund I Co., Ltd. (“CPFI”) [Member] |  |  |  |  |  |  |
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items] |  |  |  |  |  |  |
Percentage of ownership in associates |  |  |  |  |  | 50.00% |
No Of Seats Allotted | NumberofSeat |  |  |  |  | 2 |  |
Number Of Seats Available For Board Of Directors | NumberofSeat |  |  |  |  | 5 |  |
Cornerstone Ventures Co., Ltd. (“CVC”) [Member] |  |  |  |  |  |  |
Disclosure Of Significant Investments In Associates And Joint Ventures [Line Items] |  |  |  |  |  |  |
Percentage of ownership in associates |  |  |  |  |  | 49.00% |
No Of Seats Allotted | NumberofSeat |  |  |  |  | 2 |  |
Number Of Seats Available For Board Of Directors | NumberofSeat |  |  |  |  | 5 |  |

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