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Investments Accounted for Using the Equity Method - Summary of Fair Values of Investments in Associates with Available Published Price Quotation (Detail) - Level 1 of fair value hierarchy [member] $ in Thousands, $ in Thousands | Dec. 31, 2018 USD ($) | Dec. 31, 2018 TWD ($) | Dec. 31, 2017 TWD ($)
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Siliconware Precision Industries Co., Ltd. [member] |  |  |
Disclosure of associates and joint ventures [line items] |  |  |
Fair value of investments in associates with available published price quotation |  |  | $ 52,176,190
Hung Ching Development & Construction Co. [member] |  |  |
Disclosure of associates and joint ventures [line items] |  |  |
Fair value of investments in associates with available published price quotation | $ 50,222 | $ 1,537,307 | 1,695,156
Advanced Microelectronic Products Inc. [member] |  |  |
Disclosure of associates and joint ventures [line items] |  |  |
Fair value of investments in associates with available published price quotation | 12,085 | 369,925 | $ 468,572
ChipMos Technologies Inc [member] |  |  |
Disclosure of associates and joint ventures [line items] |  |  |
Fair value of investments in associates with available published price quotation | $ 126,970 | $ 3,886,561 |

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- Definition The fair value of investments in associates if there are quoted market prices for the investment. [Refer: Associates [member]; Investments in associates] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 12 -IssueDate 2018-01-01 -Paragraph 21 -Subparagraph b -Clause iii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_21_b_iii&doctype=Standard -URIDate 2018-03-16 + Details
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