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Financial Instruments - Summary of Maturity Analysis for Derivative Financial Instruments (Detail) $ in Thousands, $ in Thousands | Dec. 31, 2019 TWD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 TWD ($)
--- | --- | --- | ---
Less than 1 month [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | $ 71,041 | $ 2,375 | $ 213,624
Less than 1 month [member] | Forward exchange contracts [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Net settled | (74,864) | (2,503) | 2,040
Gross settled | 47,790 | 1,598 | 23,587
Less than 1 month [member] | Forward exchange contracts [member] | Inflows [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | 9,296,123 | 310,803 | 2,580,194
Less than 1 month [member] | Forward exchange contracts [member] | Outflows [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | (9,248,333) | (309,205) | (2,556,607)
Less than 1 month [member] | Swap contracts [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | 23,251 | 777 | 190,037
Less than 1 month [member] | Swap contracts [member] | Inflows [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | 10,187,215 | 340,595 | 14,136,620
Less than 1 month [member] | Swap contracts [member] | Outflows [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | (10,163,964) | (339,818) | (13,946,583)
1 to 3 months [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | 20,714 | 692 | 569,944
1 to 3 months [member] | Forward exchange contracts [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Net settled | (13,246) | (443) | 1,620
Gross settled | 28,163 | 941 | 5,764
1 to 3 months [member] | Forward exchange contracts [member] | Inflows [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | 4,420,233 | 147,784 | 466,489
1 to 3 months [member] | Forward exchange contracts [member] | Outflows [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | (4,392,070) | (146,843) | (460,725)
1 to 3 months [member] | Swap contracts [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | (7,449) | (249) | 564,180
1 to 3 months [member] | Swap contracts [member] | Inflows [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | 15,025,154 | 502,345 | 9,214,500
1 to 3 months [member] | Swap contracts [member] | Outflows [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | (15,032,603) | (502,594) | (8,650,320)
3 months to 1 year [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | (444,242) | (14,853) | 1,563,897
3 months to 1 year [member] | Forward exchange contracts [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | 2,506 | 83 |
3 months to 1 year [member] | Forward exchange contracts [member] | Inflows [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | 230,354 | 7,701 |
3 months to 1 year [member] | Forward exchange contracts [member] | Outflows [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | (227,848) | (7,618) |
3 months to 1 year [member] | Swap contracts [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | (446,748) | (14,936) | 1,563,897
3 months to 1 year [member] | Swap contracts [member] | Inflows [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | 34,327,100 | 1,147,680 | 38,160,316
3 months to 1 year [member] | Swap contracts [member] | Outflows [member] |  |  |
Disclosure of maturity analysis for derivative financial liabilities [line items] |  |  |
Gross settled | $ (34,773,848) | $ (1,162,616) | $ (36,596,419)

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- Definition The amount of contractual undiscounted cash flows in relation to contractual amounts to be exchanged in a derivative financial instrument for which gross cash flows are exchanged. [Refer: Derivatives [member]] + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Name IFRS -Number 7 -IssueDate 2019-01-01 -Paragraph B11D -Subparagraph d -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2019-en-r&anchor=para_B11D_d&doctype=Appendix&subtype=B -URIDate 2019-03-27 + Details
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- Definition The amount of contractual undiscounted cash flows in relation to net amounts for pay-floating (receive-fixed) interest rate swaps for which net cash flows are exchanged. [Refer: Swap contract [member]] + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Name IFRS -Number 7 -IssueDate 2019-01-01 -Paragraph B11D -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2019-en-r&anchor=para_B11D_c&doctype=Appendix&subtype=B -URIDate 2019-03-27 + Details
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