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Retirement benefit plans (Tables) | 12 Months Ended
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Dec. 31, 2019
Text block [abstract] |
Summary of Amounts Recognized in Statements of Financial Position |
| (a) | The amounts recognized in the statements of financial position are as follows:
|  | December 31, 2018 |  |  | December 31, 2019 |
|  | NT$000 |  |  | NT$000 |
Present value of defined benefit obligations |  |  | (910,081 | ) |  |  | (901,159 | )
Fair value of plan assets |  |  | 389,316 |  |  |  | 421,052 |
Net defined benefit liability |  |  | (520,765 | ) |  |  | (480,107 | )
Summary of Movements in net Defined Benefit Liability |
| (b) | Movements in net defined benefit liability are as follows:
|  | 2018 |
|  | Present value of defined benefit obligations |  |  | Fair value of plan assets |  |  | Net defined benefit liability |
|  | NT$000 |  |  | NT$000 |  |  | NT$000 |
January 1 |  |  | (838,543 | ) |  |  | 360,017 |  |  |  | (478,526 | )
Current services cost |  |  | (382 | ) |  |  | — |  |  |  | (382 | )
Interest (expense) income |  |  | (14,429 | ) |  |  | 6,291 |  |  |  | (8,138 | )
|  |  | (853,354 | ) |  |  | 366,308 |  |  |  | (487,046 | )
Remeasurements: |  |  |  |  |  |  |  |  |  |  |  |
Return on plan assets (excluding amounts included in interest income or expense) |  |  | — |  |  |  | 8,145 |  |  |  | 8,145 |
Financial assumption movement effect |  |  | (56,934 | ) |  |  | — |  |  |  | (56,934 | )
Experience adjustments |  |  | (11,172 | ) |  |  | — |  |  |  | (11,172 | )
|  |  | (68,106 | ) |  |  | 8,145 |  |  |  | (59,961 | )
Pension fund contribution |  |  | — |  |  |  | 26,242 |  |  |  | 26,242 |
Paid pension |  |  | 11,379 |  |  |  | (11,379 | ) |  |  | — |
December 31 |  |  | (910,081 | ) |  |  | 389,316 |  |  |  | (520,765 | )
|  | 2019 |
|  | Present value of defined benefit obligations |  |  | Fair value of plan assets |  |  | Net defined benefit liability |
|  | NT$000 |  |  | NT$000 |  |  | NT$000 |
January 1 |  |  | (910,081 | ) |  |  | 389,316 |  |  |  | (520,765 | )
Current services cost |  |  | (332 | ) |  |  | — |  |  |  | (332 | )
Interest (expense) income |  |  | (11,170 | ) |  |  | 4,831 |  |  |  | (6,339 | )
|  |  | (921,583 | ) |  |  | 394,147 |  |  |  | (527,436 | )
Remeasurements: |  |  |  |  |  |  |  |  |  |  |  |
Return on plan assets (excluding amounts included in interest income or expense) |  |  | — |  |  |  | 12,601 |  |  |  | 12,601 |
Financial assumption movement effect |  |  | (27,993 | ) |  |  | — |  |  |  | (27,993 | )
Experience adjustments |  |  | 36,308 |  |  |  | — |  |  |  | 36,308 |
|  |  | 8,315 |  |  |  | 12,601 |  |  |  | 20,916 |
Pension fund contribution |  |  | — |  |  |  | 26,413 |  |  |  | 26,413 |
Paid pension |  |  | 12,109 |  |  |  | (12,109 | ) |  |  | — |
December 31 |  |  | (901,159 | ) |  |  | 421,052 |  |  |  | (480,107 | )
Principal Actuarial Assumptions |
| (d) | The principal actuarial assumptions used were as follows
|  | 2018 |  |  | 2019 |
Discount rate |  |  | 1.25 | % |  |  | 1.00 | %
Future salary increase |  |  | 3.50 | % |  |  | 3.50 | %
Sensitivity Analysis of Present Value of Defined Benefit Obligations Effected by Changes of Significant Actuarial Assumptions | Because the main actuarial assumption changed, the present value of defined benefit obligations is affected. The analysis was as follows:
|  | Discount rate |  |  | Future salary increase |
|  | Increase 0.25% |  |  | Decrease 0.25% |  |  | Increase 0.25% |  |  | Decrease 0.25% |
|  | NT$000 |  |  | NT$000 |  |  | NT$000 |  |  | NT$000 |
December 31, 2018 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Effect on present value of defined benefit obligations |  |  | (29,052 | ) |  |  | 30,430 |  |  |  | 29,692 |  |  |  | (28,513 | )
December 31, 2019 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Effect on present value of defined benefit obligations |  |  | (27,993 | ) |  |  | 29,284 |  |  |  | 28,501 |  |  |  | (27,407 | )
Analysis of Timing of the Future Pension Payment |
| (f) | As of December 31, 2019, the weighted average duration of that retirement plan is 12.8 years. The analysis of timing of the future pension payment is as follows:
|  | December 31, 2019 |
|  | NT$000 |
Within 1 year |  |  | 35,272 |
1-2 years |  |  | 34,647 |
2-5 years |  |  | 122,670 |
5-10 years |  |  | 167,707 |
|  |  | 360,296 |

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- Definition The disclosure of information about the maturity profile of a defined benefit obligation. This will include the weighted average duration of the defined benefit obligation and may include other information about the distribution of the timing of benefit payments, such as a maturity analysis of the benefit payments. [Refer: Defined benefit obligation, at present value] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2019-01-01 -Paragraph 147 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_147_c&doctype=Standard -URIDate 2019-03-27 + Details
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- Definition The disclosure of a net defined benefit liability (asset). [Refer: Net defined benefit liability (asset)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2019-01-01 -Paragraph 140 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_140_a&doctype=Standard -URIDate 2019-03-27 + Details
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- Definition The disclosure of a sensitivity analysis for significant actuarial assumptions used to determine the present value of a defined benefit obligation. [Refer: Actuarial assumptions [member]; Defined benefit obligation, at present value] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2019-01-01 -Paragraph 145 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_145&doctype=Standard -URIDate 2019-03-27 + Details
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