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v3.21.1

Provisions - Movements in Provisions (Detail) - TWD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Jul. 01, 2020
Disclosure of other provisions [Line Items] |  |  |  |
Beginning balance | $ 304 | $ 207 | $ 180 |
Additional/(reversal of) provisions recognized | 221 | 184 | 192 |
Used / forfeited during the year | (125) | (87) | (165) |
Acquired by business combinations (Note 14) |  |  |  | $ 15
Ending balance | 415 | 304 | 207 |
Warranties [Member] |  |  |  |
Disclosure of other provisions [Line Items] |  |  |  |
Beginning balance | 173 | 132 | 132 |
Additional/(reversal of) provisions recognized | 131 | 127 | 164 |
Used / forfeited during the year | (122) | (86) | (164) |
Acquired by business combinations (Note 14) |  |  |  | 0
Ending balance | 182 | 173 | 132 |
Onerous Contracts [Member] |  |  |  |
Disclosure of other provisions [Line Items] |  |  |  |
Beginning balance | 67 | 19 | 0 |
Additional/(reversal of) provisions recognized | 92 | 48 | 19 |
Used / forfeited during the year | (3) | 0 | 0 |
Acquired by business combinations (Note 14) |  |  |  | 15
Ending balance | 171 | 67 | 19 |
Employee benefits [Member] |  |  |  |
Disclosure of other provisions [Line Items] |  |  |  |
Beginning balance | 59 | 51 | 43 |
Additional/(reversal of) provisions recognized | (2) | 9 | 9 |
Used / forfeited during the year | 0 | (1) | (1) |
Acquired by business combinations (Note 14) |  |  |  | 0
Ending balance | 57 | 59 | 51 |
Others [Member] |  |  |  |
Disclosure of other provisions [Line Items] |  |  |  |
Beginning balance | 5 | 5 | 5 |
Additional/(reversal of) provisions recognized | 0 | 0 | 0 |
Used / forfeited during the year | 0 | 0 | 0 |
Acquired by business combinations (Note 14) |  |  |  | $ 0
Ending balance | $ 5 | $ 5 | $ 5 |

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- Definition Additional or reversal of provisions recognized. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Provisions recognised as of acquisition date. + References No definition available. + Details
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Namespace Prefix: | cht_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Provisions used. + References No definition available. + Details
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Namespace Prefix: | cht_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
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Data Type: | xbrli:stringItemType
Balance Type: | na
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- Definition The amount of liabilities of uncertain timing or amount. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 54 -Subparagraph l -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_54_l&doctype=Standard -URIDate 2020-01-01 + Details
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |