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Summary of Significant Accounting Policies - Additional information (Detail) - Chunghwa Investment Co., Ltd. ("CHI") [Member]	Dec. 31, 2020
CHIEF Telecom Inc. ("CHIEF") [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	2.95%
Senao International Co., Ltd. (SENAO) [Member]
Disclosure of subsidiaries [Line Items]
Percentage of Ownership interests	0.39%

X

- Definition

Percentage of ownership interest in subsidiary.

+ References

No definition available.

+ Details

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Period Type:	instant

X

- 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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- Details

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X

- Details

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Balance Type:
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X

- Details

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