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v3.19.1

Segment Information - Main Products and Service Revenues (Detail) $ in Millions, $ in Millions | 12 Months Ended
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Dec. 31, 2018 TWD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 TWD ($) | Dec. 31, 2016 TWD ($)
Disclosure of products and services [Line Items] |  |  |  |
Revenues | $ 215,483 | $ 7,040 | $ 227,514 | $ 229,991
Mobile services [Member] |  |  |  |
Disclosure of products and services [Line Items] |  |  |  |
Revenues | 63,906 |  | 75,823 | 78,788
Local telephone and domestic long distance telephone services [Member] |  |  |  |
Disclosure of products and services [Line Items] |  |  |  |
Revenues | 29,996 |  | 32,247 | 34,531
Sales of product [Member] |  |  |  |
Disclosure of products and services [Line Items] |  |  |  |
Revenues | 41,289 |  | 37,649 | 35,377
Broadband access and domestic leased line services [Member] |  |  |  |
Disclosure of products and services [Line Items] |  |  |  |
Revenues | 22,453 |  | 22,950 | 23,315
Data communications internet services [Member] |  |  |  |
Disclosure of products and services [Line Items] |  |  |  |
Revenues | 21,137 |  | 21,143 | 20,906
International network and leased telephone services [Member] |  |  |  |
Disclosure of products and services [Line Items] |  |  |  |
Revenues | 8,724 |  | 9,328 | 10,634
Others [Member] |  |  |  |
Disclosure of products and services [Line Items] |  |  |  |
Revenues | $ 27,978 |  | $ 28,374 | $ 26,440

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