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v3.21.1

Equity - Adjustments of Additional Paid-in Capital (Detail) $ in Millions, $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 TWD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 TWD ($) | Dec. 31, 2018 TWD ($)
Beginning balance | $ 384,272 |  | $ 384,529 | $ 382,124
Unclaimed dividend | 2 |  | 1 | 2
Partial disposal of interests in subsidiaries |  |  |  | 1,175
Change in additional paid-in capital for not participating proportionately in the capital increase of subsidiaries | 0 |  |  | 1,477
Share-based payment transactions of subsidiaries | 89 |  | 21 | 53
Ending balance | 387,273 | $ 13,791 | 384,272 | 384,529
Share premium [Member] |  |  |  |
Beginning balance | 126,045 |  | 126,045 | 126,045
Partial disposal of interests in subsidiaries |  |  |  | 0
Share-based payment transactions of subsidiaries | 0 |  | 0 | 0
Ending balance | 126,045 |  | 126,045 | 126,045
Movements Of Additional Paid-in Capital For Associates And Joint Ventures Accounted For Using Equity Method |  |  |  |
Beginning balance | 0 |  | 0 | 0
Partial disposal of interests in subsidiaries |  |  |  | 0
Share-based payment transactions of subsidiaries | 0 |  | 0 | 0
Ending balance | 0 |  | 0 | 0
Movements of additional paid-in capital arising from changes in equities of subsidiaries [Member] |  |  |  |
Beginning balance | 2,063 |  | 2,064 | 1,221
Partial disposal of interests in subsidiaries |  |  |  | 0
Change in additional paid-in capital for not participating proportionately in the capital increase of subsidiaries | 0 |  |  | 777
Share-based payment transactions of subsidiaries | 26 |  | (1) | 11
Treasury stock transfer of subsidiaries |  |  |  | 55
Ending balance | 2,089 |  | 2,063 | 2,064
Difference between consideration received and carrying amount of the subsidiaries' net assets upon disposal [Member] |  |  |  |
Beginning balance | 987 |  | 987 | 161
Partial disposal of interests in subsidiaries |  |  |  | 826
Share-based payment transactions of subsidiaries | 0 |  | 0 | 0
Ending balance | 987 |  | 987 | 987
Donated capital [Member] |  |  |  |
Beginning balance | 19 |  | 18 | 16
Unclaimed dividend | 2 |  | 1 | 2
Partial disposal of interests in subsidiaries |  |  |  | 0
Share-based payment transactions of subsidiaries | 0 |  | 0 | 0
Ending balance | 21 |  | 19 | 18
Stockholders' contribution due to privatization [Member] |  |  |  |
Beginning balance | 20,648 |  | 20,648 | 20,648
Partial disposal of interests in subsidiaries |  |  |  | 0
Share-based payment transactions of subsidiaries | 0 |  | 0 | 0
Ending balance | 20,648 |  | 20,648 | 20,648
Additional paid-in capital [Member] |  |  |  |
Beginning balance | 149,762 |  | 149,762 | 148,091
Unclaimed dividend | 2 |  | 1 | 2
Partial disposal of interests in subsidiaries |  |  |  | 826
Change in additional paid-in capital for not participating proportionately in the capital increase of subsidiaries | 0 |  |  | 777
Share-based payment transactions of subsidiaries | 26 |  | (1) | 11
Treasury stock transfer of subsidiaries |  |  |  | 55
Ending balance | $ 149,790 | $ 5,334 | $ 149,762 | $ 149,762

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