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Income Tax - Movements of Deferred Income Tax Assets and Liabilities (Detail) - TWD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Jan. 01, 2019 | Jan. 01, 2018
Income tax [Line Items] |  |  |  |  |
Effect of Retrospective Application of IFRS 9 |  |  |  | $ 0 | $ (883)
Recognized in Profit or Loss | $ 63 | $ (208) | $ 101 |  |
Recognized in Other Comprehensive Income | (305) | 450 | 347 |  |
Deferred tax asset [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 3,554 | 2,730 | 2,322 |  |
Effect of Retrospective Application of IFRS 16 | 26 |  |  |  |
Recognized in Profit or Loss | (16) | 374 | 64 |  |
Recognized in Other Comprehensive Income | (305) | 450 | 344 |  |
Ending balance | 3,259 | 3,554 | 2,730 |  |
Deferred tax asset [Member] | Present value of funded defined benefit obligation [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 2,307 | 1,723 | 1,374 |  |
Recognized in Profit or Loss | 32 | 134 | 5 |  |
Recognized in Other Comprehensive Income | (305) | 450 | 344 |  |
Ending balance | 2,034 | 2,307 | 1,723 |  |
Deferred tax asset [Member] | Share of profits of associates and joint ventures accounted for using equity method [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 389 | 331 | 330 |  |
Recognized in Profit or Loss | 13 | 58 | 1 |  |
Ending balance | 402 | 389 | 331 |  |
Deferred tax asset [Member] | Valuation loss on inventory [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 88 | 23 | 20 |  |
Recognized in Profit or Loss | 53 | 65 | 3 |  |
Ending balance | 141 | 88 | 23 |  |
Deferred tax asset [Member] | Deferred revenue [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 111 | 106 | 117 |  |
Recognized in Profit or Loss | (13) | 5 | (11) |  |
Ending balance | 98 | 111 | 106 |  |
Deferred tax asset [Member] | Warranties [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 26 | 22 | 19 |  |
Recognized in Profit or Loss | 8 | 4 | 3 |  |
Ending balance | 34 | 26 | 22 |  |
Deferred tax asset [Member] | Impairment loss on property, plant and equipment [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 93 | 112 | 122 |  |
Recognized in Profit or Loss | (75) | (19) | (10) |  |
Ending balance | 18 | 93 | 112 |  |
Deferred tax asset [Member] | Accrued award credits liabilities [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 14 | 15 | 20 |  |
Recognized in Profit or Loss | 3 | (1) | (5) |  |
Ending balance | 17 | 14 | 15 |  |
Deferred tax asset [Member] | Unrealised foreign exchange gains (losses) [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 1 | 17 | 0 |  |
Effect of Retrospective Application of IFRS 16 | 0 |  |  |  |
Recognized in Profit or Loss | 2 | (16) | 17 |  |
Ending balance | 3 | 1 | 17 |  |
Deferred tax asset [Member] | Property, plant and equipment [member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 2 | 2 | 2 |  |
Ending balance | 2 | 2 | 2 |  |
Deferred tax asset [Member] | Trade-in right [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 10 | 15 | 0 |  |
Effect of Retrospective Application of IFRS 16 | 0 |  |  |  |
Recognized in Profit or Loss | (9) | (5) | 15 |  |
Ending balance | 1 | 10 | 15 |  |
Deferred tax asset [Member] | Others [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 37 | 29 | 34 |  |
Effect of Retrospective Application of IFRS 16 | 26 |  |  |  |
Recognized in Profit or Loss | 14 | 8 | (5) |  |
Ending balance | 77 | 37 | 29 |  |
Deferred tax asset [Member] | Temporary differences [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 3,513 | 2,684 | 2,268 |  |
Effect of Retrospective Application of IFRS 16 | 26 |  |  |  |
Recognized in Profit or Loss | (3) | 379 | 72 |  |
Recognized in Other Comprehensive Income | (305) | 450 | 344 |  |
Ending balance | 3,231 | 3,513 | 2,684 |  |
Deferred tax asset [Member] | Unused tax losses [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 41 | 46 | 54 |  |
Recognized in Profit or Loss | (13) | (5) | (8) |  |
Ending balance | 28 | 41 | 46 |  |
Deferred tax asset [Member] | Allowance for doubtful receivables over quota [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 435 | 289 | 230 |  |
Recognized in Profit or Loss | (31) | 146 | 59 |  |
Ending balance | 404 | 435 | 289 |  |
Deferred tax liability [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | (1,992) | (1,430) | (1,464) |  |
Effect of Retrospective Application of IFRS 9 |  | 1 |  |  |
Recognized in Profit or Loss | 80 | (563) | 31 |  |
Recognized in Other Comprehensive Income |  |  | 3 |  |
Ending balance | (1,912) | (1,992) | (1,430) |  |
Deferred tax liability [Member] | Present value of funded defined benefit obligation [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | (1,832) | (1,265) | (1,269) |  |
Recognized in Profit or Loss | 74 | (567) | 4 |  |
Ending balance | (1,758) | (1,832) | (1,265) |  |
Deferred tax liability [Member] | Unrealised foreign exchange gains (losses) [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | (1) | 0 | (10) |  |
Recognized in Profit or Loss | 0 | (1) | 10 |  |
Ending balance | (1) | (1) | 0 |  |
Deferred tax liability [Member] | Others [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | (1) | (1) | (1) |  |
Recognized in Profit or Loss | 1 | 0 | 0 |  |
Ending balance | 0 | (1) | (1) |  |
Deferred tax liability [Member] | Land value incremental tax [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | (95) | (95) | (95) |  |
Ending balance | (95) | (95) | (95) |  |
Deferred tax liability [Member] | Deferred revenue for award credits [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | (31) | (29) | (46) |  |
Recognized in Profit or Loss | 2 | (2) | 17 |  |
Ending balance | (29) | (31) | (29) |  |
Deferred tax liability [Member] | Intangible assets and goodwill [member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | (32) | (39) | (40) |  |
Recognized in Profit or Loss | 3 | 7 | 1 |  |
Ending balance | (29) | (32) | (39) |  |
Deferred tax liability [Member] | Valuation gain or loss on financial instruments, net [Member] |  |  |  |  |
Income tax [Line Items] |  |  |  |  |
Beginning balance | 0 | (1) | (3) |  |
Effect of Retrospective Application of IFRS 9 |  | 1 |  |  |
Effect of Retrospective Application of IFRS 16 | 0 |  |  |  |
Recognized in Profit or Loss | 0 | 0 | (1) |  |
Recognized in Other Comprehensive Income | 0 | 0 | 3 |  |
Ending balance | $ 0 | $ 0 | $ (1) |  |

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- Definition The amount of tax expense or income relating to changes in deferred tax liabilities and deferred tax assets, recognised in profit or loss. [Refer: Deferred tax assets; Deferred tax expense (income); Deferred tax liabilities] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2019-01-01 -Paragraph 81 -Subparagraph g -Clause ii -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2019-en-r&anchor=para_81_g_ii&doctype=Standard -URIDate 2019-03-27 + Details
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