Subsidiaries - Summary of Goodwill Arising from Acquisition (Detail) - IISI and its Subsidiaries [Member] $ in Millions	Jul. 01, 2020 TWD ($)
Disclosure Of Business Combinations [Line Items]
Consideration transferred	$ 234
Add: Fair value of equity interest held before the acquisition date	327
Add: Noncontrolling interest (48.46% of the identifiable net assets of IISI and its subsidiaries)	476
Less: Fair value of identifiable net assets acquired	(982)
Goodwill arising from acquisition	$ 55

The acquisition-date fair value of equity interest in the acquiree held by the acquirer immediately before the acquisition date in a business combination achieved in stages. [Refer: Business combinations [member]]

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The fair value, at acquisition date, of the consideration transferred in a business combination. [Refer: Business combinations [member]]

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The amount of non-controlling interest in the acquiree recognised at the acquisition date for business combinations in which the acquirer holds less than 100 per cent of the equity interests in the acquiree at the acquisition date. [Refer: Business combinations [member]]

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