Financial Instruments - Summary of Categories of Financial Instruments (Detail) $ in Thousands, $ in Thousands	Dec. 31, 2017 TWD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 TWD ($)
Disclosure of detailed information about financial instruments [abstract]
Designated as at FVTPL	$ 100,496	$ 3,391	$ 100,583
Held for trading	5,122,571	172,826	2,969,229
Available-for-sale financial assets	1,212,165	40,896	1,295,034
Loans and receivables (Note 1)	103,973,567	3,507,881	92,082,628
Held for trading	677,430	22,855	1,763,660
Measured at amortized cost (Note 2)	$ 139,561,999	$ 4,708,569	$ 168,397,006

The amount of current financial assets measured at fair value through profit or loss classified as held for trading. [Refer: Financial assets at fair value through profit or loss, classified as held for trading]

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The amount of current financial assets measured at fair value through profit or loss that were designated as such upon initial recognition or subsequently. [Refer: Financial assets at fair value through profit or loss, designated upon initial recognition or subsequently]

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The amount of current financial liabilities measured at fair value through profit or loss classified as held for trading. [Refer: Financial liabilities at fair value through profit or loss; Current financial liabilities]

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The amount of non-derivative financial assets that are designated as available for sale or are not classified as (a) loans and receivables; (b) held-to-maturity investments; or (c) financial assets at fair value through profit or loss. [Refer: Derivative financial assets; Financial assets at fair value through profit or loss; Held-to-maturity investments]

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The amount of financial liabilities at amortised cost. The amortised cost is the amount at which financial liabilities are measured at initial recognition minus principal repayments, plus or minus the cumulative amortisation using the effective interest method of any difference between that initial amount and the maturity amount. [Refer: Financial liabilities]

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The amount of non-derivative financial assets with fixed or determinable payments that are not quoted in an active market, other than: (a) those that the entity intends to sell immediately or in the near term, which shall be classified as held for trading, and those that the entity, upon initial recognition, designates as at fair value through profit or loss; (b) those that the entity, upon initial recognition, designates as available for sale; or (c) those for which the holder may not recover substantially all of its initial investment, other than because of credit deterioration, which shall be classified as available for sale. An interest acquired in a pool of assets that are not loans or receivables (for example, an interest in a mutual fund or a similar fund) is not a loan or receivable. [Refer: Derivative financial assets]

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