The amount of accumulated items of income and expense (including reclassification adjustments) that are not recognised in profit or loss as required or permitted by other IFRSs. [Refer: IFRSs [member]; Other comprehensive income]

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The amount of cash on hand and demand deposits, along with short-term, highly liquid investments that are readily convertible to known amounts of cash and that are subject to an insignificant risk of changes in value. [Refer: Cash; Cash equivalents]

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The amount of non-derivative financial assets with fixed or determinable payments and fixed maturity that an entity has the positive intention and ability to hold to maturity other than: (a) those that the entity upon initial recognition designates as at fair value through profit or loss; (b) those that the entity designates as available for sale; and (c) those that meet the definition of loans and receivables. An entity shall not classify any financial assets as held to maturity if the entity has, during the current financial year or during the two preceding financial years, sold or reclassified more than an insignificant amount of held-to-maturity investments before maturity (more than insignificant in relation to the total amount of held-to-maturity investments) other than sales or reclassifications that: (i) are so close to maturity or the financial asset’s call date (for example, less than three months before maturity) that changes in the market rate of interest would not have a significant effect on the financial asset’s fair value; (ii) occur after the entity has collected substantially all of the financial asset’s original principal through scheduled payments or prepayments; or (iii) are attributable to an isolated event that is beyond the entity’s control, is non-recurring and could not have been reasonably anticipated by the entity. [Refer: Derivative financial assets; Held-to-maturity investments; Prepayments]

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The increase (decrease) in the number of ordinary shares issued. [Refer: Ordinary shares [member]]

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General Information - Additional Information (Detail) € / shares in Units, $ / shares in Units, € in Thousands, $ in Millions				6 Months Ended
	Feb. 15, 2018 EUR (€)	Feb. 15, 2018 USD ($)	Feb. 13, 2018 € / shares $ / shares shares	Jun. 30, 2019 EUR (€)	Jun. 30, 2018 EUR (€)	Dec. 31, 2018 EUR (€)	Dec. 31, 2017 EUR (€)
Disclosure of general information [line items]
Accumulated loss				€ (190,100)
Cash and cash equivalents				131,993	€ 170,327	€ 143,747	€ 149,678
Investments				47,879		€ 61,800
Aggregate purchase price				€ 1	€ 44,731
Investors [member]
Disclosure of general information [line items]
Common shares issued \| shares			3,099,997
Issue price per share \| € / shares			€ 0.09
Aggregate purchase price	€ 44,800	$ 55.8
Purchase price \| $ / shares			€ 18.0