Investments - Summary of Investments (Detail) - EUR (€) € in Thousands	Jun. 30, 2019	Dec. 31, 2018
Investment [Line Items]
Investments, current portion	€ 35,560	€ 44,855
Non-current investments	12,319	16,945
Total investments	47,879	61,800
Commercial paper [member]
Investment [Line Items]
Investments, current portion	13,929	22,208
U.S. Treasury securities [member]
Investment [Line Items]
Investments, current portion	2,411	6,733
Corporate fixed income bonds [member]
Investment [Line Items]
Investments, current portion	17,465	14,185
Non-current investments	12,319	16,945
Agency bond [member]
Investment [Line Items]
Investments, current portion	€ 1,755	€ 1,729

The amount of current held-to-maturity investments. [Refer: Held-to-maturity investments]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2021-01-01
-Name IFRS
-Number 7
-IssueDate 2018-01-01
-Paragraph 8
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-02&anchor=para_8_b&doctype=Standard&book=b
-URIDate 2018-03-16

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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 amount of non-current held-to-maturity investments. [Refer: Held-to-maturity investments]

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No definition available.

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