Income/ loss per share (Details) - EUR (€) € / shares in Units, € in Thousands, shares in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income / loss per share - Basic
Result for the purpose of income / loss (-) per share	€ (115,704)	€ 54,012	€ (118,410)
Weighted average number of shares for the purpose of income / loss per share	49,479	45,696	35,700
Basic income / loss (-) per share	€ (2.34)	€ 1.18	€ (3.32)
Income / loss per share - Diluted
Result for the purpose of income / loss (-) per share	€ (115,704)	€ 54,012	€ (118,410)
Weighted average number of shares for the purpose of income / loss per share	49,479	45,696	35,700
Number of dilutive potential ordinary shares		1,612
Diluted income / loss (-) per share	€ (2.34)	€ 1.14	€ (3.32)

The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator) divided by the weighted average number of ordinary shares outstanding during the period (the denominator).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator), divided by the weighted average number of ordinary shares outstanding during the period (the denominator), both adjusted for the effects of all dilutive potential ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]]

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The number of dilutive potential ordinary shares that relate to the assumed exercise of the entity's share options.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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The profit (loss) attributable to ordinary equity holders of the parent equity. [Refer: Profit (loss)]

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The number of ordinary shares outstanding at the beginning of the period, adjusted by the number of ordinary shares bought back or issued during the period multiplied by a time-weighting factor.

+ References

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