Warrant Plans - Rollforward (Details)	12 Months Ended
Dec. 31, 2017 EUR (€) EquityInstruments	Dec. 31, 2016 EUR (€) EquityInstruments	Dec. 31, 2015 EUR (€) EquityInstruments	Dec. 31, 2014 EquityInstruments
Warrant plans
Outstanding at the beginning of the year	3,466,407	2,805,692	3,590,853
Exercisable	763,344	669,704	720,749	1,355,213
Granted during year	873,000	1,130,750	532,053
Forfeited during year		(48,500)	(72,500)
Exercised during year	(368,200)	(419,035)	(1,244,714)
Expired during year	(400)	(2,500)
Outstanding at the end of the year	3,970,807	3,466,407	2,805,692
Weighted average exercise price of other equity instruments outstanding in share-based payment arrangement at beginning of period \| €	€ 27.06	€ 16.22	€ 12.1

The number of other equity instruments (ie other than share options) exercised in a share-based payment arrangement.

No definition available.

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- Definition

Not applicable.

+ References

No definition available.

+ Details

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- Definition

The number of other equity instruments (ie other than share options) granted in a share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 47
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_47_b&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_45&doctype=Standard
-URIDate 2017-03-09

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- Definition

The number of other equity instruments (ie other than share options) exercisable in a share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_45&doctype=Standard
-URIDate 2017-03-09

+ Details

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- Definition

The number of other equity instruments (ie other than share options) expired in a share-based payment arrangement.

+ References

+ Details

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- Definition

The number of other equity instruments (ie other than share options) forfeited in a share-based payment arrangement.

+ References

+ Details

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- Definition

The number of other equity instruments (ie other than share options) outstanding in a share-based payment arrangement.

+ References

+ Details

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- Definition

The weighted average exercise price of other equity instruments (ie other than share options) outstanding in a share-based payment arrangement. [Refer: Weighted average [member]]

+ References

+ Details

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