Shareholders' equity - Earnings per share (Details)	3 Months Ended	6 Months Ended
Jun. 30, 2018 € / shares	Jun. 30, 2018 $ / shares	Mar. 31, 2018 € / shares	Mar. 31, 2018 $ / shares	Jun. 30, 2017 € / shares	Jun. 30, 2017 $ / shares	Jun. 30, 2018 $ / shares	Jun. 30, 2017 $ / shares
Earnings per share in euros
Earnings per share (in dollars or Euros per share) \| (per share)	€ 1.16	$ 1.38	€ 0.81	$ 1.00	€ 0.71	$ 0.79	$ 2.39	$ 1.93
Fully-diluted earnings per share (in dollars per share) \| (per share)	€ 1.16	$ 1.38	€ 0.81	$ 0.99	€ 0.71	$ 0.79	$ 2.38	$ 1.92

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]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 33
-IssueDate 2017-01-01
-Paragraph 66
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=33&date=2017-03-01&anchor=para_66&doctype=Standard
-URIDate 2017-03-09

Name:	ifrs-full_DilutedEarningsLossPerShare
Namespace Prefix:	ifrs-full_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration