Notes to the statement of financial position - Pension provisions and post-retirement benefits, fair value of plan assets (Details) - EUR (€) € in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of net defined benefit liability (asset) [line items]
Fair value of plan assets at the beginning of the period	€ (54,736)	€ (44,994)
Actuarial gain/(loss)	593	(10,574)
Benefits paid	2,137	827
Currency translation	110	(632)
Fair value of plan assets	(54,524)	(54,736)	€ (44,994)
Fair Value of Plan Assets
Disclosure of net defined benefit liability (asset) [line items]
Fair value of plan assets at the beginning of the period	6,643	5,595
Expected return on plan assets	159	136	160
Employer contributions	888	1,006
Employee contributions	0	50
Actuarial gain/(loss)	(68)	(30)
Benefits paid	(1,338)	(176)
Currency translation	(52)	62
Fair value of plan assets	€ 6,232	€ 6,643	€ 5,595

The decrease (increase) in net defined benefit liability (asset) resulting from contributions to a defined benefit plan by the employer. [Refer: Net defined benefit liability (asset); Defined benefit plans [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The decrease (increase) in the net defined benefit liability (asset) resulting from contributions to a defined benefit plan by plan participants. [Refer: Net defined benefit liability (asset); Defined benefit plans [member]]

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- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

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No definition available.

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The decrease (increase) in a net defined benefit liability (asset) resulting from the remeasurement of that net defined benefit liability (asset). [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The increase (decrease) in the net defined benefit liability (asset) resulting from changes in foreign exchange rates. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The increase (decrease) in the net defined benefit liability (asset) resulting from the passage of time. [Refer: Interest expense; Net defined benefit liability (asset)]

+ References

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The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling. [Refer: Defined benefit plans [member]]

+ References

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The decrease (increase) in the net defined benefit liability (asset) resulting from payments from the plan. [Refer: Net defined benefit liability (asset)]

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