Summary of Significant Accounting Policies - Summary of Lease Liabilities Recognized in Unaudited Condensed Consolidated Interim Financial Position (Detail) - EUR (€) € in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Presentation of leases for lessee [abstract]
Operating lease commitments as per December 31, 2018			€ 19,627
Short-term contracts, and low value assets			€ (169)
Undiscounted, operating lease commitments as per January 1, 2019		€ 19,458
Lease liabilities discounted by incremental borrowing rates as per January 1, 2019	€ 17,484	€ 17,700

The amount of future minimum lease payments payable under non-cancellable operating leases. Minimum lease payments are payments over the lease term that the lessee is or can be required to make, excluding contingent rent, costs for services and taxes to be paid by, and reimbursed to, the lessor, together with: (a) for a lessee, any amounts guaranteed by the lessee or by a party related to the lessee; or (b) for a lessor, any residual value guaranteed to the lessor by: (i) the lessee; (ii) a party related to the lessee; or (iii) a third party unrelated to the lessor that is financially capable of discharging the obligations under the guarantee.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2019-01-01
-Name IAS
-Number 17
-IssueDate 2018-01-01
-Paragraph 35
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=17&date=2018-03-02&anchor=para_35_a&doctype=Standard&book=b
-URIDate 2018-03-16

Name:	ifrs-full_MinimumLeasePaymentsPayableUnderNoncancellableOperatingLease
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant