Summary of significant accounting policies - IFRS 16 - Accounting for the Group's leasing activities (Details)	12 Months Ended
Dec. 31, 2019
Minimum
Disclosure of quantitative information about right-of-use assets [line items]
Term of lease	1 year
Maximum
Disclosure of quantitative information about right-of-use assets [line items]
Term of lease	7 years

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.

No definition available.

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration