Loans, borrowings and cash and cash equivalents - Policy (Details)	12 Months Ended
Dec. 31, 2018
Loans and borrowings
Capitalization rate (as a percent)	17.00%

The weighted average of interest and other costs that an entity incurs in connection with the borrowing of funds applicable to the borrowings of the entity that are outstanding during the period, other than borrowings made specifically for the purpose of obtaining a qualifying asset. [Refer: Weighted average [member]; Borrowings]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 23
-IssueDate 2018-01-01
-Paragraph 26
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=23&date=2018-03-01&anchor=para_26_b&doctype=Standard
-URIDate 2018-03-16

Name:	ifrs-full_CapitalisationRateOfBorrowingCostsEligibleForCapitalisation
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration