Equity-based compensation - Additional information (Details) - shares shares in Millions	Apr. 09, 2019	Apr. 08, 2019	Jun. 30, 2019
Share-Based Payment Arrangements [Abstract]
Number of other equity instruments granted in share-based payment arrangement (in shares)	0.6	4.2
Number of other equity instruments outstanding in share-based payment arrangement (in shares)			4.8

The number of other equity instruments (ie other than share options) granted in a share-based payment arrangement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2018-01-01
-Paragraph 47
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2018-03-01&anchor=para_47_b&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 2
-IssueDate 2018-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2018-03-01&anchor=para_45&doctype=Standard
-URIDate 2018-03-16

Name:	ifrs-full_NumberOfInstrumentsOtherEquityInstrumentsGranted
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration