| Contingent rents recognised as expense | en | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| Concept not required as it has an expiry date of 01-01-2019 | en | http://www.xbrl.org/2009/role/deprecatedLabel | http://www.xbrl.org/2003/role/link |
| 2019-01-01 | en | http://www.xbrl.org/2009/role/deprecatedDateLabel | http://www.xbrl.org/2003/role/link |
| The portion of lease payments recognised as an expense that is not fixed in amount but is based on the future amount of a factor that changes other than with the passage of time (for example, percentage of future sales, amount of future use, future price indices, future market rates of interest). | en | http://www.xbrl.org/2003/role/documentation | http://www.xbrl.org/2003/role/link |