| Revenue, discontinued operations | en | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| Concept not required as a result of 2017 annual improvements | en | http://www.xbrl.org/2009/role/deprecatedLabel | http://www.xbrl.org/2003/role/link |
| 2018-01-01 | en | http://www.xbrl.org/2009/role/deprecatedDateLabel | http://www.xbrl.org/2003/role/link |
| The amount of revenue of discontinued operations. [Refer: Discontinued operations [member]; Revenue] | en | http://www.xbrl.org/2003/role/documentation | http://www.xbrl.org/2003/role/link |