| Other comprehensive income, before tax, net movement in regulatory deferral account balances related to items that will be reclassified to profit or loss | en | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| Other comprehensive income, before tax, net movement in regulatory deferral account balances related to items that will be reclassified to profit or loss | en | http://www.xbrl.org/2003/role/totalLabel | http://www.xbrl.org/2003/role/link |
| The amount of other comprehensive income, before tax, related to the net movement in regulatory deferral account balances that is related to items that will be reclassified to profit or loss. [Refer: Regulatory deferral account balances [member]; Other comprehensive income] | en | http://www.xbrl.org/2003/role/documentation | http://www.xbrl.org/2003/role/link |
| Ioncam cuimsitheach eile, roimh cháin, glanghluaiseacht in iarmhéideanna cuntais iarchurtha rialála a bhaineann le míreanna a athaicmeofar chuig brabús nó caillteanas | ga | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| An méid ioncaim chuimsithigh eile, roimh cháin, a bhaineann leis an nglanghluaiseacht in iarmhéideanna cuntais iarchurtha rialála atá bainteach le míreanna a athaicmeofar chuig brabús nó caillteanas. [Féach: Iarmhéideanna cuntais iarchurtha rialála [member]; Ioncam cuimsitheach eile] | ga | http://www.xbrl.org/2003/role/documentation | http://www.xbrl.org/2003/role/link |
| Ioncam cuimsitheach eile, roimh cháin, glanghluaiseacht in iarmhéideanna cuntais iarchurtha rialála a bhaineann le míreanna a athaicmeofar chuig brabús nó caillteanas | ga | http://www.xbrl.org/2003/role/totalLabel | http://www.xbrl.org/2003/role/link |