{
 "documentInfo": {
  "documentType": "https://xbrl.org/2021/xbrl-json",
  "features": {
   "xbrl:canonicalValues": true
  },
  "namespaces": {
   "ifrs-full": "http://xbrl.ifrs.org/taxonomy/2020-03-16/ifrs-full",
   "iso4217": "http://www.xbrl.org/2003/iso4217",
   "scheme": "http://standards.iso.org/iso/17442",
   "severntrentplc": "http://severntrentplc.com/xbrl/2021",
   "xbrl": "https://xbrl.org/2021",
   "xbrli": "http://www.xbrl.org/2003/instance"
  },
  "taxonomy": [
   "http://severntrentplc.com/xbrl/2021/severntrentplc-2022-03-31.xsd"
  ]
 },
 "facts": {
  "fact-1": {
   "value": "Severn Trent Plc",
   "dimensions": {
    "concept": "ifrs-full:NameOfReportingEntityOrOtherMeansOfIdentification",
    "language": "en",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00"
   }
  },
  "fact-2": {
   "value": "We are two of eleven regulated water and waste water businesses in England and Wales. We provide high\u2011quality services to more than 4.8 million households and businesses in our region",
   "dimensions": {
    "concept": "ifrs-full:DescriptionOfNatureOfEntitysOperationsAndPrincipalActivities",
    "language": "en",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00"
   }
  },
  "fact-6": {
   "value": "1943300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Revenue",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-7": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Revenue",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-8": {
   "value": "1943300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Revenue",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-9": {
   "value": "1827200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Revenue",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-10": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Revenue",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-11": {
   "value": "1827200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Revenue",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-12": {
   "value": "5300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-13": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-14": {
   "value": "5300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-15": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-16": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-17": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-18": {
   "value": "1415700000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:OperatingCostsBeforeChargeForBadAndDoubtfulDebts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-19": {
   "value": "2100000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:OperatingCostsBeforeChargeForBadAndDoubtfulDebts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-20": {
   "value": "1417800000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:OperatingCostsBeforeChargeForBadAndDoubtfulDebts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-21": {
   "value": "1314400000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:OperatingCostsBeforeChargeForBadAndDoubtfulDebts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-22": {
   "value": "2100000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:OperatingCostsBeforeChargeForBadAndDoubtfulDebts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-23": {
   "value": "1316500000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:OperatingCostsBeforeChargeForBadAndDoubtfulDebts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-24": {
   "value": "24600000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ChargeForBadAndDoubtfulDebts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-25": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ChargeForBadAndDoubtfulDebts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-26": {
   "value": "24600000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ChargeForBadAndDoubtfulDebts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-27": {
   "value": "40000000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ChargeForBadAndDoubtfulDebts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-28": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ChargeForBadAndDoubtfulDebts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-29": {
   "value": "40000000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ChargeForBadAndDoubtfulDebts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-30": {
   "value": "1440300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OperatingExpense",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-31": {
   "value": "2100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OperatingExpense",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-32": {
   "value": "1442400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OperatingExpense",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-33": {
   "value": "1354400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OperatingExpense",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-34": {
   "value": "2100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OperatingExpense",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-35": {
   "value": "1356500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OperatingExpense",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-36": {
   "value": "508300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLossFromOperatingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-37": {
   "value": "-2100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLossFromOperatingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-38": {
   "value": "506200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLossFromOperatingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-39": {
   "value": "472800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLossFromOperatingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-40": {
   "value": "-2100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLossFromOperatingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-41": {
   "value": "470700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLossFromOperatingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-42": {
   "value": "54700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-43": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-44": {
   "value": "54700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-45": {
   "value": "59800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-46": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-47": {
   "value": "59800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-48": {
   "value": "324100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceCosts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-49": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceCosts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-50": {
   "value": "324100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceCosts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-51": {
   "value": "246900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceCosts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-52": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceCosts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-53": {
   "value": "246900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceCosts",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-54": {
   "value": "-269400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceIncomeCost",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-55": {
   "value": "-269400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceIncomeCost",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-56": {
   "value": "-187100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceIncomeCost",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-57": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceIncomeCost",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-58": {
   "value": "-187100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:FinanceIncomeCost",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-59": {
   "value": "200000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ReductionInExpectedCreditLossOnLoanReceivable",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-60": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ReductionInExpectedCreditLossOnLoanReceivable",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-61": {
   "value": "200000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ReductionInExpectedCreditLossOnLoanReceivable",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-62": {
   "value": "3600000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ReductionInExpectedCreditLossOnLoanReceivable",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-63": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ReductionInExpectedCreditLossOnLoanReceivable",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-64": {
   "value": "3600000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ReductionInExpectedCreditLossOnLoanReceivable",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-65": {
   "value": "39300000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:NetGainsLossesOnFinancialInstruments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-66": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:NetGainsLossesOnFinancialInstruments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-67": {
   "value": "39300000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:NetGainsLossesOnFinancialInstruments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-68": {
   "value": "-6200000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:NetGainsLossesOnFinancialInstruments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-69": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:NetGainsLossesOnFinancialInstruments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-70": {
   "value": "-6200000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:NetGainsLossesOnFinancialInstruments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-71": {
   "value": "-2200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ShareOfProfitLossOfJointVenturesAccountedForUsingEquityMethod",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-72": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ShareOfProfitLossOfJointVenturesAccountedForUsingEquityMethod",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-73": {
   "value": "-2200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ShareOfProfitLossOfJointVenturesAccountedForUsingEquityMethod",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-74": {
   "value": "-8900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ShareOfProfitLossOfJointVenturesAccountedForUsingEquityMethod",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-75": {
   "value": "-4900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ShareOfProfitLossOfJointVenturesAccountedForUsingEquityMethod",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-76": {
   "value": "-13800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ShareOfProfitLossOfJointVenturesAccountedForUsingEquityMethod",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-77": {
   "value": "276200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLossBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-78": {
   "value": "-2100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLossBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-79": {
   "value": "274100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLossBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-80": {
   "value": "274200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLossBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-81": {
   "value": "-7000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLossBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-82": {
   "value": "267200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLossBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-83": {
   "value": "-4800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentTaxExpenseIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-84": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentTaxExpenseIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-85": {
   "value": "-4800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentTaxExpenseIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-86": {
   "value": "26800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentTaxExpenseIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-87": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentTaxExpenseIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-88": {
   "value": "26800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentTaxExpenseIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-89": {
   "value": "71700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DeferredTaxExpenseIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-90": {
   "value": "294400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DeferredTaxExpenseIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-91": {
   "value": "366100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DeferredTaxExpenseIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-92": {
   "value": "28200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DeferredTaxExpenseIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-93": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DeferredTaxExpenseIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-94": {
   "value": "28200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DeferredTaxExpenseIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-95": {
   "value": "66900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxExpenseContinuingOperations",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-96": {
   "value": "294400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxExpenseContinuingOperations",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-97": {
   "value": "361300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxExpenseContinuingOperations",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-98": {
   "value": "55000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxExpenseContinuingOperations",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-99": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxExpenseContinuingOperations",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-100": {
   "value": "55000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxExpenseContinuingOperations",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-101": {
   "value": "209300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-102": {
   "value": "-296500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-103": {
   "value": "-87200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-104": {
   "value": "219200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustedMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-105": {
   "value": "-7000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "severntrentplc:ConsolidatedIncomeStatementAxis": "severntrentplc:AdjustingItemsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-106": {
   "value": "212200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-107": {
   "value": "0",
   "decimals": 3,
   "dimensions": {
    "concept": "ifrs-full:BasicEarningsLossPerShare",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP/xbrli:shares"
   }
  },
  "fact-108": {
   "value": "0.891",
   "decimals": 3,
   "dimensions": {
    "concept": "ifrs-full:BasicEarningsLossPerShare",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP/xbrli:shares"
   }
  },
  "fact-109": {
   "value": "0",
   "decimals": 3,
   "dimensions": {
    "concept": "ifrs-full:DilutedEarningsLossPerShare",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP/xbrli:shares"
   }
  },
  "fact-110": {
   "value": "0.886",
   "decimals": 3,
   "dimensions": {
    "concept": "ifrs-full:DilutedEarningsLossPerShare",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP/xbrli:shares"
   }
  },
  "fact-111": {
   "value": "-87200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-112": {
   "value": "212200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-113": {
   "value": "188500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-114": {
   "value": "-162000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-115": {
   "value": "47100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-116": {
   "value": "-30800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-117": {
   "value": "-8400000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxArisingOnRateChange",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-118": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxArisingOnRateChange",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-119": {
   "value": "149800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeThatWillNotBeReclassifiedToProfitOrLossNetOfTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-120": {
   "value": "-131200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeThatWillNotBeReclassifiedToProfitOrLossNetOfTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-121": {
   "value": "54600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-122": {
   "value": "33500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-123": {
   "value": "13000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-124": {
   "value": "6300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-125": {
   "value": "-6800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-126": {
   "value": "-8200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-127": {
   "value": "1700000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnTransferToTheIncomeStatement",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-128": {
   "value": "1600000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnTransferToTheIncomeStatement",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-129": {
   "value": "46700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeThatWillBeReclassifiedToProfitOrLossNetOfTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-130": {
   "value": "33800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeThatWillBeReclassifiedToProfitOrLossNetOfTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-131": {
   "value": "196500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-132": {
   "value": "-97400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-133": {
   "value": "109300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-134": {
   "value": "114800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-135": {
   "value": "236500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-136": {
   "value": "137000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-137": {
   "value": "67900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-138": {
   "value": "802300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-139": {
   "value": "1243700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-140": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-141": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-142": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-143": {
   "value": "212200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-144": {
   "value": "212200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-145": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-146": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-147": {
   "value": "33500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-148": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-149": {
   "value": "33500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-150": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-151": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-152": {
   "value": "6300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-153": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-154": {
   "value": "6300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-155": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-156": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-157": {
   "value": "-8200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-158": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-159": {
   "value": "-8200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-160": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnTransferToTheIncomeStatement",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-161": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnTransferToTheIncomeStatement",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-162": {
   "value": "1600000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnTransferToTheIncomeStatement",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-163": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnTransferToTheIncomeStatement",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-164": {
   "value": "1600000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnTransferToTheIncomeStatement",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-165": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-166": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-167": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-168": {
   "value": "-162000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-169": {
   "value": "-162000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-170": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-171": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-172": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-173": {
   "value": "-30800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-174": {
   "value": "-30800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-175": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-176": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-177": {
   "value": "33800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-178": {
   "value": "81000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-179": {
   "value": "114800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-180": {
   "value": "700000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsProceedsFromSharesIssued",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-181": {
   "value": "11100000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsProceedsFromSharesIssued",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-182": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsProceedsFromSharesIssued",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-183": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsProceedsFromSharesIssued",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-184": {
   "value": "11800000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsProceedsFromSharesIssued",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-185": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsValueOfEmployeesServices",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-186": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsValueOfEmployeesServices",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-187": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsValueOfEmployeesServices",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-188": {
   "value": "7800000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsValueOfEmployeesServices",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-189": {
   "value": "7800000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsValueOfEmployeesServices",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-190": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:CurrentTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-191": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:CurrentTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-192": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:CurrentTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-193": {
   "value": "-400000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:CurrentTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-194": {
   "value": "-400000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:CurrentTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-195": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-196": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-197": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-198": {
   "value": "-400000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-199": {
   "value": "-400000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-200": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DividendsPaid",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-201": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DividendsPaid",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-202": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DividendsPaid",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-203": {
   "value": "240200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DividendsPaid",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-204": {
   "value": "240200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DividendsPaid",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-205": {
   "value": "237200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-206": {
   "value": "148100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-207": {
   "value": "101700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-208": {
   "value": "651700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-209": {
   "value": "1138700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-210": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-211": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-212": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-213": {
   "value": "-87200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-214": {
   "value": "-87200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProfitLoss",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-215": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-216": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-217": {
   "value": "54600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-218": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-219": {
   "value": "54600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:GainsLossesOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-220": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-221": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-222": {
   "value": "13000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-223": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-224": {
   "value": "13000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToCashFlowHedgesOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-225": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-226": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-227": {
   "value": "-6800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-228": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-229": {
   "value": "-6800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ReclassificationAdjustmentsOnCashFlowHedgesBeforeTax",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-230": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnTransferToTheIncomeStatement",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-231": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnTransferToTheIncomeStatement",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-232": {
   "value": "1700000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnTransferToTheIncomeStatement",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-233": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnTransferToTheIncomeStatement",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-234": {
   "value": "1700000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnTransferToTheIncomeStatement",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-235": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-236": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-237": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-238": {
   "value": "188500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-239": {
   "value": "188500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherComprehensiveIncomeBeforeTaxGainsLossesOnRemeasurementsOfDefinedBenefitPlans",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-240": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-241": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-242": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-243": {
   "value": "47100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-244": {
   "value": "47100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxRelatingToRemeasurementsOfDefinedBenefitPlansOfOtherComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-245": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxArisingFromRateChange",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-246": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxArisingFromRateChange",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-247": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxArisingFromRateChange",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-248": {
   "value": "-8400000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxArisingFromRateChange",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-249": {
   "value": "-8400000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxArisingFromRateChange",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-250": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-251": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-252": {
   "value": "46700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-253": {
   "value": "62600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-254": {
   "value": "109300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ComprehensiveIncome",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-255": {
   "value": "10200000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ProceedsFromEquityPlacing",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-256": {
   "value": "235100000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ProceedsFromEquityPlacing",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-257": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ProceedsFromEquityPlacing",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-258": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ProceedsFromEquityPlacing",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-259": {
   "value": "245300000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ProceedsFromEquityPlacing",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-260": {
   "value": "700000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsProceedsFromSharesIssued",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-261": {
   "value": "11200000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsProceedsFromSharesIssued",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-262": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsProceedsFromSharesIssued",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-263": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsProceedsFromSharesIssued",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-264": {
   "value": "11900000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsProceedsFromSharesIssued",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-265": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsValueOfEmployeesServices",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-266": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsValueOfEmployeesServices",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-267": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsValueOfEmployeesServices",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-268": {
   "value": "8300000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsValueOfEmployeesServices",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-269": {
   "value": "8300000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ShareOptionsAndLTIPsValueOfEmployeesServices",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-270": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-271": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-272": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-273": {
   "value": "-4900000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-274": {
   "value": "-4900000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:DeferredTaxOnShareBasedPayments",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-275": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DividendsPaid",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-276": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DividendsPaid",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-277": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DividendsPaid",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-278": {
   "value": "254500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DividendsPaid",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-279": {
   "value": "254500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DividendsPaid",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-280": {
   "value": "248100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:IssuedCapitalMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-281": {
   "value": "394400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:SharePremiumMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-282": {
   "value": "148400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:OtherReservesMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-283": {
   "value": "473000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "ifrs-full:ComponentsOfEquityAxis": "ifrs-full:RetainedEarningsMember",
    "unit": "iso4217:GBP"
   }
  },
  "fact-284": {
   "value": "1263900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-285": {
   "value": "91400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Goodwill",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-286": {
   "value": "91400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Goodwill",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-287": {
   "value": "179600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IntangibleAssetsOtherThanGoodwill",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-288": {
   "value": "164000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IntangibleAssetsOtherThanGoodwill",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-289": {
   "value": "10208400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:PropertyPlantAndEquipment",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-290": {
   "value": "9875200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:PropertyPlantAndEquipment",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-291": {
   "value": "129900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:RightofuseAssets",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-292": {
   "value": "130800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:RightofuseAssets",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-293": {
   "value": "16500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:InvestmentsInJointVentures",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-294": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:InvestmentsInJointVentures",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-295": {
   "value": "31200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentDerivativeFinancialAssets",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-296": {
   "value": "37100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentDerivativeFinancialAssets",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-297": {
   "value": "92100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentReceivables",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-298": {
   "value": "101500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentReceivables",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-299": {
   "value": "17500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentRecognisedAssetsDefinedBenefitPlan",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-300": {
   "value": "17100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentRecognisedAssetsDefinedBenefitPlan",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-301": {
   "value": "10766600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentAssets",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-302": {
   "value": "10417100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentAssets",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-303": {
   "value": "32000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Inventories",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-304": {
   "value": "30800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Inventories",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-305": {
   "value": "606400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:TradeAndOtherCurrentReceivables",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-306": {
   "value": "515200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:TradeAndOtherCurrentReceivables",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-307": {
   "value": "6200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentTaxAssets",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-308": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentTaxAssets",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-309": {
   "value": "27600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentDerivativeFinancialAssets",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-310": {
   "value": "3800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentDerivativeFinancialAssets",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-311": {
   "value": "115400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashAndCashEquivalents",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-312": {
   "value": "56200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashAndCashEquivalents",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-313": {
   "value": "787600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentAssets",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-314": {
   "value": "606000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentAssets",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-315": {
   "value": "365200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ShorttermBorrowings",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-316": {
   "value": "503100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ShorttermBorrowings",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-317": {
   "value": "655500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:TradeAndOtherCurrentPayables",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-318": {
   "value": "557100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:TradeAndOtherCurrentPayables",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-319": {
   "value": "-0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentTaxLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-320": {
   "value": "200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentTaxLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-321": {
   "value": "38400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentProvisions",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-322": {
   "value": "18000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentProvisions",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-323": {
   "value": "1059100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-324": {
   "value": "1078400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-325": {
   "value": "-271500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentAssetsLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-326": {
   "value": "-472400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CurrentAssetsLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-327": {
   "value": "10495100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:AssetsLessCurrentLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-328": {
   "value": "9944700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:AssetsLessCurrentLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-329": {
   "value": "6365900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentPortionOfOtherNoncurrentBorrowings",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-330": {
   "value": "6112800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentPortionOfOtherNoncurrentBorrowings",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-331": {
   "value": "43300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentDerivativeFinancialLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-332": {
   "value": "126900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentDerivativeFinancialLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-333": {
   "value": "1334000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentPayables",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-334": {
   "value": "1250300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentPayables",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-335": {
   "value": "1320600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DeferredTaxLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-336": {
   "value": "906000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DeferredTaxLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-337": {
   "value": "145500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentRecognisedLiabilitiesDefinedBenefitPlan",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-338": {
   "value": "384800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentRecognisedLiabilitiesDefinedBenefitPlan",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-339": {
   "value": "21900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentProvisions",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-340": {
   "value": "25200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentProvisions",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-341": {
   "value": "9231200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-342": {
   "value": "8806000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NoncurrentLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-343": {
   "value": "1263900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NetAssetsLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-344": {
   "value": "1138700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:NetAssetsLiabilities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-345": {
   "value": "248100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IssuedCapital",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-346": {
   "value": "237200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IssuedCapital",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-347": {
   "value": "394400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:SharePremium",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-348": {
   "value": "148100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:SharePremium",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-349": {
   "value": "148400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherReserves",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-350": {
   "value": "101700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:OtherReserves",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-351": {
   "value": "473000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:RetainedEarnings",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-352": {
   "value": "651700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:RetainedEarnings",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-353": {
   "value": "1263900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-354": {
   "value": "1138700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:Equity",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-355": {
   "value": "891700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashFlowsFromUsedInOperations",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-356": {
   "value": "901700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashFlowsFromUsedInOperations",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-357": {
   "value": "1200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxesPaidRefundClassifiedAsOperatingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-358": {
   "value": "23200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncomeTaxesPaidRefundClassifiedAsOperatingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-359": {
   "value": "890500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashFlowsFromUsedInOperatingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-360": {
   "value": "878500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashFlowsFromUsedInOperatingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-361": {
   "value": "610300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:PurchaseOfPropertyPlantAndEquipmentClassifiedAsInvestingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-362": {
   "value": "613700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:PurchaseOfPropertyPlantAndEquipmentClassifiedAsInvestingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-363": {
   "value": "36300000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:PurchaseOfIntangibleAssetsClassifiedAsInvestingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-364": {
   "value": "22200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:PurchaseOfIntangibleAssetsClassifiedAsInvestingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-365": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:PaymentsToAcquireRightOfUseAssetsClassifiedAsOperatingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-366": {
   "value": "700000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:PaymentsToAcquireRightOfUseAssetsClassifiedAsOperatingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-367": {
   "value": "9500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProceedsFromSalesOfPropertyPlantAndEquipmentClassifiedAsInvestingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-368": {
   "value": "2000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProceedsFromSalesOfPropertyPlantAndEquipmentClassifiedAsInvestingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-369": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashFlowsFromLosingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-370": {
   "value": "700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashFlowsFromLosingControlOfSubsidiariesOrOtherBusinessesClassifiedAsInvestingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-371": {
   "value": "13000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashAdvancesAndLoansMadeToRelatedParties",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-372": {
   "value": "1000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashAdvancesAndLoansMadeToRelatedParties",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-373": {
   "value": "1900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:InterestReceivedClassifiedAsInvestingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-374": {
   "value": "3700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:InterestReceivedClassifiedAsInvestingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-375": {
   "value": "-648200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashFlowsFromUsedInInvestingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-376": {
   "value": "-631200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashFlowsFromUsedInInvestingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-377": {
   "value": "182900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:InterestPaidClassifiedAsFinancingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-378": {
   "value": "185600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:InterestPaidClassifiedAsFinancingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-379": {
   "value": "4000000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:InterestElementOfLeasePaymentsClassifiedAsFinancingActitivites",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-380": {
   "value": "4300000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:InterestElementOfLeasePaymentsClassifiedAsFinancingActitivites",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-381": {
   "value": "254500000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DividendsPaidToEquityHoldersOfParentClassifiedAsFinancingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-382": {
   "value": "240200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:DividendsPaidToEquityHoldersOfParentClassifiedAsFinancingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-383": {
   "value": "488900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:RepaymentsOfBorrowingsClassifiedAsFinancingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-384": {
   "value": "242900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:RepaymentsOfBorrowingsClassifiedAsFinancingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-385": {
   "value": "12100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:PaymentsOfLeaseLiabilitiesClassifiedAsFinancingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-386": {
   "value": "5600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:PaymentsOfLeaseLiabilitiesClassifiedAsFinancingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-387": {
   "value": "501000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProceedsFromBorrowingsClassifiedAsFinancingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-388": {
   "value": "415100000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProceedsFromBorrowingsClassifiedAsFinancingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-389": {
   "value": "257200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProceedsFromIssuingShares",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-390": {
   "value": "11800000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ProceedsFromIssuingShares",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-391": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:PaymentsForSwapTerminationsClassifiedAsFinancingActitivites",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-392": {
   "value": "1100000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:PaymentsForSwapTerminationsClassifiedAsFinancingActitivites",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-393": {
   "value": "5600000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ProceedsFromSwapTerminationsClassifiedAsFinancingActitivites",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-394": {
   "value": "900000",
   "decimals": -5,
   "dimensions": {
    "concept": "severntrentplc:ProceedsFromSwapTerminationsClassifiedAsFinancingActitivites",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-395": {
   "value": "-178600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashFlowsFromUsedInFinancingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-396": {
   "value": "-251900000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashFlowsFromUsedInFinancingActivities",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-397": {
   "value": "63700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncreaseDecreaseInCashAndCashEquivalents",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-398": {
   "value": "-4600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:IncreaseDecreaseInCashAndCashEquivalents",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00/2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-399": {
   "value": "44000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPosition",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-400": {
   "value": "48600000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPosition",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2020-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-401": {
   "value": "107700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPosition",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-402": {
   "value": "44000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPosition",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-403": {
   "value": "40400000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:BalancesWithBanks",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-404": {
   "value": "56200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:BalancesWithBanks",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-405": {
   "value": "7700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:BankOverdraftsClassifiedAsCashEquivalents",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-406": {
   "value": "12200000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:BankOverdraftsClassifiedAsCashEquivalents",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-407": {
   "value": "75000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ShorttermDepositsClassifiedAsCashEquivalents",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-408": {
   "value": "0",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:ShorttermDepositsClassifiedAsCashEquivalents",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-409": {
   "value": "107700000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPosition",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2022-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-410": {
   "value": "44000000",
   "decimals": -5,
   "dimensions": {
    "concept": "ifrs-full:CashAndCashEquivalentsIfDifferentFromStatementOfFinancialPosition",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00",
    "unit": "iso4217:GBP"
   }
  },
  "fact-412": {
   "value": "Severn Trent Plc",
   "dimensions": {
    "concept": "ifrs-full:NameOfParentEntity",
    "language": "en",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00"
   }
  },
  "fact-4": {
   "value": "Plc",
   "dimensions": {
    "concept": "ifrs-full:LegalFormOfEntity",
    "language": "en",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00"
   }
  },
  "fact-3": {
   "value": "United Kingdom",
   "dimensions": {
    "concept": "ifrs-full:CountryOfIncorporation",
    "language": "en",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00"
   }
  },
  "fact-411": {
   "value": "United Kingdom",
   "dimensions": {
    "concept": "ifrs-full:DomicileOfEntity",
    "language": "en",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00"
   }
  },
  "fact-5": {
   "value": "Severn Trent Centre2 St John\u2019s StreetCoventryCV1 2LZ",
   "dimensions": {
    "concept": "ifrs-full:AddressOfRegisteredOfficeOfEntity",
    "language": "en",
    "entity": "scheme:213800RPBXRETY4A4C59",
    "period": "2021-04-01T00:00:00/2022-04-01T00:00:00"
   }
  }
 }
}