Statement Of Comprehensive Income [Abstract]

United Utilities Group PLC - Filing #5473421

Concept	2023-04-01 to 2024-03-31	2023-04-01 to 2024-03-31	2023-04-01 to 2024-03-31	2023-04-01 to 2024-03-31	2023-04-01 to 2024-03-31	2022-04-01 to 2023-03-31	2022-04-01 to 2023-03-31	2022-04-01 to 2023-03-31	2022-04-01 to 2023-03-31	2022-04-01 to 2023-03-31
Statement of comprehensive income [abstract]
Profit (loss)	– GBP	126,900,000 GBP	– GBP	– GBP	126,900,000 GBP	– GBP	– GBP	204,900,000 GBP	– GBP	204,900,000 GBP
Other comprehensive income [abstract]
Components of other comprehensive income that will not be reclassified to profit or loss, before tax [abstract]
Other comprehensive income, before tax, gains (losses) on remeasurements of defined benefit plans	– GBP	368,500,000 GBP	– GBP	– GBP	368,500,000 GBP	– GBP	– GBP	445,300,000 GBP	– GBP	445,300,000 GBP
Other comprehensive income, before tax, change in fair value of financial liability attributable to change in credit risk of liability	– GBP	700,000 GBP	– GBP	– GBP	700,000 GBP	– GBP	– GBP	4,800,000 GBP	– GBP	4,800,000 GBP
Components of other comprehensive income that will be reclassified to profit or loss, before tax [abstract]
Cash flow hedges [abstract]
Gains (losses) on cash flow hedges, before tax	63,000,000 GBP	63,000,000 GBP	– GBP	– GBP	– GBP	50,600,000 GBP	– GBP	– GBP	– GBP	50,600,000 GBP
Reclassification adjustments on cash flow hedges, before tax	1,800,000 GBP	1,800,000 GBP	– GBP	– GBP	– GBP	36,600,000 GBP	– GBP	– GBP	– GBP	36,600,000 GBP
Cost of hedging [abstract]
Change in value of foreign currency basis spreads [abstract]
Other comprehensive income, before tax, change in value of foreign currency basis spreads	4,800,000 GBP	4,800,000 GBP	– GBP	– GBP	– GBP	6,300,000 GBP	– GBP	– GBP	– GBP	6,300,000 GBP
Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss [abstract]
Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss	—	151,100,000 GBP	—	—	—	—	—	—	—	151,500,000 GBP
Income tax relating to components of other comprehensive income that will be reclassified to profit or loss [abstract]
Income tax relating to cash flow hedges included in other comprehensive income	—	15,800,000 GBP	—	—	—	—	—	—	—	12,700,000 GBP
Income tax relating to components of other comprehensive income that will be reclassified to profit or loss	500,000 GBP	500,000 GBP	– GBP	– GBP	– GBP	7,000,000 GBP	– GBP	– GBP	– GBP	7,000,000 GBP
Comprehensive income	42,300,000 GBP	130,900,000 GBP	– GBP	– GBP	88,600,000 GBP	62,800,000 GBP	– GBP	82,500,000 GBP	– GBP	145,300,000 GBP