Statement Of Comprehensive Income [Abstract]

Severn Trent PLC - Filing #1912150

Concept	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	2021-04-01 to 2022-03-31	2021-04-01 to 2022-03-31	2021-04-01 to 2022-03-31	2021-04-01 to 2022-03-31	2021-04-01 to 2022-03-31
Statement of comprehensive income [abstract]
Profit (loss)	– GBP	– GBP	– GBP	132,200,000 GBP	132,200,000 GBP	– GBP	87,200,000 GBP	– GBP	– GBP	87,200,000 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	– GBP	– GBP	252,200,000 GBP	252,200,000 GBP	– GBP	188,500,000 GBP	– GBP	– GBP	188,500,000 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	2,500,000 GBP	– GBP	– GBP	– GBP	2,500,000 GBP	– GBP	– GBP	54,600,000 GBP	– GBP	54,600,000 GBP
Reclassification adjustments on cash flow hedges, before tax	4,900,000 GBP	– GBP	– GBP	– GBP	4,900,000 GBP	– GBP	– GBP	6,800,000 GBP	– GBP	6,800,000 GBP
Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss [abstract]
Income tax relating to remeasurements of defined benefit plans included in other comprehensive income	– GBP	– GBP	– GBP	63,000,000 GBP	63,000,000 GBP	– GBP	47,100,000 GBP	– GBP	– GBP	47,100,000 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	600,000 GBP	– GBP	– GBP	– GBP	600,000 GBP	– GBP	– GBP	13,000,000 GBP	– GBP	13,000,000 GBP
Other comprehensive income	—	—	—	—	187,300,000 GBP	—	—	—	—	196,500,000 GBP
Comprehensive income	1,900,000 GBP	– GBP	– GBP	57,000,000 GBP	55,100,000 GBP	– GBP	62,600,000 GBP	46,700,000 GBP	– GBP	109,300,000 GBP