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Nominal number of units used to calculate payment on derivative.

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Nominal energy measure used to calculate payments on a derivative instrument.

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Nominal volume used to calculate payments on a derivative instrument.

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Nominal or face amount used to calculate payment on derivative.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
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-Section 50
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Derivative Instruments and Hedging Activities - Schedule of Notional Amounts (Details) € in Millions, kWh in Millions, gal in Millions, DTH in Millions, $ in Millions	6 Months Ended		12 Months Ended
	Mar. 31, 2025 USD ($) DTH kWh gal	Mar. 31, 2024 USD ($) DTH kWh gal	Sep. 30, 2024 USD ($) DTH kWh gal	Mar. 31, 2025 EUR (€) DTH	Sep. 30, 2024 EUR (€) DTH	Mar. 31, 2024 EUR (€) DTH
Commodity contracts \| Regulated Utility Operations \| Natural Gas
Derivative [Line Items]
Notional amount (in units)	18	13	26	18	26	13
Commodity contracts \| Non-utility Operations \| LPG swaps
Derivative [Line Items]
LPG swaps (in gallons) \| gal	414	425	458
Commodity contracts \| Non-utility Operations \| Electricity forward and futures contracts
Derivative [Line Items]
Electricity forward and futures contracts (in kilowatt hours) \| kWh	842	544	1,113
Natural gas futures, forward, basis swap, options and pipeline contracts \| Non-utility Operations \| Natural Gas
Derivative [Line Items]
Notional amount (in units)	266	339	325	266	325	339
Interest rate swaps
Derivative [Line Items]
Notional amount	$ 1,224	$ 1,263	$ 1,231	€ 300	€ 300	€ 300
Forward foreign currency exchange contracts
Derivative [Line Items]
Notional amount	$ 202	$ 240	$ 389	€ 181	€ 181	€ 256