Derivative Instruments and Hedging Activities - Schedule of Notional Amounts (Details) € in Millions, kWh in Millions, gal in Millions, DTH in Millions, $ in Millions	Jun. 30, 2022 USD ($) DTH kWh gal	Jun. 30, 2022 EUR (€) DTH kWh gal	Sep. 30, 2021 USD ($) gal DTH kWh	Sep. 30, 2021 EUR (€) gal DTH kWh	Jun. 30, 2021 USD ($) gal kWh DTH	Jun. 30, 2021 EUR (€) gal kWh DTH
Commodity contracts | Regulated Utility Operations | Natural Gas
Derivative [Line Items]
Notional amount (in units)	13	13	20	20	12	12
Commodity contracts | Non-utility Operations | LPG
Derivative [Line Items]
Notional amount (in units) | gal	669	669	708	708	688	688
Commodity contracts | Non-utility Operations | Electricity
Derivative [Line Items]
Notional amount (in units) | kWh	2,621	2,621	4,302	4,302	4,730	4,730
Natural gas futures, forward and pipeline contracts (in dekatherms) | Non-utility Operations | Natural Gas
Derivative [Line Items]
Notional amount (in units)	353	353	355	355	344	344
Interest rate swaps
Derivative [Line Items]
Notional amount	$ 1,411	€ 300	$ 1,421	€ 300	$ 1,424	€ 300
Forward foreign currency exchange contracts
Derivative [Line Items]
Notional amount	$ 435	€ 411	$ 509	€ 173	$ 504	€ 173