Debt - Schedule of Receivables Facility (Details) - Energy Services Receivables Facility - Receivables Facility - Energy Services - USD ($)	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Short-term Debt [Line Items]
Trade receivables transferred to ESFC during the year	$ 1,324,000,000	$ 1,946,000,000	$ 2,221,000,000
ESFC trade receivables sold to the bank during the year	336,000,000	535,000,000	152,000,000
ESFC trade receivables - end of year	51,000,000	62,000,000	$ 101,000,000
Outstanding balance of trade receivables sold	$ 0	$ 46,000,000