Debt - Schedule of Receivables Facility (Details) - Energy Services - Receivables Facility - Energy Services Receivables Facility - USD ($)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Short-term Debt [Line Items]
Trade receivables transferred to ESFC during the year	$ 1,946,000,000	$ 2,221,000,000	$ 1,353,000,000
ESFC trade receivables sold to the bank during the year	535,000,000	152,000,000	308,000,000
ESFC trade receivables - end of year	62,000,000	101,000,000	$ 61,000,000
Outstanding balance of trade receivables sold	$ 46,000,000	$ 0