Supplemental Financial Information - Summary of Accounts Receivable (Details) - USD ($)	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Supplemental Financial Information [Abstract]
Trade	$ 389,000,000		$ 392,000,000
Other	13,000,000		15,000,000
Trade	402,000,000		407,000,000
Accounts Receivable, Allowance for Credit Loss, Current	7,000,000		6,000,000
Accounts receivable, net	395,000,000		$ 401,000,000
Accounts receivable sold to financial institutions	$ 0	$ 28,000,000