Debt - Narrative (Details) - USD ($)	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022
Debt Instrument [Line Items]
Long-term debt, excluding finance lease liabilities	$ 3,891,000,000	$ 3,900,000,000
Fair value
Debt Instrument [Line Items]
Long-term debt, excluding finance lease liabilities	3,200,000,000	3,300,000,000
Carrying value
Debt Instrument [Line Items]
Long-term debt, excluding finance lease liabilities	$ 3,800,000,000	$ 3,800,000,000
Secured debt | Term Loan Payable, USD, Due 2025
Debt Instrument [Line Items]
Face amount			$ 500,000,000