Summary of Significant Accounting Policies - Schedule of Cash and Restricted Cash (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023	Mar. 31, 2023	Sep. 30, 2022
Accounting Policies [Abstract]
Cash and cash equivalents	$ 263	$ 241	$ 321
Restricted cash	45	99	82
Cash, cash equivalents and restricted cash	$ 308	$ 340	$ 403	$ 469