Summary of Significant Accounting Policies - Schedule of Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 2,592,051	$ 3,388,189	$ 2,547,142
Cash, cash equivalents, and restricted cash	2,752,889	3,593,539	3,070,128	$ 4,597,746
Restricted cash (included in Prepaid Expenses and Other)
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	97,722	144,980	462,986
Restricted cash (included in Other Assets)
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 63,116	$ 60,370	$ 60,000