Revenue from Contracts with Customers - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Change in Contract with Customer, Liability [Roll Forward]
Balance, beginning of year	$ 1,775,121	$ 1,691,580	$ 1,489,842
Amounts added but not recognized as revenues	1,179,350	1,162,698	1,167,143
Deferred revenue acquired through acquisition of businesses	0	1,800	10,591
Revenues recognized related to the opening balance of deferred revenue	(1,156,512)	(1,080,957)	(975,996)
Balance, end of year	$ 1,797,959	$ 1,775,121	$ 1,691,580