Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Tax at statutory rate	$ 209,925	$ 178,901	$ 172,053
Common stock dividends deductible for tax reporting	(1,355)	(1,355)	(1,372)
State taxes (net of federal benefit)	25,129	24,669	19,647
Amortization of excess deferred taxes	(123,953)	(127,193)	(45,382)
Other, net	4,033	2,488	8,790
Income tax expense	$ 113,779	$ 77,510	$ 153,736