Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Tax at statutory rate	$ 178,901	$ 172,053	$ 156,827
Common stock dividends deductible for tax reporting	(1,355)	(1,372)	(1,419)
State taxes (net of federal benefit)	24,669	19,647	22,791
Amortization of excess deferred taxes	(127,193)	(45,382)	(16,125)
Remeasurement due to state deferred tax rate change	0	0	(20,962)
Other, net	2,488	8,790	4,241
Income tax expense (benefit)	$ 77,510	$ 153,736	$ 145,353