Income Taxes (Schedule Of Income Tax Reconciliation By Applying Federal Income Tax Rate) (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
U.S. Income (Loss) Before Income Taxes	[1]	$ 682,650	$ 478,327	$ (105,046)
Income Tax Expense (Benefit), Computed at U.S. Federal Statutory Rate of 21%		143,357	100,449	(22,060)
State Valuation Allowance	[2]	(24,850)	(5,560)	63,205
State Income Taxes (Benefit)	[3]	8,736	24,300	(18,374)
Amortization of Excess Deferred Federal Income Taxes		(5,184)	(5,215)	(4,749)
Plant Flow Through Items		(814)	(1,503)	(2,848)
Stock Compensation		820	2,239	3,867
Federal Tax Credits		(5,701)	(310)	(217)
Miscellaneous		265	282	(85)
Total Income Taxes		$ 116,629	$ 114,682	$ 18,739
Federal Statutory Rate		21.00%	21.00%	21.00%

[1] Amounts include the impact of deferred investment tax credits reported in Other Income (Deductions) on the Consolidated Statements of Income.

[2] During fiscal 2020, a valuation allowance was recorded against certain state deferred tax assets. During fiscal 2022, the valuation allowance was removed. See discussion below.

[3] The state income tax expense (benefit) shown above includes adjustments to the estimated state effective tax rates utilized in the calculation of deferred income taxes, including the Pennsylvania rate change discussed above.