Income Taxes (Tables)

12 Months Ended

Sep. 30, 2025

Income Tax Disclosure [Abstract]

Schedule of Components of Federal and State Income Taxes Included in the Consolidated Statements of Income

The components of federal and state income taxes included in the Consolidated Statements of Income are as follows:

	Year Ended September 30
	2025		2024		2023
	(Thousands)
Current Income Taxes —
Federal	$	42,089	$	6,453	$	11,744
State	12,186		5,899		1,386
Deferred Income Taxes —
Federal	90,881		894		106,801
State	30,393		(3,504)		44,602
Total Income Taxes	$	175,549	$	9,742	$	164,533

Schedule of Income Tax Reconciliation by Applying Federal Income Tax Rate

The following is a reconciliation of this difference:

	Year Ended September 30
	2025		2024		2023
	(Thousands)
U.S. Income Before Income Taxes	$	694,053	$	87,255	$	641,399
Income Tax Expense, Computed at U.S. Federal Statutory Rate of 21%	$	145,751	$	18,324	$	134,694
State Income Taxes	33,637		1,892		36,331
Amortization of Excess Deferred Federal Income Taxes	(4,617)		(5,607)		(6,053)
Plant Flow Through Items	(5,070)		(6,135)		(2,856)
Stock Compensation	2,245		1,758		957
Miscellaneous	3,603		(490)		1,460
Total Income Taxes	$	175,549	$	9,742	$	164,533

Schedule of Significant Components of Deferred Tax Liabilities and Assets

Significant components of the Company’s deferred tax liabilities and assets were as follows:

	At September 30
	2025		2024
	(Thousands)
Deferred Tax Liabilities:
Unrealized Hedging Gains	$	9,036	$	22,433
Property, Plant and Equipment	1,222,869		1,134,727
Pension and Other Post-Retirement Benefit Costs	72,691		59,877
Other	24,531		13,885
Total Deferred Tax Liabilities	1,329,127		1,230,922
Deferred Tax Assets:
Tax Loss and Credit Carryforwards	(28,364)		(31,111)
Pension and Other Post-Retirement Benefit Costs	(54,071)		(49,622)
Other	(21,430)		(39,024)
Total Deferred Tax Assets	(103,865)		(119,757)
Total Net Deferred Income Taxes	$	1,225,262	$	1,111,165

Schedule of Operating Loss and Tax Credit Carryforwards

Tax carryforwards available at September 30, 2025, were as follows:

Jurisdiction	Tax Attribute	Amount (Thousands)		Expires
Pennsylvania	Net Operating Loss	$	422,900	2031-2045