Income Taxes (Significant Components Of Deferred Tax Liabilities And Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Deferred Tax Liabilities [Abstract]
Property, Plant and Equipment	$ 920,692	$ 874,607
Pension and Other Post-Retirement Benefit Costs	23,240	54,066
Other	35,081	23,377
Total Deferred Tax Liabilities	979,013	952,050
Deferred Tax Assets [Abstract]
OCI Hedging	(170,155)	(9,546)
Tax Loss and Credit Carryforwards	(120,725)	(179,363)
Pension and Other Post-Retirement Benefit Costs	(53,765)	(95,599)
Other	(31,593)	(34,693)
Total Gross Deferred Tax Assets	(376,238)	(319,201)
Valuation Allowance	57,645	63,205	$ 0	$ 5,000
Total Deferred Tax Assets	(318,593)	(255,996)
Total Net Deferred Income Taxes	$ 660,420	$ 696,054