Summary Of Significant Accounting Policies (Components Of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 67,381	$ (293,746)	$ (55,060)	$ (625,733)
Other Comprehensive Gains and Losses Before Reclassifications	51,418	225,150	188,099	441,367
Amounts Reclassified From Other Comprehensive Income	(43,459)	13,732	(57,699)	129,502
Ending balance	75,340	(54,864)	75,340	(54,864)
Gains and Losses on Derivative Financial Instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	127,064	(240,176)	4,623	(572,163)
Other Comprehensive Gains and Losses Before Reclassifications	51,418	225,150	188,099	441,367
Amounts Reclassified From Other Comprehensive Income	(43,459)	13,732	(57,699)	129,502
Ending balance	135,023	(1,294)	135,023	(1,294)
Funded Status of the Pension and Other Post-Retirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(59,683)	(53,570)	(59,683)	(53,570)
Other Comprehensive Gains and Losses Before Reclassifications	0	0	0	0
Amounts Reclassified From Other Comprehensive Income	0	0	0	0
Ending balance	$ (59,683)	$ (53,570)	$ (59,683)	$ (53,570)