Summary Of Significant Accounting Policies (Components Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at Beginning of Period	$ (293,746)	$ (277,026)	$ (625,733)	$ (513,597)
Other Comprehensive Gains and Losses Before Reclassifications	225,150	(466,001)	441,367	(347,518)
Amounts Reclassified From Other Comprehensive Income (Loss)	13,732	94,580	129,502	212,668
Other Post-Retirement Adjustment for Regulatory Proceeding		(5,807)		(5,807)
Balance at End of Period	(54,864)	(654,254)	(54,864)	(654,254)
Gains And Losses On Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at Beginning of Period	(240,176)	(213,391)	(572,163)	(449,962)
Other Comprehensive Gains and Losses Before Reclassifications	225,150	(466,001)	441,367	(347,518)
Amounts Reclassified From Other Comprehensive Income (Loss)	13,732	94,580	129,502	212,668
Other Post-Retirement Adjustment for Regulatory Proceeding		0		0
Balance at End of Period	(1,294)	(584,812)	(1,294)	(584,812)
Funded Status Of The Pension And Other Post-Retirement Benefit Plans [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at Beginning of Period	(53,570)	(63,635)	(53,570)	(63,635)
Other Comprehensive Gains and Losses Before Reclassifications	0	0	0	0
Amounts Reclassified From Other Comprehensive Income (Loss)	0	0	0	0
Other Post-Retirement Adjustment for Regulatory Proceeding		(5,807)		(5,807)
Balance at End of Period	$ (53,570)	$ (69,442)	$ (53,570)	$ (69,442)