Summary Of Significant Accounting Policies (Components Of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income [Roll Forward]
Balance at Beginning of Period	$ (54,859)	$ 98,456	$ (5,640)	$ 93,372
Other Comprehensive Gains and Losses Before Reclassification	26,826	19,590	(4,162)	63,838
Amounts Reclassified From Other Comprehensive Income (Loss)	(6,058)	(35,860)	(24,289)	(75,024)
Balance at End of Period	(34,091)	82,186	(34,091)	82,186
Gains And Losses On Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Balance at Beginning of Period	16,570	162,728	64,782	157,197
Other Comprehensive Gains and Losses Before Reclassification	25,745	19,578	(4,705)	64,273
Amounts Reclassified From Other Comprehensive Income (Loss)	(6,058)	(35,635)	(23,820)	(74,799)
Balance at End of Period	36,257	146,671	36,257	146,671
Gains And Losses On Securities Available For Sale [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Balance at Beginning of Period	5,047	5,522	6,054	5,969
Other Comprehensive Gains and Losses Before Reclassification	1,081	12	543	(435)
Amounts Reclassified From Other Comprehensive Income (Loss)	0	(225)	(469)	(225)
Balance at End of Period	6,128	5,309	6,128	5,309
Funded Status Of The Pension And Other Post-Retirement Benefit Plans [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Balance at Beginning of Period	(76,476)	(69,794)	(76,476)	(69,794)
Other Comprehensive Gains and Losses Before Reclassification	0	0	0	0
Amounts Reclassified From Other Comprehensive Income (Loss)	0	0	0	0
Balance at End of Period	$ (76,476)	$ (69,794)	$ (76,476)	$ (69,794)