Summary Of Significant Accounting Policies (Components Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income [Roll Forward]
Balance at Beginning of Period	$ 98,456	$ 122,473	$ 93,372	$ (3,979)
Other Comprehensive Gains and Losses Before Reclassification	19,590	35,429	63,838	176,057
Amounts Reclassified From Other Comprehensive Income (Loss)	(35,860)	(31,213)	(75,024)	(45,389)
Balance at End of Period	82,186	126,689	82,186	126,689
Gains And Losses On Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Balance at Beginning of Period	162,728	170,363	157,197	43,659
Other Comprehensive Gains and Losses Before Reclassification	19,578	35,263	64,273	176,143
Amounts Reclassified From Other Comprehensive Income (Loss)	(35,635)	(31,213)	(74,799)	(45,389)
Balance at End of Period	146,671	174,413	146,671	174,413
Gains And Losses On Securities Available For Sale [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Balance at Beginning of Period	5,522	8,130	5,969	8,382
Other Comprehensive Gains and Losses Before Reclassification	12	166	(435)	(86)
Amounts Reclassified From Other Comprehensive Income (Loss)	(225)	0	(225)	0
Balance at End of Period	5,309	8,296	5,309	8,296
Funded Status Of The Pension And Other Post-Retirement Benefit Plans [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Balance at Beginning of Period	(69,794)	(56,020)	(69,794)	(56,020)
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	$ (69,794)	$ (56,020)	$ (69,794)	$ (56,020)