Summary Of Significant Accounting Policies (Components Of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income [Roll Forward]
Balance at Beginning of Period	$ 122,473	$ (22,038)	$ (3,979)	$ (19,234)
Other Comprehensive Gains and Losses Before Reclassification	35,429	(38,487)	176,057	(35,406)
Amounts Reclassified From Other Comprehensive Income (Loss)	(31,213)	15,470	(45,389)	9,585
Balance at End of Period	126,689	(45,055)	126,689	(45,055)
Gains And Losses On Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Balance at Beginning of Period	170,363	26,345	43,659	30,722
Other Comprehensive Gains and Losses Before Reclassification	35,263	(38,878)	176,143	(37,370)
Amounts Reclassified From Other Comprehensive Income (Loss)	(31,213)	15,470	(45,389)	9,585
Balance at End of Period	174,413	2,937	174,413	2,937
Gains And Losses On Securities Available For Sale [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Balance at Beginning of Period	8,130	7,910	8,382	6,337
Other Comprehensive Gains and Losses Before Reclassification	166	391	(86)	1,964
Amounts Reclassified From Other Comprehensive Income (Loss)	0	0	0	0
Balance at End of Period	8,296	8,301	8,296	8,301
Funded Status Of The Pension And Other Post-Retirement Benefit Plans [Member]
Accumulated Other Comprehensive Income [Roll Forward]
Balance at Beginning of Period	(56,020)	(56,293)	(56,020)	(56,293)
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	$ (56,020)	$ (56,293)	$ (56,020)	$ (56,293)