Summary Of Significant Accounting Policies (Components Of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ (52,155)	$ (67,750)
Other Comprehensive Gains and Losses Before Reclassifications	(7,573)	25,066
Amounts Reclassified From Other Comprehensive Income (Loss)	(55,979)	8,372
Cumulative Effect of Adoption of Authoritative Guidance for Hedging	950
Reclassification Adjustment for the Cumulative Effect of Adoption of Authoritative Guidance for Financial Assets and Liabilities		(7,437)
Reclassification of Stranded Tax Effects Related to the 2017 Tax Reform Act	0	(10,406)	$ 0
Ending balance	(114,757)	(52,155)	(67,750)
Gains and Losses on Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	34,675
Other Comprehensive Gains and Losses Before Reclassifications	7,284
Amounts Reclassified From Other Comprehensive Income (Loss)	(67,774)
Cumulative Effect of Adoption of Authoritative Guidance for Hedging	950
Ending balance	(24,865)	34,675
Gains and Losses on Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	34,675	(28,611)
Other Comprehensive Gains and Losses Before Reclassifications		58,682
Amounts Reclassified From Other Comprehensive Income (Loss)		2,738
Reclassification Adjustment for the Cumulative Effect of Adoption of Authoritative Guidance for Financial Assets and Liabilities		0
Reclassification of Stranded Tax Effects Related to the 2017 Tax Reform Act		1,866
Ending balance		34,675	(28,611)
Gains and Losses on Securities Available for Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	0	7,437
Other Comprehensive Gains and Losses Before Reclassifications	0	0
Amounts Reclassified From Other Comprehensive Income (Loss)	0	0
Cumulative Effect of Adoption of Authoritative Guidance for Hedging	0
Reclassification Adjustment for the Cumulative Effect of Adoption of Authoritative Guidance for Financial Assets and Liabilities		(7,437)
Reclassification of Stranded Tax Effects Related to the 2017 Tax Reform Act		0
Ending balance	0	0	7,437
Funded Status of the Pension and Other Post-Retirement Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(86,830)	(46,576)
Other Comprehensive Gains and Losses Before Reclassifications	(14,857)	(33,616)
Amounts Reclassified From Other Comprehensive Income (Loss)	11,795	5,634
Cumulative Effect of Adoption of Authoritative Guidance for Hedging	0
Reclassification Adjustment for the Cumulative Effect of Adoption of Authoritative Guidance for Financial Assets and Liabilities		0
Reclassification of Stranded Tax Effects Related to the 2017 Tax Reform Act		(12,272)
Ending balance	$ (89,892)	$ (86,830)	$ (46,576)

Accumulated Other Comprehensive Income [Roll Forward]

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Cumulative Effect of Adoption of Authoritative Guidance for Hedging

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Reclassification Adjustment from AOCI for Cumulative Effect of Adoption of Authoritative Guidance for Financial Assets and Liabilities

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

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Amount of increase (decrease) in accumulated other comprehensive income (AOCI) for reclassification to retained earnings of tax effect from remeasurement of deferred tax pursuant to Tax Cuts and Jobs Act.

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