Summary Of Significant Accounting Policies (Components Of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at Beginning of Period	$ (18,917)	$ (54,286)	$ (52,155)	$ (67,750)
Other Comprehensive Gains and Losses Before Reclassifications	3,563	24,376	59,388	38,185
Amounts Reclassified From Other Comprehensive Income (Loss)	(26,440)	(2,756)	(49,977)	14,742
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	0	0	(10,406)
Balance at End of Period	(41,794)	(32,666)	(41,794)	(32,666)
Gains And Losses On Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at Beginning of Period	67,913		34,675
Other Comprehensive Gains and Losses Before Reclassifications	3,563		59,388
Amounts Reclassified From Other Comprehensive Income (Loss)	(26,440)		(49,977)
Cumulative Effect of Adoption of Authoritative Guidance for Hedging			950
Balance at End of Period	45,036		45,036
Gains And Losses On Derivative Financial Instruments [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at Beginning of Period		4,562		(28,611)
Other Comprehensive Gains and Losses Before Reclassifications		24,376		38,185
Amounts Reclassified From Other Comprehensive Income (Loss)		(2,756)		14,742
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
Balance at End of Period		26,182		26,182
Gains And Losses On Securities Available For Sale [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at Beginning of Period	0	0	0	7,437
Other Comprehensive Gains and Losses Before Reclassifications	0	0	0	0
Amounts Reclassified From Other Comprehensive Income (Loss)	0	0	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
Balance at End of Period	0	0	0	0
Funded Status Of The Pension And Other Post-Retirement Benefit Plans [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at Beginning of Period	(86,830)	(58,848)	(86,830)	(46,576)
Other Comprehensive Gains and Losses Before Reclassifications	0	0	0	0
Amounts Reclassified From Other Comprehensive Income (Loss)	0	0	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				0
Reclassification of Stranded Tax Effects Related to the 2017 Tax Reform Act				(12,272)
Balance at End of Period	$ (86,830)	$ (58,848)	$ (86,830)	$ (58,848)