Capitalization and Short-Term Borrowings (Summary of Changes in Common Stock Equity) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Schedule of Capitalization, Equity [Line Items]
Beginning balance (shares)				91,181,549
Beginning balance				$ 1,017,446
Balance at Beginning of Period		$ 1,407,683	$ 1,100,718	1,191,175	$ 991,630
Balance at Beginning of Period		(654,254)	(101,988)	(513,597)	(114,757)
Net Income Available for Common Stock		108,158	86,475	407,879	276,685
Dividends Declared on Common Stock		(43,446)	(41,493)	(126,659)	(122,615)
Other Comprehensive Income (Loss), Net of Tax		$ 71,386	(136,474)	$ (69,271)	(123,705)
Ending balance (shares)		91,465,569		91,465,569
Ending balance		$ 1,022,954		$ 1,022,954
Balance at June 30		1,472,395	1,145,700	1,472,395	1,145,700
Balance at End of Period		$ (582,868)	$ (238,462)	$ (582,868)	$ (238,462)
Dividends per share		$ 0.475	$ 0.455	$ 1.385	$ 1.345
Paid-in Capital [Member]
Schedule of Capitalization, Equity [Line Items]
Beginning balance		$ 1,018,784	$ 1,009,075	$ 1,017,446	$ 1,004,158
Share-Based Payment Expense	[1]	4,094	3,196	13,826	10,975
Common Stock Issued Under Stock and Benefit Plans		76	432
Stock Repurchased under Stock and Benefit Plans				(8,318)	(2,430)
Ending balance		1,022,954	1,012,703	1,022,954	1,012,703
Earnings Reinvested in The Business [Member]
Schedule of Capitalization, Equity [Line Items]
Balance at Beginning of Period		1,407,683	1,100,718	1,191,175	991,630
Net Income Available for Common Stock		108,158	86,475	407,879	276,685
Dividends Declared on Common Stock		(43,446)	(41,493)	(126,659)	(122,615)
Balance at June 30		1,472,395	1,145,700	1,472,395	1,145,700
Accumulated Other Comprehensive Income (Loss) [Member]
Schedule of Capitalization, Equity [Line Items]
Balance at Beginning of Period		(654,254)	(101,988)	(513,597)	(114,757)
Other Comprehensive Income (Loss), Net of Tax		71,386	(136,474)	(69,271)	(123,705)
Balance at End of Period		$ (582,868)	$ (238,462)	$ (582,868)	$ (238,462)
Common Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Beginning balance (shares)		91,449,000	91,164,000	91,182,000	90,955,000
Beginning balance (value)		$ 91,449	$ 91,164	$ 91,182	$ 90,955
Common Stock Issued Under Stock and Benefit Plans (Shares)		17,000	9,000	284,000	218,000
Common Stock Issued Under Stock and Benefit Plans		$ 17	$ 9	$ 284	$ 218
Ending balance (shares)		91,466,000	91,173,000	91,466,000	91,173,000
Ending balance (value)		$ 91,466	$ 91,173	$ 91,466	$ 91,173

[1] Paid in Capital includes compensation costs associated with performance shares and/or restricted stock awards. The expense is included within Net Income Available For Common Stock, net of tax benefits.