Capitalization and Short-Term Borrowings (Summary of Changes in Common Stock Equity) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
		Dec. 31, 2022	Dec. 31, 2021
Schedule of Capitalization, Equity [Line Items]
Beginning balance (shares)		91,478,064
Beginning balance		$ 1,027,066
Balance at Beginning of Period		1,587,085	$ 1,191,175
Balance at Beginning of Period		(625,733)	(513,597)
Net Income Available for Common Stock		169,689	132,392
Dividends Declared on Common Stock		(43,598)	(41,604)
Other Comprehensive Income, Net of Tax		$ 331,987	236,571
Ending balance (shares)		91,786,806
Ending balance		$ 1,025,639
Balance at December 31		1,713,176	1,281,963
Balance at End of Period		$ (293,746)	$ (277,026)
Dividends per share		$ 0.475	$ 0.455
Paid-in Capital [Member]
Schedule of Capitalization, Equity [Line Items]
Beginning balance		$ 1,027,066	$ 1,017,446
Share-Based Payment Expense	[1]	5,118	5,039
Stock Repurchased under Stock and Benefit Plans		(6,545)	(8,664)
Ending balance		1,025,639	1,013,821
Earnings Reinvested in The Business [Member]
Schedule of Capitalization, Equity [Line Items]
Balance at Beginning of Period		1,587,085	1,191,175
Net Income Available for Common Stock		169,689	132,392
Dividends Declared on Common Stock		(43,598)	(41,604)
Balance at December 31		1,713,176	1,281,963
Accumulated Other Comprehensive Income (Loss) [Member]
Schedule of Capitalization, Equity [Line Items]
Balance at Beginning of Period		(625,733)	(513,597)
Other Comprehensive Income, Net of Tax		331,987	236,571
Balance at End of Period		$ (293,746)	$ (277,026)
Common Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Beginning balance (shares)		91,478,000	91,182,000
Beginning balance (value)		$ 91,478	$ 91,182
Common Stock Issued Under Stock and Benefit Plans (Shares)		309,000	255,000
Common Stock Issued Under Stock and Benefit Plans		$ 309	$ 255
Ending balance (shares)		91,787,000	91,437,000
Ending balance (value)		$ 91,787	$ 91,437

[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.