Capitalization and Short-Term Borrowings (Summary of Changes in Common Stock Equity) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Schedule of Capitalization, Equity [Line Items]
Beginning balance (shares)		91,181,549
Beginning balance		$ 1,017,446
Balance at Beginning of Period		1,191,175	$ 991,630
Balance at Beginning of Period		(513,597)	(114,757)
Net Income Available for Common Stock		132,392	77,774
Dividends Declared on Common Stock		(41,604)	(40,560)
Other Comprehensive Income, Net of Tax		$ 236,571	35,016
Ending balance (shares)		91,436,837
Ending balance		$ 1,013,821
Balance at December 31		1,281,963	1,028,844
Balance at End of Period		$ (277,026)	$ (79,741)
Dividends per share		$ 0.455	$ 0.445
Paid-in Capital [Member]
Schedule of Capitalization, Equity [Line Items]
Beginning balance		$ 1,017,446	$ 1,004,158
Share-Based Payment Expense	[1]	5,039	3,496
Stock Repurchased under Stock and Benefit Plans		(8,664)	(3,285)
Ending balance		1,013,821	1,004,369
Earnings Reinvested in The Business [Member]
Schedule of Capitalization, Equity [Line Items]
Balance at Beginning of Period		1,191,175	991,630
Net Income Available for Common Stock		132,392	77,774
Dividends Declared on Common Stock		(41,604)	(40,560)
Balance at December 31		1,281,963	1,028,844
Accumulated Other Comprehensive Income (Loss) [Member]
Schedule of Capitalization, Equity [Line Items]
Balance at Beginning of Period		(513,597)	(114,757)
Other Comprehensive Income, Net of Tax		236,571	35,016
Balance at End of Period		$ (277,026)	$ (79,741)
Common Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Beginning balance (shares)		91,182,000	90,955,000
Beginning balance (value)		$ 91,182	$ 90,955
Common Stock Issued Under Stock and Benefit Plans (Shares)		255,000	198,000
Common Stock Issued Under Stock and Benefit Plans		$ 255	$ 198
Ending balance (shares)		91,437,000	91,153,000
Ending balance (value)		$ 91,437	$ 91,153

[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.