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, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)				91,819,405
Beginning balance				$ 2,963,376
Net Income Available for Common Stock		$ (54,158)	$ 92,620	245,134	$ 403,189
Dividends Declared on Common Stock		(47,195)	(45,444)	(138,354)	(132,644)
Other Comprehensive Income (Loss), Net of Tax		$ (70,290)	$ 5,480	$ 60,110	$ 576,349
Ending balance (in shares)		91,612,488		91,612,488
Ending balance		$ 3,113,525		$ 3,113,525
Dividends per share (in dollars per share)		$ 0.515	$ 0.495	$ 1.505	$ 1.445
Stock and Benefit Plans
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share Repurchases (in shares)				(77,461)
Share Repurchase Plan
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share Repurchases (in shares)				(526,652)
Share Repurchases				$ (28,800)
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		92,032,000	91,795,000	91,819,000	91,478,000
Beginning balance		$ 92,032	$ 91,795	$ 91,819	$ 91,478
Common stock issued under stock and benefit plans (in shares)		11,000	9,000	320,000	326,000
Common Stock Issued Under Stock and Benefit Plans		$ 11	$ 9	$ 320	$ 326
Ending balance (in shares)		91,612,000	91,804,000	91,612,000	91,804,000
Ending balance		$ 91,612	$ 91,804	$ 91,612	$ 91,804
Common Stock | Share Repurchase Plan
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share Repurchases (in shares)		(431,000)		(527,000)
Share Repurchases		$ (431)		$ (527)
Paid In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		1,045,929	1,031,341	1,040,761	1,027,066
Share-Based Payment Expense	[1]	4,905	4,009	14,262	14,327
Common Stock Issued Under Stock and Benefit Plans		587	502
Ending balance		1,046,479	1,035,852	1,046,479	1,035,852
Paid In Capital | Stock and Benefit Plans
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share Repurchases				(2,514)	(5,541)
Paid In Capital | Share Repurchase Plan
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share Repurchases		(4,942)		(6,030)
Earnings Reinvested in the Business
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		2,090,172	1,810,454	1,885,856	1,587,085
Net Income Available for Common Stock		(54,158)	92,620	245,134	403,189
Dividends Declared on Common Stock		(47,195)	(45,444)	(138,354)	(132,644)
Share Repurchases		(18,435)	0	(22,252)	0
Ending balance		1,970,384	1,857,630	1,970,384	1,857,630
Earnings Reinvested in the Business | Share Repurchase Plan
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share Repurchases		(18,435)		(22,252)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		75,340	(54,864)	(55,060)	(625,733)
Other Comprehensive Income (Loss), Net of Tax		(70,290)	5,480	60,110	576,349
Ending balance		$ 5,050	$ (49,384)	$ 5,050	$ (49,384)

[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.