Capitalization and Short-Term Borrowings - Summary of Changes in Common Stock Equity (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Sep. 30, 2024		Sep. 30, 2023	Sep. 30, 2022
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		77,513		$ 476,866	$ 566,021
Dividends Declared on Common Stock		(185,220)		(178,095)	(170,111)
Other Comprehensive Income (Loss), Net of Tax		$ 39,584		$ 570,673	$ (112,136)
Ending balance (in shares)		91,005,993		91,819,405
Ending balance		$ 2,848,343		$ 2,963,376
Dividend per share (in dollars per share)		$ 2.02		$ 1.94	$ 1.86
Accumulated earnings free from limitations		$ 1,600,000
Stock And Benefit Plans
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share repurchases (in shares)		(78,141)
Share Repurchase Plan
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share repurchases (in shares)		(1,146,259)
Share Repurchases		$ (65,200)
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		91,819,000		91,478,000	91,182,000
Beginning balance		$ 91,819		$ 91,478	$ 91,182
Common stock issued under stock and benefit plans (in shares)		333,000		341,000	296,000
Common stock issued under stock and benefit plans		$ 333		$ 341	$ 296
Ending balance (in shares)		91,006,000		91,819,000	91,478,000
Ending balance		$ 91,006		$ 91,819	$ 91,478
Common Stock | Share Repurchase Plan
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share repurchases (in shares)		(1,146,000)
Share Repurchases		$ (1,146)
Paid In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		1,040,761		1,027,066	1,017,446
Share-Based Payment Expense	[1]	19,868		18,746	17,699
Ending balance		1,045,487		1,040,761	1,027,066
Paid In Capital | Stock And Benefit Plans
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share Repurchases		(1,955)		(5,051)	(8,079)
Paid In Capital | Share Repurchase Plan
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share Repurchases		(13,187)
Earnings Reinvested in the Business
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		1,885,856		1,587,085	1,191,175
Net Income Available for Common Stock		77,513		476,866	566,021
Dividends Declared on Common Stock		(185,220)		(178,095)	(170,111)
Share Repurchases		(50,823)		0	0
Ending balance		1,727,326	[2]	1,885,856	1,587,085
Earnings Reinvested in the Business | Share Repurchase Plan
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share Repurchases		(50,823)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		(55,060)		(625,733)	(513,597)
Other Comprehensive Income (Loss), Net of Tax		39,584		570,673	(112,136)
Ending balance		$ (15,476)		$ (55,060)	$ (625,733)

[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.

[2] The availability of consolidated earnings reinvested in the business for dividends payable in cash is limited under terms of the indentures covering long-term debt. At September 30, 2024, $1.6 billion of accumulated earnings was free of such limitations.