Shareholders' Equity - Changes in Certain Components of Shareholders' Equity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 25,890
Net income	303	$ 281
Ending balance	$ 25,205
Dividends per Common Share (USD per share)	$ 1.04	$ 0.95
Common Stock  Issued at Par Value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 371	$ 371
Ending balance	371	371
Capital in Excess of Par Value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	19,893	19,720
Issuance of shares under employee and other plans, net	(65)	(62)
Share-based compensation	90	83
Repurchase of common stock	(150)
Ending balance	19,768	19,741
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	16,139	15,535
Net income	303	281
Common dividends	(302)	(275)
Ending balance	16,141	15,540
Deferred Compensation
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	25	24
Ending balance	25	24
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ (8,807)	$ (8,305)
Beginning balance (shares)	(81,493)	(80,203)
Issuance of shares under employee and other plans, net	$ (12)	$ (20)
Common stock issued for share-based compensation and other plans, net (in shares)	679	647
Common stock held in trusts, net (in shares)	(8)	(19)
Repurchase of common stock (in shares)	(2,637)	(2,118)
Repurchase of common stock	$ (606)	$ (503)
Ending balance	$ (9,425)	$ (8,828)
Ending balance (shares)	(83,459)	(81,692)