Shareholders' Equity - Changes in Certain Components of Shareholders' Equity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended				6 Months Ended
	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2023	Mar. 31, 2022	Nov. 30, 2021	Sep. 24, 2013
Beginning balance		$ 25,282			$ 25,282
Net income	$ 460		$ 454		969	$ 1,131
Ending balance	$ 25,689				$ 25,689
Dividends per Common Share (USD per share)	$ 0.91	$ 0.91	$ 0.87	$ 0.87	$ 1.82	$ 1.74
Number of shares authorized to be repurchased (in shares)								10,000
Number of additional shares authorized to be repurchased (in shares)							10,000
Common Stock  Issued at Par Value
Beginning balance	$ 365	$ 365	$ 365	$ 365	$ 365	$ 365
Ending balance	365	365	365	365	365	365
Capital in Excess of Par Value
Beginning balance	19,590	19,553	19,435	19,272	19,553	19,272
Issuance of shares under employee and other plans, net	(7)	(52)	(21)	(71)
Share-based compensation	56	89	56	83
Common stock held in trusts, net			24
Repurchase of common stock				150
Ending balance	19,639	19,590	19,495	19,435	19,639	19,495
Retained Earnings
Beginning balance	15,384	15,157	14,233	13,826	15,157	13,826
Net income	460	509	454	677
Common dividends	(259)	(259)	(248)	(248)
Preferred dividends	(23)	(23)	(23)	(23)
Ending balance	15,563	15,384	14,416	14,233	15,563	14,416
Deferred Compensation
Beginning balance	24	23	24	23	23	23
Issuance of shares under employee and other plans, net			1
Ending balance	24	24	24	24	24	24
Treasury Stock
Beginning balance	$ (8,333)	$ (8,330)	$ (7,855)	$ (7,723)	$ (8,330)	$ (7,723)
Beginning balance (shares)	(80,738)	(81,283)	(79,869)	(80,164)	(81,283)	(80,164)
Issuance of shares under employee and other plans, net	$ 5	$ (3)	$ 14	$ 19
Common stock issued for share-based compensation and other plans, net (in shares)	21	556	284	762
Common stock held in trusts, net			$ (24)
Common stock held in trusts, net (in shares)	92	(11)	9	(5)
Repurchase of common stock				$ (150)
Repurchase of common stock (in shares)				(462)
Ending balance	$ (8,327)	$ (8,333)	$ (7,866)	$ (7,855)	$ (8,327)	$ (7,866)
Ending balance (shares)	(80,625)	(80,738)	(79,575)	(79,869)	(80,625)	(79,575)