Debt - Summary of Debt (Details) - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Debt Instrument [Line Items]
Unamortized discounts and debt issuance costs	$ (151)	$ (159)
Hedge accounting fair value adjustments	(238)	(314)
Total carrying value of debt	20,603	20,463
Current maturities of debt	0	0
Long-term debt	20,603	20,463
Senior Notes
Debt Instrument [Line Items]
Total debt	20,992	20,936
Senior Notes | 3.15% Senior Notes due December 2025 | U.S.
Debt Instrument [Line Items]
Total debt	$ 4,000	4,000
Effective interest rate (percent)	3.26%
Stated interest rate (percent)	3.15%
Senior Notes | 1.90% Senior Notes due April 2027 | U.S.
Debt Instrument [Line Items]
Total debt	$ 1,500	1,500
Effective interest rate (percent)	2.02%
Stated interest rate (percent)	1.90%
Senior Notes | 0.75% Senior Notes due August 2027 | U.S.
Debt Instrument [Line Items]
Total debt	$ 500	500
Effective interest rate (percent)	0.84%
Stated interest rate (percent)	0.75%
Senior Notes | 2.75% Senior Notes due September 2027 | U.S.
Debt Instrument [Line Items]
Total debt	$ 750	750
Effective interest rate (percent)	2.91%
Stated interest rate (percent)	2.75%
Senior Notes | 2.05% Senior Notes due April 2030 | U.S.
Debt Instrument [Line Items]
Total debt	$ 1,500	1,500
Effective interest rate (percent)	2.13%
Stated interest rate (percent)	2.05%
Senior Notes | 1.10% Senior Notes due February 2031 | U.S.
Debt Instrument [Line Items]
Total debt	$ 1,000	1,000
Effective interest rate (percent)	1.20%
Stated interest rate (percent)	1.10%
Senior Notes | 4.15% Senior Notes due December 2035 | U.S.
Debt Instrument [Line Items]
Total debt	$ 1,500	1,500
Effective interest rate (percent)	4.23%
Stated interest rate (percent)	4.15%
Senior Notes | 2.70% Senior Notes due April 2040 | U.S.
Debt Instrument [Line Items]
Total debt	$ 1,000	1,000
Effective interest rate (percent)	2.80%
Stated interest rate (percent)	2.70%
Senior Notes | 4.30% Senior Notes due December 2045 | U.S.
Debt Instrument [Line Items]
Total debt	$ 3,500	3,500
Effective interest rate (percent)	4.37%
Stated interest rate (percent)	4.30%
Senior Notes | 3.65% Senior Notes due September 2047 | U.S.
Debt Instrument [Line Items]
Total debt	$ 750	750
Effective interest rate (percent)	3.73%
Stated interest rate (percent)	3.65%
Senior Notes | 2.00% Senior Notes due August 2050 | U.S.
Debt Instrument [Line Items]
Total debt	$ 1,750	1,750
Effective interest rate (percent)	2.09%
Stated interest rate (percent)	2.00%
Senior Notes | 1.50% Senior Notes due June 2026 | Europe
Debt Instrument [Line Items]
Total debt	$ 1,459	1,434
Effective interest rate (percent)	1.71%
Stated interest rate (percent)	1.50%
Senior Notes | 2.00% Senior Notes due June 2029 | Europe
Debt Instrument [Line Items]
Total debt	$ 1,081	1,062
Effective interest rate (percent)	2.13%
Stated interest rate (percent)	2.00%
Senior Notes | 2.375% Senior Notes due June 2034 | Europe
Debt Instrument [Line Items]
Total debt	$ 702	$ 690
Effective interest rate (percent)	2.53%
Stated interest rate (percent)	2.375%