Debt - Summary of Long-Term Debt (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
Debt Instrument [Line Items]
Long-Term Debt	$ 17,940	$ 14,738
3.734% Notes due December 15, 2024
Debt Instrument [Line Items]
Interest rate (percent)	3.734%
Long-Term Debt	$ 0	874
3.020% Notes due May 24, 2025
Debt Instrument [Line Items]
Interest rate (percent)	3.02%
Long-Term Debt	$ 0	306
0.034% Notes due August 13, 2025
Debt Instrument [Line Items]
Interest rate (percent)	0.034%
Long-Term Debt	$ 0	528
1.208% Notes due June 4, 2026
Debt Instrument [Line Items]
Interest rate (percent)	1.208%
Long-Term Debt	$ 671	634
6.700% Notes due December 1, 2026
Debt Instrument [Line Items]
Interest rate (percent)	6.70%
Long-Term Debt	$ 158	161
1.900% Notes due December 15, 2026
Debt Instrument [Line Items]
Interest rate (percent)	1.90%
Long-Term Debt	$ 559	528
3.700% Notes due June 6, 2027
Debt Instrument [Line Items]
Interest rate (percent)	3.70%
Long-Term Debt	$ 1,721	1,719
7.000% Debentures due August 1, 2027
Debt Instrument [Line Items]
Interest rate (percent)	7.00%
Long-Term Debt	$ 118	119
4.693% Notes due February 13, 2028
Debt Instrument [Line Items]
Interest rate (percent)	4.693%
Long-Term Debt	$ 797	796
6.700% Debentures due August 1, 2028
Debt Instrument [Line Items]
Interest rate (percent)	6.70%
Long-Term Debt	$ 115	115
0.334% Notes due August 13, 2028
Debt Instrument [Line Items]
Interest rate (percent)	0.334%
Long-Term Debt	$ 1,004	949
4.874% Notes due February 8, 2029
Debt Instrument [Line Items]
Interest rate (percent)	4.874%
Long-Term Debt	$ 622	0
5.081% Notes due June 7, 2029
Debt Instrument [Line Items]
Interest rate (percent)	5.081%
Long-Term Debt	$ 596	0
3.553% Notes due September 13, 2029
Debt Instrument [Line Items]
Interest rate (percent)	3.553%
Long-Term Debt	$ 891	842
2.823% Notes due May 20, 2030
Debt Instrument [Line Items]
Interest rate (percent)	2.823%
Long-Term Debt	$ 746	745
3.519% Notes due February 8, 2031
Debt Instrument [Line Items]
Interest rate (percent)	3.519%
Long-Term Debt	$ 835	0
1.957% Notes due February 11, 2031
Debt Instrument [Line Items]
Interest rate (percent)	1.957%
Long-Term Debt	$ 994	993
3.828% Notes due June 7, 2032
Debt Instrument [Line Items]
Interest rate (percent)	3.828%
Long-Term Debt	$ 1,113	0
4.298% Notes due August 22, 2032
Debt Instrument [Line Items]
Interest rate (percent)	4.298%
Long-Term Debt	$ 496	496
5.110% Notes due February 8, 2034
Debt Instrument [Line Items]
Interest rate (percent)	5.11%
Long-Term Debt	$ 545	0
1.213% Notes due February 12, 2036
Debt Instrument [Line Items]
Interest rate (percent)	1.213%
Long-Term Debt	$ 668	631
4.029% Notes due June 7, 2036
Debt Instrument [Line Items]
Interest rate (percent)	4.029%
Long-Term Debt	$ 889	0
6.000% Notes due May 15, 2039
Debt Instrument [Line Items]
Interest rate (percent)	6.00%
Long-Term Debt	$ 121	121
5.000% Notes due November 12, 2040
Debt Instrument [Line Items]
Interest rate (percent)	5.00%
Long-Term Debt	$ 90	90
1.336% Notes due August 13, 2041
Debt Instrument [Line Items]
Interest rate (percent)	1.336%
Long-Term Debt	$ 999	945
4.875% Notes due May 15, 2044
Debt Instrument [Line Items]
Interest rate (percent)	4.875%
Long-Term Debt	$ 244	245
4.685% Notes due December 15, 2044
Debt Instrument [Line Items]
Interest rate (percent)	4.685%
Long-Term Debt	$ 934	899
4.669% Notes due June 6, 2047
Debt Instrument [Line Items]
Interest rate (percent)	4.669%
Long-Term Debt	$ 1,460	1,445
3.794% Notes due May 20, 2050
Debt Instrument [Line Items]
Interest rate (percent)	3.794%
Long-Term Debt	$ 554	554
Other long-term debt
Debt Instrument [Line Items]
Long-Term Debt	$ 1	$ 2