Debt - Extinguishments of Debt (Details) € in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2023 EUR (€)
Extinguishment of Debt [Line Items]
Long-Term Debt	$ 13,886	$ 14,738	$ 13,886
Extinguishment of Debt, Gain (Loss), Net of Tax		$ 0	24	$ 178
0.000% Notes due August 13, 2023
Extinguishment of Debt [Line Items]
Interest rate		0.00%			0.00%
0.000% Notes due August 13, 2023 | Euro Member Countries, Euro
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount | €					€ 400
0.000% Notes due August 13, 2023 | United States of America, Dollars
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount		$ 439
0.632% Notes due June 4, 2023
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount		$ 857
Interest rate		0.632%			0.632%
0.632% Notes due June 4, 2023 | Euro Member Countries, Euro
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount | €					€ 800
1.401% Notes due May 24, 2023
Extinguishment of Debt [Line Items]
Interest rate		1.401%			1.401%
1.401% Notes due May 24, 2023 | Euro Member Countries, Euro
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount | €					€ 300
1.401% Notes due May 24, 2023 | United States of America, Dollars
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount		$ 325
1.000% Notes due December 15, 2022
Extinguishment of Debt [Line Items]
Interest rate		1.00%			1.00%
1.000% Notes due December 15, 2022 | Euro Member Countries, Euro
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount | €					€ 500
1.000% Notes due December 15, 2022 | United States of America, Dollars
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount		$ 528
3.794% Notes due May 20, 2050
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount	190		190
Interest rate		3.794%			3.794%
Long-Term Debt	554	$ 554	554
Debt Instrument, Repurchase Amount	163		163
Extinguishment of Debt, Gain (Loss), Net of Tax	(25)
3.794% Notes due May 20, 2050 | Long-term Debt
Extinguishment of Debt [Line Items]
Long-Term Debt	188		188
7.000% Debentures due August 1, 2027
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount	52		52
Interest rate		7.00%			7.00%
Long-Term Debt	119	$ 119	119
Debt Instrument, Repurchase Amount	59		59
Extinguishment of Debt, Gain (Loss), Net of Tax	5
7.000% Debentures due August 1, 2027 | Long-term Debt
Extinguishment of Debt [Line Items]
Long-Term Debt	54		54
6.700% Debentures due August 1, 2028
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount	55		55
Interest rate		6.70%			6.70%
Long-Term Debt	116	$ 115	116
Debt Instrument, Repurchase Amount	62		62
Extinguishment of Debt, Gain (Loss), Net of Tax	5
6.700% Debentures due August 1, 2028 | Long-term Debt
Extinguishment of Debt [Line Items]
Long-Term Debt	56		56
6.000% Notes due May 15, 2039
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount	127		127
Interest rate		6.00%			6.00%
Long-Term Debt	121	$ 121	121
Debt Instrument, Repurchase Amount	145		145
Extinguishment of Debt, Gain (Loss), Net of Tax	20
6.000% Notes due May 15, 2039 | Long-term Debt
Extinguishment of Debt [Line Items]
Long-Term Debt	125		125
5.000% Notes due November 12, 2040
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount	34		34
Interest rate		5.00%			5.00%
Long-Term Debt	90	$ 90	90
Debt Instrument, Repurchase Amount	35		35
Extinguishment of Debt, Gain (Loss), Net of Tax	1
5.000% Notes due November 12, 2040 | Long-term Debt
Extinguishment of Debt [Line Items]
Long-Term Debt	34		34
4.685% Notes due December 15, 2044
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchased Face Amount	42		42
Interest rate		4.685%			4.685%
Long-Term Debt	911	$ 899	911
Debt Instrument, Repurchase Amount	42		42
Extinguishment of Debt, Gain (Loss), Net of Tax	(1)
4.685% Notes due December 15, 2044 | Long-term Debt
Extinguishment of Debt [Line Items]
Long-Term Debt	$ 43		$ 43