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Fair Value Measurements - Carrying and Estimated Fair Value of Debt (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Convertible Debt \| 1.25% Convertible Notes due 2025
Debt Instrument [Line Items]
Carrying value	$ 1,611
Unsecured Debt \| 5.25% Notes due 2025
Debt Instrument [Line Items]
Carrying value	1,302
Unsecured Debt \| 3.00% Notes due 2026
Debt Instrument [Line Items]
Carrying value	300
Unsecured Debt \| 7.375% Debentures due 2027
Debt Instrument [Line Items]
Carrying value	111
Unsecured Debt \| 3.45% Notes due 2027
Debt Instrument [Line Items]
Carrying value	300
Unsecured Debt \| 5.125% Notes due 2027
Debt Instrument [Line Items]
Carrying value	1,727
Unsecured Debt \| 2.625% due 2030
Debt Instrument [Line Items]
Carrying value	500
Unsecured Debt \| 1.000% Payroll Support Program Loan due 2030 (a)
Debt Instrument [Line Items]
Carrying value	976
Unsecured Debt \| 1.000% Payroll Support Program Loan due 2031 (a)
Debt Instrument [Line Items]
Carrying value	566
Unsecured Debt \| 1.000% Payroll Support Program Loan due 2031 (a)
Debt Instrument [Line Items]
Carrying value	$ 526
Level 2 \| Convertible Debt \| 1.25% Convertible Notes due 2025
Debt Instrument [Line Items]
Stated interest rate	1.25%	1.25%
Notes payable, Estimated Fair Value	$ 1,616
Level 2 \| Unsecured Debt \| 5.25% Notes due 2025
Debt Instrument [Line Items]
Stated interest rate	5.25%	5.25%
Notes payable, Estimated Fair Value	$ 1,287
Level 2 \| Unsecured Debt \| 3.00% Notes due 2026
Debt Instrument [Line Items]
Stated interest rate	3.00%
Notes payable, Estimated Fair Value	$ 278
Level 2 \| Unsecured Debt \| 7.375% Debentures due 2027
Debt Instrument [Line Items]
Stated interest rate	7.375%
Loans payable, Estimated Fair Value	$ 104
Level 2 \| Unsecured Debt \| 3.45% Notes due 2027
Debt Instrument [Line Items]
Stated interest rate	3.45%
Notes payable, Estimated Fair Value	$ 275
Level 2 \| Unsecured Debt \| 5.125% Notes due 2027
Debt Instrument [Line Items]
Stated interest rate	5.125%	5.125%
Notes payable, Estimated Fair Value	$ 1,683
Level 2 \| Unsecured Debt \| 2.625% due 2030
Debt Instrument [Line Items]
Stated interest rate	2.625%
Notes payable, Estimated Fair Value	$ 414
Level 3 \| Unsecured Debt \| 1.000% Payroll Support Program Loan due 2030 (a)
Debt Instrument [Line Items]
Stated interest rate	1.00%
Notes payable, Estimated Fair Value	$ 893
Level 3 \| Unsecured Debt \| 1.000% Payroll Support Program Loan due 2031 (a)
Debt Instrument [Line Items]
Stated interest rate	1.00%
Notes payable, Estimated Fair Value	$ 500
Level 3 \| Unsecured Debt \| 1.000% Payroll Support Program Loan due 2031 (a)
Debt Instrument [Line Items]
Stated interest rate	1.00%
Notes payable, Estimated Fair Value	$ 457