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Fair Value Measurements - Carrying and Estimated Fair Value of Debt (Details) - Unsecured Debt - USD ($) $ in Millions	Apr. 20, 2025	Sep. 30, 2025
3.00% Notes
Debt Instrument [Line Items]
Carrying value		$ 300
7.375% Debentures
Debt Instrument [Line Items]
Carrying value		105
3.45% Notes
Debt Instrument [Line Items]
Carrying value		300
5.125% Notes
Debt Instrument [Line Items]
Carrying value		1,727
2.625% Notes
Debt Instrument [Line Items]
Carrying value		500
1.000% Payroll Support Program Loan due January 2031
Debt Instrument [Line Items]
Carrying value		566
Variable rate (as a percent)	2.00%
1.000% Payroll Support Program Loan due April 2031
Debt Instrument [Line Items]
Carrying value		$ 526
Variable rate (as a percent)	2.00%
Level 2 \| 3.00% Notes
Debt Instrument [Line Items]
Stated interest rate		3.00%
Notes payable, estimated fair value		$ 296
Level 2 \| 7.375% Debentures
Debt Instrument [Line Items]
Stated interest rate		7.375%
Loans payable, estimated fair value		$ 109
Level 2 \| 3.45% Notes
Debt Instrument [Line Items]
Stated interest rate		3.45%
Notes payable, estimated fair value		$ 295
Level 2 \| 5.125% Notes
Debt Instrument [Line Items]
Stated interest rate		5.125%
Notes payable, estimated fair value		$ 1,749
Level 2 \| 2.625% Notes
Debt Instrument [Line Items]
Stated interest rate		2.625%
Notes payable, estimated fair value		$ 461
Level 3 \| 1.000% Payroll Support Program Loan due January 2031
Debt Instrument [Line Items]
Stated interest rate		1.00%
Notes payable, estimated fair value		$ 573
Level 3 \| 1.000% Payroll Support Program Loan due April 2031
Debt Instrument [Line Items]
Stated interest rate		1.00%
Notes payable, estimated fair value		$ 524