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Benefit Plans Fair Value Measurements (Details) $ in Millions	12 Months Ended
	Sep. 30, 2023 USD ($) Years	Sep. 30, 2022 USD ($)	Oct. 01, 2019 USD ($)
Defined Benefit Plan Disclosure
Fair value of gross plan assets	$ 8,605	$ 8,566
Derivative liabilities	128	176
Net payables	167	100
Payables for collateral on loaned securities	$ 181	196
Voting percentage required to desolve partnership in private equity	80.00%
Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	$ 1,748	1,916
Derivative liabilities	6	10
Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	2,167	2,328
Derivative liabilities	122	166
Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	60	62	$ 74
Derivative liabilities	0	0
Equity securities
Defined Benefit Plan Disclosure
Fair value of gross plan assets	732	709
Equity securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	731	707
Equity securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Equity securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	1	2
Preferred securities
Defined Benefit Plan Disclosure
Fair value of gross plan assets	4	6
Preferred securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	1
Preferred securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	4	5
Preferred securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Corporate debt securities
Defined Benefit Plan Disclosure
Fair value of gross plan assets	1,109	1,087
Corporate debt securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Corporate debt securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	1,107	1,087
Corporate debt securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	2	0
Residential mortgage-backed securities
Defined Benefit Plan Disclosure
Fair value of gross plan assets	330	293
Residential mortgage-backed securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Residential mortgage-backed securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	323	289
Residential mortgage-backed securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	7	4
Debt securities issued by U.S. Treasury and other U.S. government agencies
Defined Benefit Plan Disclosure
Fair value of gross plan assets	602	616
Debt securities issued by U.S. Treasury and other U.S. government agencies | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	602	616
Debt securities issued by U.S. Treasury and other U.S. government agencies | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Debt securities issued by U.S. Treasury and other U.S. government agencies | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Asset-backed securities
Defined Benefit Plan Disclosure
Fair value of gross plan assets	173	176
Asset-backed securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Asset-backed securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	130	136
Asset-backed securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	43	40
Debt securities issued by state/local governments
Defined Benefit Plan Disclosure
Fair value of gross plan assets	21	23
Debt securities issued by state/local governments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Debt securities issued by state/local governments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	21	23
Debt securities issued by state/local governments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Debt securities issued by foreign governments
Defined Benefit Plan Disclosure
Fair value of gross plan assets	12	130
Debt securities issued by foreign governments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Debt securities issued by foreign governments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	10	130
Debt securities issued by foreign governments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	2	0
Commercial mortgage-backed securities
Defined Benefit Plan Disclosure
Fair value of gross plan assets	113	161
Commercial mortgage-backed securities | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Commercial mortgage-backed securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	108	145
Commercial mortgage-backed securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	5	16
Equity security commingled funds
Defined Benefit Plan Disclosure
Fair value of gross plan assets	360	436
Equity security commingled funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Equity security commingled funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Equity security commingled funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Debt security commingled funds
Defined Benefit Plan Disclosure
Fair value of gross plan assets	544	657
Debt security commingled funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Debt security commingled funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Debt security commingled funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Blended security commingled funds
Defined Benefit Plan Disclosure
Fair value of gross plan assets	101	111
Blended security commingled funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Blended security commingled funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Blended security commingled funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Institutional mutual funds
Defined Benefit Plan Disclosure
Fair value of gross plan assets	363	454
Institutional mutual funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	363	454
Institutional mutual funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Institutional mutual funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Cash equivalents and other short-term investments
Defined Benefit Plan Disclosure
Fair value of gross plan assets	315	431
Cash equivalents and other short-term investments | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	51	133
Cash equivalents and other short-term investments | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	264	298
Cash equivalents and other short-term investments | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Private Credit [Member]
Defined Benefit Plan Disclosure
Fair value of gross plan assets	694	522
Private Credit [Member] | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Private Credit [Member] | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Private Credit [Member] | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Private equity funds measured at net asset value
Defined Benefit Plan Disclosure
Fair value of gross plan assets	1,769	1,454
Private equity funds measured at net asset value | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Private equity funds measured at net asset value | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Private equity funds measured at net asset value | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Private real estate funds
Defined Benefit Plan Disclosure
Fair value of gross plan assets	1,162	1,080
Private real estate funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Private real estate funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Private real estate funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Securities lending commingled funds
Defined Benefit Plan Disclosure
Fair value of gross plan assets	181	196
Securities lending commingled funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Securities lending commingled funds | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	181	196
Securities lending commingled funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Futures
Defined Benefit Plan Disclosure
Fair value of gross plan assets	1	5
Derivative liabilities	5	10
Futures | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	1	5
Derivative liabilities	5	10
Futures | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Derivative liabilities	0	0
Futures | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Derivative liabilities	0	0
Purchased options
Defined Benefit Plan Disclosure
Fair value of gross plan assets	17	17
Purchased options | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Purchased options | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	17	17
Purchased options | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Interest Rate Swap
Defined Benefit Plan Disclosure
Derivative liabilities	26	54
Interest Rate Swap | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Derivative liabilities	0	0
Interest Rate Swap | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Derivative liabilities	26	54
Interest Rate Swap | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Derivative liabilities	0	0
Foreign currency forward
Defined Benefit Plan Disclosure
Fair value of gross plan assets	2	2
Derivative liabilities		1
Foreign currency forward | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Derivative liabilities		0
Foreign currency forward | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Fair value of gross plan assets	2	2
Derivative liabilities		1
Foreign currency forward | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Fair value of gross plan assets	0	0
Derivative liabilities		0
Credit default swaps
Defined Benefit Plan Disclosure
Derivative liabilities	1
Credit default swaps | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Derivative liabilities	1
Credit default swaps | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Derivative liabilities	0
Credit default swaps | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Derivative liabilities	0
Securities Sold under Agreements to Repurchase [Member]
Defined Benefit Plan Disclosure
Derivative liabilities	96	111
Securities Sold under Agreements to Repurchase [Member] | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure
Derivative liabilities	0	0
Securities Sold under Agreements to Repurchase [Member] | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure
Derivative liabilities	96	111
Securities Sold under Agreements to Repurchase [Member] | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure
Derivative liabilities	$ 0	$ 0
Minimum
Defined Benefit Plan Disclosure
Number of years partnerships in private equity generally continue | Years	10
Number of one year extensions for partnerships in private equity | Years	2
Maximum
Defined Benefit Plan Disclosure
Number of years partnerships in private equity generally continue | Years	14
Number of one year extensions for partnerships in private equity | Years	3

X

- Definition

Fair value of liabilities as of the measurement date resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements. These liabilities have been segregated and restricted (usually in a trust) for the purpose of defined benefit plan benefits.

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No definition available.

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- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. This amount is not reduced by non-benefit liabilities.

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