Postretirement Plans (Reconciliations Of Actuarial Present Value Of Accumulated Postretirement Benefit Obligations) (Details) - Postretirement Plans [Member] - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Postretirement Benefit Plans [Line Items]
Benefit obligation, beginning	$ 149	$ 174
Service cost	1	1	$ 1
Interest cost	5	6	6
Actuarial (gain) loss	5	(19)
Benefits paid	(13)	(13)
Benefit obligation, ending (recognized in balance sheet)	$ 147	$ 149	$ 174

Postretirement Benefit Plans [Line Items]

No definition available.

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- Definition

Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

+ References

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- Definition

Amount of asset (liability), recognized in statement of financial position, for defined benefit pension and other postretirement plans.

+ References

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- Definition

Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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- Definition

Amount of cost recognized for passage of time related to defined benefit plan.

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- Definition

Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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