Retirement Plans (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension plan, projected benefit obligation (ABO)	$ 204	$ 225
Pension plan, accumulated benefit obligation (ABO)	182	201
Pension plan, fair value of plan assets (ABO)	72	79
Pension plan, projected benefit obligation (PBO)	204	226
Pension plan, accumulated benefit obligation (PBO)	182	202
Pension plan, fair value of plan assets (PBO)	72	80
Amounts in AOCI	3	3
Pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, contributions	23	19
Expected contributions in the next fiscal year	16
Savings and investment plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution expense	$ 44	$ 36

Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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