Retirement Plans (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension plan, projected benefit obligation	$ 257	$ 208
Pension plan, accumulated benefit obligation	230	188
Pension plan, fair value of plan assets	105	82
Amounts in AOCI	3	1
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions in current fiscal year	19
Expected contributions in fiscal 2020	17
Savings and Investment Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution expense	$ 56	$ 37

Defined Benefit Plan, Plan Assets, Contributions by Employer, Gross

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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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Amount of accumulated benefit obligation for defined benefit plan with accumulated benefit obligation in excess of plan assets.

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