Benefit Obligations - Narrative (Details)	6 Months Ended
	Mar. 31, 2020 USD ($)
Post-retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 7,000,000
Reimbursement of prior period payments	3,000,000
U.S. | Postretirement Health Coverage
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions in current fiscal year	6,000,000
Non-US
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	14,000,000
Non-US | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions in current fiscal year	9,000,000
Not Pre-Funded | U.S.
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 9,000,000