Restructuring and Impairment Costs (Details) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020 USD ($) numberOfEmployees plant	Mar. 31, 2019 USD ($)	Mar. 31, 2020 USD ($) plant numberOfEmployees	Mar. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	$ 52	$ 113	$ 54	$ 144
Restructuring reserve	$ 146		$ 146		$ 123
Number of positions eliminated to date | numberOfEmployees	10,000		10,000
Number of positions eliminated | numberOfEmployees			6,700
Number of plants expected to close | plant	18		18
Number of plants closed | plant	16
2020 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs			$ 64
Restructuring reserve	$ 59		59		64
2020 Restructuring Plan | Employee Severance and Termination Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	58		58		63
2020 Restructuring Plan | Currency Translation
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	0		0		0
2020 Restructuring Plan | Asia
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs			4
2020 Restructuring Plan | Americas
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs			4
2020 Restructuring Plan | EMEA
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs			56
2019 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring reserve accrual adjustment			6
Restructuring reserve	46		46		70
2019 Restructuring Plan | Employee Severance and Termination Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring reserve accrual adjustment			6
Restructuring reserve	45		45		69
2019 Restructuring Plan | Currency Translation
Restructuring Cost and Reserve [Line Items]
Restructuring reserve accrual adjustment			0
Restructuring reserve	(2)		(2)		(2)
2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring reserve accrual adjustment			2
Restructuring reserve	11		11		20
2018 Restructuring Plan | Employee Severance and Termination Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring reserve accrual adjustment			3
Restructuring reserve	14		14		24
2018 Restructuring Plan | Currency Translation
Restructuring Cost and Reserve [Line Items]
Restructuring reserve accrual adjustment			(1)
Restructuring reserve	(3)		(3)		$ (4)
2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	5		5
2016 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	$ 25		$ 25