Restructuring and Impairment Costs - Narrative (Details) employee in Thousands, $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($) employee	Mar. 31, 2020 USD ($)	Mar. 31, 2021 USD ($) plant employee	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)
Restructuring Cost and Reserve [Line Items]
Noncash adjustment					$ 20
Restructuring and impairment costs	$ 5	$ 52	$ 12	$ 54
Restructuring reserve	$ 150		$ 150		237
Number of positions eliminated to date | employee	18		18
Number of positions eliminated | employee			13
Number of plants expected to close | plant			24
Number of plants closed | plant			19
2021 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Expected restructuring costs	$ 13		$ 13
Noncash adjustment			9
Restructuring reserve	13		13		13
2021 Restructuring Plan | Americas
Restructuring Cost and Reserve [Line Items]
Expected restructuring costs	1		1
2021 Restructuring Plan | EMEA
Restructuring Cost and Reserve [Line Items]
Expected restructuring costs	12		12
2020 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Noncash adjustment			(1)
Restructuring and impairment costs					205
Restructuring reserve	108		108		169
2020 Restructuring Plan | Americas
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs					20
2020 Restructuring Plan | EMEA
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs					175
2020 Restructuring Plan | Asia
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs					$ 10
2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	4		4
2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	3		3
2016 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	$ 4		$ 4