Accounts Receivable Factoring and Securitization (Details) € in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2021 EUR (€)	Mar. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2020 EUR (€)
Accounts Receivable Factoring And Securitization [Line Items]
On-balance sheet arrangement, Total Facility Size	$ 110		$ 110
On-balance sheet arrangement, Utilized	4		4				$ 3
Off-balance sheet arrangement, Total Facility Size	322		322		€ 210
Off-balance sheet arrangement, Utilized	196		196		129		154	€ 107
Costs associated with off balance sheet factoring arrangements	1	$ 1	2	$ 2
Committed U.S. accounts receivable securitization
Accounts Receivable Factoring And Securitization [Line Items]
On-balance sheet arrangement, Total Facility Size	110		110
On-balance sheet arrangement, Utilized	4		4				3
Off-balance sheet arrangement, Total Facility Size	110		110			$ 95
Committed U.S. accounts receivable securitization | Letter of Credit
Accounts Receivable Factoring And Securitization [Line Items]
Letters of credit outstanding	4		4				3
Committed Swedish factoring facility
Accounts Receivable Factoring And Securitization [Line Items]
Off-balance sheet arrangement, Total Facility Size	183		183		155
Off-balance sheet arrangement, Utilized	105		$ 105		89		100	86
Liquidity commitment			364 days
Committed U.S. factoring facility
Accounts Receivable Factoring And Securitization [Line Items]
Off-balance sheet arrangement, Total Facility Size	75		$ 75
Off-balance sheet arrangement, Utilized	44		44				30
Uncommitted U.K. factoring facility
Accounts Receivable Factoring And Securitization [Line Items]
Off-balance sheet arrangement, Total Facility Size	29		29		25
Off-balance sheet arrangement, Utilized	5		5		4		1	1
Uncommitted Italy factoring facility
Accounts Receivable Factoring And Securitization [Line Items]
Off-balance sheet arrangement, Total Facility Size	35		35		30
Off-balance sheet arrangement, Utilized	22		22		19		9	8
Other uncommitted factoring facilities
Accounts Receivable Factoring And Securitization [Line Items]
Off-balance sheet arrangement, Utilized	$ 20		$ 20		€ 17		$ 14	€ 12