Goodwill and Other Intangible Assets - Goodwill (Details) - USD ($)	3 Months Ended		6 Months Ended	12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Goodwill [Roll Forward]
Goodwill, beginning balance				$ 2,182,000,000	$ 2,515,000,000
Business acquisitions					(15,000,000)
Impairment	$ 0	$ 0	$ 0		(299,000,000)
Currency translation and other				(32,000,000)	(19,000,000)
Goodwill, ending balance	2,150,000,000		2,182,000,000	2,150,000,000	2,182,000,000
Americas
Goodwill [Roll Forward]
Goodwill, beginning balance				642,000,000	731,000,000
Business acquisitions					(18,000,000)
Impairment					(71,000,000)
Currency translation and other				(4,000,000)	0
Goodwill, ending balance	638,000,000		642,000,000	638,000,000	642,000,000
EMEA
Goodwill [Roll Forward]
Goodwill, beginning balance				469,000,000	708,000,000
Business acquisitions					0
Impairment					(228,000,000)
Currency translation and other				(40,000,000)	(11,000,000)
Goodwill, ending balance	429,000,000		469,000,000	429,000,000	469,000,000
Asia
Goodwill [Roll Forward]
Goodwill, beginning balance				1,071,000,000	1,076,000,000
Business acquisitions					3,000,000
Impairment					0
Currency translation and other				12,000,000	(8,000,000)
Goodwill, ending balance	$ 1,083,000,000		$ 1,071,000,000	$ 1,083,000,000	$ 1,071,000,000