Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 682	$ 709	$ 1,397	$ 1,447
Common Stock
Disaggregation of Revenue [Line Items]
Shares, Outstanding	82.7	110.7	82.7	110.7	100.5	111.0	110.7	110.2
U.S.
Disaggregation of Revenue [Line Items]
Revenue	$ 384	$ 375	$ 778	$ 769
International
Disaggregation of Revenue [Line Items]
Revenue	298	334	619	678
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue	172	188	358	387
Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue	70	79	147	157
Americas International - Canada and Latin America
Disaggregation of Revenue [Line Items]
Revenue	56	67	114	134
Products & Solutions
Disaggregation of Revenue [Line Items]
Revenue	245	289	543	615
Products & Solutions | U.S.
Disaggregation of Revenue [Line Items]
Revenue	119	130	268	280
Products & Solutions | International
Disaggregation of Revenue [Line Items]
Revenue	126	159	275	335
Products & Solutions | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue	78	93	171	199
Products & Solutions | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue	27	37	60	75
Products & Solutions | Americas International - Canada and Latin America
Disaggregation of Revenue [Line Items]
Revenue	21	29	44	61
Services
Disaggregation of Revenue [Line Items]
Revenue	438	425	857	847
Services | U.S.
Disaggregation of Revenue [Line Items]
Revenue	266	248	512	499
Services | International
Disaggregation of Revenue [Line Items]
Revenue	172	177	345	348
Services | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue	94	96	188	190
Services | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue	43	43	87	84
Services | Americas International - Canada and Latin America
Disaggregation of Revenue [Line Items]
Revenue	35	38	70	74
Unallocated
Disaggregation of Revenue [Line Items]
Revenue	(1)	(5)	(3)	(15)
Unallocated | U.S.
Disaggregation of Revenue [Line Items]
Revenue	(1)	(3)	(2)	(10)
Unallocated | International
Disaggregation of Revenue [Line Items]
Revenue	0	(2)	(1)	(5)
Unallocated | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue	0	(1)	(1)	(2)
Unallocated | Asia Pacific
Disaggregation of Revenue [Line Items]
Revenue	0	(1)	0	(2)
Unallocated | Americas International - Canada and Latin America
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 0	$ 0	$ (1)