Reportable Segment Information - Sales and Property, Plant and Equipment by Geographical Area (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Sales	$ 629	$ 613	$ 591	$ 557	$ 594	$ 577	$ 569	$ 545	$ 2,390	$ 2,285	$ 2,084
Property, plant and equipment, net	498				420				498	420
United States
Segment Reporting Information [Line Items]
Sales									1,766	1,652	1,504
Property, plant and equipment, net	431				384				431	384
International
Segment Reporting Information [Line Items]
Sales									624	633	$ 580
Property, plant and equipment, net	$ 67				$ 36				$ 67	$ 36