Business Segment Information Geographic Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Net sales	$ 4,570	$ 4,248	$ 8,717	$ 8,064
Reportable Geographical Components [Member]
Disaggregation of Revenue [Line Items]
Net sales	4,571	4,254	8,708	8,078
Reportable Geographical Components [Member] | Americas
Disaggregation of Revenue [Line Items]
Net sales	2,605	2,355	4,917	4,419
Reportable Geographical Components [Member] | Asia, Middle East & Africa
Disaggregation of Revenue [Line Items]
Net sales	1,195	1,208	2,301	2,346
Reportable Geographical Components [Member] | Europe [Member]
Disaggregation of Revenue [Line Items]
Net sales	771	691	1,490	1,313
Reportable Geographical Components [Member] | Automation Solutions [Member]
Disaggregation of Revenue [Line Items]
Net sales	3,010	2,771	5,809	5,343
Reportable Geographical Components [Member] | Automation Solutions [Member] | Americas
Disaggregation of Revenue [Line Items]
Net sales	1,523	1,372	2,928	2,658
Reportable Geographical Components [Member] | Automation Solutions [Member] | Asia, Middle East & Africa
Disaggregation of Revenue [Line Items]
Net sales	910	868	1,751	1,658
Reportable Geographical Components [Member] | Automation Solutions [Member] | Europe [Member]
Disaggregation of Revenue [Line Items]
Net sales	577	531	1,130	1,027
Reportable Geographical Components [Member] | Commercial & Residential Solutions [Member]
Disaggregation of Revenue [Line Items]
Net sales	1,561	1,483	2,899	2,735
Reportable Geographical Components [Member] | Commercial & Residential Solutions [Member] | Americas
Disaggregation of Revenue [Line Items]
Net sales	1,082	983	1,989	1,761
Reportable Geographical Components [Member] | Commercial & Residential Solutions [Member] | Asia, Middle East & Africa
Disaggregation of Revenue [Line Items]
Net sales	285	340	550	688
Reportable Geographical Components [Member] | Commercial & Residential Solutions [Member] | Europe [Member]
Disaggregation of Revenue [Line Items]
Net sales	$ 194	$ 160	$ 360	$ 286