Acquisitions and Divestitures - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Acquisitions And Discontinued Operations [Line Items]
Purchase price, net of cash acquired		$ 63	$ 16
Cash paid for business acquisition		59	16
Goodwill, Acquired During Period		42
Business divestitures, net of cash divested		0	12
Power Solutions
Acquisitions And Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses	$ 13,200		13,200
Disposal Group, Discontinued Operations, Consideration, net	11,600		11,600
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax	5,200		5,200
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	4,000
Business Divestitures, Not Specific [Member]
Acquisitions And Discontinued Operations [Line Items]
Proceeds from Divestiture of Businesses	$ 18		18
Business divestitures, net of cash divested			12
Global Products
Acquisitions And Discontinued Operations [Line Items]
Goodwill, Acquired During Period		19
Global Products | Individually Immaterial Acquisitions
Acquisitions And Discontinued Operations [Line Items]
Goodwill, Acquired During Period		19	9
Building Solutions EMEA/LA
Acquisitions And Discontinued Operations [Line Items]
Goodwill, Acquired During Period		23
Goodwill, Written off Related to Sale of Business Unit			1
Building Solutions EMEA/LA | Individually Immaterial Acquisitions
Acquisitions And Discontinued Operations [Line Items]
Goodwill, Acquired During Period		23	$ 1
Building Solutions Asia Pacific
Acquisitions And Discontinued Operations [Line Items]
Goodwill, Acquired During Period		$ 0