Acquisitions and Divestitures - Additional Information (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)
Acquisitions And Discontinued Operations [Line Items]
Cash paid for business acquisition	$ 0	$ 3
Goodwill, Acquired During Period	0
Reduction in goodwill related to business divestitures	18
Proceeds from business divestitures, net of cash divested	2,011	47
Adjustment to purchase price of previous acquisition	0	$ 45
Scott Safety business [Member]
Acquisitions And Discontinued Operations [Line Items]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	114
Reduction in goodwill related to business divestitures	1,200
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	84
Proceeds from business divestitures, net of cash divested	2,000
Business Divestitures, Not Specific [Member]
Acquisitions And Discontinued Operations [Line Items]
Number Of Businesses Divested		1
Proceeds from Divestiture of Businesses		$ 4
Cash Divested from Deconsolidation		5
Proceeds from business divestitures, net of cash divested		$ 52
Individually Immaterial Acquisitions
Acquisitions And Discontinued Operations [Line Items]
Number of acquisitions		2
Purchase price, net of cash acquired		$ 6
Cash paid for business acquisition		3
Goodwill, Acquired During Period		$ 1
Power Solutions
Acquisitions And Discontinued Operations [Line Items]
Goodwill, Acquired During Period	0
Reduction in goodwill related to business divestitures	0
Tyco International Holding S.a.r.L. (TSarL) [Member]
Acquisitions And Discontinued Operations [Line Items]
Repayments of Debt	1,900
Long-term Debt	$ 1,800		$ 4,000