Acquisitions and Divestitures Narrative (Details) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($) $ / shares	Jul. 17, 2018 USD ($)	Jul. 02, 2018 USD ($)	Dec. 01, 2017 USD ($)
Business Acquisition & Disposal [Line Items]
Purchase price of businesses, net of cash acquired			$ 243	$ 770
Net sales	$ 4,570	$ 4,248	8,717	8,064
Goodwill	6,509		6,509			$ 6,455
Proceeds from divestiture of business			$ 5	$ 221
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition & Disposal [Line Items]
Net sales					$ 240
Number of additional businesses acquired			6			4
Aventics [Member]
Business Acquisition & Disposal [Line Items]
Net sales						$ 425
Cash paid, net of cash acquired							$ 622
Goodwill							354
Goodwill expected tax deductible amount							20
Intangibles							$ 278
Intangible assets, weighted average useful life						12 years
Textron's Tools & Test [Member]
Business Acquisition & Disposal [Line Items]
Net sales						$ 470
Cash paid, net of cash acquired								$ 810
Goodwill								361
Goodwill expected tax deductible amount								17
Intangibles								$ 358
Intangible assets, weighted average useful life						14 years
Paradigm [Member]
Business Acquisition & Disposal [Line Items]
Net sales						$ 140
Cash paid, net of cash acquired									$ 505
Goodwill									309
Goodwill expected tax deductible amount									170
Intangibles									$ 238
Intangible assets, weighted average useful life						11 years
ClosetMaid [Member]
Business Acquisition & Disposal [Line Items]
Proceeds from divestiture of business						$ 200
Gain (Loss) on sales of business, net of tax						$ (24)
After-tax disposal gain (loss) impact on diluted earnings per share | $ / shares						$ (0.04)
After-tax proceeds on sale of business						$ 150
Automation Solutions [Member]
Business Acquisition & Disposal [Line Items]
Goodwill	5,421		$ 5,421			$ 5,355
Automation Solutions [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition & Disposal [Line Items]
Number of additional businesses acquired						2
Climate Technologies [Member]
Business Acquisition & Disposal [Line Items]
Goodwill	$ 672		$ 672			$ 670
Climate Technologies [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition & Disposal [Line Items]
Number of additional businesses acquired						2