Acquisitions and Divestitures Narrative (Details) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) $ / shares	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jan. 10, 2018 USD ($)	Dec. 01, 2017 USD ($)	Apr. 28, 2017 USD ($)
Business Acquisition & Disposal [Line Items]
Net sales	$ 4,456	$ 4,039	$ 12,520	$ 10,829
Goodwill	5,745		5,745		$ 5,745			$ 5,316
Purchase price of businesses, net of cash acquired			770	2,991
Proceeds from divestiture of businesses			$ 223	$ 40
Textron's Tools & Test [Member]
Business Acquisition & Disposal [Line Items]
Net sales					470
Aventics [Member]
Business Acquisition & Disposal [Line Items]
Net sales					425
Cooper-Atkins [Member]
Business Acquisition & Disposal [Line Items]
Cash paid, net of cash acquired									$ 247
Goodwill									114
Goodwill expected tax deductible amount									114
Intangibles									$ 127
Intangible assets, weighted average useful life			12 years
Pentair's Valves & Controls [Member]
Business Acquisition & Disposal [Line Items]
Cash paid, net of cash acquired											$ 2,960
Net sales								1,400
Cash acquired											$ 207
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition & Disposal [Line Items]
Number of additional businesses acquired			3
Cooper-Atkins & Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition & Disposal [Line Items]
Net sales						$ 70
Paradigm [Member]
Business Acquisition & Disposal [Line Items]
Cash paid, net of cash acquired										$ 505
Net sales							$ 140
Goodwill										332
Goodwill expected tax deductible amount										160
Intangibles										$ 238
Intangible assets, weighted average useful life			11 years
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | ClosetMaid [Member]
Business Acquisition & Disposal [Line Items]
Proceeds from divestiture of businesses			$ 200
Gain (loss) on divestiture of business, after tax			$ (24)
Disposal gain (loss) impact on diluted earnings per share | $ / shares			$ (0.04)
After-tax proceeds on sale of business			$ 150
Current assets held-for-sale								73
Other noncurrent assets held-for-sale								176
Accrued expenses & other liabilities held-for-sale								61
Automation Solutions [Member]
Business Acquisition & Disposal [Line Items]
Goodwill	5,018		$ 5,018		5,018			4,704
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	$ 671		$ 671		$ 671			$ 555
Climate Technologies [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition & Disposal [Line Items]
Number of additional businesses acquired			1