Acquisitions And Divestitures (Narrative) (Details) $ / shares in Units, $ in Millions			3 Months Ended								12 Months Ended
	Oct. 01, 2020 USD ($)	Jul. 17, 2018 USD ($)	Sep. 30, 2020 USD ($) $ / shares	Jun. 30, 2020 USD ($) $ / shares	Mar. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares	Sep. 30, 2019 USD ($) $ / shares	Jun. 30, 2019 USD ($) $ / shares	Mar. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($) $ / shares	Sep. 30, 2018 USD ($) $ / shares	Jul. 02, 2018 USD ($)	Dec. 01, 2017 USD ($)
Business Acquisition [Line Items]
Purchases of businesses, net of cash acquired											$ 126	$ 469	$ 2,203
Net sales			$ 4,558	$ 3,914	$ 4,162	$ 4,151	$ 4,971	$ 4,684	$ 4,570	$ 4,147	16,785	18,372	17,408
Deferred tax liabilities			933				920				933	920
Goodwill			6,734				6,536				6,734	6,536	6,455
Net income (loss)											1,990	2,328	2,224
Restructuring expense											284	95	65
Amortization of intangible assets											369	359	314
Intangible assets, net (excluding goodwill)			$ 2,468				$ 2,615				2,468	2,615
Earnings before income taxes											$ 2,335	$ 2,859	$ 2,667
Diluted net earnings (loss) per common share | $ / shares			$ 1.20	$ 0.67	$ 0.84	$ 0.53	$ 1.16	$ 0.97	$ 0.84	$ 0.74	$ 3.24	$ 3.71	$ 3.46
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Purchases of businesses, net of cash acquired												$ 469
Annualized sales												300
Goodwill							$ 209					209
Goodwill, expected tax deductible amount							155					155
Number of businesses acquired											3		4
Intangibles							158					$ 158
Intangible assets, weighted average useful life												9 years
Aventics [Member]
Business Acquisition [Line Items]
Purchases of businesses, net of cash acquired		$ 622
Annualized sales													$ 425
Goodwill		372
Goodwill, expected tax deductible amount		20
Intangibles		$ 278
Intangible assets, weighted average useful life													12 years
Textron's Tools & Test [Member]
Business Acquisition [Line Items]
Cash paid, net of cash acquired														$ 810
Annualized sales													$ 470
Goodwill														366
Goodwill, expected tax deductible amount														11
Intangibles														$ 358
Intangible assets, weighted average useful life													14 years
Paradigm [Member]
Business Acquisition [Line Items]
Cash paid, net of cash acquired															$ 505
Annualized sales													$ 140
Goodwill															309
Goodwill, expected tax deductible amount															170
Intangibles															$ 238
Intangible assets, weighted average useful life													11 years
Total acquired businesses
Business Acquisition [Line Items]
Cash paid, net of cash acquired													$ 2,214
Net sales													365
Goodwill													1,176
Net income (loss)													(3)
Restructuring expense													3
Amortization of intangible assets													40
Intangibles													1,013
Pentair's Valves & Controls [Member]
Business Acquisition [Line Items]
Restructuring expense													19
Automation Solutions [Member]
Business Acquisition [Line Items]
Goodwill			$ 5,583				5,467				$ 5,583	$ 5,467	5,355
Restructuring expense											232	$ 65	$ 41
Automation Solutions [Member] | Open Systems International Inc. [Member]
Business Acquisition [Line Items]
Purchases of businesses, net of cash acquired	$ 1,600
Annualized sales											$ 170
Deferred tax liabilities	180
Goodwill	1,000
Goodwill, expected tax deductible amount	0
Intangibles	$ 800
Intangible assets, weighted average useful life	11 years
Automation Solutions [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Number of businesses acquired											2	8	2
Climate Technologies [Member]
Business Acquisition [Line Items]
Goodwill			$ 730				$ 668				$ 730	$ 668	$ 670
Restructuring expense											$ 23	$ 20	$ 20
Climate Technologies [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Number of businesses acquired											1		2
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | ClosetMaid [Member]
Business Acquisition [Line Items]
Proceeds from divestitures 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
Fair Value Adjustment to Inventory [Member] | Total acquired businesses
Business Acquisition [Line Items]
Earnings before income taxes													(39)
Deferred Revenue [Domain] | Total acquired businesses
Business Acquisition [Line Items]
Earnings before income taxes													$ (11)