Acquisitions And Divestitures (Narrative) (Details) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2019 USD ($) $ / shares	Jun. 30, 2019 USD ($) $ / shares	Mar. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares	Sep. 30, 2018 USD ($) $ / shares	Jun. 30, 2018 USD ($) $ / shares	Mar. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares	Sep. 30, 2019 USD ($) $ / shares	Sep. 30, 2018 USD ($) $ / shares	Sep. 30, 2017 USD ($) $ / shares	Jul. 17, 2018 USD ($)	Jul. 02, 2018 USD ($)	Dec. 01, 2017 USD ($)	Apr. 28, 2017 USD ($)
Business Acquisition [Line Items]
Net sales	$ 4,971	$ 4,684	$ 4,570	$ 4,147	$ 4,888	$ 4,456	$ 4,248	$ 3,816	$ 18,372	$ 17,408	$ 15,264
Goodwill	6,536				6,455				6,536	6,455	5,316
Purchases of businesses, net of cash acquired									469	2,203	2,990
Net income (loss)									2,328	2,224	1,550
Restructuring expense									95	65	78
Amortization of intangible assets									359	314	222
Intangible assets, net (excluding goodwill)	$ 2,615				$ 2,751				2,615	2,751
Pretax earnings (loss)									2,859	2,667	2,335
Net income (loss)									$ 2,328	$ 2,224	$ 1,675
Diluted net earnings (loss) per common share | $ / shares	$ 1.16	$ 0.97	$ 0.84	$ 0.74	$ 0.97	$ 1.12	$ 0.76	$ 0.61	$ 3.71	$ 3.46	$ 2.35
Aventics [Member]
Business Acquisition [Line Items]
Cash paid, 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
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Annualized sales									$ 300
Goodwill	$ 210								210
Goodwill, expected tax deductible amount	173								173
Number of businesses acquired										4
Purchases of businesses, net of cash acquired									469
Restructuring expense									7
Intangibles	155								$ 155
Intangible assets, weighted average useful life									9 years
Total acquired businesses
Business Acquisition [Line Items]
Cash paid, net of cash acquired					$ 2,214					$ 2,214
Net sales										365
Goodwill					1,176					1,176
Net income (loss)										(3)
Restructuring expense										3
Amortization of intangible assets										40
Intangibles					1,013					1,013
Pentair's Valves & Controls [Member]
Business Acquisition [Line Items]
Cash paid, net of cash acquired											$ 2,960
Annualized sales											1,400
Net sales											600
Cash acquired															$ 207
Goodwill															1,500
Goodwill, expected tax deductible amount															0
Net income (loss)											(97)
Restructuring expense											25
Amortization of intangible assets											$ 29
Intangibles															$ 1,100
Intangible assets, weighted average useful life											14 years
Diluted net earnings (loss) per common share | $ / shares											$ (0.15)
Automation Solutions [Member]
Business Acquisition [Line Items]
Goodwill	5,467				5,355				$ 5,467	5,355	$ 4,704
Restructuring expense									$ 65	$ 41	$ 63
Automation Solutions [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Number of businesses acquired									8	2	2
Climate Technologies [Member]
Business Acquisition [Line Items]
Goodwill	$ 668				$ 670				$ 668	$ 670	$ 555
Restructuring expense									$ 20	$ 20	10
Climate Technologies [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Number of businesses acquired										2
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | ClosetMaid [Member]
Business Acquisition [Line Items]
Net sales											298
Pretax earnings (loss)											15
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]
Pretax earnings (loss)										(39)
Fair Value Adjustment to Inventory [Member] | Pentair's Valves & Controls [Member]
Business Acquisition [Line Items]
Pretax earnings (loss)											(74)
Order or Production Backlog [Member] | Pentair's Valves & Controls [Member]
Business Acquisition [Line Items]
Pretax earnings (loss)											(19)
Deferred Revenue [Domain] | Total acquired businesses
Business Acquisition [Line Items]
Pretax earnings (loss)										$ (11)
Acquisition-related Costs [Member] | Pentair's Valves & Controls [Member]
Business Acquisition [Line Items]
Pretax earnings (loss)											(52)
Fair value adjustment to inventory & backlog member [Member] | Pentair's Valves & Controls [Member]
Business Acquisition [Line Items]
Pretax earnings (loss)											(93)
Net income (loss)											$ (65)
Diluted net earnings (loss) per common share | $ / shares											$ (0.10)