Acquisitions And Divestitures (Narrative) (Details) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2018 USD ($) $ / shares	Jun. 30, 2018 USD ($) $ / shares	Mar. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares	Sep. 30, 2017 USD ($) $ / shares	Jun. 30, 2017 USD ($) $ / shares	Mar. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($) $ / shares	Sep. 30, 2018 USD ($) $ / shares	Sep. 30, 2017 USD ($) $ / shares	Sep. 30, 2016 USD ($) $ / shares	Jul. 17, 2018 USD ($)	Jul. 02, 2018 USD ($)	Dec. 01, 2017 USD ($)	Apr. 28, 2017 USD ($)
Business Acquisition [Line Items]
Goodwill	$ 6,455				$ 5,316				$ 6,455	$ 5,316	$ 3,909
Purchases of businesses, net of cash acquired									2,203	2,990	132
Net sales	4,888	$ 4,456	$ 4,248	$ 3,816	4,435	$ 4,039	$ 3,574	$ 3,216	17,408	15,264	14,522
Net income (loss)									2,224	1,550	1,664
Restructuring expense									65	78	96
Amortization of intangible assets									314	222	177
Intangible assets, net (excluding goodwill)	$ 2,751				$ 1,890				2,751	1,890
Pretax earnings (loss)									2,667	2,335	2,316
Net income (loss)									$ 2,224	$ 1,675	$ 1,619
Diluted net earnings (loss) per common share | $ / shares	$ 0.97	$ 1.12	$ 0.76	$ 0.61	$ 0.78	$ 0.64	$ 0.45	$ 0.48	$ 3.46	$ 2.35	$ 2.52
Aventics [Member]
Business Acquisition [Line Items]
Cash paid, net of cash acquired												$ 622
Goodwill												358
Goodwill, expected tax deductible amount												20
Net sales									$ 425
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
Goodwill													374
Goodwill, expected tax deductible amount													17
Net sales									$ 470
Intangibles													$ 358
Intangible assets, weighted average useful life									14 years
Paradigm [Member]
Business Acquisition [Line Items]
Cash paid, net of cash acquired														$ 505
Goodwill														328
Goodwill, expected tax deductible amount														160
Net sales									$ 140
Intangibles														$ 238
Intangible assets, weighted average useful life									11 years
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Goodwill											$ 83
Goodwill, expected tax deductible amount											$ 27
Number of businesses acquired									4		6
Purchases of businesses, net of cash acquired											$ 132
Net sales											51
Intangible assets, net (excluding goodwill)											$ 50
Intangible assets, weighted average useful life											9 years
Total acquired businesses
Business Acquisition [Line Items]
Cash paid, net of cash acquired	$ 2,219								$ 2,219
Goodwill	1,188								1,188
Net sales									365
Net income (loss)									(3)
Restructuring expense									3
Amortization of intangible assets									40
Intangibles	1,012								1,012
Pentair's Valves & Controls [Member]
Business Acquisition [Line Items]
Cash paid, net of cash acquired					$ 2,960					$ 2,960					$ 2,942
Cash acquired															207
Annualized sales										1,400
Goodwill															1,476
Goodwill, expected tax deductible amount															0
Net sales										600
Net income (loss)										(97)
Restructuring expense										25
Amortization of intangible assets										$ 29
Intangibles															$ 1,076
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	5,355				4,704				5,355	$ 4,704	$ 3,160
Restructuring expense									$ 41	$ 63	$ 80
Automation Solutions [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Number of businesses acquired									2	2	4
Climate Technologies [Member]
Business Acquisition [Line Items]
Goodwill	$ 670				555				$ 670	$ 555	$ 553
Restructuring expense									$ 20	10	$ 5
Climate Technologies [Member] | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Number of businesses acquired									2		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 impact on diluted earnings per share | $ / shares									$ (0.04)
After-tax proceeds on sale of business									$ 150
Current assets held-for-sale					73					73
Other non-current assets held-for-sale					176					176
Accrued expenses and other liabilities held-for-sale					$ 61					61
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)