Equity and Noncontrolling Interests Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2019
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated other comprehensive loss, end of period		$ (776)	$ (795)	$ (946)
Realized and unrealized gains (losses) on derivatives
Divestiture of Power Solutions		8	6	(29)
Realized and unrealized gains (losses) on marketable securities
Reclassification to income	[1]	0	0	(1)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax		0	0	(1)
Pension and postretirement plans
Stock repurchase program, authorized amount					$ 8,500
Proceeds from Sale and Maturity of Marketable Securities				3
Marketable Securities, Realized Gain (Loss)				2
Foreign Currency Translation
Foreign currency translation adjustments
Balance at beginning of period		(785)	(939)	(481)
Aggregate adjustment for the period	[2]	7	(325)	(458)
Balance at end of period		(778)	(785)	(939)
Aggregate adjustment for the period, tax		1	0	(3)
Realized And Unrealized Gains Losses On Derivatives
Realized and unrealized gains (losses) on derivatives
Balance at beginning of period		(2)	(13)	6
Current period changes in fair value		3	(1)	(8)
Reclassification to income	[3]	1	8	(11)
Balance at end of period		2	(2)	(13)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax		0	2	(5)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax		1	(1)	(4)
Unrealized Gain Loss On Marketable Securities
Realized and unrealized gains (losses) on marketable securities
Balance at beginning of period		0	8	4
Current period changes in fair value		0	0	5
Balance at end of period		0	0	8
Current period changes in fair value, tax		0	0	1
Pension And Other Postretirement Benefit Plans Assets
Pension and postretirement plans
Balance at beginning of period		(8)	(2)	(2)
Balance at end of period		0	(8)	(2)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Reclassification Adjustment, before Tax		1	0	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax		9	(6)	0
Reclassification to income, tax		(1)	0	0
Other changes (tax)		4	0	0
Power Solutions
Foreign currency translation adjustments
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax		0	479	0
Realized and unrealized gains (losses) on derivatives
Divestiture of Power Solutions		0	4	0
Pension and postretirement plans
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax		0	479	0
Power Solutions | Realized And Unrealized Gains Losses On Derivatives
Realized and unrealized gains (losses) on derivatives
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax		0	1	0
Scott Safety business [Member]
Foreign currency translation adjustments
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax				12
Pension and postretirement plans
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax				12
Accounting Standards Update 2016-01 [Member]
Realized and unrealized gains (losses) on marketable securities
Balance at beginning of period			8
Balance at end of period				8
Accumulated Other Comprehensive Income (Loss) | Accounting Standards Update 2016-01 [Member]
Realized and unrealized gains (losses) on marketable securities
Balance at beginning of period	[4]	$ 0	(8)	0
Balance at end of period	[4]		$ 0	$ (8)

[1] During fiscal 2018, the Company sold certain marketable common stock for approximately $3 million. As a result, the Company recorded $2 million of realized gains within selling, general and administrative expenses.

[2] During fiscal 2018, $12 million of cumulative CTA was recognized as part of the divestiture-related gain recognized as part of the divestiture of Scott Safety.

[3] Refer to Note 10, "Derivative Instruments and Hedging Activities," of the notes to consolidated financial statements for disclosure of the line items in the consolidated statements of income affected by reclassifications from AOCI into income related to derivatives.

[4] The Company adopted ASU 2016-01, "Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities" effective October 1, 2018 and, as a result, reclassified $8 million of unrealized gains on marketable securities to retained earnings.