Equity and Noncontrolling Interests - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018
Realized and unrealized gains (losses) on derivatives
Current period changes in fair value		$ 2	$ (1)
Pension and postretirement plans
Other changes		0	0
Accumulated other comprehensive loss		(1,080)	(414)	$ (946)
Foreign currency translation adjustments
Foreign currency translation adjustments
Balance at beginning of period		(939)	(481)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent		(127)	58
Balance at end of period		(1,066)	(423)
Aggregate adjustment for period, tax effect	[1]	0	1
Realized and unrealized gains (losses) on derivatives
Realized and unrealized gains (losses) on derivatives
Balance at beginning of period		(13)	6
Current period changes in fair value		(4)	6
Reclassification to income		5	(5)
Balance at end of period		(12)	7
Current period changes in fair value, tax effect		(2)	3
Reclassifcation to income, tax effect	[2]	1	(2)
Realized and unrealized gains (losses) on marketable securities
Realized and unrealized gains (losses) on marketable securities
Balance at beginning of period		8	4
Balance at end of period		0	4
Pension and postretirement plans
Pension and postretirement plans
Balance at beginning of period		(2)	(2)
Balance at end of period		(2)	(2)
Scott Safety business [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
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]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax		0
Retained Earnings | Accounting Standards Update 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax		8
AOCI Attributable to Parent [Member] | Accounting Standards Update 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax		$ (8)	$ 0

[1] * During the three months ended December 31, 2017, $12 million of cumulative CTA was recognized as part of the divestiture-related gain recognized as part of the divestiture of Scott Safety.

[2] ** Refer to Note 15, "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.*** As previously disclosed, during the quarter ended December 31, 2018, the Company adopted ASU 2016-01, "Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities." As a result the Company reclassified $8 million of unrealized gains on marketable securities to retained earnings as of October 1, 2018.