Equity and Noncontrolling Interests Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Accumulated other comprehensive loss, end of period		$ (946)	$ (473)	$ (1,153)
Realized and unrealized gains (losses) on derivatives
Current period changes in fair value		(29)	(14)	9
Reclassification to income, tax		(1)	0
Pension and postretirement plans
Stock repurchase program, authorized amount		1,000			$ 1,000
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax		(1)	0	0
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		(481)	(1,152)	(1,047)
Aggregate adjustment for the period	[1]	(458)	108	(105)
Balance at end of period		(939)	(481)	(1,152)
Aggregate adjustment for the period, tax		(3)	1	(43)
Pension and postretirement plans
Other Comprehensive Income, Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Adient spin-off		0	563	0
Realized And Unrealized Gains Losses On Derivatives
Realized and unrealized gains (losses) on derivatives
Balance at beginning of period		6	4	(7)
Current period changes in fair value		(8)	9	(10)
Reclassification to income	[2]	(11)	(23)	21
Adient spin-off impact		0	16	0
Balance at end of period		(13)	6	4
Current period changes in fair value, tax		(4)	4	(5)
Reclassification to income, tax		(5)	(10)	11
Other Comprehensive Income, Unrealized Gain on Derivatives Arising Due to Adient spin-off, Tax		0	6
Unrealized Gain Loss On Marketable Securities
Realize and unrealized gains (losses) on marketable securities
Balance at beginning of period		4	(1)	0
Current period changes in fair value		5	5	(1)
Balance at end of period		8	4	(1)
Current period changes in fair value, tax		1	1	0
Pension And Other Postretirement Benefit Plans Assets
Pension and postretirement plans
Balance at beginning of period		(2)	(4)	(3)
Reclassification to income	[3]	0	0	(1)
Adient spin-off impact		0	2	0
Balance at end of period		(2)	(2)	(4)
Reclassification to income, tax		0	0	0
Adient spin-off, tax		0	0	$ 0
Other Comprehensive Income, Pension and Other Postretirement Benefit Plan, Tax, due to Adient spin-off			$ 0
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

[1] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmNkYmRiMTQwN2NmNzQyMWFiMTk2ODVmODAzOTk1MTMxfFRleHRTZWxlY3Rpb246OTI2N0UxOEE4REFFNDc4M0NBREQ4MTQxQzEyNEQ3MUQM}

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

[3] Refer to Note 15, "Retirement Plans," of the notes to consolidated financial statements for disclosure of the components of the Company's net periodic benefit costs associated with its defined benefit pension and postretirement plans. For the year ended September 30, 2016 the amounts reclassified from AOCI into income for pension and postretirement plans were primarily recorded in selling, general and administrative expenses on the consolidated statements of income.