Contingencies - Additional Information (Details) $ in Millions		9 Months Ended		12 Months Ended
	Jan. 22, 2019 USD ($)	Jun. 30, 2020 USD ($) site claim	Jun. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) claim
Loss Contingencies [Line Items]
Environmental accrual balance		$ 16		$ 15
Discounted amount environmental accrual for on-going operations maintenance and monitoring		14
Undiscounted amount environmental accrual for on-going operations maintenance and monitoring		15
Asbestos related liability remeasurement		$ 0	$ 31
Maremont Asbestos
Loss Contingencies [Line Items]
Damages sought	$ 51
Asbestos related liability remeasurement	$ 31		$ 31
Obligation period for asbestos personal injury claims				40 years
Rockwell Asbestos
Loss Contingencies [Line Items]
Number of pending claims | claim		1,400		1,400
Pending and future claims		$ 86		$ 91
Asbestos-related insurance recoveries		$ 59		61
Low Range
Loss Contingencies [Line Items]
Site contingency, accrual, discount rate		1.50%
Low Range | Rockwell Asbestos
Loss Contingencies [Line Items]
Possible loss				91
High Range
Loss Contingencies [Line Items]
Site contingency, accrual, discount rate		2.25%
High Range | Rockwell Asbestos
Loss Contingencies [Line Items]
Possible loss				181
Superfund Sites
Loss Contingencies [Line Items]
Number of Superfund environmental sites | site		10
Environmental costs reasonably possible		$ 25
Environmental accrual balance		12		11
Non-Superfund Sites
Loss Contingencies [Line Items]
Environmental costs reasonably possible		14
Environmental accrual balance		$ 4		$ 4