Restructuring - Restructuring Activities and Related Reserves (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2020 USD ($)
Restructuring Cost And Reserve [Line Items]
Reserve balance	$ 9
Charges (gain)	3
Cost charged against assets	(2)
Cash paid	(3)
Reserve balance	7
Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	5
Cash paid	(2)
Reserve balance	3
Non-cash Asset Impairment [Member]
Restructuring Cost And Reserve [Line Items]
Charges (gain)	2
Cost charged against assets	(2)
Other [Member]
Restructuring Cost And Reserve [Line Items]
Charges (gain)	1
Cash paid	(1)
Environmental Remediation [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	4
Reserve balance	$ 4