Restructuring - Restructuring Activities and Related Reserves (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2018 USD ($)
Restructuring Cost And Reserve [Line Items]
Reserve balance	$ 5
Charges	9
Cash received (paid)	(2)
Reserve balance	12
Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	1
Charges	7
Cash received (paid)	(1)
Reserve balance	7
Environmental Remediation [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	4
Costs charged against assets / (liabilities)	1
Reserve balance	5
Asset Impairment and Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Charges	1
Costs charged against assets / (liabilities)	(1)
Other [Member]
Restructuring Cost And Reserve [Line Items]
Charges	1
Cash received (paid)	$ (1)