Restructuring - Restructuring Activities Including Merak Facility Closure (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2015 USD ($)
Restructuring Cost And Reserve [Line Items]
Reserve balance	$ 9
Charges	48
Cash paid	(7)
Reserve balance	22
Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	5
Charges	25
Cash paid	(11)
Reserve balance	19
Asset Impairment and Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Charges	23
Other [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	2
Charges	2
Cash paid	(3)
Reserve balance	1
2016 Plan [Member]
Restructuring Cost And Reserve [Line Items]
Charges	48
Costs charged against assets / liabilities	(21)
Cash paid	(11)
Reserve balance	16
2016 Plan [Member] | Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Charges	25
Costs charged against assets / liabilities	1
Cash paid	(10)
Reserve balance	16
2016 Plan [Member] | Asset Impairment and Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Charges	22
Costs charged against assets / liabilities	(22)
2016 Plan [Member] | Other [Member]
Restructuring Cost And Reserve [Line Items]
Charges	1
Cash paid	$ (1)