Restructuring - Restructuring Activities and Related Reserves (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2016
Restructuring Cost And Reserve [Line Items]
Reserve balance	$ 22	$ 9	$ 9
Charges (credit)	(5)		43
Costs charged against assets	(2)		(30)
Cash (paid) received	(2)		(9)
Reserve balance	13	22	13
Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	19	5	5
Charges (credit)	1		26
Cash (paid) received	(9)		(20)
Reserve balance	11	19	11
Environmental Remediation [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	2	2	2
Reserve balance	2	2	2
Asset Sales [Member]
Restructuring Cost And Reserve [Line Items]
Charges (credit)	(8)		(9)
Costs charged against assets	(1)		(7)
Cash (paid) received	9		16
Asset Impairment and Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Charges (credit)	1		23
Costs charged against assets	(1)		(23)
Other [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	1	2	2
Charges (credit)	1		3
Cash (paid) received	$ (2)		$ (5)
Reserve balance		$ 1