Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0		$ 0	$ 13
Interest cost	9	$ 10	18	21
Expected return on assets	(17)	(18)	(35)	(35)
Amortization of:
Prior service credit	0		0	(1)
Actuarial loss	4	2	8	4
Curtailment gain	0	0	0	(8)
Settlement loss	11	0	13	0
Total net periodic benefit cost	7	(6)	4	(6)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	0
Interest cost	0	0	0	0
Expected return on assets	0	0	0	0
Amortization of:
Prior service credit	0	(1)	(1)	(2)
Actuarial loss	0	0	0	0
Curtailment gain	0	0	0	0
Settlement loss	0	0	0	0
Total net periodic benefit cost	0	$ (1)	(1)	$ (2)
Foreign Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	1		3
Interest cost	2		5
Expected return on assets	(4)		(8)
Amortization of:
Prior service credit	0		0
Actuarial loss	1		1
Curtailment gain	0		0
Settlement loss	0		0
Total net periodic benefit cost	$ 0		$ 1