Pension and Postretirement Plans - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 2	$ 2
Expected return on plan assets	(2)	(2)
Net periodic benefit credit	0	0
UNITED STATES | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	25	23
Expected return on plan assets	(46)	(50)
Net periodic benefit credit	(21)	(27)
Non-U.S. | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	5
Interest cost	14	14
Expected return on plan assets	(27)	(28)
Net periodic benefit credit	$ (8)	$ (9)