Benefit Plans (Detail) - Pension Plans - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 22	$ 22	$ 47	$ 46
Interest cost	35	32	74	67
Expected return on plan assets	(38)	(35)	(80)	(73)
Amortization of prior service credit	(1)	(2)	(2)	(3)
Amortization of loss	14	15	30	32
Settlement loss	0	1	0	1
Net pension cost	$ 33	$ 34	$ 69	$ 70