PENSION & POSTRETIREMENT PLANS - Schedule of Pension and Postretirement Plan Expenses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Retirement Benefits [Abstract]
Service cost	$ 18	$ 9	$ 36	$ 18
Interest cost	48	55	96	110
Expected return on plan assets	(73)	(74)	(146)	(148)
Net amortization	4	(14)	8	(28)
Total	$ (3)	$ (24)	$ (6)	$ (48)