RETIREMENT-RELATED BENEFITS - Net Periodic Pension Cost for Defined Benefit Pension Plans (Details) - Defined Benefit Pension Plans - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Cost/(Income) of Pension Plans
Service cost	$ 10	$ 12	$ 28	$ 36
Interest cost	$ 14	$ 9	$ 43	$ 27
Interest cost - income statement location	Other expense	Other expense	Other expense	Other expense
Expected return on plan assets	$ (15)	$ (10)	$ (46)	$ (32)
Expected return on plan assets - income statement location	Other expense	Other expense	Other expense	Other expense
Amortization of prior service costs (credits)			$ 1
Amortization of prior service costs/(credits) - income statement location			Other expense
Recognized actuarial losses (gains)	$ 1	$ 10	$ 3	$ 30
Recognized actuarial losses (gains) - income statement location	Other expense	Other expense	Other expense	Other expense
Curtailments and settlements	$ 3		$ 3
Curtailments and settlements - income statement location	Other expense	Other expense	Other expense	Other expense
Total net periodic pension cost	$ 14	$ 20	$ 33	$ 61