RETIREMENT-RELATED BENEFITS - Net Periodic Pension Cost for Defined Benefit Pension Plans (Details) - Defined Benefit Pension Plans - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Cost/(Income) of Pension Plans
Service cost	$ 9.0	$ 12.0	$ 19.0	$ 24.0
Interest cost	$ 15.0	$ 9.0	$ 29.0	$ 18.0
Interest cost - income statement location	Other expense (income)	Other expense (income)	Other expense (income)	Other expense (income)
Expected return on plan assets	$ (16.0)	$ (10.0)	$ (30.0)	$ (21.0)
Expected return on plan assets - income statement location	Other expense (income)	Other expense (income)	Other expense (income)	Other expense (income)
Amortization of prior service costs (credits)			$ 1.0
Amortization of prior service costs/(credits) - income statement location			Other expense (income)
Recognized actuarial losses (gains)	$ 1.0	$ 10.0	$ 3.0	$ 20.0
Recognized actuarial losses (gains) - income statement location	Other expense (income)	Other expense (income)	Other expense (income)	Other expense (income)
Total net periodic pension cost	$ 9.0	$ 21.0	$ 21.0	$ 41.0