FINANCIAL ASSETS AND LIABILITIES - Gains and Losses (Details) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2024
Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Amounts Excluded from Effectiveness Testing	$ 0	$ 0	$ 0
Designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Recognized in OCI	(73)	(9)	11
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Reclassified from AOCI	8	(11)	21
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Amounts Excluded from Effectiveness Testing	37	22	1
Not designated as hedging instruments - economic hedges
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (loss) from derivatives	5	(15)	(48)
Foreign exchange contracts \| Designated as hedging instruments \| Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Recognized in OCI	2	(14)	22
Foreign exchange contracts \| Designated as hedging instruments \| Net investment hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Recognized in OCI	(103)	(5)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Amounts Excluded from Effectiveness Testing	$ 26	$ 10
Derivative, Excluded Component, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest Expense	Interest Expense
Foreign exchange contracts \| Not designated as hedging instruments - economic hedges
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (loss) from derivatives	$ 5	$ (15)	$ (48)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Income and Expense	Other Income and Expense	Other Income and Expense
Cross-currency swap contracts \| Designated as hedging instruments \| Net investment hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Recognized in OCI	$ 28	$ 10	$ (11)
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Amounts Excluded from Effectiveness Testing	$ 12	$ 12	$ 1
Derivative, Excluded Component, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest Expense	Interest Expense	Interest Expense
Cost of services. \| Foreign exchange contracts \| Designated as hedging instruments \| Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Reclassified from AOCI	$ (2)	$ (11)	$ 21
Other expense \| Foreign exchange contracts \| Designated as hedging instruments \| Derivative instruments in cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Earnings and Other Comprehensive Income - Reclassified from AOCI	$ 11

Amount of gain (loss) from excluded component of derivative hedge, recognized in earnings. Excludes recognition under systematic and rational method.

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