Financial Instruments and Commodity Contracts - Summary of the Impact on AOCI and Earnings (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Total cash flow hedging derivatives	$ 6	$ (179)	$ (145)	$ 54
Cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Total cash flow hedging derivatives	16	(179)	(138)	54
Cash flow hedges | Metal Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Total cash flow hedging derivatives	(8)	(154)	(128)	72
Cash flow hedges | Currency Exchange Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Total cash flow hedging derivatives	35	(26)	(1)	(18)
Cash flow hedges | Energy Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Total cash flow hedging derivatives	(3)	0	(3)	(1)
Cash flow hedges | Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total cash flow hedging derivatives	(8)	1	(6)	1
Net investment hedges | Currency Exchange Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Total cash flow hedging derivatives	$ (10)	$ 0	$ (7)	$ 0