Financial Instruments and Commodity Contracts (Gain (Loss) Reclassification) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2024
Derivative Instruments, Gain (Loss) [Line Items]
Income tax provision (benefit)	$ (1)	$ (159)	$ (218)
Net income	15	683	600
Cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Income before income tax provision	(237)	(225)	178
Income tax provision (benefit)	60	58	(47)
Net income	(177)	(167)	131
Cash flow hedges \| Interest rate swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Income before income tax provision	(1)	2	2
Cost of goods sold \| Cash flow hedges \| Energy contracts
Derivative Instruments, Gain (Loss) [Line Items]
Income before income tax provision	0	(8)	(5)
Cost of goods sold \| Cash flow hedges \| Metal contracts
Derivative Instruments, Gain (Loss) [Line Items]
Income before income tax provision	0	(1)	5
Cost of goods sold \| Cash flow hedges \| Currency exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Income before income tax provision	8	(9)	17
Net sales \| Cash flow hedges \| Metal contracts
Derivative Instruments, Gain (Loss) [Line Items]
Income before income tax provision	(245)	(185)	181
Net sales \| Cash flow hedges \| Currency exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Income before income tax provision	4	(21)	(19)
Depreciation and amortization \| Cash flow hedges \| Currency exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Income before income tax provision	$ (3)	$ (3)	$ (3)