Financial Instruments and Commodity Contracts (Impact on AOCI and Earnings) (Details) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	$ (121)	$ 99	$ 894
Amount of Gain (Loss) Recognized in Other expenses (income), net (Ineffective and Excluded Portion)	4	1	4
Cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	(122)	99	894
Amount of Gain (Loss) Recognized in Other expenses (income), net (Ineffective and Excluded Portion)	0	1	4
Cash flow hedges \| Metal contracts
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	(48)	119	951
Amount of Gain (Loss) Recognized in Other expenses (income), net (Ineffective and Excluded Portion)	0	0	0
Cash flow hedges \| Currency exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	(77)	(12)	(55)
Amount of Gain (Loss) Recognized in Other expenses (income), net (Ineffective and Excluded Portion)	0	1	4
Cash flow hedges \| Energy contracts
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	4	(8)	(2)
Amount of Gain (Loss) Recognized in Other expenses (income), net (Ineffective and Excluded Portion)	0	0	0
Cash flow hedges \| Interest rate swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	(1)	0	0
Amount of Gain (Loss) Recognized in Other expenses (income), net (Ineffective and Excluded Portion)	0	0	0
Net investment hedges \| Currency exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	1	0	0
Amount of Gain (Loss) Recognized in Other expenses (income), net (Ineffective and Excluded Portion)	$ 4	$ 0	$ 0

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4E

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The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4C
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C

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- Definition

Amount, before reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 12
-Publisher FASB
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