Financial Instruments and Commodity Contracts (Summary of Gross Fair Value) (Details) - USD ($) $ in Millions	Mar. 31, 2026	Mar. 31, 2025
Assets
Derivative Assets, Current	$ 234	$ 176
Derivative Asset, Noncurrent	11	5
Liabilities
Derivative Liabilities, Current	(824)	(106)
Derivative Liabilities, Noncurrent	(6)	(7)
Derivative Assets (Liabilities), at Fair Value, Net	(585)	68
Derivatives designated as hedging instruments:
Assets
Derivative Assets, Current	23	106
Derivative Asset, Noncurrent	6	4
Liabilities
Derivative Liabilities, Current	(473)	(33)
Derivative Liabilities, Noncurrent	(2)	(6)
Derivative Assets (Liabilities), at Fair Value, Net	(446)	71
Derivatives designated as hedging instruments: \| Cash flow hedges \| Metal contracts
Assets
Derivative Assets, Current	5	89
Derivative Asset, Noncurrent	1	4
Liabilities
Derivative Liabilities, Current	(445)	(5)
Derivative Liabilities, Noncurrent	(2)	0
Derivative Assets (Liabilities), at Fair Value, Net	(441)	88
Derivatives designated as hedging instruments: \| Cash flow hedges \| Currency exchange contracts
Assets
Derivative Assets, Current	10	6
Derivative Asset, Noncurrent	1	0
Liabilities
Derivative Liabilities, Current	(22)	(27)
Derivative Liabilities, Noncurrent	0	(1)
Derivative Assets (Liabilities), at Fair Value, Net	(11)	(22)
Derivatives designated as hedging instruments: \| Cash flow hedges \| Energy contracts
Assets
Derivative Assets, Current	8	6
Derivative Asset, Noncurrent	0	0
Liabilities
Derivative Liabilities, Current	(3)	(1)
Derivative Liabilities, Noncurrent	0	0
Derivative Assets (Liabilities), at Fair Value, Net	5	5
Derivatives designated as hedging instruments: \| Cash flow hedges \| Interest rate swap contracts
Assets
Derivative Assets, Current	0	0
Derivative Asset, Noncurrent	0	0
Liabilities
Derivative Liabilities, Current	(3)	0
Derivative Liabilities, Noncurrent	0	(5)
Derivative Assets (Liabilities), at Fair Value, Net	(3)	(5)
Derivatives designated as hedging instruments: \| Net investment hedges \| Currency exchange contracts
Assets
Derivative Assets, Current	0	5
Derivative Asset, Noncurrent	4	0
Liabilities
Derivative Liabilities, Current	0	0
Derivative Liabilities, Noncurrent	0	0
Derivative Assets (Liabilities), at Fair Value, Net	4	5
Derivatives not designated as hedging instruments:
Assets
Derivative Assets, Current	211	70
Derivative Asset, Noncurrent	5	1
Liabilities
Derivative Liabilities, Current	(351)	(73)
Derivative Liabilities, Noncurrent	(4)	(1)
Derivative Assets (Liabilities), at Fair Value, Net	(139)	(3)
Derivatives not designated as hedging instruments: \| Metal contracts
Assets
Derivative Assets, Current	187	58
Derivative Asset, Noncurrent	4	1
Liabilities
Derivative Liabilities, Current	(320)	(56)
Derivative Liabilities, Noncurrent	0	(1)
Derivative Assets (Liabilities), at Fair Value, Net	(129)	2
Derivatives not designated as hedging instruments: \| Currency exchange contracts
Assets
Derivative Assets, Current	15	12
Derivative Asset, Noncurrent	1	0
Liabilities
Derivative Liabilities, Current	(31)	(17)
Derivative Liabilities, Noncurrent	(4)	0
Derivative Assets (Liabilities), at Fair Value, Net	(19)	$ (5)
Derivatives not designated as hedging instruments: \| Cash flow hedges \| Energy contracts
Assets
Derivative Assets, Current	9
Derivative Asset, Noncurrent	0
Liabilities
Derivative Liabilities, Current	0
Derivative Liabilities, Noncurrent	0
Derivative Assets (Liabilities), at Fair Value, Net	$ 9

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-10

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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

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