Financial Instruments and Commodity Contracts - Summary of Gross Fair Values of Financial Instruments and Commodity Contracts (Details) - USD ($) $ in Millions	Jun. 30, 2026	Mar. 31, 2026
Assets
Derivative Assets, Current	$ 418	$ 234
Derivative Asset, Noncurrent	6	11
Liabilities
Derivative Liabilities, Current	(330)	(824)
Derivative Liabilities, Noncurrent	(10)	(6)
Net Fair Value Assets/Liabilities	84	(585)
Designated as Hedging Instrument
Assets
Derivative Assets, Current	201	23
Derivative Asset, Noncurrent	6	6
Liabilities
Derivative Liabilities, Current	(107)	(473)
Derivative Liabilities, Noncurrent	(2)	(2)
Net Fair Value Assets/Liabilities	98	(446)
Designated as Hedging Instrument \| Cash flow hedges \| Metal Contracts
Assets
Derivative Assets, Current	185	5
Derivative Asset, Noncurrent	0	1
Liabilities
Derivative Liabilities, Current	(77)	(445)
Derivative Liabilities, Noncurrent	(1)	(2)
Net Fair Value Assets/Liabilities	107	(441)
Designated as Hedging Instrument \| Cash flow hedges \| Currency Exchange Contracts
Assets
Derivative Assets, Current	11	10
Derivative Asset, Noncurrent	1	1
Liabilities
Derivative Liabilities, Current	(27)	(22)
Derivative Liabilities, Noncurrent	(1)	0
Net Fair Value Assets/Liabilities	(16)	(11)
Designated as Hedging Instrument \| Cash flow hedges \| Energy Contracts
Assets
Derivative Assets, Current	5	8
Derivative Asset, Noncurrent	0	0
Liabilities
Derivative Liabilities, Current	(2)	(3)
Derivative Liabilities, Noncurrent	0	0
Net Fair Value Assets/Liabilities	3	5
Designated as Hedging Instrument \| Cash flow hedges \| Interest Rate Swap
Assets
Derivative Assets, Current	0	0
Derivative Asset, Noncurrent	0	0
Liabilities
Derivative Liabilities, Current	(1)	(3)
Derivative Liabilities, Noncurrent	0	0
Net Fair Value Assets/Liabilities	(1)	(3)
Designated as Hedging Instrument \| Net investment hedges \| Currency Exchange Contracts
Assets
Derivative Assets, Current	0	0
Derivative Asset, Noncurrent	5	4
Liabilities
Derivative Liabilities, Current	0	0
Derivative Liabilities, Noncurrent	0	0
Net Fair Value Assets/Liabilities	5	4
Not Designated as Hedging Instrument
Assets
Derivative Assets, Current	217	211
Derivative Asset, Noncurrent	0	5
Liabilities
Derivative Liabilities, Current	(223)	(351)
Derivative Liabilities, Noncurrent	(8)	(4)
Net Fair Value Assets/Liabilities	(14)	(139)
Not Designated as Hedging Instrument \| Metal Contracts
Assets
Derivative Assets, Current	195	187
Derivative Asset, Noncurrent	0	4
Liabilities
Derivative Liabilities, Current	(189)	(320)
Derivative Liabilities, Noncurrent	(3)	0
Net Fair Value Assets/Liabilities	3	(129)
Not Designated as Hedging Instrument \| Currency Exchange Contracts
Assets
Derivative Assets, Current	18	15
Derivative Asset, Noncurrent	0	1
Liabilities
Derivative Liabilities, Current	(34)	(31)
Derivative Liabilities, Noncurrent	(5)	(4)
Net Fair Value Assets/Liabilities	(21)	(19)
Not Designated as Hedging Instrument \| Energy Contracts
Assets
Derivative Assets, Current	4	9
Derivative Asset, Noncurrent	0	0
Liabilities
Derivative Liabilities, Current	0	0
Derivative Liabilities, Noncurrent	0	0
Net Fair Value Assets/Liabilities	$ 4	$ 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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Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

+ 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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