XML 53 R46.htm IDEA: XBRL DOCUMENT
v3.25.3

Equity Investments - Schedule of Equity Investments (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Mar. 31, 2025
--- | --- | ---
Investments, All Other Investments [Abstract] |  |
Equity method investments under fair value option | $ 294 | $ 300
Equity investments in publicly listed companies | 94 | 98
Equity method investments under equity method | 17 | 16
Non-marketable equity securities | 151 | 151
Total equity investments | $ 556 | $ 565

X
- Definition Equity Method Investments, Excluding Fair Value Option + References No definition available. + Details
Name: | arm_EquityMethodInvestmentsExcludingFairValueOption
Namespace Prefix: | arm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Equity Method Investments, Fair Value Option + References No definition available. + Details
Name: | arm_EquityMethodInvestmentsFairValueOption
Namespace Prefix: | arm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI) and investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 321 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479536/321-10-50-3 + Details
Name: | us-gaap_EquitySecuritiesFvNiAndWithoutReadilyDeterminableFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 321 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479536/321-10-50-3 + Details
Name: | us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_InvestmentsAllOtherInvestmentsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(12)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_LongTermInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant