XML 56 R49.htm IDEA: XBRL DOCUMENT
v3.26.1

Equity Investments - Schedule of Gains (Losses) on Non-Marketable Securities (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Jun. 30, 2026 | Jun. 30, 2025
Investments, All Other Investments [Abstract] |  |
Observable price adjustments on non-marketable equity securities (includes NAV) | $ 10 | $ 1
Total income (loss) from equity investments in non-marketable securities, net | $ 10 | $ 1

X
- Definition Equity Securities Without Readily Determinable Fair Value, Including Fair Value Option, Price Adjustment, Annual Amount + References No definition available. + Details
Name: | arm_EquitySecuritiesWithoutReadilyDeterminableFairValueIncludingFairValueOptionPriceAdjustmentAnnualAmount
Namespace Prefix: | arm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Income (Loss) From Equity Securities without Readily Determinable Fair Value, Including Fair Value Option + References No definition available. + Details
Name: | arm_IncomeLossFromEquitySecuritiesWithoutReadilyDeterminableFairValueIncludingFairValueOption
Namespace Prefix: | arm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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