{
 "version": "2.2",
 "instance": {
  "arm-20240207.htm": {
   "nsprefix": "arm",
   "nsuri": "http://www.arm.com/20240207",
   "dts": {
    "inline": {
     "local": [
      "arm-20240207.htm"
     ]
    },
    "schema": {
     "local": [
      "arm-20240207.xsd"
     ],
     "remote": [
      "http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd",
      "http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd",
      "http://www.xbrl.org/2003/xl-2003-12-31.xsd",
      "http://www.xbrl.org/2003/xlink-2003-12-31.xsd",
      "http://www.xbrl.org/2005/xbrldt-2005.xsd",
      "http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd",
      "http://www.xbrl.org/lrr/role/net-2009-12-16.xsd",
      "https://www.xbrl.org/dtr/type/2022-03-31/types.xsd",
      "https://xbrl.sec.gov/dei/2023/dei-2023.xsd"
     ]
    },
    "labelLink": {
     "local": [
      "arm-20240207_lab.xml"
     ]
    },
    "presentationLink": {
     "local": [
      "arm-20240207_pre.xml"
     ]
    }
   },
   "keyStandard": 8,
   "keyCustom": 0,
   "axisStandard": 0,
   "axisCustom": 0,
   "memberStandard": 0,
   "memberCustom": 0,
   "hidden": {
    "total": 7,
    "http://xbrl.sec.gov/dei/2023": 7
   },
   "contextCount": 2,
   "entityCount": 1,
   "segmentCount": 0,
   "elementCount": 9,
   "unitCount": 0,
   "baseTaxonomies": {
    "http://xbrl.sec.gov/dei/2023": 8
   },
   "report": {
    "R1": {
     "role": "http://www.arm.com/role/Cover",
     "longName": "0000001 - Document - Cover",
     "shortName": "Cover",
     "isDefault": "true",
     "groupType": "document",
     "subGroupType": "",
     "menuCat": "Cover",
     "order": "1",
     "firstAnchor": {
      "contextRef": "c-1",
      "name": "dei:DocumentType",
      "unitRef": null,
      "xsiNil": "false",
      "lang": "en-US",
      "decimals": null,
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "reportCount": 1,
      "baseRef": "arm-20240207.htm",
      "first": true,
      "unique": true
     },
     "uniqueAnchor": {
      "contextRef": "c-1",
      "name": "dei:DocumentType",
      "unitRef": null,
      "xsiNil": "false",
      "lang": "en-US",
      "decimals": null,
      "ancestors": [
       "span",
       "div",
       "body",
       "html"
      ],
      "reportCount": 1,
      "baseRef": "arm-20240207.htm",
      "first": true,
      "unique": true
     }
    }
   },
   "tag": {
    "dei_AmendmentFlag": {
     "xbrltype": "booleanItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2023",
     "localname": "AmendmentFlag",
     "presentation": [
      "http://www.arm.com/role/Cover"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Amendment Flag",
        "label": "Amendment Flag",
        "documentation": "Boolean flag that is true when the XBRL content amends previously-filed or accepted submission."
       }
      }
     },
     "auth_ref": []
    },
    "dei_CoverAbstract": {
     "xbrltype": "stringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2023",
     "localname": "CoverAbstract",
     "lang": {
      "en-us": {
       "role": {
        "label": "Cover [Abstract]",
        "documentation": "Cover page."
       }
      }
     },
     "auth_ref": []
    },
    "dei_CurrentFiscalYearEndDate": {
     "xbrltype": "gMonthDayItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2023",
     "localname": "CurrentFiscalYearEndDate",
     "presentation": [
      "http://www.arm.com/role/Cover"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Current Fiscal Year End Date",
        "label": "Current Fiscal Year End Date",
        "documentation": "End date of current fiscal year in the format --MM-DD."
       }
      }
     },
     "auth_ref": []
    },
    "dei_DocumentFiscalPeriodFocus": {
     "xbrltype": "fiscalPeriodItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2023",
     "localname": "DocumentFiscalPeriodFocus",
     "presentation": [
      "http://www.arm.com/role/Cover"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Document Fiscal Period Focus",
        "label": "Document Fiscal Period Focus",
        "documentation": "Fiscal period values are FY, Q1, Q2, and Q3.  1st, 2nd and 3rd quarter 10-Q or 10-QT statements have value Q1, Q2, and Q3 respectively, with 10-K, 10-KT or other fiscal year statements having FY."
       }
      }
     },
     "auth_ref": []
    },
    "dei_DocumentFiscalYearFocus": {
     "xbrltype": "gYearItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2023",
     "localname": "DocumentFiscalYearFocus",
     "presentation": [
      "http://www.arm.com/role/Cover"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Document Fiscal Year Focus",
        "label": "Document Fiscal Year Focus",
        "documentation": "This is focus fiscal year of the document report in YYYY format. For a 2006 annual report, which may also provide financial information from prior periods, fiscal 2006 should be given as the fiscal year focus. Example: 2006."
       }
      }
     },
     "auth_ref": []
    },
    "dei_DocumentPeriodEndDate": {
     "xbrltype": "dateItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2023",
     "localname": "DocumentPeriodEndDate",
     "presentation": [
      "http://www.arm.com/role/Cover"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Document Period End Date",
        "label": "Document Period End Date",
        "documentation": "For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period.  The format of the date is YYYY-MM-DD."
       }
      }
     },
     "auth_ref": []
    },
    "dei_DocumentType": {
     "xbrltype": "submissionTypeItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2023",
     "localname": "DocumentType",
     "presentation": [
      "http://www.arm.com/role/Cover"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Document Type",
        "label": "Document Type",
        "documentation": "The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'."
       }
      }
     },
     "auth_ref": []
    },
    "dei_EntityCentralIndexKey": {
     "xbrltype": "centralIndexKeyItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2023",
     "localname": "EntityCentralIndexKey",
     "presentation": [
      "http://www.arm.com/role/Cover"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity Central Index Key",
        "label": "Entity Central Index Key",
        "documentation": "A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK."
       }
      }
     },
     "auth_ref": [
      "r0"
     ]
    },
    "dei_EntityRegistrantName": {
     "xbrltype": "normalizedStringItemType",
     "nsuri": "http://xbrl.sec.gov/dei/2023",
     "localname": "EntityRegistrantName",
     "presentation": [
      "http://www.arm.com/role/Cover"
     ],
     "lang": {
      "en-us": {
       "role": {
        "terseLabel": "Entity Registrant Name",
        "label": "Entity Registrant Name",
        "documentation": "The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC."
       }
      }
     },
     "auth_ref": [
      "r0"
     ]
    }
   }
  }
 },
 "std_ref": {
  "r0": {
   "role": "http://www.xbrl.org/2003/role/presentationRef",
   "Publisher": "SEC",
   "Name": "Exchange Act",
   "Number": "240",
   "Section": "12",
   "Subsection": "b-2"
  }
 }
}
