<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Version>2.4.1.9</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>157</ContextCount>
  <ElementCount>214</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>35</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>4</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001501 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002000 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/ConsolidatedStatementsOfOperations</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF OPERATIONS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/ConsolidatedStatementsOfComprehensiveIncomeLoss</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1003001 - Statement - CONSOLIDATED STATMENTS OF COMPREHENSIVE INCOME (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/ConsolidatedStatmentsOfComprehensiveIncomeParenthetical</Role>
      <ShortName>CONSOLIDATED STATMENTS OF COMPREHENSIVE INCOME (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1004000 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/ConsolidatedStatementsOfStockholdersEquity</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1005000 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - BASIS OF PRESENTATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/BasisOfPresentation</Role>
      <ShortName>BASIS OF PRESENTATION</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - NEW ACCOUNTING STANDARDS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/NewAccountingStandards</Role>
      <ShortName>NEW ACCOUNTING STANDARDS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - ACQUISITIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/Acquisitions</Role>
      <ShortName>ACQUISITIONS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - FAIR VALUE MEASUREMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/FairValueMeasurements</Role>
      <ShortName>FAIR VALUE MEASUREMENTS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - INVENTORIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/Inventories</Role>
      <ShortName>INVENTORIES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/GoodwillAndOtherIntangibleAssets</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - ACCRUED LIABILITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/AccruedLiabilities</Role>
      <ShortName>ACCRUED LIABILITIES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - INCOME TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/IncomeTaxes</Role>
      <ShortName>INCOME TAXES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - PRODUCT WARRANTIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/ProductWarranties</Role>
      <ShortName>PRODUCT WARRANTIES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/AccumulatedOtherComprehensiveIncomeLoss</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - STOCK INCENTIVE PLANS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/StockIncentivePlans</Role>
      <ShortName>STOCK INCENTIVE PLANS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2116100 - Disclosure - EARNINGS PER COMMON SHARE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/EarningsPerCommonShare</Role>
      <ShortName>EARNINGS PER COMMON SHARE</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2117100 - Disclosure - DEFINED BENEFIT PLANS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/DefinedBenefitPlans</Role>
      <ShortName>DEFINED BENEFIT PLANS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2118100 - Disclosure - SEGMENT AND GEOGRAPHIC INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/SegmentAndGeographicInformation</Role>
      <ShortName>SEGMENT AND GEOGRAPHIC INFORMATION</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2119100 - Disclosure - ENTERPRISE WIDE INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/EnterpriseWideInformation</Role>
      <ShortName>ENTERPRISE WIDE INFORMATION</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2120100 - Disclosure - TREASURY STOCK</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/TreasuryStock</Role>
      <ShortName>TREASURY STOCK</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - BASIS OF PRESENTATION Basis of Presentation (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/BasisOfPresentationBasisOfPresentationPolicies</Role>
      <ShortName>BASIS OF PRESENTATION Basis of Presentation (Policies)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - FAIR VALUE MEASUREMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/FairValueMeasurementsTables</Role>
      <ShortName>FAIR VALUE MEASUREMENTS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2306301 - Disclosure - INVENTORIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/InventoriesTables</Role>
      <ShortName>INVENTORIES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/GoodwillAndOtherIntangibleAssetsTables</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - ACCRUED LIABILITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/AccruedLiabilitiesTables</Role>
      <ShortName>ACCRUED LIABILITIES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2313301 - Disclosure - PRODUCT WARRANTIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/ProductWarrantiesTables</Role>
      <ShortName>PRODUCT WARRANTIES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2314301 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/AccumulatedOtherComprehensiveIncomeLossTables</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2315301 - Disclosure - STOCK INCENTIVE PLANS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/StockIncentivePlansTables</Role>
      <ShortName>STOCK INCENTIVE PLANS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2316301 - Disclosure - EARNINGS PER COMMON SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/EarningsPerCommonShareTables</Role>
      <ShortName>EARNINGS PER COMMON SHARE (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2317301 - Disclosure - DEFINED BENEFIT PLANS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/DefinedBenefitPlansTables</Role>
      <ShortName>DEFINED BENEFIT PLANS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2318301 - Disclosure - SEGMENT AND GEOGRAPHIC INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/SegmentAndGeographicInformationTables</Role>
      <ShortName>SEGMENT AND GEOGRAPHIC INFORMATION (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2319301 - Disclosure - ENTERPRISE WIDE INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/EnterpriseWideInformationTables</Role>
      <ShortName>ENTERPRISE WIDE INFORMATION (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2403401 - Disclosure - ACQUISITIONS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/AcquisitionsDetails</Role>
      <ShortName>ACQUISITIONS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - FAIR VALUE MEASUREMENTS Assets and Liabilities Measured on a Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/FairValueMeasurementsAssetsAndLiabilitiesMeasuredOnRecurringBasisDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS Assets and Liabilities Measured on a Recurring Basis (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2406402 - Disclosure - Inventories, Net of Obsolescence and Lower of Cost or Market Reserves (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/InventoriesNetOfObsolescenceAndLowerOfCostOrMarketReservesDetail</Role>
      <ShortName>Inventories, Net of Obsolescence and Lower of Cost or Market Reserves (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/GoodwillAndOtherIntangibleAssetsAdditionalInformationDetail</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - ACCRUED LIABILITIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/AccruedLiabilitiesDetails</Role>
      <ShortName>ACCRUED LIABILITIES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2412401 - Disclosure - INCOME TAXES - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/IncomeTaxesAdditionalInformationDetail</Role>
      <ShortName>INCOME TAXES - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2413402 - Disclosure - PRODUCT WARRANTIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/ProductWarrantiesDetails</Role>
      <ShortName>PRODUCT WARRANTIES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2414402 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/AccumulatedOtherComprehensiveIncomeLossDetails</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2415402 - Disclosure - STOCK INCENTIVE PLANS - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/StockIncentivePlansAdditionalInformationDetail</Role>
      <ShortName>STOCK INCENTIVE PLANS - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2416402 - Disclosure - EARNINGS PER COMMON SHARE - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/EarningsPerCommonShareAdditionalInformationDetail</Role>
      <ShortName>EARNINGS PER COMMON SHARE - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2417402 - Disclosure - DEFINED BENEFIT PLANS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/DefinedBenefitPlansDetails</Role>
      <ShortName>DEFINED BENEFIT PLANS (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2418402 - Disclosure - SEGMENT AND GEOGRAPHIC INFORMATION (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/SegmentAndGeographicInformationDetails</Role>
      <ShortName>SEGMENT AND GEOGRAPHIC INFORMATION (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2419402 - Disclosure - ENTERPRISE WIDE INFORMATION (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/EnterpriseWideInformationDetails</Role>
      <ShortName>ENTERPRISE WIDE INFORMATION (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2420401 - Disclosure - TREASURY STOCK (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.rofin.com/role/TreasuryStockDetails</Role>
      <ShortName>TREASURY STOCK (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">Element rsti_SubsidiaryOrEquityMethodInvesteeAdditionalPercentageAcquired had a mix of decimals attribute values: 2 3.</Log>
    <Log type="Info">Element us-gaap_EquityMethodInvestmentOwnershipPercentage had a mix of decimals attribute values: 2 3.</Log>
    <Log type="Info">Columns in Cash Flows statement 'CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)' have maximum duration 181 days and at least 26 values. Shorter duration columns must have at least one fourth (6) as many values. Column '1/1/2014 - 3/31/2014' is shorter (89 days) and has only 2 values, so it is being removed.</Log>
    <Log type="Info">Columns in Cash Flows statement 'CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)' have maximum duration 181 days and at least 26 values. Shorter duration columns must have at least one fourth (6) as many values. Column '1/1/2015 - 3/31/2015' is shorter (89 days) and has only 2 values, so it is being removed.</Log>
    <Log type="Info">'Monetary' elements on report '2415402 - Disclosure - STOCK INCENTIVE PLANS - Additional Information (Detail)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2420401 - Disclosure - TREASURY STOCK (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 1001000 - Statement - CONSOLIDATED BALANCE SHEETS</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2014'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Mar. 31, 2014'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Sep. 30, 2013'</Log>
    <Log type="Info">Process Flow-Through: 1001501 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1002000 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS</Log>
    <Log type="Info">Process Flow-Through: 1003000 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</Log>
    <Log type="Info">Process Flow-Through: 1003001 - Statement - CONSOLIDATED STATMENTS OF COMPREHENSIVE INCOME (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1005000 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</Log>
  </Logs>
  <InputFiles>
    <File>rsti-20150331.xml</File>
    <File>rsti-20150331.xsd</File>
    <File>rsti-20150331_cal.xml</File>
    <File>rsti-20150331_def.xml</File>
    <File>rsti-20150331_lab.xml</File>
    <File>rsti-20150331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
