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Note 9 Pension Plans (Narratives) (Details) (USD $)
12 Months Ended
Mar. 31, 2015
Pension and Other Postretirement Benefits Disclosure [Abstract]  
Number of Defined Benefit Plans three
Defined Benefit Plan, Measurement Date March 31
Defined Benefit Plan, Amount to be Amortized from Accumulated Other Comprehensive Income (Loss) Next Fiscal Year $ 189,000us-gaap_DefinedBenefitPlanAmountToBeAmortizedFromAccumulatedOtherComprehensiveIncomeLossNextFiscalYear
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year $ 994,000us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInNextFiscalYear
German Plan [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Percentage of the Accrued Pension Liability, by Each Plan 68.00%ixys_DefinedBenefitPlanPercentageOfAccruedPensionLiabilityByEachPlan
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= ixys_GermanPlanMember
United Kingdom Plan [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Percentage of the Accrued Pension Liability, by Each Plan 31.00%ixys_DefinedBenefitPlanPercentageOfAccruedPensionLiabilityByEachPlan
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= ixys_UnitedKingdomPlanMember
United Kingdom Plan [Member] | Marketable Equity Securities [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Defined Benefit Plan, Target Plan Asset Allocations 75.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= ixys_UnitedKingdomPlanMember
Defined Benefit Plan, Actual Plan Asset Allocations 79.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= ixys_UnitedKingdomPlanMember
United Kingdom Plan [Member] | Debt Securities [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Defined Benefit Plan, Target Plan Asset Allocations 25.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= ixys_UnitedKingdomPlanMember
Defined Benefit Plan, Actual Plan Asset Allocations 21.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= ixys_UnitedKingdomPlanMember
Philippine Plan [Member] | Marketable Equity Securities [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Defined Benefit Plan, Target Plan Asset Allocations 20.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= ixys_PhilippinePlanMember
Defined Benefit Plan, Actual Plan Asset Allocations 33.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_EquitySecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= ixys_PhilippinePlanMember
Philippine Plan [Member] | Debt Securities [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Defined Benefit Plan, Target Plan Asset Allocations 75.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= ixys_PhilippinePlanMember
Defined Benefit Plan, Actual Plan Asset Allocations 62.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= us-gaap_DebtSecuritiesMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= ixys_PhilippinePlanMember
Philippine Plan [Member] | Other Plan Assets [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Defined Benefit Plan, Target Plan Asset Allocations 5.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= ixys_OtherPlanAssetsMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= ixys_PhilippinePlanMember
Defined Benefit Plan, Actual Plan Asset Allocations 5.00%us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= ixys_OtherPlanAssetsMember
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= ixys_PhilippinePlanMember