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Note 10 Employee Equity Incentive Plans (Fair Value and Assumptions) (Details) (USD $)
 12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Mar. 31, 2013
Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Line Items]      
Weighted Average Estimated Per Share Fair Value of Grant $ 5.54ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRightsGrantsInPeriodWeightedAverageGrantDateFairValue
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= us-gaap_EmployeeStockOptionMember		 $ 5.31ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRightsGrantsInPeriodWeightedAverageGrantDateFairValue
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= us-gaap_EmployeeStockOptionMember		 $ 5.26ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRightsGrantsInPeriodWeightedAverageGrantDateFairValue
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= us-gaap_EmployeeStockOptionMember
Risk-free Interest Rate 1.80%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= us-gaap_EmployeeStockOptionMember		 1.80%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= us-gaap_EmployeeStockOptionMember		 1.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= us-gaap_EmployeeStockOptionMember
Expected Term in Years 6 years 3 months 0 days 6 years 0 months 18 days 6 years 4 months 3 days
Volatility 52.20%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= us-gaap_EmployeeStockOptionMember		 54.90%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= us-gaap_EmployeeStockOptionMember		 55.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= us-gaap_EmployeeStockOptionMember
Dividend Yield 1.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= us-gaap_EmployeeStockOptionMember		 [1] 1.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= us-gaap_EmployeeStockOptionMember		 [1] 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= us-gaap_EmployeeStockOptionMember		 [1]
Employee Stock Purchase Plan 1999 [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Line Items]      
Weighted Average Estimated Per Share Fair Value of Grant $ 2.90ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRightsGrantsInPeriodWeightedAverageGrantDateFairValue
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= ixys_EmployeeStockPurchasePlan1999Member		 $ 2.75ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRightsGrantsInPeriodWeightedAverageGrantDateFairValue
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= ixys_EmployeeStockPurchasePlan1999Member		 $ 3.22ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRightsGrantsInPeriodWeightedAverageGrantDateFairValue
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= ixys_EmployeeStockPurchasePlan1999Member
Risk-free Interest Rate 0.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= ixys_EmployeeStockPurchasePlan1999Member		 0.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= ixys_EmployeeStockPurchasePlan1999Member		 0.20%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= ixys_EmployeeStockPurchasePlan1999Member
Expected Term in Years 0 years 6 months 0 days 0 years 6 months 0 days 0 years 6 months 0 days
Volatility 36.90%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= ixys_EmployeeStockPurchasePlan1999Member		 37.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= ixys_EmployeeStockPurchasePlan1999Member		 46.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= ixys_EmployeeStockPurchasePlan1999Member
Dividend Yield 1.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= ixys_EmployeeStockPurchasePlan1999Member		 [1] 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= ixys_EmployeeStockPurchasePlan1999Member		 [1] 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ ixys_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAxis
= ixys_EmployeeStockPurchasePlan1999Member		 [1]
[1] Prior to October 1, 2013, the fair value of our equity awards was based on 0% dividend yield.