Significant Accounting Policies (Policies)	9 Months Ended
Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	The accompanying interim unaudited condensed consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and do not include all of the information and footnotes required by accounting principles generally accepted in the United States of America for complete financial statements. The unaudited condensed consolidated financial statements include the accounts of IXYS Corporation and its wholly-owned subsidiaries. The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and judgments that affect the amounts reported in the financial statements and accompanying notes. The accounting estimates that require management’s most difficult judgments include, but are not limited to, revenue reserves, inventory valuation, accounting for income taxes and allocation of purchase price in business combinations. All significant intercompany transactions have been eliminated in consolidation. All adjustments of a normal recurring nature that, in the opinion of management, are necessary for a fair statement of the results for the interim periods have been made. The condensed balance sheet as of March 31, 2015 has been derived from our audited balance sheet as of that date. It is recommended that the interim financial statements be read in conjunction with our audited consolidated financial statements and notes thereto for the fiscal year ended March 31, 2015, or fiscal 2015, contained in our Annual Report on Form 10-K. Interim results are not necessarily indicative of the operating results expected for later quarters or the full fiscal year.
New Accounting Pronouncements, Policy [Policy Text Block]	In May 2014, the Financial Accounting Standards Board, or FASB, issued a new standard on the recognition of revenue from contracts with customers, which includes a single set of rules and criteria for revenue recognition to be used across all industries. The revenue standard’s core principle is built on the contract between a vendor and a customer for the provision of goods and services. It attempts to depict the exchange of rights and obligations between the parties in the pattern of revenue recognition based on the consideration to which the vendor is entitled. To accomplish this objective, the standard requires five basic steps: identify the contract with the customer, identify the performance obligations in the contract, determine the transaction price, allocate the transaction price to the performance obligations in the contract, and recognize revenue when or as the entity satisfies a performance obligation. This standard is effective for annual reporting periods beginning after December 15, 2017, including interim periods during the annual period. Early adoption is prohibited for annual periods commencing before December 15, 2016. Different transition methods are available — full retrospective method, retrospective with certain practical expedients and a modified retrospective (cumulative effect) approach. We are currently evaluating the impact of the adoption of the standard on our consolidated financial statements including selection of the transition method. In April 2015, FASB issued the authoritative guidance that requires debt issuance costs related to a recognized debt liability to be presented in the balance sheet as a direct deduction from the debt liability rather than as an asset. The guidance will be effective for fiscal years beginning after December 15, 2015, and interim periods during the annual period, with early adoption permitted for financial statements that have not been previously issued. The new standard is required to be applied retrospectively to all prior periods presented in the financial statements. An entity is also required in the year of adoption (and in interim periods within that year) to provide certain disclosures about the change in accounting principle, including the nature of and reason for the change, the transition method, a description of the prior period information that has been retrospectively adjusted and the effect of the change on the financial statements line items (that is, debt issuance cost asset and the debt liability). In August 2015, FASB issued the authoritative guidance that added Securities and Exchange Commission, or SEC, content. The guidance issued in April 2015 did not directly address the manner in which debt issuance costs relating to a line of credit arrangement are treated. The SEC staff clarified that they would not object to the balance sheet presentation of such costs as an asset (i.e., a deferred charge) to be subsequently amortized ratably over the term of the line of credit arrangement, even if there are no borrowings outstanding on the underlying line of credit arrangement. We have adopted the guidance effective the quarter ended December 31, 2015 and applied the new rules to our new revolving credit agreement effective as of November 20, 2015. Based on the guidance, the debt issuance costs are presented in the balance sheet as a direct deduction from the debt liability rather than as an asset in our financial statements. There is no other significant impact from the adoption of this guidance. See Note 9, “Borrowing Arrangements” for further information regarding our credit arrangements. In July 2015, FASB issued an amendment to modify the inventory measurement guidance in Topic 330, Inventory , for inventory that is measured using the methods other than last-in, first-out, or LIFO, and the retail inventory method. It requires that an entity measure inventory within the scope of this update at the lower of cost and net realizable value. It eliminated the guidance in Topic 330 that required a reporting entity measuring inventory at the lower of cost or market to consider the replacement cost of inventory and the net realizable value of inventory less an approximately normal profit margin along with net realizable value in determining the market value. The guidance will be effective for annual reporting periods beginning after December 15, 2016 , and interim periods during the annual period. The new standard is required to be applied prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. We do not expect this change to have a significant impact on our consolidated financial statements. In September 2015, FASB issued an amendment to modify the guidance related to measurement-period adjustments in Topic 805, Business Combinations . The amendment requires that an acquirer recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. It also requires that the acquirer record, in the same period’s financial statements, the effect on earnings of changes in depreciation, amortization or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date. It eliminates the requirement to retrospectively account for those adjustments. The guidance will be effective for public companies for financial statements issued for fiscal years beginning after December 15, 2015, and interim periods during the annual period. The new standard is required to be applied prospectively to adjustments to provisional amounts that occur after the aforementioned effective date with earlier application permitted for financial statements that have not yet been issued. We do not expect this guidance to have a significant impact on our consolidated financial statements. The impact on earnings due to measurement period adjustments will be disclosed in the relevant notes to the financial statements. In October 2015, FASB ratified a proposed Accounting Standards Update, or ASU, which requires presentation of deferred tax assets and liabilities as noncurrent in a classified balance sheet. This standard is effective for annual reporting periods beginning after December 15, 2016, including interim periods during the annual period. Early application is permitted as of the beginning of any interim or annual reporting period. We adopted this accounting standard update, on a retrospective basis, during the quarter ended December 31, 2015. All deferred tax assets and liabilities as of December 31, 2015 and March 31, 2015 have been classified as noncurrent in the accompanying unaudited condensed consolidated balance sheets and the notes thereto. The adoption during this quarter resulted in a $7.1 million decrease in current deferred tax assets and a corresponding increase of an equal amount in the noncurrent deferred tax assets at December 31, 2015. Our prior period ended March 31, 2015 reflected a decrease of $7.1 million in the current deferred tax assets and a corresponding increase in the noncurrent deferred tax assets. In January 2016, FASB issued the authoritative guidance that requires equity investments to be measured at fair value with changes in fair value recognized in net income; simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; requires an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments; requires separate presentation of financial assets and financial liabilities by measurement category and form of financial assets on the balance sheet or the accompanying notes to the financial statements; eliminates the requirement for public business entities to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; and clarifies that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity’s other deferred tax assets. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. It permits early adoption as of the beginning of the fiscal year of adoption. We are currently evaluating the impact of the adoption of the standard on our consolidated financial statements.

In May 2014, the Financial Accounting Standards Board, or

FASB, issued a new standard on the recognition of revenue from contracts with customers, which includes a single set of rules and criteria for revenue recognition to be used across all industries. The revenue standard’s core principle is built on the contract between a vendor and a customer for the provision of goods and services. It attempts to depict the exchange of rights and obligations between the parties in the pattern of revenue recognition based on the consideration to which the vendor is entitled. To accomplish this objective, the standard requires five basic steps: identify the contract with the customer, identify the performance obligations in the contract, determine the transaction price, allocate the transaction price to the performance obligations in the contract, and recognize revenue when or as the entity satisfies a performance obligation. This standard is effective for annual reporting periods beginning after December 15, 2017, including interim periods during the annual period. Early adoption is prohibited for annual periods commencing before December 15, 2016. Different transition methods are available — full retrospective method, retrospective with certain practical expedients and a modified retrospective (cumulative effect) approach. We are currently evaluating the impact of the adoption of the standard on our consolidated financial statements including selection of the transition method.

In April 2015, FASB issued the authoritative guidance that requires debt issuance costs related to a recognized debt liability to be presented in the balance sheet as a direct deduction from the debt liability rather than as an asset. The guidance will be effective for fiscal years beginning after December 15, 2015, and interim periods during the annual period, with early adoption permitted for financial statements that have not been previously issued. The new standard is required to be applied retrospectively to all prior periods presented in the financial statements. An entity is also required in the year of adoption (and in interim periods within that year) to provide certain disclosures about the change in accounting principle, including the nature of and reason for the change, the transition method, a description of the prior period information that has been retrospectively adjusted and the effect of the change on the financial statements line items (that is, debt issuance cost asset and the debt liability). In August 2015, FASB issued the authoritative guidance that added Securities and Exchange Commission, or SEC, content. The guidance issued in April 2015 did not directly address the manner in which debt issuance costs relating to a line of credit arrangement are treated. The SEC staff clarified that they would not object to the balance sheet presentation of such costs as an asset (i.e., a deferred charge) to be subsequently amortized ratably over the term of the line of credit arrangement, even if there are no borrowings outstanding on the underlying line of credit arrangement. We have adopted the guidance effective the quarter ended December 31, 2015 and applied the new rules to our new revolving credit agreement effective as of November 20, 2015.

Based on the guidance, the debt issuance costs are presented in the balance sheet as a direct deduction from the debt liability rather than as an asset in our financial statements. There is no other significant impact from the adoption of this guidance. See Note 9, “Borrowing Arrangements” for further information regarding our credit arrangements.

In July 2015, FASB issued an amendment to modify the inventory measurement guidance in Topic 330,

Inventory

, for inventory that is measured using the methods other than last-in, first-out, or LIFO, and the retail inventory method. It requires that an entity measure inventory within the scope of this update at the lower of cost and net realizable value. It eliminated the guidance in Topic 330 that required a reporting entity measuring inventory at the lower of cost or market to consider the replacement cost of inventory and the net realizable value of inventory less an approximately normal profit margin along with net realizable value in determining the market value. The guidance will be effective for annual reporting periods beginning after December

15, 2016

, and interim periods during the annual period. The new standard is required to be applied prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. We do not expect this change to have a significant impact on our consolidated financial statements.

In September 2015, FASB issued an amendment to modify the guidance related to measurement-period adjustments in Topic 805,

Business Combinations

. The amendment requires that an acquirer recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. It also requires that the acquirer record, in the same period’s financial statements, the effect on earnings of changes in depreciation, amortization or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date. It eliminates the requirement to retrospectively account for those adjustments.

The guidance will be effective for public companies for financial statements issued for fiscal years beginning after December 15, 2015, and interim periods during the annual period. The new standard is required to be applied prospectively to adjustments to provisional amounts that occur after the aforementioned effective date with earlier application permitted for financial statements that have not yet been issued. We do not expect this guidance to have a significant impact on our consolidated financial statements. The impact on earnings due to measurement period adjustments will be disclosed in the relevant notes to the financial statements.

In October 2015, FASB ratified a proposed Accounting Standards Update, or ASU, which requires presentation of deferred tax assets and liabilities as noncurrent in a classified balance sheet. This standard is effective for annual reporting periods beginning after December 15, 2016, including interim periods during the annual period. Early application is permitted as of the beginning of any interim or annual reporting period. We adopted this accounting standard update, on a retrospective basis, during the quarter ended December 31, 2015. All deferred tax assets and liabilities as of December 31, 2015 and March 31, 2015 have been classified as noncurrent in the accompanying unaudited condensed consolidated balance sheets and the notes thereto. The adoption during this quarter resulted in a $7.1 million decrease in current deferred tax assets and a corresponding increase of an equal amount in the noncurrent deferred tax assets at December 31, 2015. Our prior period ended March 31, 2015 reflected a decrease of $7.1 million in the current deferred tax assets and a corresponding increase in the noncurrent deferred tax assets.

In January 2016, FASB issued the authoritative guidance that requires equity investments to be measured at fair value with changes in fair value recognized in net income; simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; requires an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments; requires separate presentation of financial assets and financial liabilities by measurement category and form of financial assets on the balance sheet or the accompanying notes to the financial statements; eliminates the requirement for public business entities to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; and clarifies that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity’s other deferred tax assets. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. It permits early adoption as of the beginning of the fiscal year of adoption. We are currently evaluating the impact of the adoption of the standard on our consolidated financial statements.