Deferred income tax benefit Deferred Income Taxes and Tax Credits Net (decrease) increase in cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Excluding Exchange Rate Effect, Including Discontinued Operation Cash and cash equivalents, beginning of year Cash and cash equivalents, end of year Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Increase of fixed deposits with original maturities over three months Increase In Fixed Deposits Maturing Over Three Months This element represents cash inflow from a fixed deposits having initial term of repayment over three months. (Increase) decrease in held-to-maturity investment Increase Decrease In Heldtomaturity Investment Amount of increase decrease in held-to-maturity investment. Income taxes Income before income tax Income Taxes Paid Loss (gain) on disposal of property, plant and equipment Gain (Loss) on Disposition of Property Plant Equipment Interest Interest Paid, Excluding Capitalized Interest, Operating Activity Exchange loss arising from marketable securities Unrealized Gain (Loss), Foreign Currency Transaction, before Tax Unrealized holding gain on marketable securities Unrealized gain (loss) on marketable securities Unrealized gain from marketable securities Marketable Security, Unrealized Gain (Loss) Changes in operating assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Inventories Increase (Decrease) in Inventories Net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Accounts payable Increase (Decrease) in Accounts Payable Income taxes payable Increase (Decrease) in Income Taxes Payable Gain on sales of marketable securities Realized gain from sale of marketable securities Realized gain from sales of marketable securities Marketable Security, Realized Gain (Loss) Scrip dividend received Increase (Decrease) in Interest and Dividends Receivable Accounts receivable Increase (Decrease) in Accounts Receivable Prepaid expenses and other current assets Prepaid expenses and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Accrued payroll and employee benefits Increase (Decrease) in Employee Related Liabilities Other accrued liabilities Increase (Decrease) in Other Accrued Liabilities Organization and Basis of Financial Statements [Abstract] Supplementary disclosures of cash flow information: Supplemental Cash Flow Information [Abstract] Provision for (reversal of) credit losses, net (Provision for) reversal of credit losses, net Provision for Other Credit Losses Proceeds from sales of marketable securities Proceeds from sale of marketable securities Proceeds from Sale, Debt Security, Trading, and Equity Security, FV-NI, Held-for-Investment Decrease of fixed deposits with original maturities over twelve months Payment for (Proceeds from) Other Investing Activity Organization and Basis of Financial Statements Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Purchase of marketable securities Payments to Acquire Marketable Securities Purchase of property, plant and equipment Capital expenditure Payments to Acquire Property, Plant, and Equipment Cash flows from financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Repurchase of treasury stock Payments for Repurchase of Other Equity Summary of Significant Accounting Policies [Abstract] Prepaid Expenses and Other Current Assets Other Current Assets [Text Block] Marketable Securities Marketable Securities1 Text Block The entire disclosure for marketable securities of the reporting entity. Inventories, Net [Abstract] Inventories, net Inventory Disclosure [Text Block] Marketable Securities [Abstract] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Prepaid Expenses and Other Current Assets [Abstract] Net cash provided by investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Dividends paid Payments of Dividends Proceeds from sale of property, plant and equipment, net of transaction costs Proceeds from Sale of Property, Plant, and Equipment Cash flows from operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Cash flows from investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Statement of Cash Flows [Abstract] Net cash (used in) provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Net income Net income Net income attribute to Deswell Industries, Inc. Cash and cash equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Minimum [Member] Minimum [Member] Schedule of Estimated Useful Lives of Property, Plant and Equipment [Line Items] Schedule of Property, Plant and Equipment, Net [Line Items] Property, Plant and Equipment, Net [Line Items] Fair value of financial instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Recently Adopted Accounting Pronouncements Accounting Standards Update and Change in Accounting Principle [Text Block] Schedule Of Estimated Useful Lives Of Property Plant And Equipment Abstract Long-Lived Tangible Asset [Axis] Plant and Machinery [Member] Plant and machinery [Member] Machinery and Equipment [Member] Motor Vehicles [Member] Motor vehicles [Member] Vehicles [Member] Estimated useful lives (years) Property, Plant and Equipment, Useful Life Cost Marketable Securities Property, Plant and Equipment [Table] Long-Lived Tangible Asset [Domain] Impairment [Member] Impairment Member Schedule of Long-Lived Assets Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] Schedule of Land Use Rights and Long Term Leased Land Land Use Rights And Long Term Leased Land Table Text Block Tabular disclosure land use rights and long term leased land. Other Accrued Liabilities [Abstract] Cost of land use rights Cost Of Land Use Rights Amount of cost of land use rights of state-owned land and buildings. Raw materials Inventory, Raw Materials, Net of Reserves Less: accumulated depreciation and amortization Amortization expenses Less: accumulated amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Impairment Impairment Property Plant And Equipment Impairment on property plant and equipment. Schedule Of Land Use Rights And Long Term Leased Land Abstract Land use rights and long term leased land Cost Property, Plant and Equipment, Gross Leasehold land and buildings [Member] Leasehold Land And Buildings Member Land use right of state-owned land Land Use Right Of Stateowned Land Land use right of state-owned land. Property, Plant and Equipment, Net [Abstract] Canada [Member] CANADA United States of America [Member] United States of America [Member] UNITED STATES Product and Service [Domain] Electronic Products [Member] Electronic Products Member Electronic Products [Member] Total net sales Net sales from continuing operations Revenue from Contract with Customer, Including Assessed Tax Schedule of Accounts Receivable, Net [Abstract] Less: Allowance for credit losses Allowances for credit losses Accounts Receivable, Allowance for Credit Loss, Current Balance at beginning of the year Allowance for credit losses Accounts Receivable, Allowance for Credit Loss Written off Accounts receivable written off Accounts Receivable, Allowance for Credit Loss, Writeoff Effect of dilutive securities – Options Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Diluted net income per share (in Dollars per share) Net income per share Earnings Per Share, Diluted Schedule of Other Accrued Liabilities [Abstract] Others Other Liabilities, Current Related and Nonrelated Parties [Domain] Finite-Lived Intangible Assets by Major Class [Axis] Use Rights [Member] Use Rights [Member] PRC [Member] PRCMember PRC [Member] PRC [Member] CHINA Hong Kong [Member] HONG KONG Schedule Of Disaggregates Product Sales By Business Segment And By Geography Abstract Statistical Measurement [Axis] Maximum [Member] Maximum [Member] United Kingdom [Member] UNITED KINGDOM Europe [Member] Europe [Member] Others [Member] Segments Geographical Location Other Member Segments Geographical Location Other [Member] Product and Service [Axis] Injection Molded Plastic Parts [Member] Injection Molded Plastic Parts Member Injection Molded Plastic Parts [Member] Recent Accounting Pronouncement Not Yet Adopted New Accounting Pronouncements, Policy [Policy Text Block] Property, Plant and Equipment, Net (Details) [Table] Related and Nonrelated Parties [Axis] Dongguan Chang An Xiaobian [Member] Dongguan Chang An Xiaobian Member Income Tax Jurisdiction [Domain] Foreign Tax Jurisdiction [Member] Other foreign jurisdictions [Member] Foreign Tax Jurisdiction [Member] Net income before taxes Total income before income tax Income before income taxes Income before income taxes Total income before taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Effective income tax rate reconciliation withholding tax rate Effective Income Tax Rate Reconciliation Withholding Tax Rate Effective income tax rate reconciliation withholding tax rate. Summary of Significant Accounting Policies (Details) [Table] Geographical [Domain] Schedule of Non-Operating Income, Net Schedule of Other Nonoperating Income, by Component [Table Text Block] Operating Risk [Abstract] Chinese Renminbi, Dollars [Member] China, Yuan Renminbi Interest income on investments Interest and Other Income Concentration Risk [Line Items] Schedule of Operating Risk [Line Items] Schedule of Major Activities for Reportable Segments Reconciliation of Revenue from Segments to Consolidated [Table Text Block] Schedule of Asset Information for Reportable Segments Schedule of Liability for Future Policy Benefits, by Product Segment [Table Text Block] Schedule of Property, Plant and Equipment, Net Property, Plant and Equipment [Table Text Block] Schedule of Operating Risks Schedules of Concentration of Risk, by Risk Factor [Table Text Block] Segment Information [Abstract] Segment: Schedule of Profitability Information for Reportable Segments Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Breakdown of Sales by Destination Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block] Shipping and handling costs Shipping And Handling Costs Shipping and handling costs. Summary of Significant Accounting Policies [Line Items] Hong Kong, Dollars [Member] Hong Kong, Dollars Geographical [Axis] Entity Incorporation, Date of Incorporation Entity Incorporation, Date of Incorporation Statistical Measurement [Domain] Concentration Risk Benchmark [Domain] Standard income tax rate Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Macau Patacas [Member] Macau, Patacas Income Tax Jurisdiction [Axis] Schedule of Cash Payments For Tax Liabilities Schedule of cash payments for tax liabilities. Concentration Risk Benchmark [Axis] Accounts Receivable [Member] Accounts Receivable [Member] Property, Plant and Equipment, Net - Schedule of Land Use Rights and Long Term Leased Land (Details) [Table] Land use rights and long term leased land [Member] Land Use Rights And Long Term Leased Land Member Schedule of Land Use Rights and Long Term Leased Land [Line Items] Net book value Total long-lived assets Net value Property, plant and equipment, net Work-in-progress Inventory, Work in Process, Net of Reserves Schedule of Inventories, Net of Allowances [Abstract] Cost [Member] Cost Member Leasehold improvements [Member] Leasehold Improvements [Member] Furniture, fixtures and equipment [Member] Furniture, Fixtures and Equipment [Member] Furniture and Fixtures [Member] Schedule of Basic Net Income Per Share and Diluted Net Income Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Fair value measurements Fair Value Measurement, Policy [Policy Text Block] Use of estimates Use of Estimates, Policy [Policy Text Block] Impairment of long-lived assets Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Foreign currency translation Foreign Currency Transactions and Translations Policy [Policy Text Block] Shipping and handling cost Shipping and Handling Cost, Policy [Policy Text Block] Stock Option Plan [Abstract] Plan Name [Axis] Stock Option Plan Three [Member] Stock Option Plan Three Member Equity Component [Domain] Purchase shares of common stock Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Net of Forfeitures Total shares of common stock Stock Issued During Period, Shares, Employee Stock Purchase Plans Stock option plan, shares authorized Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized Expiration period of options Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period Options available for future grant Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Amounts due from subsidiaries Increase (Decrease) in Due from Related Parties, Current Segments [Axis] Segment Information - Schedule of Asset Information for Reportable Segments (Details) [Table] Non-deductible expenses, Percent Effective Income Tax Rate Reconciliation, Nondeductible Expense, Percent, Total Change of valuation allowance, Percent Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent Changes in unrecognized tax benefits, Percent Changes in Unrecognized Tax Benefits Percentage Changes in unrecognized tax benefits. Effect of foreign rate differences, Percent Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent Effect of other non-taxable income, Percent Effective Income Tax Rate Reconciliation, Tax Exempt Income, Percent Prior years true up, Percent Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Percent Income tax expense (income), Percent Effective Income Tax Rate Reconciliation, Percent, Total Repurchase of treasury stock Stock Issued During Period, Value, Treasury Stock Reissued Repurchase of treasury stock (in Shares) Stock Issued During Period, Shares, Treasury Stock Reissued Intrinsic value of options outstanding (in Dollars) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Net assets of subsidiaries restricted amount Net Assets Of Subsidiaries Restricted From Transfer To Parent Company The amount of net assets recorded by subsidiaries restricted from transfer to the parent. The amounts restricted include paid-in capital and statutory reserves, as determined pursuant to PRC generally accepted accounting principles. Dividends received from subsidiary Proceeds from Dividends Received Changes in operating assets and liabilities: Increase (Decrease) in Operating Assets [Abstract] Investments in subsidiaries Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Current liabilities: Liabilities, Current [Abstract] Other accrued liabilities Total other accrued liabilities Other Accrued Liabilities, Current Total shareholders’ equity Balance Balance Total shareholders’ equity Equity, Attributable to Parent Condensed Income Statement [Table] Outstanding, Weighted Average Exercise price Outstanding, Weighted Average Exercise price Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price Exercised during the year, Number of stock options (in Shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Operating cash flows from operating leases as lessor Operating Lease, Lease Income, Lease Payments Total leases costs Lease, Cost Exercised during the year, Weighted Average Grant Date Fair Value Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercised Weighted Average Grant Date Fair Value The weighted average grant-date fair value of options exercised during the reporting period as calculated by applying the disclosed option pricing methodology. Expired and cancelled during the year, Weighted Average Exercise price Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Outstanding, Number of stock options (in Shares) Outstanding, Number of stock options (in Shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Outstanding, Weighted Average Grant Date Fair Value Outstanding, Weighted Average Grant Date Fair Value Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value (Loss) gain on disposal of property, plant and equipment, net Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property (Provision for) reversal of credit losses, net (76)  67 (2) Provision for Other Losses Other income (expense), net Other income (expense), net (note 13) Other Operating Income (Expense), Net Schedule of Option Activity [Line Items] Year ending March 31, 2027 Lessee, Operating Lease, Liability, to be Paid, Year One Hong Kong and Macao [Member] Hong Kong And Macao Member Hong Kong And Macao [Member] Number of vested shares Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Amendment Flag Document Fiscal Year Focus Entity Voluntary Filers Entity Filer Category Entity Central Index Key Entity Shell Company Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Incorporation, State or Country Code Entity Addresses, Address Type [Axis] Interest income from bank deposits Interest Income, Deposits with Financial Institutions Segment Reporting Information [Line Items] Income tax expenses computed at PRC statutory income tax rate of 25% Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Deferred tax Deferred Income Tax Expense (Benefit) City Area Code Current assets: Assets, Current [Abstract] Time deposits with original maturities over three months Fixed Deposits Current Fixed deposits having initial term of repayment over three months. Marketable securities Market value Marketable Securities, Current Statement [Line Items] Schedule Of Provision For Income Taxes Abstract Schedule of provision for income taxes [Line Items] Schedule of provision for income taxes [Abstract] Additional deduction for R&D expenses Effective Income Tax Rate Reconciliation, Deduction, Other, Amount Effect of other non-taxable income Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount Non-deductible expenses Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amount Prior years true up Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount Deferred income tax assets Deferred Tax Assets, Net of Valuation Allowance Stock Options [Member] Equity Option [Member] Exercised during the year, Weighted Average Exercise price Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Operating lease costs Operating Lease, Cost Expired and cancelled during the year, Number of stock options (in Shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period Expired and cancelled during the year, Weighted Average Grant Date Fair Value Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Additional deduction for R&D expenses, Percent Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other deductions. Injection Molded Plastic Parts [Member] Electronic Products [Member] Income Taxes - Schedule of Provision for Income Taxes (Details) [Table] Accumulated other comprehensive income AOCI Attributable to Parent [Member] Treasury Stock Treasury Stock, Common [Member] Statement of Stockholders' Equity [Abstract] Equity Components [Axis] Total comprehensive income attributable to Deswell Industries, Inc. Comprehensive Income (Loss), Net of Tax, Attributable to Parent Weighted average common shares outstanding (shares in thousands) Diluted weighted average common and potential common shares outstanding Weighted Average Number of Shares Outstanding, Diluted Diluted: Earnings Per Share, Diluted [Abstract] Net income per share Basic net income per share (in Dollars per share) Earnings Per Share, Basic Gross profit Gross Profit Net sales Revenues Operating income Total operating income Operating Income (Loss) Common shares, issued Common Stock, Shares, Issued Statement [Table] Contact Personnel Email Address Entity Common Stock, Shares Outstanding Security Exchange Name Cash flows from financing activities Cash Provided by (Used in) Financing Activity, Continuing Operation [Abstract] Operating expenses Operating Expenses Schedule of Condensed Income Statement [Line Items] Consolidated Entities [Axis] Schedule of Condensed Income Statement [Abstract] Total liabilities and shareholders’ equity Liabilities and Equity Total current liabilities Liabilities, Current Customer [Domain] Purchase Commitment, Excluding Long-Term Commitment [Domain] Consolidated Entities [Domain] Derivative Contract [Domain] Title of 12(b) Security Entity File Number Entity Current Reporting Status ICFR Auditor Attestation Flag Income Taxes [Line Items] Schedule of Condensed Balance Sheet [Abstract] Condensed Balance Sheet Statements, Captions [Line Items] Schedule of Long Lived Assets [Abstract] Derivative Instrument [Axis] Liabilities and shareholders’ equity Liabilities and Equity [Abstract] Assets [Abstract] Repurchase of treasury stock Repurchase of Treasury Stock The amount of repurchase of treasury stock. Cost of sales, operating expenses and other income Operating Expenses [Abstract] Net sales Revenues [Abstract] Corporate Expenses [Member] Corporate Expenses Member Accounts payable Accounts Payable, Current Customer deposits Deposit Liability, Current Total assets Assets Other foreign jurisdictions Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Income tax expenses computed at PRC statutory income tax rate of 25%, Percent Percentage of statutory income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Other Income, Net [Abstract] Parent Company [Member] Parent Company [Member] Equity in earnings of subsidiaries Equity in earnings of subsidiaries Income (Loss) from Subsidiaries, before Tax Schedule of Non-Operating Income, Net [Abstract] Others Other Nonoperating Income (Expense) Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Customer, Extent of Reliance [Table] Schedule of Condensed Cash Flow Statement [Line Items] Segment Information - Schedule of Asset Information for Reportable Segments (Details) [Line Items] Segment Information Segment Reporting Disclosure [Text Block] Condensed Financial Information of Deswell Industries, Inc. [Abstract] Commitments and Contingencies [Abstract] Employee Benefits Compensation and Employee Benefit Plans [Text Block] Other Accrued Liabilities Accounts Payable and Accrued Liabilities Disclosure [Text Block] Income Taxes [Abstract] Lease Lessee, Operating Leases [Text Block] Stock Option Plan Share-Based Payment Arrangement [Text Block] Property, Plant and Equipment, Net Property, Plant and Equipment Disclosure [Text Block] Condensed Financial Information of Deswell Industries, Inc. Condensed Financial Information of Parent Company Only Disclosure [Text Block] Operating Risk Concentration Risk Disclosure [Text Block] Non-Operating Income, Net [Abstract] Other income, net Other Income and Other Expense Disclosure [Text Block] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Lease [Abstract] Income Taxes Income Tax Disclosure [Text Block] Non-Operating Income, Net Non-Operating Income, Net [Text Block] Non-Operating Income, Net. Employee Benefits [Abstract] Other foreign jurisdictions [Member] Income Tax Jurisdiction, Foreign, Other [Member] Income Tax Paid, by Individual Jurisdiction [Line Items] Income Tax Paid, by Individual Jurisdiction [Table] Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag] Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag] Schedule of Cash Payments for Tax Liabilities [Abstract] Non-recurring fair value measurements Fair Value Measurement Policy Nonrecurring Policy Text Block Disclosure of accounting policy for fair value measurements of financial and non-financial assets, liabilities and instruments classified in shareholders' equity that are measured on a non-recurring basis. Disclosures include, but are not limited to, how an entity that manages a group of financial assets and liabilities on the basis of its net exposure measures the fair value of those assets and liabilities. Cybersecurity Risk Management Third Party Engaged [Flag] Cybersecurity Risk Management Third Party Engaged [Flag] Cybersecurity Risk Board of Directors Oversight [Text Block] Cybersecurity Risk Board of Directors Oversight [Text Block] Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Text Block] Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Text Block] Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag] Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag] Cybersecurity Risk Management, Strategy, and Governance [Abstract] Cybersecurity Risk Management, Strategy, and Governance [Line Items] Segment information Segment Reporting, Expense Information Used by CODM, Description CODM Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration] Cybersecurity Risk Management, Strategy, and Governance [Table] Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block] Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block] Cybersecurity Risk Role of Management [Text Block] Cybersecurity Risk Role of Management [Text Block] Number of reportable segments Number of Reportable Segments Held-to-maturity investment Held To Maturity Investment Policy Text Block Disclosure of accounting policy for held-to-maturity investment. Computer Equipment [Member] Computer Equipment [Member] Summary of Significant Accounting Policies - Schedule of Disaggregates Product Sales by Business Segment and by Geography (Details) [Table] Schedule of Option Activity Share-Based Payment Arrangement, Option, Activity [Table Text Block] Schedule of Minimum Future Rental Income Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block] Schedule of Components of Net Deferred Income Tax Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of Statutory Tax Rate Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Other Accrued Liabilities Schedule of Accrued Liabilities [Table Text Block] Schedule of Obsolescence Allowance for Inventory Schedule Of Inventory Obsolescence Allowance Table Text Block Tabular disclosure of the change in allowance for inventory obsolescence. Schedule of Company Acquired Equity Securities Marketable Securities [Table Text Block] Schedule of Accounts Receivable, Net Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Schedule of Estimated Useful Lives of Property, Plant and Equipment Property Plant And Equipment Useful Life Table Text Block Tabular disclosure of the estimated useful lives of property, plant and equipment. Long Term Leased Land And Buildings [Member] Long Term Leased Land And Buildings Member Long Term Leased Land And Buildings [Member] Schedule of Condensed Income Statement Condensed Income Statement [Table Text Block] Finished goods Inventory, Finished Goods, Net of Reserves Balance at beginning of the year Balance at the end of the year Inventory Valuation Reserves Schedule of Prepaid Expenses and Other Current Assets [Abstract] Advance to suppliers Advances on Inventory Purchases Dividend receivable Other Receivables, Gross, Current Total prepaid expenses and other current assets Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Schedule Of Property Plant And Equipment Net Abstract Leasehold land and buildings [Member] Land and Building [Member] Principles of consolidation Consolidation, Policy [Policy Text Block] Marketable securities Marketable Securities, Policy [Policy Text Block] Allowance for credit losses Credit Loss, Financial Instrument [Policy Text Block] Inventories Inventory, Policy [Policy Text Block] Leases Lessee, Leases [Policy Text Block] Income taxes Income Tax, Policy [Policy Text Block] Post-retirement and post-employment benefits Pension and Other Postretirement Plans, Policy [Policy Text Block] Net income per share Earnings Per Share, Policy [Policy Text Block] Finite-Lived Intangible Assets, Major Class Name [Domain] Lease terms Lease Terms The amount of lease terms. Accrued expenses Other Accrued Liabilities Long term leased land Plant and machinery, and leasehold improvement totaling Leasehold Improvements, Gross Depreciation of property, plant and equipment Depreciation and amortization Depreciation, Depletion and Amortization Schedule of Allowance for Credit Losses Accounts Receivable, Allowance for Credit Loss [Table Text Block] Schedule of Disaggregates Product Sales by Business Segment and by Geography Revenue from External Customers by Geographic Areas [Table Text Block] Reclassifications Reclassification, Comparability Adjustment [Policy Text Block] Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Property, Plant and Equipment (Details) [Table] Leasehold Land and Buildings [Member] Land, Buildings and Improvements [Member] Stock-based compensation Share-Based Payment Arrangement [Policy Text Block] Impairment on property plant and equipment It represents impairment on property plant and equipment. Basic weighted average common shares outstanding Weighted average common shares outstanding (shares in thousands) Weighted Average Number of Shares Outstanding, Basic Schedule of Basic Net Income Per Share and Diluted Net Income Per Share [Abstract] Provision for (reversal of) credit losses, net Accounts Receivable, Credit Loss Expense (Reversal) Schedule of Allowance for Credit Losses [Abstract] Accounts receivable, net Accounts receivable, less allowances for credit losses of $24 and $22 at March 31, 2025 and 2026, respectively Accounts Receivable, after Allowance for Credit Loss, Current Schedule of Inventories, Net of Allowances Schedule of Inventory, Current [Table Text Block] Operating Risk (Tables) [Table] Sales Revenue, Net [Member] Sales Revenue, Net [Member] Revenue, Segment Benchmark [Member] Schedule of Prepaid Expenses and Other Current Assets Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Table Text Block] Schedule of Disaggregates Product Sales by Business Segment and by Geography [Line Items] Schedule of Provision for Income Taxes Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of Net Deferred Income Tax Schedule Of Deferred Income Tax Assets And Liabilities Table Text Block Schedule of Unrecognized Tax Benefits Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] Schedule of Lease Lease, Cost [Table Text Block] Schedule of Other Income, Net Schedule of Other Nonoperating Income (Expense) [Table Text Block] Schedule of Condensed Balance Sheet Condensed Balance Sheet [Table Text Block] Schedule of Condensed Cash Flow Statement Condensed Cash Flow Statement [Table Text Block] Total inventories Inventories, net Inventory, Net Schedule of Obsolescence Allowance for Inventory [Abstract] Additional charges (written off), net Inventory Write-down Rental and utility deposit Deposits Assets, Current Prepayment Other Prepaid Expense, Current Others Prepaid Expense and Other Assets Accounts receivable Accounts Receivable, before Allowance for Credit Loss, Current Exchange rate Foreign Currency Exchange Rate, Translation Property, plant and equipment Property, Plant and Equipment, Policy [Policy Text Block] Revenue recognition Revenue from Contract with Customer [Policy Text Block] Income Taxes (Details) [Table] Percentage of greater than tax Effective Income Tax Rate Reconciliation, Other Reconciling Items, Percent Statute of limitations period Net Operating Loss Carry Forward Period Net operating loss carry forward period. Schedule Of Option Activity Abstract Segment Reporting, Entity-Wide Information Not Provided as Part of Reportable Segment, Customer, Extent of Reliance [Line Items] Operating cash paid for operating lease Operating Lease, Payments Customer [Axis] Concentration Risk Type [Axis] Net (decrease) increase in cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Schedule of Condensed Cash Flow Statement [Abstract] Others Deferred Tax Assets, Other Depreciation and amortization Deferred Tax Liabilities, Property, Plant and Equipment Net operating loss carry forwards Operating Loss Carryforwards Schedule Of Components Of Net Deferred Income Tax Abstract Net deferred income tax (liabilities) assets Net Deferred Income Tax Liabilities Assets Net deferred income tax liabilities. Local Phone Number Entity Address, Postal Zip Code Entity Address, Address Line Two Document Accounting Standard Entity Interactive Data Current Condensed Cash Flow Statement [Table] Share of other comprehensive income of subsidiaries Other Comprehensive Income (Loss), Tax Income taxes Income tax expense (income) (note 8) Income tax expense (income) Income tax expense Income Tax Expense (Benefit) Balance (in Shares) Balance (in Shares) Shares, Outstanding Selling, general and administrative expenses Selling, General and Administrative Expense Non-operating income, net (note 14) Non-operating income, net Nonoperating Income (Expense) Basic: Earnings Per Share, Basic [Abstract] Effective Income Tax Rate Reconciliation, Percent [Abstract] The 2001 Stock Option [Member] The2001 Stock Option Member Stock Option Plan [Line Items] Increased shares of common stock Increased Shares Of Common Stock Increased shares of common stock. Stock option plan, additional shares authorized Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized Aggregate of common shares Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross Stock-based compensation expense (in Dollars) Share-Based Payment Arrangement, Expense Contact Personnel Name Contact Personnel Fax Number Trading Symbol Total current assets Assets, Current Accrued payroll and employee benefits Employee-related Liabilities, Current Business Contact Business Contact [Member] Deferred tax assets Deferred Income Tax Assets, Net Stock Option Plan - Schedule of Option Activity (Details) [Table] Concentration risk, percentage Concentration Risk, Percentage Commitments and Contingencies [Line Items] Pension expense Pension Cost (Reversal of Cost) Other foreign jurisdictions, Percent Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Common Stock [Member] Common stock Common Stock [Member] Common shares, outstanding Common Stock, Shares, Outstanding Cost of sales Cost of Revenue Additional paid-in capital Additional Paid-in Capital [Member] Retained earnings Retained Earnings (Accumulated Deficit) Statement of Financial Position [Abstract] Treasury stock, at cost Balance (in Shares) Balance (in Shares) Treasury Stock, Common, Shares Income Statement [Abstract] Common shares, authorized Common Stock, Shares Authorized Concentration Risk Type [Domain] Document Annual Report Document Transition Report Dividends ($0.2 per share) Dividends, Common Stock, Cash Customer B [Member] Customer E [Member] Customer G [Member] Customer GMember Customer H [Member] Customer HMember Document Registration Statement Document Financial Statement Error Correction [Flag] Document Shell Company Report Entity Address, Address Line One Entity Address, City or Town Entity Address, Country Schedule of Major Activities for Reportable Segments [Abstract] Auditor Name Auditor Location Others Other Operating Income Cover [Abstract] Document Information [Line Items] Held-to-maturity investment Heldtomaturity Investment Amount of held-to-maturity investment. Schedule of Revenues from External Customers and Long-Lived Assets [Table] Condensed Balance Sheet Statement [Table] Document Information [Table] Document Type Commitments and contingencies Commitments and Contingencies Common shares nil par value; authorized 30,000,000 shares as of March 31, 2025 and 2026; 17,081,810 shares issued as of March 31, 2025 and 2026; 15,935,239 shares outstanding as of March 31, 2025 and 15,885,239 shares outstanding as of March 31,2026 Common Stock, Value, Issued Income taxes payable Accrued Income Taxes, Current Deferred income tax liabilities Deferred Income Tax Liabilities, Net Additional paid-in capital Additional Paid in Capital, Common Stock Income (loss) before income taxes Income (Loss) Attributable to Parent, before Tax [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Subsegments [Domain] Interest expenses Interest Expense, Operating and Nonoperating Schedule of Asset Information for Reportable Segments [Abstract] Identifiable assets Business Combination, Recognized Asset Acquired to Liability Assumed, Excess (Less) Common shares, par value (in Dollars per share) Common Stock, No Par Value Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Treasury stock at cost; 1,146,571 shares as of March 31, 2025 and 1,196,571 shares as of March 31, 2026 Treasury Stock, Value Shareholders’ equity: Equity, Attributable to Parent [Abstract] Total liabilities Liabilities Accrued payroll and employee benefits Accrued Employee Benefits, Current Document Period End Date Document Fiscal Period Focus Income Tax Authority, Name [Domain] Schedule of Unrecognized Tax Benefits [Abstract] Operating lease income Operating Lease Income Operating lease income. Increase (decrease) related to current year tax positions Increasedecrease Related To Current Year Tax Positions Segments [Domain] Total cost of sales, operating expenses and other income Other Cost of Operating Revenue Cash flows from investing activities Cash Provided by (Used in) Investing Activity, Continuing Operation [Abstract] 1995 Stock Option [Member] The1995 Stock Option Member The 2003 Stock Option [Member] The2003 Stock Option Member Cash and cash equivalents Cash and Cash Equivalent Time deposit with original maturities over twelve months – current Fixed Deposits Current1 Time deposit with original maturities current. Tax Jurisdiction of Domicile [Extensible Enumeration] Concentration Risk [Table] Customer Concentration Risk [Member] Customer Concentration Risk [Member] Schedule of Profitability Information for Reportable Segments [Abstract] Subsegments [Axis] Income Tax Authority, Name [Axis] Unrecognized tax benefits Balance at the beginning of the year Balance at end of the year Unrecognized Tax Benefits Lease (Details) [Table] Lease [Line Items] Lessor, Lease, Description [Line Items] Commitments and Contingencies [Table] Commitments and Contingencies (Details) [Table] Purchase Commitment [Member] Purchase Commitment [Member] Deferred income tax liabilities Deferred Tax Liabilities, Gross Operating income (loss) Operating Income (Loss) [Abstract] Amounts due from subsidiaries Accounts and Financing Receivable, after Allowance for Credit Loss, Current Stock Option Plan [Table] Stock Option Plan (Details) [Table] Plan Name [Domain] Other comprehensive income Other Comprehensive Income (Loss), Net of Tax Schedule of Long-Lived Assets [Line Items] Adjustments to reconcile net income to net cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Entity Registrant Name Entity Emerging Growth Company Address Type [Domain] Dividend income from marketable securities Investment Income, Dividend Rental income, net of depreciation charges Rental Income, Nonoperating Schedule Of Operating Risks [Abstract] Schedule of Net Deferred Income Tax [Abstract] Change of valuation allowance Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount Changes in unrecognized tax benefits Effective Income Tax Rate Reconciliation Unrecognized Tax Benefits Represent the amount of unrecognized tax benefits. Effect of foreign rate differences Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount Schedule of Statutory Tax Rate [Abstract] Current tax Current Income Tax Expense (Benefit) Retained earnings Retained Earnings [Member] Range of exercise price per share, Weighted Average Exercise price Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Exercise Price Foreign exchange (loss) gain, net Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax, Portion Attributable to Parent Deferred income tax assets (liabilities): Deferred Tax Liabilities, Net [Abstract] Provision of employee benefits Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Benefits Revenue and cost of sales recognized for financial reporting purpose before being recognized for tax purpose Deferred Tax Liabilities, Tax Deferred Income Less: Valuation allowances Deferred Tax Assets, Valuation Allowance Total minimum future rental income Lessee, Operating Lease, Liability, to be Paid Schedule of Lease [Abstract] Schedule of Minimum Future Rental Income [Abstract] Lease term Lessor, Operating Lease, Term of Contract Purchase Commitment, Excluding Long-Term Commitment [Axis] Schedule of Breakdown of Sales by Destination [Abstract] Auditor Firm ID Auditor Opinion [Text Block] Auditor [Line Items] Dividends Common Stock, Dividends, Per Share, Declared Allowance for obsolete inventories, net Additional Chargesusage Net Additional charges usage, net. Customer deposits Increase Decrease Customer Deposits Amount of customer deposits. Chief Executive Officer Income Tax Jurisdiction, Domestic Federal, State, and Local