Statement of Financial Position [Abstract] ASSETS ASSETS [Abstract] Current assets: Current assets: [Abstract] Cash and cash equivalents Marketable securities Accounts receivable, net Unbilled receivables Other current assets Total current assets Property and equipment, net Patents, net Restricted cash Other noncurrent assets Total assets LIABILITIES AND STOCKHOLDERS' EQUITY LIABILITIES AND STOCKHOLDERS' EQUITY [Abstract] Current liabilities: Current liabilities: [Abstract] Accounts payable Accrued expenses Deferred credits payable Unearned revenues Current portion of long-term debt Total current liabilities Long-term unearned revenues Long-term debt Deferred credits payable-noncurrent Total liabilities Commitments and contingencies (note 13) Ocean Power Technologies, Inc. Stockholders’ equity: Ocean Power Technologies, Inc. Stockholders’ equity: [Abstract] Preferred stock, $0.001 par value; authorized 5,000,000 shares, none issued or outstanding Common stock, $0.001 par value; authorized 105,000,000 shares, issued 10,403,215 and 10,407,389 shares, respectively Treasury stock, at cost; 33,771 and 23,544 shares, respectively Additional paid-in capital Accumulated deficit Accumulated other comprehensive loss Total Ocean Power Technologies, Inc. stockholders’ equity Noncontrolling interest in Ocean Power Technologies (Australasia) Pty Ltd… Total equity Total liabilities and stockholders’ equity Preferred stock par value (in Dollars per share) Preferred stock, shares authorized Preferred stock, shares issued Preferred stock, shares outstanding Common stock par value (in Dollars per share) Common stock, shares authorized Common stock, shares issued Treasury stock, shares Income Statement [Abstract] Revenues Cost of revenues Gross profit Operating expenses: Operating expenses: [Abstract] Product development costs Selling, general and administrative costs Total operating expenses Operating loss Interest income, net Foreign exchange loss Loss before income taxes Income tax benefit Net loss Less: Net loss attributable to the noncontrolling interest in Ocean Power Technologies (Australasia) Pty Ltd. Net loss attributable to Ocean Power Technologies, Inc Basic and diluted net loss per share (in Dollars per share) Weighted average shares used to compute basic and diluted net loss per share (in Shares) Statement of Comprehensive Income [Abstract] Net Loss Foreign currency translation adjustment Total comprehensive loss Comprehensive loss attributable to the noncontrolling interest in Ocean Power Technologies (Australasia) Pty Ltd. Comprehensive loss attributable to Ocean Power Technologies, Inc. Statement of Stockholders' Equity [Abstract] Equity Component [Domain] Balance, April 30 Balance, April 30 Balance, April 30 (in Shares) Balance, April 30 (in Shares) Net loss Total comprehensive loss Stock based compensation Issuance (forfeiture) of restricted stock, net Issuance (forfeiture) of restricted stock, net (in Shares) Acquisition of treasury stock Acquisition of treasury stock (in Shares) Statement of Cash Flows [Abstract] Scenario, Unspecified [Domain] Cash flows from operating activities: Cash flows from operating activities: [Abstract] Adjustments to reconcile net loss to net cash used in operating activities: Adjustments to reconcile net loss to net cash used in operating activities: [Abstract] Foreign exchange loss Depreciation and amortization Loss on disposals of property, plant and equipment Impairment of long-lived assets Provision for doubtful accounts Treasury note discount amortization Compensation expense related to stock option grants and restricted stock Changes in operating assets and liabilities: Changes in operating assets and liabilities: [Abstract] Accounts receivable Unbilled receivables Other current assets Other noncurrent assets Accounts payable Accrued expenses Unearned revenues Net cash used in operating activities Cash flows from investing activities: Cash flows from investing activities: [Abstract] Purchases of marketable securities Maturities of marketable securities Restricted cash Purchases of equipment Payments of patent costs Net cash provided by investing activities Cash flows from financing activities: Cash flows from financing activities: [Abstract] Repayment of debt Acquisition of treasury stock Net cash used in financing activities Effect of exchange rate changes on cash and cash equivalents Net (decrease) increase in cash and cash equivalents Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Supplemental disclosure of noncash investing and financing activities: Supplemental disclosure of noncash investing and financing activities: [Abstract] Capitalized purchases of equipment financed through accounts payable and accrued expenses Disclosure Text Block [Abstract] Business Description and Basis of Presentation [Text Block] Significant Accounting Policies [Abstract] Significant Accounting Policies [Text Block] Significant Accounting Policies [Text Block] Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Abstract] Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Property, Plant and Equipment Disclosure [Abstract] Property, Plant and Equipment Disclosure [Text Block] Property, Plant and Equipment Disclosure [Text Block] Supplemental Balance Sheet Disclosures [Abstract] Supplemental Balance Sheet Disclosures [Text Block] Supplemental Balance Sheet Disclosures [Text Block] Related Party Transactions Disclosure [Abstract] Related Party Transactions Disclosure [Text Block] Related Party Transactions Disclosure [Text Block] Debt Disclosure [Abstract] Debt Disclosure [Text Block] Debt Disclosure [Text Block] Customer Advances And Deposits Disclosure [Abstract] Customer Advances And Deposits Disclosure [Text Block] Customer Advances And Deposits Disclosure Customer Advances And Deposits Disclosure [Text Block] Stockholders' Equity Note Disclosure [Abstract] Stockholders' Equity Note Disclosure [Text Block] Stockholders' Equity Note Disclosure [Text Block] Preferred Stock [Abstract] Preferred Stock [Text Block] Preferred Stock [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Income Tax Disclosure [Abstract] Income Tax Disclosure [Text Block] Income Tax Disclosure [Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Disclosure [Text Block] Segment Reporting Disclosure [Abstract] Segment Reporting Disclosure [Text Block] Segment Reporting Disclosure [Text Block] Subsequent Events [Abstract] Subsequent Events [Text Block] Subsequent Events [Text Block] Accounting Policies [Abstract] Consolidation, Policy [Policy Text Block] Use of Estimates, Policy [Policy Text Block] Revenue Recognition, Policy [Policy Text Block] Cash and Cash Equivalents, Policy [Policy Text Block] Marketable Securities, Policy [Policy Text Block] Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Property, Plant and Equipment, Policy [Policy Text Block] Foreign Currency Transactions and Translations Policy [Policy Text Block] Intangible Assets, Finite-Lived, Policy [Policy Text Block] Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Concentration Risk, Credit Risk, Policy [Policy Text Block] Earnings Per Share, Policy [Policy Text Block] Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Income Tax, Policy [Policy Text Block] Comprehensive Income, Policy [Policy Text Block] New Accounting Pronouncements, Policy [Policy Text Block] Schedule of foreign exchange gain (loss). Schedule of Cash and Cash Equivalents [Table Text Block] Schedule of Restricted Cash and Cash Equivalents [Table Text Block] Schedule of Foreign Exchange Gain (Loss) [Table Text Block] Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block] Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Major Types of Debt and Equity Securities [Domain] Note 3 - Marketable Securities (Tables) [Table] Note 3 - Marketable Securities (Tables) [Line Items] Marketable Securities [Table Text Block] Property, Plant and Equipment [Table Text Block] Schedule of Other Assets and Other Liabilities [Table Text Block] Schedule of Related Party Transactions [Table Text Block] Schedule of Debt [Table Text Block] Schedule of Share-based Compensation, Activity [Table Text Block] Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block] Schedule of components of loss before income taxes. Schedule of Components of Loss Before Income Taxes [Table Text Block] Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]