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 Accounts receivable 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 Unearned revenues Current portion of long-term debt Total current liabilities Long-term debt Long-term unearned revenues Deferred credits Total liabilities Commitments and contingencies (note 8) 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 11,726,883 and 10,403,215 shares, respectively Treasury stock, at cost; 37,852 and 33,771 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 (in Shares) Preferred stock, shares issued (in Shares) Preferred stock, shares outstanding (in Shares) Common stock par value (in Dollars per share) Common stock, shares authorized (in Shares) Common stock, shares issued (in Shares) Treasury stock, shares (in 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 gain (loss) 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 Cash Flows [Abstract] Scenario, Unspecified [Domain] Cash flows from operating activities: Cash flows from operating activities: [Abstract] Net loss 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 (gain) loss Depreciation and amortization Treasury note premium 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 Increase or decrease In long-term accounts receivables. Long-term receivables 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 Net cash provided by investing activities Cash flows from financing activities: Cash flows from financing activities: [Abstract] Proceeds from the sale of common stock, net of issuance costs Proceeds from the exercise of stock options Repayment of debt Acquisition of treasury stock Net cash provided by (used in) financing activities Effect of exchange rate changes on cash and cash equivalents Net 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 Statement of Stockholders' Equity [Abstract] Equity Component [Domain] Balance Balance Balance (in Shares) Balance (in Shares) 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) Other comprehensive loss Stock issued upon exercise of stock options Stock issued upon exercise of stock options (in Shares) Sale of stock, net Sale of stock, net (in Shares) Disclosure Text Block [Abstract] Business Description and Basis of Presentation [Text Block] Accounting Policies [Abstract] Significant Accounting Policies [Text Block] Investments, Debt and Equity Securities [Abstract] Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Disclosure Text Block Supplement [Abstract] Supplemental Balance Sheet Disclosures [Text Block] Debt Disclosure [Abstract] Debt Disclosure [Text Block] Customer Advances And Deposits Disclosure [Abstract] Customer Advances And Deposits Disclosure [Abstract] Customer Advances And Deposits Disclosure Customer Advances And Deposits Disclosure [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Text Block] Income Tax Disclosure [Abstract] Income Tax Disclosure [Text Block] Segment Reporting [Abstract] Segment Reporting Disclosure [Text Block] Subsequent Events [Abstract] Subsequent Events [Text Block] Basis of Accounting, Policy [Policy Text Block] Liquidity Disclosure [Policy Text Block] 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] Foreign Currency Transactions and Translations 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] New Accounting Pronouncements, Policy [Policy Text Block] Schedule of foreign exchange gain (loss). Schedule Of Foreign Currency Denominated Certificates of Deposit and Cash Accounts Schedule of Cash and Cash Equivalents [Table Text Block] Schedule of Restricted Cash and Cash Equivalents [Table Text Block] Schedule Of Foreign Currency Denominated Certificates of Deposit and Cash Accounts Schedule of Revenue by Major Customers by Reporting Segments [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] Schedule of Other Assets and Other Liabilities [Table Text Block] Schedule of Debt [Table Text Block] Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [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 Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] Cash and Cash Equivalents Cash and Cash Equivalents [Abstract] CashAndCashEquivalents_ [Domain] Schedule of Cash and Cash Equivalents [Table] Cash and Cash Equivalents [Line Items] Cash Restricted Under Security Agreements Cash Restricted Under Security Agreements [Abstract] RestrictedCashAndCashEquivalentsCashAndCashEquivalents [Domain] Schedule of Restricted Cash and Cash Equivalents [Table] Restricted Cash and Cash Equivalents Items [Line Items] Restricted Cash Foreign Exchange Gain (Loss) Foreign Exchange Gain (Loss) [Abstract] Foreign Currency Denominated Certificates Of Deposit And Cash Accounts Foreign Currency Denominated Certificates Of Deposit And Cash Accounts [Abstract] Note 2 - Summary of Significant Accounting Policies (Details) - Foreign Currency Denominated Certificates Of Deposit And Cash Accounts [Table] Note 2 - Summary of Significant Accounting Policies (Details) - Foreign Currency Denominated Certificates Of Deposit And Cash Accounts [Line Items] Foreign currency denominated certificates of deposit and cash accounts: Foreign currency denominated certificates of deposit and cash accounts: [Abstract] Foreign currency denominated certificates of deposit and cash accounts. Foreign currency denominated certificates of deposit and cash accounts Percentage of the Company’s Revenues Derived From Major Customers Percentage of the Company’s Revenues Derived From Major Customers [Abstract] Customer [Domain] Concentration Risk Benchmark [Domain] Schedule of Revenue by Major Customers, by Reporting Segments [Table]