Statement of Financial Position [Abstract] Cash and cash equivalents Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Cash and Cash Equivalents Marketable securities Certificates of Deposit and US Treasury obligations Restricted cash Restricted cash carrying value Accounts receivable Unbilled receivables Other current assets Total current assets Property and equipment, net Patents, net Restricted cash Restricted cash noncurrent Other noncurrent assets Total assets Total assets Accounts payable Accrued expenses Advance payment received from customer Unearned revenues Current portion of long-term debt Current portion of long-term debt Total current liabilities Long-term debt Deferred credits Customer Advances or Deposits, Noncurrent Total liabilities Commitments and contingencies (note 9) Preferred stock, $0.001 par value; authorized 5,000,000 shares, none issued or outstanding Preferred stock par value (in Dollars per share) Preferred stock, shares authorized Preferred stock, shares issued Preferred stock, shares outstanding Common stock, $0.001 par value; authorized 105,000,000 shares, issued 18,393,269 and 17,593,637 shares, respectively Treasury stock, at cost; 38,658 and 37,852 shares, respectively Common stock par value (in Dollars per share) Common stock, shares authorized Common stock, shares issued Treasury stock Additional paid-in capital Accumulated deficit Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Total Ocean Power Technologies, Inc. stockholders’ equity Noncontrolling interest in Ocean Power Technologies (Australasia) Pty Ltd. Total equity Balance Balance Total liabilities and stockholders’ equity Income Statement [Abstract] Revenues Revenues from external customers Cost of revenues Gross (loss) profit Product development costs Selling, general and administrative costs Total operating expenses Operating loss Operating loss Interest income (expense), net Other income Foreign exchange (loss) gain Foreign exchange loss (gain) Loss before income taxes Income tax benefit Income Tax Expense (Benefit) Net loss Net 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] Foreign currency translation adjustment Total comprehensive loss Comprehensive (income) loss attributable to the noncontrolling interest in Ocean Power Technologies (Australasia) Pty Ltd. Comprehensive loss attributable to Ocean Power Technologies, Statement of Stockholders' Equity [Abstract] 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) Treasury Stock, Shares, Acquired Sale of stock Other comprehensive income Equity Components [Axis] Common Stock [Member] Treasury Stock [Member] Additional Paid-in Capital [Member] Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) [Member] Noncontrolling Interest [Member] Statement of Cash Flows [Abstract] Depreciation and amortization Loss on disposals of property, plant and equipment Treasury note premium amortization Compensation expense related to stock option grants & restricted stock Allowance for doubtful accounts receivable Accounts receivable Long-term receivables Unbilled receivables Other current assets Other noncurrent assets Accounts payable Accrued expenses Return of advanced payment to customer Scenario [Axis] Short-Term [Member] Unearned Revenues Long-Term [Member] Net cash used in operating activities Purchases of marketable securities Maturities of marketable securities Restricted cash Purchases of equipment Net cashed provided by investing activities Proceeds from the sale of common stock, net of issuance costs Proceeds from Issuance of Common Stock Exercise of stock options Repayment of debt Acquisition of treasury stock Net cash (used in) provided by financing activities Effect of exchange rate changes on cash and cash equivalents Net increase (decrease) in cash and cash equivalents Capitalized purchases of equipment financed through accounts payable and accrued expenses Disclosure Text Block [Abstract] Accounting Policies [Abstract] Cash and Cash Equivalents [Abstract] Cash and Cash Equivalents [Axis] Checking and Savings Accounts [Member] Overnight Repurchase Account [Member] Certificates of Deposits and US Treasury Obligations [Member] Money Market Funds [Member] Cash Restricted Under Security Agreements [Abstract] Restricted Cash and Cash Equivalents [Axis] Australian Renewable Energy Agency [Member] NJBPU Agreement [Member] Oregon Department of State Lands [Member] Barclays Bank Agreement [Member] Foreign Exchange Gain (Loss) [Abstract] Foreign Currency Denominated Certificates of Deposit and Cash Accounts [Abstract] Restricted [Member] Foreign currency denominated certificates of deposit and cash accounts Unrestricted [Member] Revenues by Major Customers [Abstract] Customer [Axis] US Department of Energy [Member] Revenue Mitsui Engineering And Ship Building [Member] European Union (WaverPort Project) [Member] UK Government's Technology Strategy Board [Member] Investments, Debt and Equity Securities [Abstract] Major Types of Debt and Equity Securities [Axis] Current [Member] Marketable Securities That Mature Within One Year [Abstract] US Treasury obligations [Member] Disclosure Text Block Supplement [Abstract] Balance Sheet Detail [Abstract] Accounts receivable Patents Accumulated amortization Project costs Contract loss reserve Employee incentive payments Accrued salary and benefits Legal and accounting fees Goods and services tax (GST) due to Australian Tax Office Goods and Services Tax Due to Foreign Office Other Related Party Transactions [Abstract] Related party consulting expense Debt Disclosure [Abstract] Long-term Debt, Unclassified [Abstract] Total debt Long-term Debt Customer Advances And Deposits [Abstract] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Weighted Average Fair Value Assumptions for Stock-Based Compensation [Abstract] Stock Options Under the Plans [Abstract] Shares Under Options Shares Under Options Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Weighted Average Exercise Price Weighted Average Exercise Price Weighted Average Remaining Contractual Term Forfeited Forfeited Granted Granted Exercisable as of January 31, 2015 Exercisable as of January 31, 2015 Exercisable as of January 31, 2015 Non-Vested Restricted Stock Under the Plans [Abstract] Award Type [Axis] Non-vested Restricted Stock [Member] Number of Shares Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Weighted Average Price Per Share Weighted Average Price Per Share Granted Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Granted Forfeited Forfeited