Document and Entity Information Abstract Document And Entity Information Statement [Table] Statement [Line Items] Document Type Amendment Flag Document Period End Date Document Fiscal Period Focus Document Fiscal Year Focus Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Entity Filer Category Entity Common Stock, Shares Outstanding Consolidated Balance Sheets Assets Abstract ASSETS Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents, end of period Cash and cash equivalents, beginning of period Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value, Total Marketable Securities, Current Marketable securities Marketable Securities, Current, Total Accounts Receivable, Net, Current Accounts receivable Accounts Receivable, Net, Current, Total Receivables, Long-term Contracts or Programs Unbilled receivables Receivables, Long-term Contracts or Programs, Total Other Assets, Current Other current assets Assets, Current Total current assets Property, Plant and Equipment, Net Property, Plant and Equipment, Net, Ending Balance Property, Plant and Equipment, Net, Beginning Balance Property and equipment, net Property, Plant and Equipment, Net, Total Finite-Lived Intangible Assets, Net Patents, net Finite-Lived Intangible Assets, Net, Total Restricted Cash and Cash Equivalents, Noncurrent Restricted cash Marketable Securities, Noncurrent Marketable securities Marketable Securities, Noncurrent, Total Other Assets, Noncurrent Other noncurrent assets Other Assets, Noncurrent, Total Assets Total assets LIABILITIES AND STOCKHOLDERS' EQUITY Accounts Payable, Current Accounts payable Accounts Payable, Current, Total Accrued Liabilities, Current Accrued expenses Accrued Liabilities, Current, Total Deferred Revenue, Current Unearned revenues Deferred Revenue, Current, Total Long-term Debt, Current Maturities Current portion of long-term debt Long-term Debt, Current Maturities, Total Liabilities, Current Total current liabilities Long-term Debt, Excluding Current Maturities Long-term debt Long-term Debt, Excluding Current Maturities, Total Customer Advances or Deposits, Noncurrent Deferred credits Customer Advances or Deposits, Noncurrent, Total Liabilities Total liabilities Commitments and Contingencies (note 9) Commitments and contingencies (note 9) Ocean Power Technologies, Inc. Stockholders' equity: Preferred Stock, Value, Issued Preferred Stock, Value, Issued, Ending Balance Preferred Stock, Value, Issued, Beginning Balance Preferred stock, $0.001 par value; authorized 5,000,000 shares, none issued or outstanding Preferred Stock, Value, Issued, Total Common Stock, Value, Issued Common Stock, Value, Issued, Ending Balance Common Stock, Value, Issued, Beginning Balance Common stock, $0.001 par value; authorized 105,000,000 shares, issued 10,411,295 and 10,419,183 shares, respectively Common Stock, Value, Issued, Total Treasury Stock, Value Treasury stock, at cost; 13,485 and 7,685 shares, respectively Treasury Stock, Value, Ending Balance Treasury Stock, Value, Beginning Balance Treasury stock, at cost; 6,673 and 1,072 shares, respectively Additional Paid in Capital, Common Stock Additional Paid in Capital, Common Stock, Ending Balance Additional Paid in Capital, Common Stock, Beginning Balance Additional paid-in capital Retained Earnings (Accumulated Deficit) Retained Earnings (Accumulated Deficit), Ending Balance Retained Earnings (Accumulated Deficit), Beginning Balance Accumulated deficit Retained Earnings (Accumulated Deficit), Total Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax, Total Stockholders' Equity Attributable to Parent Balance Balance Total Ocean Power Technologies, Inc. stockholders' equity Stockholders' Equity Attributable to Noncontrolling Interest Stockholders' Equity Attributable to Noncontrolling Interest, Ending Balance Stockholders' Equity Attributable to Noncontrolling Interest, Beginning Balance Noncontrolling interest in Ocean Power Technologies (Australasia) Pty Ltd. Stockholders' Equity Attributable to Noncontrolling Interest, Total Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Balance Balance Total equity Liabilities and Equity Total liabilities and stockholders' equity Preferred Stock, Par or Stated Value Per Share Preferred stock, par value Preferred Stock, Shares Authorized Preferred stock, shares authorized Preferred Stock, Shares Issued Preferred stock, shares issued Preferred Stock, Shares Issued, Total Preferred Stock, Shares Outstanding Preferred Stock, Shares Outstanding, Ending Balance Preferred Stock, Shares Outstanding, Beginning Balance Preferred stock, shares outstanding Common Stock, Par or Stated Value Per Share Common stock, par value Common Stock, Shares Authorized Common stock, shares authorized Common Stock, Shares, Issued Common stock, shares issued Common Stock, Shares, Issued, Total Treasury Stock, Shares Treasury Stock, Shares, Ending Balance Treasury Stock, Shares, Beginning Balance Treasury stock, shares Consolidated Statements Of Operations Revenues Revenues Revenues, Total Cost of Revenue Cost of revenues Cost of Revenue, Total Gross Profit Gross profit (loss) Operating expenses: Research and Development Expense (Excluding Acquired in Process Cost) Product development costs Selling, General and Administrative Expense Selling, general and administrative costs Selling, General and Administrative Expense, Total Operating Expenses Total operating expenses Operating Income (Loss) Operating loss Operating loss Investment Income, Nonoperating Interest income, net Investment Income, Nonoperating, Total Foreign Currency Transaction Gain (Loss), before Tax Foreign exchange loss Foreign exchange loss Foreign Currency Transaction Gain (Loss), before Tax, Total Net loss Net loss Net loss Net loss Net loss Net Income (Loss) Attributable to Noncontrolling Interest Less: Net loss attributable to the noncontrolling interest in Ocean Power Technologies (Australasia) Pty Ltd. Less: Net loss attributable to the noncontrolling interest in Ocean Power Technologies (Australasia) Pty Ltd. Net Income (Loss) Attributable to Noncontrolling Interest, Total Net Income (Loss) Attributable to Parent Net loss attributable to Ocean Power Technologies, Inc. Earnings Per Share, Basic and Diluted Basic and diluted net loss per share Earnings Per Share, Basic and Diluted, Total The average number of shares or units issued and outstanding that are used in calculating basic and diluted EPS. Weighted Average Number Of Shares Outstanding Basic And Diluted1 Weighted average shares used to compute basic and diluted net loss per share Consolidated Statements Of Cash Flows Cash flows from operating activities: Adjustments to reconcile net loss to net cash used in operating activities: Depreciation, Depletion and Amortization Depreciation and amortization Depreciation, Depletion and Amortization, Total Gain (Loss) on Sale of Property Plant Equipment Loss on disposals of property, plant and equipment Loss on disposals of property, plant and equipment Gain (Loss) on Sale of Property Plant Equipment, Total Amortization of Debt Discount (Premium) Treasury note premium amortization Share-based Compensation, net Compensation expense related to stock option grants and restricted stock Share-based Compensation, Total Changes in operating assets and liabilities: Increase (Decrease) in Accounts Receivable Accounts receivable Accounts receivable Increase (Decrease) in Unbilled Receivables Unbilled receivables Unbilled receivables Increase (Decrease) in Other Current Assets Other current assets Other current assets Increase (Decrease) in Other Noncurrent Assets Other noncurrent assets Other noncurrent assets Increase (Decrease) in Accounts Payable Accounts payable Increase (Decrease) in Accounts Payable, Total Increase (Decrease) in Accrued Liabilities Accrued expenses Increase (Decrease) in Accrued Liabilities, Total Increase (Decrease) in Deferred Revenue Unearned revenues Increase (Decrease) in Other Noncurrent Liabilities Other noncurrent liabilities Net Cash Provided by (Used in) Operating Activities Net cash used in operating activities Cash flows from investing activities: Payments to Acquire Marketable Securities Purchases of marketable securities Purchases of marketable securities Payments to Acquire Marketable Securities, Total Proceeds from Sale and Maturity of Marketable Securities Maturities of marketable securities Proceeds from Sale and Maturity of Marketable Securities, Total Increase (Decrease) in Restricted Cash Restricted cash Restricted cash Increase (Decrease) in Restricted Cash, Total Payments to Acquire Machinery and Equipment Purchases of equipment Purchases of equipment Payments to Acquire Intangible Assets Payments of patent costs Payments of patent costs Net Cash Provided by (Used in) Investing Activities Net cash provided by investing activities Cash flows from financing activities: Proceeds from Issuance of Long-term Debt Proceeds from long-term debt Proceeds from Issuance of Long-term Debt, Total Repayments of Debt Repayment of debt Repayment of debt Payments for Repurchase of Common Stock Acquisition of treasury stock Acquisition of treasury stock Net Cash Provided by (Used in) Financing Activities Net cash (used in) provided by financing activities Effect of Exchange Rate on Cash and Cash Equivalents Effect of exchange rate changes on cash and cash equivalents Effect of Exchange Rate on Cash and Cash Equivalents, Total Cash and Cash Equivalents, Period Increase (Decrease) Net increase (decrease) in cash and cash equivalents Supplemental disclosure of noncash investing and financing activities: Noncash or Part Noncash Acquisition, Intangible Assets Acquired Capitalized patent costs financed through accounts payable and accrued expenses Noncash or Part Noncash Acquisition, Fixed Assets Acquired Capitalized purchases of equipment financed through accounts payable and accrued expenses Consolidated Statements Of Stockholders' Equity And Comprehensive Loss Statement, Equity Components [Axis] Equity Component [Domain] Common Shares [Member] Additional Paid-In Capital [Member] Treasury Shares [Member] Accumulated Other Comprehensive Loss [Member] Accumulated Deficit [Member] Total Ocean Power Technologies, Inc, Stockholders Equity [Member] Noncontrolling Interest [Member] Shares, Outstanding Balance, shares Balance, shares Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Foreign currency translation adjustment Foreign currency translation adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Total Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Total comprehensive loss Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Stock based compensation Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Total Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Issuance (forfeiture) of restricted stock, net Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures, Total Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Issuance (forfeiture) of restricted stock net, shares Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures, Total Treasury Stock, Value, Acquired, Cost Method Acquisition of treasury stock Acquisition of treasury stock Treasury Stock, Shares, Acquired Acquisition of treasury stock, shares Acquisition of treasury stock ,shares Background And Basis Of Presentation Background and Basis of Presentation text block Background And Basis Of Presentation Summary Of Significant Accounting Policies Significant Accounting Policies [Text Block] Summary Of Significant Accounting Policies Marketable Securities Marketable Securities [Text Block] Marketable Securities Balance Sheet Detail Supplemental Balance Sheet Disclosures [Text Block] Balance Sheet Detail Related Party Transactions Related Party Transactions Disclosure [Text Block] Related Party Transactions Debt Debt Disclosure [Text Block] Debt Deferred Credits Deferred Revenue Disclosure [Text Block] Deferred Credits Stock-Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Stock-Based Compensation Commitments And Contingencies Commitments and Contingencies Disclosure [Text Block] Commitments And Contingencies Income Taxes Income Tax Disclosure [Text Block] Income Taxes Operating Segments And Geographic Information Segment Reporting Disclosure [Text Block] Operating Segments And Geographic Information