Abingworth LLP [Member] Abingworth L L P [Member] Abingworth LLP Accounts Payable and Accrued Liabilities [Line Items] Accounts Payable And Accrued Liabilities [Line Items] Accounts Payable and Accrued Liabilities [Line Items] Accounts Payable and Accrued Liabilities [Table] Accounts Payable And Accrued Liabilities [Table] Accounts Payable and Accrued Liabilities [Table] Accounts Payable Current Accounts payable Accrued expenses and other current liabilities Accrued Expenses And Other Current Liabilities Accrued expenses and other liabilities Accrued expenses and other liabilities Discloses the breakout of accrued expenses and other liabilities that are not individually material for a separate caption on the statement of financial position between the current portion (payable within 12 months of year end or the operating cycle) and non-current (payable after 12 months from year end). Accrued Expenses And Other Liabilities Disclosure [Text Block] Accrued Expenses and Other Liabilities Accrued Income Taxes Current Income taxes payable Accrued Research and Development Expense, Current Accrued Research And Development Expense Current Research and development expenses Accumulated Depreciation Depletion And Amortization Property Plant And Equipment Accumulated depreciation and amortization Additional Paid In Capital Common Stock Additional paid-in capital Additional Paid In Capital [Member] Additional Paid-in Capital Additional Square Feet Leased Additional Square Feet Leased Additional office space leased (in square feet) Adjustments To Additional Paid In Capital Equity Component Of Convertible Debt Transfer of fair value of bridge loan and December 2007 warrants from liabilities to equity Adjustments To Additional Paid In Capital Other Fair value of the warrant derivative liability reclassified from liabilities to equity Fair value of derivative liability transferred to equity Fair value of October 2009 warrants reclassed from derivative liability to equity Transfers to equity Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Stock based compensation Adjustments To Additional Paid In Capital Tax Effect From Share Based Compensation Tax benefits realized from stock-based compensation Adjustments To Additional Paid In Capital Warrant Issued Fair value of October 2009 warrant derivative liability Initial fair value of the warrant derivative liability Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Adjustments to reconcile loss to net cash used in operating activities: Amarin Pharmaceuticals Ireland Limited [Member] Amarin Pharmaceuticals Ireland Limited [Member] Amarin Pharmaceuticals Ireland Limited Amendment Flag Amendment Flag American Depositary Share [Member] American Depositary Share [Member] American Depositary Share American Depository Share [Member] American Depository Share [Member] American Depository Share American Depository Shares to Shares Ratio American Depository Shares To Shares Ratio Number of shares that each ADS represents Amr One Hundred One [Member] Amr One Hundred One [Member] Amr One Hundred One Annual Payment Under Service Agreement Annual Payment Under Service Agreement Annual Payment under agreement for consultancy services Assets TOTAL ASSETS Assets [Abstract] ASSETS Assets Current Total current assets Assets Current [Abstract] Current Assets: Assets Fair Value Disclosure [Abstract] Asset: Assumed Sales Revenue for Royalty Payments Assumed Sales Revenue For Royalty Payments Net sales for potential royalty payments Bedminster [Member] Bedminster [Member] Bedminster Bridge Loan Loan payable Bridge Loan [Member] Bridge Loan Business Acquisition Acquiree [Domain] Business Acquisition, Acquiree [Domain] Business Acquisition [Axis] Business Acquisition [Axis] Business Combination Disclosure [Text Block] Ester Asset Purchase Business Developments [Axis] Business Developments [Axis] Business Developments [Axis] Business Developments [Domain] Business Developments [Domain] Business Developments [Domain] Capital Lease Obligations Total principal obligations Capital Lease Obligations Current Less: current portion Capital Lease Obligations Noncurrent Long-term capital lease Capital Leases Future Minimum Payments Due Total Capital Leases Future Minimum Payments Due [Abstract] Capital Capital Leases Future Minimum Payments Due Current 2012 Capital Leases Future Minimum Payments Due In Three Years 2014 Capital Leases Future Minimum Payments Due In Two Years 2013 Capital Leases Future Minimum Payments Interest Included In Payments Less: amount representing interest 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 Fair Value Disclosure Cash equivalents Cash And Cash Equivalents Period Increase Decrease NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS Cash And Cash Equivalents Policy [Text Block] Cash and Cash Equivalents Cash Paid During Period For [Abstract] Cash Paid During Period For [Abstract] Cash paid during the year for: Chemport [Member] Chemport [Member] Chemport Class Of Warrant Or Right [Axis] Class of Warrant or Right [Axis] Class Of Warrant Or Right Common Stock Exchange Ratio Class Of Warrant Or Right Common Stock Exchange Ratio Number of ADS that can be purchased for each warrant received Class Of Warrant Or Right [Domain] Class of Warrant or Right [Domain] Class of Warrant or Right, Exercisable Period Class Of Warrant Or Right Exercisable Period Warrants issued, exercisable period Class Of Warrant Or Right Exercise Price Of Warrants Or Rights Exercise price of warrants Exercise Price Exercise price of the warrants Class of Warrant or Right, Expiration Date Class Of Warrant Or Right Expiration Date Expiration Date Class of Warrant or Right, Fair Value Assumption, Expected Life Class Of Warrant Or Right Fair Value Assumption Expected Life Warrant derivative liability valuation assumptions, remaining term Class of Warrant or Right, Fair Value Assumption, Risk Free Interest Rate Class Of Warrant Or Right Fair Value Assumption Risk Free Interest Rate Warrant derivative liability valuation assumptions, risk-free rate Class of Warrant or Right, Fair Value Assumption, Stock Volatility Class Of Warrant Or Right Fair Value Assumption Stock Volatility Warrant derivative liability valuation assumptions, volatility rate Class Of Warrant Or Right [Line Items] Class of Warrant or Right [Line Items] Class Of Warrant Or Right Number Of Securities Called By Warrants Or Rights Warrants issued, number of shares called by the warrant Class of Warrant or Right, Number of Warrants or Rights Cancelled Class Of Warrant Or Right Number Of Warrants Or Rights Cancelled Number of warrants cancelled Class Of Warrant Or Right Outstanding Amount Class Of Warrant Or Right [Table] Class of Warrant or Right [Table] Class of Warrant or Right, Term Class Of Warrant Or Right Term Warrant term Class Of Warrant Or Right Unissued Number of warrants issued Commitments And Contingencies Commitments and contingencies (Note 9) Commitments and Contingencies Disclosure [Line Items] Commitments And Contingencies Disclosure [Line Items] Commitments and Contingencies Disclosure [Line Items] Commitments and Contingencies Disclosure [Table] Commitments And Contingencies Disclosure [Table] Commitments and Contingencies Disclosure [Table] Commitments And Contingencies Disclosure [Text Block] Commitments and Contingencies Commitments To Purchase Or Fund Investments Commitments To Purchase Or Fund Investments Minority share equity investment commitment Common Stock, Conversion Rate Common Stock Conversion Rate Convertible senior notes, number of shares of common stock per $1,000 principal amount of notes Common Stock [Member] Common Shares Common Stock Par Or Stated Value Per Share Common stock, par Common Stock Shares Issued Common stock, issued Common Stock Shares Outstanding Common stock, outstanding Common Stock Value Common stock, £0.50 par value, unlimited authorized; 135,832,542 issued, 135,812,463 outstanding at December 31, 2011; 106,856,731 issued, 106,836,652 outstanding at December 31, 2010 Compensation And Employee Benefit Plans [Text Block] Defined Contribution Plans Computer Equipment and Capitalized Software [Member] Computer Equipment And Capitalized Software [Member] Computer Equipment and Capitalized Software Computer equipment, Gross Computer Equipment Gross Computer equipment Concentrations Of Credit Risk [Policy Text Block] Concentrations Of Credit Risk Policy [Text Block] Concentration of Credit Risk Consolidation Policy [Text Block] Principles of Consolidation Construction In Progress Gross Construction in Progress Contract Termination [Member] Contract Termination Convertible 8 Percent Bridge Loans, due August 2009 [Member] Convertible 8 Percent Bridge Loans Due August 2009 [Member] Convertible 8 Percent Bridge Loans, due August 2009 Convertible 8 Percent Bridge Loans, due September 2009 [Member] Convertible 8 Percent Bridge Loans Due September 2009 [Member] Convertible 8 Percent Bridge Loans, due September 2009 Convertible Debt, Conversion Starting Date Convertible Debt Conversion Starting Date Convertible senior notes, conversion starting date Convertible Notes Payable Convertible senior notes Cost Of Services Licenses And Maintenance Agreements Payment under service agreement Current Federal Tax Expense Benefit Federal-U.S. Current Fiscal Year End Date Current Fiscal Year End Date Current Foreign Tax Expense Benefit United Kingdom Current Income Tax Expense Benefit Total Current Current Income Tax Expense Benefit [Abstract] Current: Current State And Local Tax Expense Benefit State-U.S. Dalriada Ltd Agreement [Member] Dalriada Ltd Agreement [Member] Dalriada Ltd Agreement Debt Conversion By Unique Description [Axis] Debt Conversion by Unique Description [Axis] Debt Conversion Converted Instrument Shares Issued 1 Bridge notes converted in conjunction with the private placement, shares of common stock issued Debt Conversion Name [Domain] Debt Conversion, Name [Domain] Debt Conversion Original Debt Amount 1 Bridge notes converted in conjunction with the private placement, amount Debt Disclosure [Line Items] Debt Disclosure [Line Items] Debt Disclosure [Line Items] Debt Disclosure [Table] Debt Disclosure [Table] Debt Disclosure [Table] Debt Disclosure [Text Block] Debt Debt Instrument Carrying Amount Outstanding bridge loan notes Debt Instrument Conversion Circumstance Percentage Stock Price Of Stock Conversion Threshold Debt Instrument Conversion Circumstance Percentage Stock Price Of Stock Conversion Threshold Convertible senior notes, conversion circumstance, last reported sale price of common stock as percentage of conversion price Debt Instrument Conversion Circumstance Trading Price per Certain Principal Amount of Debt as Percentage of Common Stock Price Debt Instrument Conversion Circumstance Trading Price Per Certain Principal Amount Of Debt As Percentage Of Common Stock Price Convertible senior notes, conversion circumstance, trading price per $1,000 principal amount of notes as percentage of the product of the last reported sale price Debt Instrument Convertible Conversion Price 1 Bridge notes converted in conjunction with the private placement, price per share Convertible senior notes, conversion price per share of common stock Debt Instrument Date Of First Required Payment Convertible senior notes, payment start date Debt Instrument Face Amount Convertible bridge loans issued under private placement, face amount Debt Instrument Interest Rate Stated Percentage Convertible bridge loans issued under private placement, interest rate Convertible senior notes, stated interest rate Debt Instrument Maturity Date Convertible senior notes, maturity date Debt Policy [Text Block] Debt Issuance Costs December 2007 Direct Public Offering [Member] December 2007 Direct Public Offering [Member] December 2007 Direct Public Offering Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items] Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items] Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items] Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Table] Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Table] Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Table] Deferred Federal Income Tax Expense Benefit Federal-U.S. Deferred Foreign Income Tax Expense Benefit Ireland and United Kingdom Deferred Income Tax Expense Benefit Deferred income taxes Total Deferred Deferred Income Tax Expense Benefit [Abstract] Deferred: Deferred State And Local Income Tax Expense Benefit State-U.S. Deferred Tax Assets, Depreciation and Amortization Deferred Tax Assets Depreciation And Amortization Depreciation Deferred Tax Assets Gross Net deferred tax asset Deferred Tax Assets Net Deferred Tax Assets, Net, Total Deferred Tax Assets Net [Abstract] Deferred tax assets: Deferred Tax Assets Net Current Deferred tax asset Deferred Tax Assets Net Noncurrent Deferred tax asset Deferred Tax Assets Operating Loss Carryforwards Net operating losses Deferred Tax Assets Operating Loss Carryforwards Foreign Foreign net operating loss carryforwards Deferred Tax Assets Tax Credit Carryforwards Tax credit carryforwards Tax credits Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost Stock based compensation Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Reserves Other reserves and accrued liabilities Deferred Tax Assets Valuation Allowance Less: valuation allowance Deferred Tax Liabilities, Subject to Expiration Deferred Tax Liabilities Subject To Expiration Gross liabilities to expire in 2012 Defined Benefit Plan Contributions By Employer Contributions made under defined contribution plan Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Depreciation Depreciation expense Depreciation And Amortization Depreciation and amortization Derivative By Nature [Axis] Derivative, by Nature [Axis] Derivative Fair Value Of Derivative Liability Fair value of derivative liability Warrant derivative liability, fair value Derivative Financial Instruments Liabilities Fair Value Disclosure Warrant derivative liability Derivative Instruments And Hedging Activities Disclosure [Text Block] Warrants and Derivative Liability Derivative Liabilities Warrant derivative liability Derivative Liabilities Noncurrent Ending Balance Beginning Balance Fair value of derivative liability Warrant derivative liability Derivative [Line Items] Derivative [Line Items] Derivative Name [Domain] Derivative, Name [Domain] Derivatives Policy [Text Block] Derivative Instruments Derivative [Table] Derivative [Table] Development Fees Committed Development Fees Committed Development fees committed Disclosure - Accrued Expenses [Abstract] Disclosure Accrued Expenses [Abstract] Disclosure - Accrued Expenses [Abstract] Disclosure - Assumptions Used to Estimate Fair Value of Share-Based Payment Awards [Abstract] Disclosure Assumptions Used To Estimate Fair Value Of Share Based Payment Awards [Abstract] Disclosure - Assumptions Used to Estimate Fair Value of Share-Based Payment Awards [Abstract] Disclosure - Change in Fair Value of Warrant Derivative Liabilities [Abstract] Disclosure Change In Fair Value Of Warrant Derivative Liabilities [Abstract] Disclosure - Change in Fair Value of Warrant Derivative Liabilities [Abstract] Disclosure - Commitments and Contingencies - Additional Information [Abstract] Disclosure Commitments And Contingencies Additional Information [Abstract] Disclosure - Commitments and Contingencies - Additional Information [Abstract] Disclosure - Components of Loss from Operations Before Taxes [Abstract] Disclosure Components Of Loss From Operations Before Taxes [Abstract] Disclosure - Components of Loss from Operations Before Taxes [Abstract] Disclosure - Debt - Additional Information [Abstract] Disclosure Debt Additional Information [Abstract] Disclosure - Debt - Additional Information [Abstract] Disclosure - Defined Contribution Plans - Additional Information [Abstract] Disclosure Defined Contribution Plans Additional Information [Abstract] Disclosure - Defined Contribution Plans - Additional Information [Abstract] Disclosure - Difference between Benefit from Income Taxes and Amount Computed by Applying Statutory Income Tax Rate to Income Before Taxes [Abstract] Disclosure Difference Between Benefit From Income Taxes And Amount Computed By Applying Statutory Income Tax Rate To Income Before Taxes [Abstract] Disclosure - Difference between Benefit from Income Taxes and Amount Computed by Applying Statutory Income Tax Rate to Income Before Taxes [Abstract] Disclosure - Equity - Additional Information [Abstract] Disclosure Equity Additional Information [Abstract] Disclosure - Equity - Additional Information [Abstract] Disclosure - Ester Asset Purchase - Additional Information [Abstract] Disclosure Ester Asset Purchase Additional Information [Abstract] Disclosure - Ester Asset Purchase - Additional Information [Abstract] Disclosure - Estimated Useful Lives [Abstract] Disclosure Estimated Useful Lives [Abstract] Disclosure - Estimated Useful Lives [Abstract] Disclosure - Expense (Benefit) from Income Taxes [Abstract] Disclosure Expense Benefit From Income Taxes [Abstract] Disclosure - Expense (Benefit) from Income Taxes [Abstract] Disclosure - Future Minimum Lease Payments [Abstract] Disclosure Future Minimum Lease Payments [Abstract] Disclosure - Future Minimum Lease Payments [Abstract] Disclosure - Income Tax Effect of Each Type of Temporary Difference Comprising Net Deferred Tax Asset [Abstract] Disclosure Income Tax Effect Of Each Type Of Temporary Difference Comprising Net Deferred Tax Asset [Abstract] Disclosure - Income Tax Effect of Each Type of Temporary Difference Comprising Net Deferred Tax Asset [Abstract] Disclosure - Income Taxes - Additional Information [Abstract] Disclosure Income Taxes Additional Information [Abstract] Disclosure - Income Taxes - Additional Information [Abstract] Disclosure - Jurisdictions in which the Company Remains Subject to Tax Examinations [Abstract] Disclosure Jurisdictions In Which The Company Remains Subject To Tax Examinations [Abstract] Disclosure - Jurisdictions in which the Company Remains Subject to Tax Examinations [Abstract] Disclosure - Liability Measured at Fair Value on a Recurring Basis [Abstract] Disclosure Liability Measured At Fair Value On A Recurring Basis [Abstract] Disclosure - Liability Measured at Fair Value on a Recurring Basis [Abstract] Disclosure - Nature of Business and Basis of Presentation - Additional Information [Abstract] Disclosure Nature Of Business And Basis Of Presentation Additional Information [Abstract] Disclosure - Nature of Business and Basis of Presentation - Additional Information [Abstract] Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Stock Incentive Plans and Stock Based Compensation Disclosure - Other Current Assets [Abstract] Disclosure Other Current Assets [Abstract] Disclosure - Other Current Assets [Abstract] Disclosure - Property, Plant and Equipment [Abstract] Disclosure Property Plant And Equipment [Abstract] Disclosure - Property, Plant and Equipment [Abstract] Disclosure - Property Plant and Equipment - Additional Information [Abstract] Disclosure Property Plant And Equipment Additional Information [Abstract] Disclosure - Property Plant and Equipment - Additional Information [Abstract] Disclosure - Quarterly Summarized Financial Information (Unaudited) [Abstract] Disclosure Quarterly Summarized Financial Information Unaudited [Abstract] Disclosure - Quarterly Summarized Financial Information (Unaudited) [Abstract] Disclosure - Reconciliation of Total Amounts of Unrecognized Tax Benefits [Abstract] Disclosure Reconciliation Of Total Amounts Of Unrecognized Tax Benefits [Abstract] Disclosure - Reconciliation of Total Amounts of Unrecognized Tax Benefits [Abstract] Disclosure - Related Party Transactions - Additional Information [Abstract] Disclosure Related Party Transactions Additional Information [Abstract] Disclosure - Related Party Transactions - Additional Information [Abstract] Disclosure - Significant Accounting Policies - Additional Information [Abstract] Disclosure Significant Accounting Policies Additional Information [Abstract] Disclosure - Significant Accounting Policies - Additional Information [Abstract] Disclosure - Stock-Based Compensation Expense Related to Option Awards [Abstract] Disclosure Stock Based Compensation Expense Related To Option Awards [Abstract] Disclosure - Stock-Based Compensation Expense Related to Option Awards [Abstract] Disclosure - Stock Incentive Plans and Stock Based Compensation - Additional Information [Abstract] Disclosure Stock Incentive Plans And Stock Based Compensation Additional Information [Abstract] Disclosure - Stock Incentive Plans and Stock Based Compensation - Additional Information [Abstract] Disclosure - Stock Option Activity [Abstract] Disclosure Stock Option Activity [Abstract] Disclosure - Stock Option Activity [Abstract] Disclosure - Subsequent Event - Additional Information [Abstract] Disclosure Subsequent Event Additional Information [Abstract] Disclosure - Subsequent Event - Additional Information [Abstract] Disclosure - Warrants and Derivative Liability - Additional Information [Abstract] Disclosure Warrants And Derivative Liability Additional Information [Abstract] Disclosure - Warrants and Derivative Liability - Additional Information [Abstract] Disclosure - Warrants to Purchase Common Shares Outstanding [Abstract] Disclosure Warrants To Purchase Common Shares Outstanding [Abstract] Disclosure - Warrants to Purchase Common Shares Outstanding [Abstract] Document - Document and Entity Information [Abstract] Document Documentand Entity Information [Abstract] Document - Document and Entity Information [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Document Fiscal Year Focus Document Fiscal Year Focus Document Information [Line Items] Document Information [Line Items] Document Period End Date Document Period End Date Document Type Document Type Domestic Country [Member] U.S. Federal Dr John Climax [Member] Dr John Climax [Member] Dr John Climax Dublin [Member] Dublin [Member] Dublin Earnings Per Share Basic Basic Earnings Per Share Basic And Diluted Loss per basic and diluted share: Net loss per basic and diluted share: Earnings Per Share Basic And Diluted [Abstract] Net income (loss) per share: Earnings Per Share Diluted Diluted