Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Stock options Employee Stock Option [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Number of Options Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Weighted-Average Exercise Price (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Weighted-Average Fair Value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Income Tax Disclosure [Abstract] U.S. federal statutory tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Remeasurement of Deferred Tax Assets due to US Tax Reform Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit) Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit) Recognition of provisional charge Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit) Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit) Adjustment to provisional amount recorded Tax Cuts and Jobs Act of 2017, Measurement Period Adjustment, Income Tax Expense (Benefit) Tax Cuts and Jobs Act of 2017, Measurement Period Adjustment, Income Tax Expense (Benefit) Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Unrecognized tax benefits that would impact effective tax rate Unrecognized Tax Benefits that Would Impact Effective Tax Rate Accounting Policies [Abstract] Business Overview and Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Project [Axis] Project [Axis] Project [Domain] Project [Domain] Sanofi Sanofi Collaboration Agreement [Member] Sanofi Collaboration Agreement [Member] Other Bayer, Teva Pharmaceuticals, And Other Agreements [Member] Bayer, Teva Pharmaceuticals, And Other Agreements [Member] Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition [Domain] Initial Application Period Cumulative Effect Transition [Domain] Balance Without Adoption of ASC 606 Calculated under Revenue Guidance in Effect before Topic 606 [Member] Adjustments Difference between Revenue Guidance in Effect before and after Topic 606 [Member] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2014-09 Accounting Standards Update 2014-09 [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Inventories Inventory, Net Deferred tax assets Deferred Income Tax Assets, Net Total assets Assets Accrued expenses and other current liabilities Accrued Liabilities and Other Liabilities Deferred revenue, current Contract with Customer, Liability, Current Total current liabilities Liabilities, Current Deferred revenue, noncurrent Contract with Customer, Liability, Noncurrent Total liabilities Liabilities Retained earnings Retained Earnings (Accumulated Deficit) Total stockholders' equity Stockholders' Equity Attributable to Parent Total liabilities and stockholders' equity Liabilities and Equity Impact of change in U.S. corporate tax rate (the Act) Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Sale of non-inventory related assets between foreign subsidiaries Effective Income Tax Rate Reconciliation, Sale Of Non-Inventory Related Assets Between Foreign Subsidiaries, Percent Effective Income Tax Rate Reconciliation, Sale Of Non-Inventory Related Assets Between Foreign Subsidiaries, Percent Stock-based compensation Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent Taxation of non-U.S. operations Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent Income tax credits Effective Income Tax Rate Reconciliation, Tax Credit, Percent Non-deductible Branded Prescription Drug Fee Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent Foreign-derived intangible income deduction Effective Income Tax Rate Reconciliation, Deduction, Foreign Intangible Income, Percent Effective Income Tax Rate Reconciliation, Deduction, Foreign Intangible Income, Percent Domestic production activities deduction Effective Income Tax Rate Reconciliation, Deduction, Qualified Production Activity, Percent State and local income taxes Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Other permanent differences Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent Effective income tax rate Statement of Stockholders' Equity [Abstract] Statement [Table] Adjustments for Change in Accounting Principle [Axis] Adjustments for Change in Accounting Principle [Axis] Adjustments for Change in Accounting Principle [Domain] Adjustments for Change in Accounting Principle [Domain] Accounting Standards Update 2014-09 And 2016-01 Accounting Standards Update 2014-09 And 2016-01 [Member] Accounting Standards Update 2014-09 And 2016-01 [Member] Accounting Standards Update 2016-01 Accounting Standards Update 2016-01 [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Class A Stock Common Class A [Member] Common Stock Common Stock [Member] Restricted stock Restricted Stock [Member] Equity Components [Axis] Equity Component [Domain] Additional Paid-in Capital Additional Paid-in Capital [Member] Retained Earnings Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Treasury Stock Treasury Stock [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning Balance (in shares) Shares, Outstanding Beginning Balance Issuance of Common Stock in connection with exercise of stock options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Issuance of Common Stock in connection with exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Common Stock tendered upon exercise of stock options and vesting of restricted stock in connection with employee tax obligations (in shares) Shares Paid for Tax Withholding for Share Based Compensation Common Stock tendered upon exercise of stock options and vesting of restricted stock in connection with employee tax obligations Adjustments Related to Tax Withholding for Share-based Compensation Issuance of Common Stock in connection with conversion of convertible notes (in shares) Debt Conversion, Converted Instrument, Shares Issued Issuance of Common Stock in connection with conversion of convertible notes Stock Issued During Period, Value, Conversion of Convertible Securities Issuance of restricted stock under Long-Term Incentive Plan (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Issuance of restricted stock under Long-Term Incentive Plan Stock Issued During Period, Value, Restricted Stock Award, Gross Issuance of Common Stock in connection with Company 401(k) Savings Plan contribution (in shares) Stock Issued During Period, Shares, Employee Benefit Plan Issuance of Common Stock in connection with Company 401(k) Savings Plan Stock Issued During Period, Value, Employee Benefit Plan Stock-based compensation charges Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Acquisition of Common Stock (in shares) Treasury Stock, Shares, Acquired Acquisition of Common Stock Treasury Stock, Value, Acquired, Cost Method Reduction of warrants Adjustments to Additional Paid in Capital, Other Reduction of equity component of convertible notes Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments Change in accounting standards Cumulative Effect on Retained Earnings, Net of Tax Net income Net Income (Loss) Attributable to Parent Other comprehensive loss, net of tax Other Comprehensive Income (Loss), Net of Tax Ending Balance (in shares) Ending Balance Investments, Debt and Equity Securities [Abstract] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Table] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Corporate bonds Corporate Bond Securities [Member] U.S. government and government agency obligations US Treasury and Government [Member] Sovereign bonds Sovereign Debt Securities [Member] Municipal and sovereign bonds Municipal Bonds And Sovereign Debt Securities [Member] Municipal Bonds And Sovereign Debt Securities [Member] Commercial paper Commercial Paper [Member] Certificates of deposit Certificates of Deposit [Member] Classification of Investment [Axis] Classification of Investment [Axis] This element represents the general categories of investments, which may be classified as Unrestricted or Restricted. Classification of Investment [Domain] Classification of Investment [Domain] Provides general categories of investments for which information is required or determined to be disclosed. Unrestricted Unrestricted [Member] Investments whose use is not restricted in whole or in part, by contractual agreements or regulatory requirements. Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Amortized Cost Basis Debt Securities, Available-for-sale, Amortized Cost Unrealized Gains Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Unrealized Losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Fair Value Debt Securities, Available-for-sale Commitments and Contingencies Disclosure [Abstract] Schedule of Operating Leased Assets [Table] Schedule of Operating Leased Assets [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Facilities Building [Member] Equipment Equipment [Member] Operating Leased Assets [Line Items] Operating Leased Assets [Line Items] Rent expense under operating leases Operating Leases, Rent Expense, Net Long-Term Incentive Plans Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Quarterly Financial Information Disclosure [Abstract] Unaudited Quarterly Results Quarterly Financial Information [Text Block] Revenues Revenue from Contract with Customer, Excluding Assessed Tax Net income per share - basic (in dollars per share) Earnings Per Share, Basic Net income per share - diluted (in USD per shares) Earnings Per Share, Diluted Supplemental Cash Flow Information [Abstract] Condensed Cash Flow Statement [Table] Condensed Cash Flow Statement [Table] Sanofi Collaboration Agreement, Immuno-oncology Sanofi Collaboration Agreement, Immuno-oncology [Member] Sanofi Collaboration Agreement, Immuno-oncology [Member] Condensed Cash Flow Statements, Captions [Line Items] Condensed Cash Flow Statements, Captions [Line Items] Accrued capital expenditures Accrued Capital Expenditures Carrying value as of the balance sheet date of obligations incurred and payable for purchases of fixed assets. Included in accounts payable and accrued expenses. Treasury stock, shares acquired (in shares) Cost of Treasury stock shares received Capital lease obligations incurred Capital Lease Obligations Incurred Number of business segments Number of Reportable Segments Equity Components [Axis] Equity Component [Domain] Customer [Axis] Customer [Axis] Customer [Domain] Customer [Domain] Three individual customers Three Individual Customers [Member] Three Individual Customers [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Pro Forma Pro Forma [Member] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Customer concentration risk Customer Concentration Risk [Member] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Gross Sales Revenue Accounts Receivable [Member] Equity Securities Equity Securities [Member] Accounting Standards Update 2016-02 Accounting Standards Update 2016-02 [Member] Deferred revenue Contract with Customer, Liability Cumulative effect on retained earnings, net of tax Cumulative Effect of New Accounting Principle in Period of Adoption Reclassification from accumulated other comprehensive income, current period, before tax Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax Concentration risk, percentage Concentration Risk, Percentage Allowance for doubtful accounts receivable, current Allowance for Doubtful Accounts Receivable, Current Provision for doubtful accounts Provision for Doubtful Accounts Right-of-use asset Operating Lease, Right-of-Use Asset Lease liabilities Operating Lease, Liability Debt Disclosure [Abstract] Debt Debt Disclosure [Text Block] Earnings Per Share [Abstract] Basic and Diluted Net Income (Loss) Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Antidilutive Securities Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Net income - basic Convertible senior notes - interest expense and amortization of discount and note issuance costs Interest on Convertible Debt, Net of Tax Net income - diluted Net Income (Loss) Attributable to Parent, Diluted Weighted average shares outstanding - basic (in shares) Weighted Average Number of Shares Outstanding, Basic Effect of dilutive securities: Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract] Effect of dilutive securities (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Warrants (in shares) Incremental Common Shares Attributable to Dilutive Effect of Call Options and Warrants Dilutive potential shares (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Weighted average shares - diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Net income per share - diluted (in dollars per share) Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities Disclosure [Text Block] Revenue from Contract with Customer [Abstract] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Research and Development Arrangement, Contract to Perform for Others, Type [Axis] Research and Development Arrangement, Contract to Perform for Others, Type [Axis] Research and Development Arrangement, Contract to Perform for Others, Type [Domain] Research and Development Arrangement, Contract to Perform for Others, Type [Domain] Praluent, Kevzara, and Dupixent Praluent, Kevzara, and Dupixent [Member] [Member] Praluent, Kevzara, and Dupixent [Member] [Member] Sanofi Collaboration Agreement, Antibody Sanofi Collaboration Agreement, Antibody [Member] Sanofi Collaboration Agreement, Antibody [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Common Stock, shares issued (in shares) Common Stock, Shares, Issued Proceeds from collaborators Proceeds from Collaborators Annual funding maximum of research activities per amended agreement Annual funding maximum of research activities per amended agreement The maximum annual amount of funding for research activities through 2017 per the amended agreement. Percentage of Trial Costs borne by collaborating party Percentage of Trial Costs borne by collaborating party The percentage of subsequent Shared Phase 3 Trial costs borne by the collaborating party upon receipt of the first positive Phase 3 trial results for a co-developed drug candidate. Percentage of Trial Costs borne by entity Percentage of Trial Costs borne by entity The percentage of subsequent Shared Phase 3 Trial costs borne by the Company upon receipt of the first positive Phase 3 trial results for a co-developed drug candidate. Research and development Research and Development Expense Percentage of repayment of development balance out of profits Percentage of repayment of development balance out of profits Percentage of repayment of development balance out of profits under the collaboration agreement. Percentage of trial costs to be reimbursed due to profitability of agreement Percentage of trial costs to be reimbursed due to profitability of agreement The percentage of Shared Phase 3 trial costs to be reimbursed due to profitability of agreement. Excess share of profit not required to to be applied to reimburse development cost Excess Share of profit not required to to be applied to reimburse development cost The excess percentage of profits from collaboration not required to be used to reimburse development cost in any calendar quarter. Contingent reimbursement obligation Contingent reimbursement obligation The Company's total contingent reimbursement obligation to its collaboration partner for development expenses previously funded by its collaboration partner. Starting share of profits outside the United States, based on sales, for collaborating party Starting share of profits outside the United States, based on sales, for collaborating party On a sliding scale, this element represents the starting share of profits outside the United States, based on sales, for the collaborating party. Starting share of profits outside the United States, based on sales, for Company Starting share of profits outside the United States, based on sales, for Company On a sliding scale, this element represents the starting share of profits outside the United States, based on sales, for the Company. Ending share of profits outside the United States, based on sales, for collaborating party Ending share of profits outside the United States, based on sales, for collaborating party On a sliding scale, this element represents the ending share of profits outside the United States, based on sales, for the collaborating party. Ending share of profits outside the United States, based on sales, for Company Ending share of profits outside the United States, based on sales, for Company On a sliding scale, this element represents the ending share of profits outside the United States, based on sales, for the Company. Share of losses outside the United States, for collaborating party Share of losses outside the United States, for collaborating party This element represents the share of losses outside the United States for the collaborating party. Share of losses outside the United States, for Company Share of losses outside the United States, for Company This element represents the share of losses outside the United States for the Company. Maximum amount of sales milestone payments if total sales achieve specific levels Maximum amount of sales milestone payments if total sales achieve specific levels The maximum amount of sales milestone payments the Company is eligible to receive when and if total annual sales achieve certain specified levels. Levels of twelve month sales at which sales milestone payments would be received Levels of twelve month sales at which sales milestone payments would be received Aggregate amount of twelve month sales upon which sales milestone would be received. Period for achieving sales target for milestone payment, rolling basis Period for Achieving Sales Target for Milestone Payment, Rolling Basis Period for Achieving Sales Target for Milestone Payment, Rolling Basis Period of notice to opt out of further development and or commercialization Period of Notice to Opt Out of Further Development and or Commercialization The period of notice (in months) for either party under the agreement to opt-out of further development and/or commercialization of each antibody product which enters development. Schedule of commitments under operating leases Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of rent expense under operating leases Schedule of Rent Expense [Table Text Block] Schedule of commitments under facility lease obligation Schedule of Future Minimum Lease Payments for Capital Leases [Table Text Block] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Senior unsecured revolving credit facility Revolving Credit Facility [Member] Letters of credit Letter of Credit [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Convertible senior notes Convertible Debt [Member] Line of credit Line of Credit [Member] Class of Warrant or Right [Axis] Class of Warrant or Right [Axis] Class of Warrant or Right [Domain] Class of Warrant or Right [Domain] November 2016 Agreement [Member] [Member] November 2016 Agreement [Member] November 2016 Agreement repurchase of warrants Warrant Warrant [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Aggregate principal amount Debt Instrument, Face Amount Interest rate, stated percentage Debt Instrument, Interest Rate, Stated Percentage Initial conversion price (in dollars per share) Debt Instrument, Convertible, Conversion Price Repayments of convertible senior notes Repayments of Convertible Debt Stock issued, new shares (in shares) Stock Issued During Period, Shares, New Issues Reduction of equity component of convertible notes Payments in connection with reduction of outstanding warrants Payments for Repurchase of Warrants Warrants outstanding Warrants and Rights Outstanding Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Debt term Line of Credit Facility, Expiration Period Borrowings outstanding Long-term Line of Credit Increase Limit Line of Credit Facility, Increase Limit Line of Credit Facility, Increase Limit Deferred tax assets: Components of Deferred Tax Assets [Abstract] Deferred compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits Fixed assets and intangible assets Deferred Tax Assets, Property, Plant and Equipment Deferred revenue Deferred Tax Assets, Deferred Income Accrued expenses Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities Other Deferred Tax Assets, Other Deferred tax assets, gross Deferred Tax Assets, Gross Valuation allowance Deferred Tax Assets, Valuation Allowance Total deferred tax assets Deferred Tax Assets, Net of Valuation Allowance Deferred tax liabilities: Components of Deferred Tax Liabilities [Abstract] Fixed assets and intangible assets Deferred Tax Liabilities, Property, Plant and Equipment Other Deferred Tax Liabilities, Other Total deferred tax liabilities Deferred Tax Liabilities, Gross Net deferred tax assets Deferred Tax Assets, Net Loss Contingencies [Table] Loss Contingencies [Table] Litigation Case [Axis] Litigation Case [Axis] Litigation Case [Domain] Litigation Case [Domain] Regeneron v.s. Merus N.V. Regeneron v.s. Merus N.V. [Member] Regeneron v.s. Merus N.V. [Member] Amgen v.s. Regeneron Amgen v.s. Regeneron [Member] Amgen v.s. Regeneron [Member] Litigation Status [Axis] Litigation Status [Axis] Litigation Status [Domain] Litigation Status [Domain] Settled litigation Settled Litigation [Member] Pending litigation Pending Litigation [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Common stock purchased (in shares) Litigation Settlement, Consideration Transferred, Common Stock Purchased, Shares Litigation Settlement, Consideration Transferred, Common Stock Purchased, Shares Purchase price of common stock Litigation Settlement, Consideration Transferred, Common Stock Purchased, Amount Litigation Settlement, Consideration Transferred, Common Stock Purchased, Amount Loss Contingency, damages sought, per unit produced Loss Contingency, Damages Sought, per unit produced. Loss Contingency, Damages Sought, per unit produced. Loss contingency, damages sought Loss Contingency, Damages Sought, Value Teva Teva Pharmaceuticals Collaboration Agreement [Member] Teva Pharmaceuticals Collaboration Agreement [Member] Increase as a result of cumulative-effect adjustment arising from the adoption of ASC 606 Increase (Decrease) in Contract with Customer, Liability Increase due to amounts invoiced, excluding amounts recognized as revenue during the period Increase (Decrease) in Contract with Customer, Asset Revenue recognized that was included in deferred revenue at the beginning of the period Contract with Customer, Liability, Revenue Recognized Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Long-Term Incentive Plan 2000 Long-Term Incentive Plan 2000 [Member] Long-Term Incentive Plan 2000 [Member] Amended & Restated Long-Term Incentive Plan 2014 Amended & Restated Long-Term Incentive Plan 2014 [Member] Amended & Restated Long-Term Incentive Plan 2014 Long-Term Incentive Plan 2014 Long-Term Incentive Plan 2014 [Member] Long-Term Incentive Plan 2014 Non-performance based stock options Non-Performance Based Stock Options [Member] A stock option whose vesting is not contingent upon performance achievements. Phantom stock Phantom Share Units (PSUs) [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Number of shares authorized for issuance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Additional shares registered (in shares) Additional Shares Registered Additional shares registered under the Amended and Restated 2014 Long-Term Incentive Plan. Award vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Maximum term of awards Share Based Compensation Arrangement By Share Based Payment Award Expiration The term (in years) when the equity-based award expires as specified in the award agreement. Period within vesting date that awards may be received Share Based Compensation Arrangement By Share Based Payment Award Period From Vesting Date Awards May Be Received The period (in days) from the vesting date during which the Participant has the right to receive, an amount, in cash and/or shares of the Company's Common Stock as determined by the Committee, equal to the sum of the fair market value of a share of Common Stock on the date such share of Phantom Stock vests and the aggregate amount of cash dividends paid with respect to a share of Common Stock during the period from the grant date of the share of Phantom Stock to the date on which the share vests. Number of shares available for future grants (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Total intrinsic value - of stock options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Non-cash stock-based compensation expense Allocated Share-based Compensation Expense Capitalized to inventory Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount Unrecognized stock-based compensation cost, net of estimated forfeitures Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Weighted average period for recognition of total unrecognized compensation expense (in years) Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Expected dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Ang2 antibody Ang2 Antibody [Member] Ang2 Antibody [Member] Ang2 antibody and PDGFR-beta antibody Ang2 Antibody And PDGFR-beta Antibody [Member] Ang2 Antibody And PDGFR-beta Antibody Bayer Bayer Collaboration Agreement [Member] Bayer Collaboration Agreement [Member] Up-front payment received Up-front payment received Up-front payment received upon the execution of a collaboration agreement. Minimum advance notice required to terminate collaboration agreement Minimum advance notice required to terminate collaboration agreement The minimum advance notice required of the collaborating party to terminate the agreement without cause. Maximum advance notice required to terminate collaboration agreement maximum advance notice required to terminate collaboration agreement maximum advance notice required to terminate collaboration agreement Revenue based on percentage of annual sales in Japan Revenue based on percentage of annual sales in Japan The percentage on annual sales in Japan that the Company is entitled to receive, subject to certain potential adjustments. Current: Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Current Federal Tax Expense (Benefit) State Current State and Local Tax Expense (Benefit) Foreign Current Foreign Tax Expense (Benefit) Total current tax expense Current Income Tax Expense (Benefit) Deferred: Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Deferred Federal Income Tax Expense (Benefit) State Deferred State and Local Income Tax Expense (Benefit) Foreign Deferred Foreign Income Tax Expense (Benefit) Total deferred tax (benefit) expense Deferred Income Tax Expense (Benefit) Total income tax expense (benefit) Income Tax Expense (Benefit) Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Outstanding at beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Granted (in shares) Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Expired (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period Exercised (in shares) Outstanding at end of period (in shares) Vested and expected to vest (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Exercisable (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Weighted-Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Outstanding at beginning of period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Granted (in dollars per share) Forfeited (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Expired (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Outstanding at end of period (in dollars per share) Vested and expected to vest (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price Exercisable (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Weighted average remaining contractual term (in years) - outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Weighted average remaining contractual term - vested and expected to vest Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term Weighted average remaining contractual term - exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Instrinsic value - outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Intrinsic value - vested and expected to vest Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Intrinsic value - exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Inventory Disclosure [Abstract] Raw materials Inventory, Raw Materials, Net of Reserves Work-in-process Inventory, Work in Process, Net of Reserves Finished goods Inventory, Finished Goods, Net of Reserves Deferred costs Other Inventory, Net of Reserves Total Inventories Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Building and improvements Building and Building Improvements [Member] Laboratory and other equipment Furniture and fixtures Furniture and Fixtures [Member] Estimated useful life Property, Plant and Equipment, Useful Life Net decrease as a result of cumulative catch-up adjustments arising from changes in the estimate of the stage of completion Contract with Customer, Asset, Cumulative Catch-up Adjustment to Revenue, Modification of Contract Schedule of transactions involving stock option awards Share-based Compensation, Stock Options, Activity [Table Text Block] Schedule of weighted-average exercise prices and weighted-average grant-date fair values of options issued Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value [Table Text Block] Schedule of weighted-average values of assumptions used in computing fair value of option grants Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Schedule of activity related to restricted stock awards Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block] Revenues [Abstract] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] Rebates, Chargebacks, and Discounts Rebates and Chargebacks [Member] A valuation allowance for rebates and chargebacks under governmental programs (including Medicaid), which are netted against revenue from product sales. Distribution- Related Fees Distribution Related Fees [Member] A valuation allowance for distribution-related fees which are netted against revenue from product sales. Other Sales- Related Deductions Other Sales Related Deductions [Member] A valuation allowance for other sales-related deductions which are netted against revenue from product sales. SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] Beginning Balance SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount Provisions SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Other Account Credits/payments SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction Ending Balance Facility purchase price Facility Purchase Price Agreed to purchase price for entire Tarrytown, New York facility, subject to certain customary adjustments. Payment towards purchase price of Tarrytown facility Payment towards purchase price of Tarrytown facility Payment towards purchase price of Tarrytown facility. A proportionate amount of which was recorded as a reduction of capital and facility lease obligations. Aggregate funding advanced by the participants Aggregate funding advanced by the participants Aggregate funding advanced by the participants, and used by Banc of America Leasing and Capital to acquire the Tarrytown facility. Reimbursement received by the Company Reimbursement received by the Company Reimbursement received by the Company upon closing of the purchase agreement. Initial term of lease Initial term of lease Initial term of lease Potential extended term of lease Potential extended term of lease Potential extended term of lease Loss on extinguishment of debt Gain (Loss) on Extinguishment of Debt Tarrytown facility capital and facility lease obligations Tarrytown facility capital and facility lease obligations Capital and facility lease obligations recorded by the Company related to the Tarrytown facility. Interest expense in connection with capital and facility leases Interest Expense, Lessee, Assets under Capital Lease Statement of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Non-cash compensation expense Share-based Compensation Other non-cash items, net Other Noncash Income (Expense) Deferred taxes Increase (Decrease) in Deferred Income Taxes Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Increase in Sanofi, Bayer, and trade accounts receivable Increase (Decrease) in Accounts Receivable Increase in inventories Increase (Decrease) in Inventories (Increase) decrease in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets (Decrease) increase in deferred revenue Increase (decrease) in accounts payable, accrued expenses, and other liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Total adjustments Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Purchases of marketable and other securities Payments to Acquire Marketable Securities Sales or maturities of marketable securities Proceeds from Sale and Maturity of Marketable Securities Capital expenditures Payments to Acquire Productive Assets Other Payments for (Proceeds from) Other Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Proceeds in connection with capital and facility lease obligations Proceeds from (Repayments of) Long-term Debt and Capital Securities Payments in connection with capital and facility lease obligations Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities Repayments of convertible senior notes Payments in connection with reduction of outstanding warrants Proceeds from issuance of Common Stock Proceeds from Issuance of Common Stock Payments in connection with Common Stock tendered for employee tax obligations Payments Related to Tax Withholding for Share-based Compensation Repurchases of Common Stock Payments for Repurchase of Common Stock Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities Net increase (decrease) in cash, cash equivalents, and restricted cash Cash and Cash Equivalents, Period Increase (Decrease) Cash, cash equivalents, and restricted cash at beginning of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents, and restricted cash at end of period Supplemental disclosure of cash flow information Cash paid for interest (net of amounts capitalized) Interest Paid, Excluding Capitalized Interest, Operating Activities Cash paid for income taxes Income Taxes Paid, Net Schedule of Gain (Loss) on Securities [Table] Schedule of Gain (Loss) on Securities [Table] Gain (Loss) on Securities [Line Items] Gain (Loss) on Securities [Line Items] Other-than-temporary Impairment charges Other than Temporary Impairment Losses, Investments Net unrealized gain (loss) on securities Equity Securities, FV-NI, Unrealized Gain (Loss) Expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Expected lives from grant date Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Number of Shares/Units Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Beginning balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited/Cancelled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Ending balance (in shares) Weighted-Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Beginning balance (in dollars of shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in dollars of shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Vested (in dollars of shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited/Cancelled (in dollars of shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Intrinsic Value, Amount Per Share Ending balance (in dollars of shares) Other Other Collaboration Agreements [Member] Other Collaboration Agreements [Member] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Product and service, other Product and Service, Other [Member] Collaboration and contract manufacturing Collaboration and Contract Manufacturing [Member] Collaboration and Contract Manufacturing [Member] Cost of collaboration and contract manufacturing Cost of Goods and Services Sold Income from operations Operating Income (Loss) Income before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income tax expense Equity [Abstract] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Class of Stock [Line Items] Class of Stock [Line Items] Common Stock, shares authorized (in shares) Common Stock, Shares Authorized Common Stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Number of votes per share Number Of Votes Per Share Number Of Votes Per Share Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Number of shares of Common Stock purchased Number of Newly Issued Shares Purchased The number of newly issued shares of the Company's Common Stock purchased in connection with the Sanofi collaboration agreement. Number of demand rights to require the Company to conduct registered underwritten public offering Number Of Demand Rights To Require The Company To Conduct Registered Underwritten Public Offering Number of demand rights to require the Company to use all reasonable efforts to conduct registered underwritten public offering with respect to shares of the Company's Common Stock held by Sanofi from time to time. Maximum shares the collaborator could sell (in shares) Maximum shares the collaborator could sell Maximum shares the collaborator could sell through September 30, 2020. Maximum percentage of outstanding shares that may be acquired, under 'standstill' provisions Maximum Percentage Of Outstanding Shares That May Be Acquired, Under 'Standstill' Provisions The maximum percentage of outstanding shares of the Company's Class A Stock and Common Stock that may be acquired under the 'standstill' provisions, in effect after the specified date. Percentage of outstanding shares or voting rights under amended investor agreement Percentage Of Outstanding Shares Or Voting Rights Under Amended Investor Agreement The percentage of the then outstanding shares or voting rights of the Company's Class A Stock and Common Stock, which if a stock issuance equals or exceeds such amount, the collaborator has not contractually agreed to vote, and cause its affiliates to vote, either as recommended by the Company's board of directors or proportionally with the votes cast by the Company's other shareholders. Percentage of outstanding shares that the Company is required to appoint an individual agreed upon by the Company and the Collaborator to the Company's board of directors Percentage Of Outstanding Shares That The Company Is Required To Appoint An Individual Agreed Upon By The Company And The Collaborator To The Company's Board Of Directors The percentage outstanding shares that the Company is required to appoint an individual agreed upon by the Company and the collaborator to the Company's board of directors. Statement of Financial Position [Abstract] Liabilities and Equity [Abstract] Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, issued (in shares) Preferred Stock, Shares Issued Preferred stock, outstanding (in shares) Preferred Stock, Shares Outstanding Common Stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Treasury stock, outstanding (in shares) Treasury Stock, Shares Marketable Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Schedule of inventory Schedule of Inventory, Current [Table Text Block] Research Collaboration and Licensing Arrangements [Table] Research Collaboration and Licensing Arrangements [Table] -- None. No documentation exists for this element. -- Research Collaboration and Licensing Agreements [Axis] Research Collaboration and Licensing Agreements [Axis] The research collaboration and licensing agreements entered into. Research Collaboration and Licensing Agreements [Domain] Research Collaboration and Licensing Agreements [Domain] Research collaboration and licensing agreements, by name. Agreements with Royalty Provisions Royalty Agreement Terms [Member] Research Collaboration and Licensing Arrangements [Line Items] Research Collaboration and Licensing Arrangements [Line Items] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Royalty rate minimum Royalty rate minimum The minimum royalty rate to be paid to the Company under the agreements. Royalty rate maximum Royalty rate maximum The maximum royalty rate to be paid to the Company under the agreements. Royalty expense Royalty Expense Revenue recognition, milestone method, revenue recognized Revenue Recognition, Milestone Method, Revenue Recognized Aggregate future development milestone payments the Company is eligible to receive Aggregate future development milestone payments the Company is eligible to receive Aggregate future development milestone payments the Company is eligible to receive. Collaborative arrangement, additional eligible aggregate payments Collaborative Arrangement, Additional Eligible Aggregate Payments The aggregate amount of additional payments the Company is entitled to receive upon the achievement of specified annual net sales amounts. Remaining performance obligation Revenue, Remaining Performance Obligation, Amount Property, Plant and Equipment [Abstract] Schedule of Property, Plant and Equipment [Table] Land Land [Member] Leasehold improvements Leasehold Improvements [Member] Construction-in-progress Construction in Progress [Member] Furniture, computer and office equipment, and other Office Equipment [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Property, plant, and equipment, gross Property, Plant and Equipment, Gross Less, accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Property, plant, and equipment, net Property, Plant and Equipment, Net Statement of Cash Flows Cash Flow, Supplemental Disclosures [Text Block] Legal Matters Legal Matters and Contingencies [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Significant Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Securities owned not readily marketable Securities Owned Not Readily Marketable Derivative [Table] Derivative [Table] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest rate swap contracts Interest Rate Swap [Member] Interest rate cap contracts Interest Rate Cap [Member] Derivative [Line Items] Derivative [Line Items] Derivative, notional amount Derivative, Notional Amount Gain (loss) related to ineffective portion of the derivative instruments Gain (Loss) on Interest Rate Cash Flow Hedge Ineffectiveness Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Outside United States Non-US [Member] Net profit in connection with commercialization Net Profit In Connection With Commercialization [Member] Net Profit In Connection With Commercialization [Member] Reimbursement of Regeneron research and development expenses Reimbursement Of Research And Development Expenses [Member] Reimbursement Of Research And Development Expenses [Member] Other Other [Member] Other [Member] Weighted average number of shares (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Accounts receivable (recorded within Prepaid expenses and other current assets) Prepaid Expense and Other Assets, Current Accounts receivable Accounts Receivable, Related Parties, Current Schedule of collaboration revenue Disaggregation of Revenue [Table Text Block] Schedule of accounts receivable and deferred revenue information Contract with Customer, Asset and Liability [Table Text Block] United States UNITED STATES EYLEA EYLEA Net Product Sales [Member] Revenue during the period derived from a specified product line (EYLEA), after deducting applicable provisions for discounts, returns, rebates, chargebacks, distribution fees, and other sales-related deductions. Libtayo LIBTAYO Net Product Sales [Member] LIBTAYO Net Product Sales [Member] ARCALYST Arcalyst Net Product Sales [Member] Revenue during the period derived from a specified product line (ARCALYST), after deducting applicable provisions for discounts, returns, rebates, chargebacks, distribution fees, and other sales-related deductions. Product Product [Member] Schedule of Quarterly Financial Information Quarterly Financial Information [Table Text Block] Fair Value Measurements Fair Value Disclosures [Text Block] Document And Entity Information [Abstract] -- None. No documentation exists for this element. -- Entities [Table] Entity Information [Line Items] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Emerging Growth Company Entity Emerging Growth Company Entity Small Business Entity Small Business Entity Shell Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Public Float Entity Public Float Product Sales Product Sales and Concentration Risk [Text Block] Product Sales and Concentration Risk Disclosure [Text Block] Schedule of restrictions on cash and cash equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] 2019 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2020 Operating Leases, Future Minimum Payments, Due in Two Years 2021 Operating Leases, Future Minimum Payments, Due in Three Years 2022 Operating Leases, Future Minimum Payments, Due in Four Years 2023 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total Operating Leases, Future Minimum Payments Due Payables and Accruals [Abstract] Accounts Payable and Accrued Liabilities, Current [Abstract] Accrued payroll and related costs Employee-related Liabilities, Current Accrued clinical trial expense Accrued Clinical Trial Expense Current Carrying value as of the balance sheet date of obligations incurred (and for which invoices have not been received) in connection with clinical trials. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued sales-related charges, deductions, and royalties Accrued sales-related charges, deductions and royalties Carrying value as of the balance sheet date of sales-related charges, deductions and obligations incurred through that date and accrual for royalties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Income taxes payable Taxes Payable, Current Other accrued expenses and liabilities Other Accrued Liabilities, Current Accrued expenses and other current liabilities Accounts Payable and Accrued Liabilities, Current Deferred Revenue Revenue from Contract with Customer [Text Block] Schedule of Notional Amounts of Outstanding Derivative Positions Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Schedule of income before income tax Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] Schedule of components of income tax expense Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of effective income tax rate reconciliation Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of deferred tax assets and liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of unrecognized tax benefits Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Estimate of Fair Value Measurement Estimate of Fair Value Measurement [Member] Restricted Restricted [Member] Restricted [Member] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Measured on a recurring basis Fair Value, Measurements, Recurring [Member] Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Available-for-sale debt securities: Debt Securities, Available-for-sale [Abstract] Available-for-sale debt securities Equity securities Equity Securities, FV-NI Total marketable securities Marketable Securities Available-for-sale Debt Securities Debt Securities, Available-for-sale [Table Text Block] Marketable Securities, Based on Contractual Maturity Dates Investments Classified by Contractual Maturity Date [Table Text Block] Fair Value and Unrealized Losses of Marketable Securities Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value [Table Text Block] Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Balance as of January 1 Unrecognized Tax Benefits Gross increases related to current year tax positions Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Gross increases (decreases) related to prior year tax positions Unrecognized Tax Benefits, Period Increase (Decrease) Gross decrease due to settlements, recapture, filed returns, and lapse of statutes of limitation Unrecognized Tax Benefits, Decrease Resulting From Settlements With Taxing Authorities And Reduction Resulting From Lapse Of Applicable Statute Of Limitations Unrecognized Tax Benefits, Decrease Resulting From Settlements With Taxing Authorities And Reduction Resulting From Lapse Of Applicable Statute Of Limitations Balance as of December 31 Europe Europe [Member] Property, plant, and equipment, net Depreciation and amortization expense Depreciation, Depletion And Amortization, Excluding Intangible Assets Depreciation, Depletion And Amortization, Excluding Intangible Assets Capital and facility leases, at cost Capital And Facility Leases, At Cost Property, plant, and equipment, at cost, of leased property under the Company's capital and facility leases. Accumulated amortization of capital and facility leases Accumulated Amortization Of Capital And Facility Leases Accumulated Amortization Of Capital And Facility Leases Other Other Agreements [Member] Other Agreements [Member] Current portion: Contract With Customer, Liability, Current [Abstract] Contract With Customer, Liability, Current [Abstract] Deferred revenue, current Long-term portion: Contract With Customer, Liability, Noncurrent [Abstract] Contract With Customer, Liability, Noncurrent [Abstract] Deferred revenue, noncurrent Accrued Expenses and Other Current Liabilities Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block] Net Income Per Share Earnings Per Share [Text Block] Collaboration and License Agreements Collaborative Arrangement Disclosure [Text Block] Schedule of accrued expenses and other current liabilities Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Schedule of Property, Plant and Equipment Property, Plant and Equipment [Table Text Block] Schedule of New Accounting Pronouncements and Changes in Accounting Principles Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Schedule of Estimated Useful Lives of Property, Plant, and Equipment Estimated Useful Lives Of Property, Plant, And Equipment [Table Text Block] Tabular disclosure of the estimated useful lives of property, plant, and equipment. Reimbursement of Regeneron commercialization-related expenses Reimbursement Of Commercialization-Related Expenses [Member] Reimbursement Of Commercialization-Related Expenses [Member] Regeneron's share of losses in connection with commercialization of antibodies Share Of Losses In Connection With Commercialization [Member] Share Of Losses In Connection With Commercialization [Member] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted cash included in Other noncurrent assets Restricted Cash Total cash, cash equivalents, and restricted cash shown in the Consolidated Statement of Cash Flows Retirement Benefits [Abstract] Employee Savings Plan Pension and Other Postretirement Benefits Disclosure [Text Block] Schedule of assets measured at fair value on a recurring basis Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block] Maturities within one year Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value Maturities after one year through five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value Total Commitments and Contingencies Commitments Disclosure [Text Block] Property, Plant and Equipment Property, Plant and Equipment Disclosure [Text Block] Fair Value - Less than 12 Months Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months Unrealized Loss - Less than 12 months Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Fair Value - 12 Months or Greater Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer Unrealized Loss - 12 Months or Greater Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Fair Value - Total Debt Securities, Available-for-sale, Unrealized Loss Position Unrealized Loss - Total Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss Schedule of Product Sales Schedules of Concentration of Risk, by Risk Factor Schedules of Concentration of Risk, by Risk Factor [Table Text Block] Sales Related Deductions Activity Schedule of Sales Related Deductions Activity [Table Text Block] Tabular disclosure of the activity of sales-related deductions during the period, which includes rebates, chargebacks, discounts, and distributor-related fees. Concentration Risk [Table] Concentration Risk [Table] Gross Sales Revenue Gross Sales Revenue [Member] Gross Sales Revenue [Member] Besse Medical, a subsidiary of AmerisourceBergen Corporation Besse Medical [Member] Besse Medical [Member] McKesson Corporation McKesson Corporation [Member] McKesson Corporation [Member] Curascript SD Specialty Distribution, a subsidiary of Express Scripts Curascript SD [Member] Curascript SD [Member] Concentration Risk [Line Items] Concentration Risk [Line Items] Schedule of deferred revenue Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Marketable Securities Marketable Securities, Policy [Policy Text Block] Accounts Receivable - Trade Trade and Other Accounts Receivable, Policy [Policy Text Block] Inventories Inventory, Policy [Policy Text Block] Property, Plant and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Revenue Recognition Revenue from Contract with Customer [Policy Text Block] Research and Development Expenses Research and Development Expense, Policy [Policy Text Block] Stock-based Compensation Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Per Share Data Earnings Per Share, Policy [Policy Text Block] Concentration of Credit Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] Recently Issued Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Legal Costs Legal Costs, Policy [Policy Text Block] Income Taxes Income Tax Disclosure [Text Block] Statement of Comprehensive Income [Abstract] Statement [Table] Statements of Operations Income Statement [Abstract] Revenues: Expenses: Costs and Expenses [Abstract] Selling, general, and administrative Selling, General and Administrative Expense Cost of goods sold Total expenses Costs and Expenses Income from operations Other income (expense): Nonoperating Income (Expense) [Abstract] Other income (expense), net Other Nonoperating Income (Expense) Interest expense Interest Expense Total other income (expense) Nonoperating Income (Expense) Income before income taxes Net income Weighted average shares outstanding - diluted (in shares) Statements of Comprehensive Income Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Unrealized (loss) gain on marketable securities Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax Unrealized gain on cash flow hedges Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Employer contribution expense to 401(k) Savings Plan Defined Contribution Plan, Cost Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] United States Domestic Tax Authority [Member] Foreign Foreign Tax Authority [Member] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Contract with Customer, Duration [Axis] Contract with Customer, Duration [Axis] Contract with Customer, Duration [Domain] Contract with Customer, Duration [Domain] Through December 31, 2023 Through December 31, 2023 [Member] Through December 31, 2023 [Member] January 1, 2024 Through December 31, 2026 January 1, 2024 Through December 31, 2026 [Member] January 1, 2024 Through December 31, 2026 [Member] Research and Development Arrangement Contract to Perform for Others by Product [Axis] Research and Development Arrangement Contract to Perform for Others by Product [Axis] Research and Development Arrangement Contract to Perform for Others by Product [Axis] Research and Development Arrangement Contract to Perform for Others by Product [Domain] Research and Development Arrangement Contract to Perform for Others by Product [Domain] [Domain] for Research and Development Arrangement Contract to Perform for Others by Product [Axis] IO Discovery Agreement IO Discovery Agreement [Member] In July 2015, the Company entered into a collaboration agreement (Immuno-Oncology agreement) with Sanofi, to jointly develop and commercialize Immuno-Oncology programs. Amended IO Discovery Agreement Amended IO Discovery Agreement [Member] Amended IO Discovery Agreement [Member] BCMAxCD3 Program Amended IO Discovery Agreement, BCMAxCD3 Program [Member] Amended IO Discovery Agreement, BCMAxCD3 Program [Member] MUC16xCD3 Program Amended IO Discovery Agreement, MUC16xCD3 Program [Member] Amended IO Discovery Agreement, MUC16xCD3 Program [Member] IO Agreement IO Agreement [Member] IO Agreement IO License and Collaboration Agreement IO License and Collaboration Agreement [Member] In July 2015, the Company entered into a Immuno-oncology License and Collaboration Agreement (the "IO License and Collaboration Agreement") with Sanofi, to jointly develop and commercialize Immuno-oncology products. PD-1 PD-1 [Member] Programed Cell Death protein 1, or PD-1 ("REGN2810") Potential future R&D expenses Potential future R&D expenses The total potential amount of research and development expenses the Company may pay to identify and validate potential immuno-oncology targets and develop therapeutic antibodies against such targets through clinical proof-of-concept. Funding maximum of research activities per agreement Funding Maximum of Research Activities Per Agreement The maximum amount of cost reimbursement the Company will receive, subject to certain annual limits. License agreement term License agreement term Potential agreement term, from the effective date of agreement. Additional years to extend the agreement Additional years to extend the agreement Additional years to extend the agreement Aggregate payment received with regards to amendment Aggregate Payment Received With Regards To Amendment Aggregate Payment Received With Regards To Amendment Expenditure costs cap Expenditure Costs Cap Expenditure Costs Cap Potential maximum expenditure Potential Maximum Expenditure Potential Maximum Expenditure Optional payment to increase development cost funding Optional Payment To Increase Development Cost Funding Optional Payment To Increase Development Cost Funding Upfront payment made Upfront Payment Made Upfront payment made under a collaboration agreement Percentage of royalties to be paid Payments For Royalties, Percentage Payments For Royalties, Percentage Cumulative catch-up adjustment to revenue, modification of contract 2019 Capital Leases, Future Minimum Payments Due, Next Twelve Months 2020 Capital Leases, Future Minimum Payments Due in Two Years 2021 Capital Leases, Future Minimum Payments Due in Three Years 2022 Capital Leases, Future Minimum Payments Due in Four Years 2023 Capital Leases, Future Minimum Payments Due in Five Years Thereafter Capital Leases, Future Minimum Payments Due Thereafter Total Capital Leases, Future Minimum Payments Due Inventories Inventory Disclosure [Text Block] ASSETS Assets [Abstract] Current assets: Assets, Current [Abstract] Marketable securities Marketable Securities, Current Accounts receivable - trade, net Accounts Receivable, Net, Current Accounts receivable from Sanofi Accounts receivable from Bayer Accounts and Notes Receivable, Net Inventories Prepaid expenses and other current assets Total current assets Assets, Current Marketable securities Marketable Securities, Noncurrent Other noncurrent assets Other Assets, Noncurrent Total assets LIABILITIES AND STOCKHOLDERS' EQUITY Current liabilities: Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Total current liabilities Capital and facility lease obligations Capital and facility lease obligations, noncurrent Represents the noncurrent portion of a lease liability Other noncurrent liabilities Other Liabilities, Noncurrent Total liabilities Commitments and contingencies Commitments and Contingencies Stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Preferred Stock, $.01 par value; 30,0000,000 shares authorized; issued and outstanding - none Preferred Stock, Value, Issued Common stock Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Retained earnings Accumulated other comprehensive (loss) income Accumulated Other Comprehensive Income (Loss), Net of Tax Treasury Stock, at cost; 3,990,021 shares in 2018 and 3,763,868 shares in 2017 Treasury Stock, Value Total stockholders' equity Total liabilities and stockholders' equity