Revenues [Abstract] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] United States UNITED STATES Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] 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] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Revenues Revenue from Contract with Customer, Excluding Assessed Tax Accounting Policies [Abstract] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Concentration of Credit Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Debt and Equity Securities Marketable Securities, Policy [Policy Text Block] Accounts Receivable Accounts Receivable [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 Payment Arrangement [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Per Share Data Earnings Per Share, Policy [Policy Text Block] Recently Issued Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Leases Lessee, Leases [Policy Text Block] Legal Costs Legal Costs, Policy [Policy Text Block] Commitments and Contingencies Disclosure [Abstract] 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 Remaining lease term (in years) Finance Lease, Remaining Lease Term Finance Lease, Remaining Lease Term Discount rate Lessee, Finance Lease, Discount Rate Revenue from Contract with Customer [Abstract] Statistical Measurement [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Project [Axis] Project [Axis] Project [Domain] Project [Domain] Bayer Bayer Collaboration Agreement [Member] Bayer Collaboration Agreement [Member] 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. 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. 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. Debt Disclosure [Abstract] Credit Facility Debt Disclosure [Text Block] Product Sales Revenue from Contract with Customer [Text Block] Schedule of deferred revenue Contract with Customer, Asset and Liability [Table Text Block] Schedule of collaboration revenue Disaggregation of Revenue [Table Text Block] Schedule of accounts receivable and deferred revenue information Income Tax Disclosure [Abstract] Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Recognition of provisional charge Tax Cuts and Jobs Act, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit) Adjustment to provisional amount recorded Tax Cuts and Jobs Act, Measurement Period Adjustment, Income Tax Expense (Benefit) Unrecognized tax benefits that would impact effective tax rate Unrecognized Tax Benefits that Would Impact Effective Tax Rate Equity [Abstract] Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Property, Plant and Equipment [Abstract] Schedule of Property, Plant and Equipment Property, Plant and Equipment [Table Text Block] Business Overview and Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] 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] Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] 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 Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Quarterly Financial Information Disclosure [Abstract] Schedule of Quarterly Financial Information Quarterly Financial Information [Table Text Block] 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) Schedule of Property, Plant and Equipment [Table] Property, Plant and Equipment [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] Land Land [Member] Building and improvements Building and Building Improvements [Member] Leasehold improvements Leasehold Improvements [Member] Construction in progress Construction in Progress [Member] Laboratory and other equipment Equipment [Member] Computer equipment and software Computer Equipment And Software [Member] Computer Equipment And Software [Member] Furniture, office equipment, and other Furniture, Office Equipment And Other [Member] Furniture, Office Equipment And Other [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 And Finance Lease Right-Of-Use Asset, After Accumulated Depreciation And Amortization Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, After Accumulated Depreciation And Amortization Property, Plant, And Equipment And Finance Lease Right-Of-Use Asset, After Accumulated Depreciation And Amortization Property, plant, and equipment, net Property, Plant and Equipment, Net Supplemental Cash Flow Information [Abstract] 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 Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Alnylam Pharmaceuticals, Inc. Collaboration Agreement Alnylam Pharmaceuticals, Inc. Collaboration Agreement [Member] Alnylam Pharmaceuticals, Inc. Collaboration Agreement [Member] Alnylam Pharmaceuticals, Inc. Stock Purchase Agreement Alnylam Pharmaceuticals, Inc. Stock Purchase Agreement [Member] Alnylam Pharmaceuticals, Inc. Stock Purchase Agreement [Member] Upfront payment made Upfront Payment Made Upfront payment made under a collaboration agreement Collaborative arrangement additional payment eligible Collaborative Arrangement, Additional Payment Eligible, Milestone Collaborative Arrangement, Additional Payment Eligible, Milestone Initial research term Initial Research Term Initial Research Term Potential extension of research term Potential Extension Of Research Term Potential Extension Of Research Term Extension of research term fee Extension Of Research Term Fee Extension Of Research Term Fee Payments made to acquire equity Payments Made To Acquire Equity Within A Collaboration Agreement Payments Made To Acquire Equity Within A Collaboration Agreement 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. Finance lease, term of contract Lessee, Finance Lease, Term of Contract Finance lease, extension option Lessee, Finance Lease, Renewal Term Property, plant, and equipment, at cost Capital Leased Assets, Gross Accumulated amortization Capital Leases, Net Investment in Direct Financing Leases, Accumulated Amortization 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] Sanofi Collaboration Agreement, Immuno-oncology Sanofi Collaboration Agreement, Immuno-oncology [Member] Sanofi Collaboration Agreement, Immuno-oncology [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") Up-front payment received Up-front payment received Up-front payment received upon the execution of a collaboration agreement. 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. Maximum funding amount of research activities to be reimbursed 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 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. Maximum shares the collaborator could sell (in shares) Maximum shares the collaborator could sell Maximum shares the collaborator could sell through September 30, 2020. Number of shares the collaborator available to sell (in shares) Number Of Shares The Collaborator Available To Sell Number Of Shares The Collaborator Available To Sell Amount related to obligation to pay gross profits sharing Amount Related To Obligation To Pay Gross Profits Sharing Amount Related To Obligation To Pay Gross Profits Sharing 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 Percentage of royalties to be paid Payments For Royalties, Percentage Payments For Royalties, Percentage 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. Increase as a result of payment received from Sanofi in connection with the termination of the 2015 IO Discovery Agreement Contract with Customer, Asset, Cumulative Catch-up Adjustment to Revenue, Modification of Contract Remaining performance obligation Revenue, Remaining Performance Obligation, Amount Sanofi Sanofi Collaboration Agreement [Member] Sanofi Collaboration Agreement [Member] Teva Teva Pharmaceuticals Collaboration Agreement [Member] Teva Pharmaceuticals Collaboration Agreement [Member] Other Other Agreements [Member] Other Agreements [Member] Current portion: Deferred Revenue, Current [Abstract] Deferred revenue, current Contract with Customer, Liability, Current Noncurrent portion: Deferred Revenue, Noncurrent [Abstract] Deferred revenue, noncurrent Contract with Customer, Liability, Noncurrent Accounts receivable, net Contract With Customer, Asset (Liability), Net Contract With Customer, Asset (Liability), Net Deferred revenue Contract with Customer, Liability Payables and Accruals [Abstract] Accrued Expenses and Other Current Liabilities Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block] Statement of Comprehensive Income [Abstract] Statement [Table] Statement [Table] Other Other Collaboration Agreements [Member] Other Collaboration Agreements [Member] Product and service, other Product and Service, Other [Member] Collaboration and contract manufacturing Collaboration and Contract Manufacturing [Member] Collaboration and Contract Manufacturing [Member] Statement [Line Items] Statement [Line Items] Statements of Operations Income Statement [Abstract] Revenues: Expenses: Costs and Expenses [Abstract] Research and development Research and Development Expense Selling, general, and administrative Selling, General and Administrative Expense Cost of goods sold Cost of Goods and Services Sold Total expenses Costs and Expenses Income from operations Operating Income (Loss) 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 Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income tax expense Net income Net Income (Loss) Attributable to Parent Net income per share - basic (in dollars per share) Earnings Per Share, Basic Net income per share - diluted (in dollars per share) Earnings Per Share, Diluted Weighted average shares outstanding - basic (in shares) Weighted Average Number of Shares Outstanding, Basic Weighted average shares outstanding - diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Statements of Comprehensive Income Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Net income Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Unrealized gain (loss) on marketable securities Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax Unrealized (loss) gain on cash flow hedges Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax Unrealized (loss) 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 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 Payment Arrangement, Noncash Expense 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 in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Increase (decrease) in deferred revenue Increase (Decrease) in Contract with Customer, Liability 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 finance lease liabilities Proceeds from Long-term Capital Lease Obligations Payments in connection with finance lease liabilities Repayments of Long-term Capital Lease Obligations Proceeds from issuance of Common Stock Proceeds from Issuance of Common Stock Payments in connection with Common Stock tendered for employee tax obligations Payment, Tax Withholding, Share-based Payment Arrangement 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 in cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash, cash equivalents, and restricted cash at beginning of period 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 Inventory Disclosure [Abstract] Inventories Inventory Disclosure [Text Block] Schedule of inventory Schedule of Inventory, Current [Table Text Block] 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] Revenue recognized that was included in deferred revenue at the beginning of the period Contract with Customer, Liability, Revenue Recognized Schedule of accrued expenses and other current liabilities Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Accounts receivable (recorded within Prepaid expenses and other current assets) Prepaid Expense and Other Assets, Current Loss Contingencies [Table] Loss Contingencies [Table] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] '165 Patent '165 Patent [Member] '165 Patent [Member] '741 Patent '741 Patent [Member] '741 Patent [Member] '487 Patent '487 Patent [Member] '487 Patent [Member] '688 Patent '688 Patent [Member] '688 Patent [Member] Litigation Case [Axis] Litigation Case [Axis] Litigation Case [Domain] Litigation Case [Domain] 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] Pending Litigation Pending Litigation [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Accruals for loss contingencies Loss Contingency Accrual Pending claims Loss Contingency, Pending Claims, Number Invalid claims Loss Contingency, Claims Invalid, Number Loss Contingency, Claims Invalid, Number 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 Number of IPR filed Gain Contingency, Inter Partes Review Filed, Number Gain Contingency, Inter Partes Review Filed, Number Number of claims invalidated Gain Contingency, Claims Invalidated, Number Gain Contingency, Claims Invalidated, Number Asserted claims Loss Contingency, Claims Asserted, Number Loss Contingency, Claims Asserted, Number Deferred Revenue Reimbursement of research and development expenses Reimbursement Of Research And Development Expenses [Member] Reimbursement Of Research And Development Expenses [Member] Reimbursement of commercialization-related expenses Reimbursement Of Commercialization-Related Expenses [Member] Reimbursement Of Commercialization-Related Expenses [Member] Reimbursement for manufacturing of commercial supplies Reimbursement For Manufacturing Of Commercial Supplies [Member] Reimbursement For Manufacturing Of Commercial Supplies [Member] Regeneron's share of profits (losses) in connection with commercialization of antibodies Share Of Profits (Losses) In Connection With Commercialization [Member] Share Of Profits (Losses) In Connection With Commercialization [Member] Amounts recognized in connection with up-front payments received Amounts Recognized In Connection With Up-Front Payments [Member] Amounts Recognized In Connection With Up-Front Payments [Member] Other Other [Member] Other [Member] Sanofi Collaboration Agreement, Antibody Sanofi Collaboration Agreement, Antibody [Member] Sanofi Collaboration Agreement, Antibody [Member] Retirement Benefits [Abstract] Employee Savings Plans Pension and Other Postretirement Benefits Disclosure [Text Block] Unaudited Quarterly Results Quarterly Financial Information [Text Block] Marketable Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Earnings Per Share [Abstract] Net Income Per Share Earnings Per Share [Text Block] Share-based Payment Arrangement [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] Award Type [Domain] Award Type [Domain] Stock options Share-based Payment Arrangement, 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 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) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures 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) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period 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) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price 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 Intrinsic 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 Accrued payroll and related costs Employee-related Liabilities, Current Accrued clinical expenses 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 Number of Options Granted (in shares) Weighted-Average Exercise Price (in dollars per share) 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 Legal Matters Legal Matters and Contingencies [Text Block] Sovereign bonds Sovereign Debt Securities [Member] Commercial paper Commercial Paper [Member] Certificates of deposit Certificates of Deposit [Member] 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 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] Weighted average number of shares (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount 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] 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 Accrued expenses Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities Deferred revenue Deferred Tax Assets, Deferred Income Other Deferred Tax Assets, Other Total deferred tax assets Deferred Tax Assets, Gross Valuation allowance Deferred Tax Assets, Valuation Allowance Deferred tax assets, net of valuation allowance Deferred Tax Assets, Net of Valuation Allowance Deferred tax liabilities: Components of Deferred Tax Liabilities [Abstract] Other Deferred Tax Liabilities, Other Net deferred tax assets Deferred Tax Assets, Net Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Concentration Risk [Table] Concentration Risk [Table] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Gross Sales Revenue Gross Sales Revenue [Member] Gross Sales Revenue [Member] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Customer concentration risk Customer Concentration Risk [Member] Customer [Axis] Customer [Axis] Customer [Domain] Customer [Domain] 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] Concentration risk, percentage Concentration Risk, Percentage 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] Long-Term Incentive Plans Share-based Payment Arrangement [Text Block] Operating Leases Lessee, Operating Lease, Liability, Payment, Due [Abstract] 2020 Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months 2021 Lessee, Operating Lease, Liability, Payments, Due Year Two 2022 Lessee, Operating Lease, Liability, Payments, Due Year Three 2023 Lessee, Operating Lease, Liability, Payments, Due Year Four 2024 Lessee, Operating Lease, Liability, Payments, Due Year Five Thereafter Lessee, Operating Lease, Liability, Payments, Due after Year Five Total undiscounted lease payments Lessee, Operating Lease, Liability, Payments, Due Imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Debt financing costs Lessee, Operating Lease, Liability, Debt Financing Costs Lessee, Operating Lease, Liability, Debt Financing Costs Total operating lease liabilities Operating Lease, Liability Finance Leases Finance Lease, Liability, Payment, Due [Abstract] 2020 Finance Lease, Liability, Payments, Due Next Twelve Months 2021 Finance Lease, Liability, Payments, Due Year Two 2022 Finance Lease, Liability, Payments, Due Year Three 2023 Finance Lease, Liability, Payments, Due Year Four 2024 Finance Lease, Liability, Payments, Due Year Five Thereafter Finance Lease, Liability, Payments, Due after Year Five Total undiscounted lease payments Finance Lease, Liability, Payment, Due Imputed interest Finance Lease, Liability, Undiscounted Excess Amount Debt financing costs Lessee, Finance Lease, Liability, Debt Financing Costs Lessee, Finance Lease, Liability, Debt Financing Costs Total finance lease liabilities Finance Lease, Liability 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] Schedule of restrictions on cash and cash equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] 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 Long-Term Incentive Plan 2000 Long-Term Incentive Plan 2000 [Member] Long-Term Incentive Plan 2000 [Member] 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] Restricted stock Restricted Stock [Member] Additional shares registered (in shares) Additional Shares Registered Additional shares registered under the Amended and Restated 2014 Long-Term Incentive Plan. Number of shares authorized for issuance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized 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 Share-based Payment Arrangement, Expense Capitalized to inventory Share-based Payment Arrangement, Amount Capitalized Unrecognized stock-based compensation cost, net of estimated forfeitures Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Weighted average period for recognition of total unrecognized compensation expense (in years) Share-based Payment Arrangement, Nonvested Award, 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 Net income - basic and diluted 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 Weighted average shares - diluted (in shares) Realized loss on sales of marketable securities Marketable Securities, Realized Gain (Loss) Restructuring Type [Axis] Restructuring Type [Axis] Type of Restructuring [Domain] Type of Restructuring [Domain] Employee severance costs Employee Severance [Member] 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] 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. 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. Treasury stock, shares acquired (in shares) Treasury Stock, Shares, Acquired Cost of treasury stock shares received Treasury Stock, Value, Acquired, Cost Method 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. Restructuring-related costs Restructuring Charges Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Estimate of Fair Value Measurement Estimate of Fair Value Measurement [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. Restricted Restricted [Member] Restricted [Member] Measurement Frequency [Axis] Measurement Frequency [Axis] Measurement Frequency [Domain] Measurement Frequency [Domain] Measured on a recurring basis Fair Value, Recurring [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] 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] 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 Assets, Fair Value Disclosure Schedule of amounts recognized in the Condensed Consolidated Balance Sheet Assets And Liabilities, Lessee [Table Text Block] Assets And Liabilities, Lessee [Table Text Block] Schedule of lease cost and other information Lease, Cost [Table Text Block] Schedule of maturities of operating lease liabilities Lessee, Operating Lease, Liability, Maturity [Table Text Block] Schedule of maturities of finance lease liabilities Finance Lease, Liability, Maturity [Table Text Block] Schedule of future minimum noncancelable lease commitments Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of future minimum noncancelable lease commitments Schedule of Future Minimum Lease Payments for Capital Leases [Table Text Block] Employer contribution expense to 401(k) Savings Plan Defined Contribution Plan, Cost Schedule of transactions involving stock option awards Share-based Payment Arrangement, Option, 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 Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block] Property, Plant and Equipment [Table] Europe Europe [Member] Depreciation and amortization expense Depreciation, Depletion And Amortization, Excluding Intangible Assets Depreciation, Depletion And Amortization, Excluding Intangible Assets Property, plant, and equipment, net Operating Leases Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 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 Operating Leases Operating Leases, Future Minimum Payments Due Capital and Facility Lease Obligations Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 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 Capital and Facility Lease Obligations Capital Leases, Future Minimum Payments Due Statement of Financial Position [Abstract] Other Bayer, Teva Pharmaceuticals, And Other Agreements [Member] Bayer, Teva Pharmaceuticals, And Other Agreements [Member] Class of Stock [Axis] Class of Stock [Domain] Class A Stock Common Class A [Member] Common Stock Common Stock [Member] ASSETS Assets [Abstract] Current assets: Assets, Current [Abstract] Marketable securities Marketable Securities, Current Accounts receivable - trade, net Accounts Receivable, after Allowance for Credit Loss, Current Accounts receivable from Sanofi Accounts Receivable, Related Parties, Current Accounts receivable from Bayer Accounts and Financing Receivable, after Allowance for Credit Loss Inventories Inventory, Net Prepaid expenses and other current assets Total current assets Assets, Current Marketable securities Marketable Securities, Noncurrent Property, plant, and equipment, net Deferred tax assets Deferred Income Tax Assets, Net Other noncurrent assets Other Assets, Noncurrent Total assets Assets LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Accrued expenses and other current liabilities Accrued Liabilities and Other Liabilities Total current liabilities Liabilities, Current Finance lease liabilities Finance Lease, Liability, Noncurrent Finance lease liabilities Capital Lease Obligations, Noncurrent Other noncurrent liabilities Other Liabilities, Noncurrent Total liabilities Liabilities Commitments and contingencies Commitments and Contingencies Stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Preferred Stock, $.01 par value; 30,000,000 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 Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Treasury Stock, at cost; 4,860,123 shares in 2019 and 3,990,021 shares in 2018 Treasury Stock, Value Total stockholders' equity Stockholders' Equity Attributable to Parent Total liabilities and stockholders' equity Liabilities and Equity Cover page. Entities [Table] Entities [Table] Class of Stock [Axis] Class of Stock [Domain] Entity Information [Line Items] Entity Information [Line Items] Document Type Document Type Document Annual Report Document Annual Report Document Period End Date Document Period End Date Document Transition Report Document Transition Report Entity File Number Entity File Number Entity Registrant Name Entity Registrant Name Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Tax Identification Number Entity Address, Address Line One Entity Address, Address Line One Entity Address, City or Town Entity Address, City or Town Entity Address, State or Province Entity Address, State or Province Entity Address, Postal Zip Code Entity Address, Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Title of 12(b) Security Title of 12(b) Security Trading Symbol Trading Symbol Security Exchange Name Security Exchange Name 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 Interactive Data Current Entity Interactive Data Current Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company Entity Public Float Entity Public Float Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Documents Incorporated by Reference Documents Incorporated by Reference [Text Block] Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag 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. Furniture and fixtures Furniture and Fixtures [Member] Estimated useful life Property, Plant and Equipment, Useful Life Income Taxes Income Tax Disclosure [Text Block] Outside United States Non-US [Member] Regeneron's net profit in connection with commercialization of EYLEA outside the United States Net Profit In Connection With Commercialization [Member] Net Profit In Connection With Commercialization [Member] Reimbursement of EYLEA development expenses Condensed Cash Flow Statement [Table] Condensed Cash Flow Statement [Table] 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. Capital lease obligations incurred Lease Obligation Incurred Net unrealized gains (losses) on equity securities in other income (expense) Equity Securities, FV-NI, Unrealized Gain (Loss) Net unrealized gains on equity securities in other comprehensive income (loss) Available-For-Sale Equity Securities, Net Unrealized Gains (Losses), Recognized In Other Comprehensive Income (Loss) Available-For-Sale Equity Securities, Net Unrealized Gains (Losses), Recognized In Other Comprehensive Income (Loss) Securities without readily determinable fair value Equity Securities without Readily Determinable Fair Value, Amount Inventory write-downs and reserves Inventory Write-down Schedule of Estimated Useful Lives of Property, Plant, and Equipment 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 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] SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] 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 Statement of Cash Flows Cash Flow, Supplemental Disclosures [Text Block] Revenue recognition, milestone method, revenue recognized Revenue Recognition, Milestone Method, Revenue Recognized Development milestone achieved Revenue Recognition, Development Milestone Achieved Revenue Recognition, Development Milestone Achieved 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. 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 Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Preferred stock, issued (in shares) Preferred Stock, Shares Issued Preferred stock, outstanding (in shares) Preferred Stock, Shares Outstanding Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Treasury stock, outstanding (in shares) Treasury Stock, Shares Income before income taxes, United States Income (Loss) from Continuing Operations before Income Taxes, Domestic Income before income taxes, Foreign Income (Loss) from Continuing Operations before Income Taxes, Foreign 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] Prior Credit Agreement Prior Credit Agreement [Member] Prior Credit Agreement [Member] 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] Line of credit Line of Credit [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Line of credit facility, expiration period 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 Statement of Stockholders' Equity [Abstract] 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] Accounting Standards Update 2016-02 Accounting Standards Update 2016-02 [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] 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 for equity awards granted under long-term incentive plans (in shares) Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture Issuance of Common Stock for equity awards granted under long-term incentive plans Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations (in shares) Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation Common Stock tendered upon exercise of stock options and vesting of restricted stock for employee tax obligations Share-based Payment Arrangement, Decrease for Tax Withholding Obligation Issuance/distribution of Common Stock for 401(k) Savings Plan (in shares) Stock Issued/Distributed During Period, Shares, Employee Benefit Plan Stock Issued/Distributed During Period, Shares, Employee Benefit Plan Issuance/distribution of Common Stock for 401(k) Savings Plan Stock Issued/Distributed During Period, Value, Employee Benefit Plan Stock Issued/Distributed During Period, Value, Employee Benefit Plan Stock-based compensation charges APIC, Share-based Payment Arrangement, Increase for Cost Recognition Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Cumulative-effect adjustment upon adoption of new accounting standards Cumulative Effect of New Accounting Principle in Period of Adoption Repurchases of Common Stock (in shares) Stock Repurchased During Period, Shares Repurchases of Common Stock Stock Repurchased During Period, Value Conversion of Class A Stock to Common Stock Stock Issued During Period, Shares, Conversion of Units Ending Balance (in shares) Ending Balance Amortization of right-of-use assets Finance Lease, Right-of-Use Asset, Amortization Interest on lease liabilities Finance Lease, Interest Expense Finance lease costs Finance Lease, Cost Finance Lease, Cost Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Class of Stock [Line Items] Class of Stock [Line Items] Number of votes per share Number Of Votes Per Share Number Of Votes Per Share Stock repurchase program, authorized amount Stock Repurchase Program, Authorized Amount Number of shares of common stock purchased (in shares) 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 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. Number of business segments Number of Reportable Segments New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Equity Components [Axis] Equity Component [Domain] Three individual customers Three Individual Customers [Member] Three Individual Customers [Member] Gross Sales Revenue Accounts Receivable [Member] Equity Securities Equity Securities [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Right-of-use asset Operating Lease, Right-of-Use Asset Reclassification from accumulated other comprehensive income, current period, before tax Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax Allowance for doubtful accounts receivable, current Accounts Receivable, Allowance for Credit Loss, Current Provision for doubtful accounts Accounts Receivable, Credit Loss Expense (Reversal) Period prior to products expiration date for returns accepted Revenue From Contract With Customer, Period Prior To Products Expiration Date For Returns Accepted Revenue From Contract With Customer, Period Prior To Products Expiration Date For Returns Accepted Period up to products expiration date for returns accepted Revenue From Contract With Customer, Period Up To Products Expiration Date For Returns Accepted Revenue From Contract With Customer, Period Up To Products Expiration Date For Returns Accepted Collaboration revenue for non-refundable up-front payments, development milestones, and payments for development activities, for which used an input method Collaboration Revenue For Non-Refundable Up-Front Payments, Development Milestones, And Payments For Development Activities, For Which Used An Input Method Collaboration Revenue For Non-Refundable Up-Front Payments, Development Milestones, And Payments For Development Activities, For Which Used An Input Method U.S. federal statutory tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Income tax credits Effective Income Tax Rate Reconciliation, Tax Credit, Percent Stock-based compensation Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Payment Arrangement, 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 Taxation of non-U.S. operations Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent Non-deductible Branded Prescription Drug Fee Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, 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 Impact of change in U.S. corporate tax rate (the Act) Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Domestic production activities deduction Effective Income Tax Rate Reconciliation, Deduction, Qualified Production Activity, Percent Other permanent differences Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent Effective income tax rate Property, Plant and Equipment Property, Plant and Equipment Disclosure [Text Block] Finance lease right-of-use assets Finance Lease, Right-of-Use Asset Accumulated amortization Finance Lease, Right-of-Use Asset, Accumulated Amortization Finance Lease, Right-of-Use Asset, Accumulated Amortization Collaboration and License Agreements Collaborative Arrangement Disclosure [Text Block] Accounts receivable Schedule of assets measured at fair value on a recurring basis Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block] Operating expenses Net income per share - diluted (in dollars per shares) 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 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 related to prior year tax positions Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Gross decreases related to prior year tax positions Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions Gross decreases due to settlements and lapse of statutes of limitations 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 Revenue recognized that was included in deferred revenue at the beginning of the period Revenue recognized that was added to deferred revenue during the period 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)