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] Organization, Consolidation and Presentation of Financial Statements [Abstract] Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions [Table] Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, Forecast [Member] Scenario, Forecast [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 [Member] Accounting Standards Update 2014-09 [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] Teva Pharmaceuticals [Member] Teva Pharmaceuticals [Member] Teva Pharmaceuticals Collaboration Agreement 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] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Type of Arrangement and Non-arrangement Transactions [Axis] Type of Arrangement and Non-arrangement Transactions [Axis] Arrangements and Non-arrangement Transactions [Domain] Arrangements and Non-arrangement Transactions [Domain] Collaborative Arrangement [Member] Collaborative Arrangement [Member] Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] Up-front payment received Up-front payment received Up-front payment received upon the execution of a collaboration agreement. Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Deferred Revenue Revenue, Remaining Performance Obligation Deferred Revenue Deferred Revenue Deferred Revenue, Period Increase (Decrease) Deferred Revenue, Period Increase (Decrease) Revenue Recognition, Milestone Method, Revenue Recognized Revenue Recognition, Milestone Method, Revenue Recognized Deferred Revenue, Revenue Recognized Deferred Revenue, 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. Collaboration revenue Collaboration revenue Revenue recognized in the period, inclusive of amounts recognized which were previously deferred. New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] 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] Adjustments Difference between Revenue Guidance in Effect before and after Topic 606 [Member] Balance Without Adoption of ASC 606 Calculated under Revenue Guidance in Effect before Topic 606 [Member] Accounting Standards Update 2016-01 [Member] Accounting Standards Update 2016-01 [Member] 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] 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 [Member] Unrestricted [Member] Investments whose use is not restricted in whole or in part, by contractual agreements or regulatory requirements. Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] 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] Cumulative Effect on Retained Earnings, Net of Tax Cumulative Effect on Retained Earnings, Net of Tax Reclassification from AOCI to Retained Earnings Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax (Decrease) increase in deferred revenue Revenue from Related Parties Revenue from Related Parties Deferred tax assets Deferred Tax Assets, Net, Noncurrent Total assets Assets Accrued Liabilities and Other Liabilities Accrued Liabilities and Other Liabilities Deferred Revenue From Related Party Current Deferred Revenue From Related Party Current The current portion of deferred revenue from related parties as of balance sheet date. Current deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized, and is expected to be recognized in the next twelve months. Generally, an entity records deferred revenue when it receives consideration before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP. Deferred Revenue, Current Deferred Revenue, Current Liabilities, Current Liabilities, Current Deferred Revenue From Related Party Noncurrent Deferred Revenue From Related Party Noncurrent The noncurrent portion of deferred revenue from related parties as of balance sheet date. Noncurrent deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized, and is not expected to be recognized in the next twelve months. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP. Deferred Revenue, Noncurrent Deferred Revenue, Noncurrent Liabilities Liabilities Retained earnings Retained Earnings (Accumulated Deficit) Total stockholders' equity Stockholders' Equity Attributable to Parent Liabilities and Equity Liabilities and Equity Other revenue Other Revenue, Net Revenues Revenues Operating Income (Loss) Operating Income (Loss) Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income Tax Expense (Benefit) Income Tax Expense (Benefit) Net Income (Loss) Attributable to Parent Net Income (Loss) Attributable to Parent Statement of Financial Position [Abstract] Statement [Table] Class of Stock [Axis] Class of Stock [Domain] Class A Stock Common Class A [Member] Common Stock Common Stock [Member] Statement [Line Items] Statement [Line Items] Liabilities and Equity [Abstract] Stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] 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, shares issued (in shares) Preferred Stock, Shares Issued Preferred stock, shares 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 issued (in shares) Common Stock, Shares, Issued Common Stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Treasury Stock, shares outstanding (in shares) Treasury Stock, Shares Inventory Disclosure [Abstract] Inventory Inventory Disclosure [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Statement of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net income 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 charges and expenses, net Other Noncash Income (Expense) Deferred taxes Increase (Decrease) in Deferred Income Taxes Changes in assets and liabilites Increase (Decrease) in Operating Capital [Abstract] Decrease (increase) in Sanofi, Bayer, and trade accounts receivable Increase (Decrease) in Accounts Receivable Increase in Inventories Increase (Decrease) in Inventories Decrease (increase) in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets (Decrease) increase in deferred revenue Increase (Decrease) in Deferred Revenue Increase 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 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 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 Proceeds from issuance of Common Stock Proceeds from Issuance of Common Stock Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Net increase 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 Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Text Block] Derivative Instruments and Hedging Activities Disclosure [Text Block] New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Description of New Accounting Pronouncements Not yet Adopted [Text Block] Description of New Accounting Pronouncements Not yet Adopted [Text Block] Collaboration Agreement [Abstract] Collaboration Agreement Collaboration Agreements Collaborative Arrangement Disclosure [Text Block] Investments, Debt and Equity Securities [Abstract] Schedule of Available-for-sale Securities [Table] Corporate Bond Securities [Member] Corporate Bond Securities [Member] U.S. government and government agency obligations US Treasury and Government [Member] Municipal bonds Municipal Bonds [Member] Commercial Paper [Member] Commercial Paper [Member] Certificates of Deposit [Member] Certificates of Deposit [Member] Schedule of Available-for-sale Securities [Line Items] Document Period End Date Document Period End Date Marketable Securities, Realized Gain (Loss) Marketable Securities, Realized Gain (Loss) Unrealized Gain on Securities Unrealized Gain on Securities Amortized Cost Basis Available-for-sale Securities, Amortized Cost Basis Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax Available-for-sale Securities Available-for-sale Securities Available-for-sale Securities, Debt Maturities, Fair Value [Abstract] Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract] Maturities within one year Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value Maturities after one year through five years Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value Total Available-for-sale Securities, Debt Securities Continuous Unrealized Loss Position, Fair Value [Abstract] Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract] Fair Value - Less than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value Fair Value - 12 Months or Greater Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Fair Value - Total Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value Continuous Unrealized Loss Position, Aggregate Losses [Abstract] Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract] Unrealized Loss - Less than 12 months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Unrealized Loss - 12 Months or Greater Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Unrealized Loss - Total Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss Commitments and Contingencies Disclosure [Abstract] Legal Costs, Policy [Policy Text Block] Legal Costs, Policy [Policy Text Block] Revenues [Abstract] Revenue from External Customers by Products and Services [Table] Revenue from External Customers by Products and Services [Table] Products and Services [Axis] Products and Services [Axis] Products and Services [Domain] Products and Services [Domain] Revenue from External Customer [Line Items] Revenue from External Customer [Line Items] Revenue from External Customers by Products and Services [Table Text Block] Revenue from External Customers by Products and Services [Table Text Block] Schedules of Concentration of Risk, by Risk Factor [Table Text Block] 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 may include rebates and chargebacks, and distributor-related fees. Statement of Comprehensive Income [Abstract] Statement [Table] Income Statement [Abstract] Income Statement [Abstract] Revenues: Net product sales Sales Revenue, Goods, Net Sanofi collaboration revenue Bayer Collaboration Revenue Other Collaboration Revenue Revenue realized from sharing of profits/losses on commercialized products, reimbursement of research and development expenses, and other transactions with our collaborator Bayer during the period. Total 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 Sold Cost of collaboration and contract manufacturing Cost of manufacturing Total cost related to third-party royalties the Company is obligated to pay based on sales of commercial product by the Company’s collaborators, as well as costs in connection with producing commercial supplies for the Company’s collaborators and others. Total expenses Costs and Expenses Income from operations Other income (expense): Nonoperating Income (Expense) [Abstract] Other income, net Other Nonoperating Income (Expense) Interest Expense Interest Expense Total other income (expense) Nonoperating Income (Expense) Income before income taxes Income tax expense Net income per share - basic Earnings Per Share, Basic Net income per share - diluted Earnings Per Share, Diluted Weighted average shares outstanding - basic Weighted Average Number of Shares Outstanding, Basic Weighted average shares outstanding - diluted Weighted Average Number of Shares Outstanding, Diluted 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 gain (loss) on marketable securities Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of 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 Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Class A Stock Common Stock ASSETS Assets [Abstract] Current assets: Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Marketable securities Marketable Securities, Current Accounts receivable - trade, net Accounts Receivable, Net, Current Accounts Receivable from Sanofi Accounts Receivable, Related Parties, Current Accounts receivable from Bayer Accounts and Notes Receivable, Net Inventories Inventory, Net Total current assets Assets, Current Marketable securities Marketable Securities, Noncurrent Property, Plant, and Equipment, Net Property, Plant and Equipment, Net Other assets Other Assets, Noncurrent Total assets LIABILITIES and STOCKHOLDERS' EQUITY Current liabilities: Liabilities, Current [Abstract] Accounts Payable Accounts Payable Deferred revenue from Sanofi, current portion Total current liabilities Capital and facility lease obligations Capital and facility lease obligations, noncurrent Represents the noncurrent portion of a lease liability Deferred revenue from Sanofi Other long-term liabilities Other Liabilities, Noncurrent Total liabilities Preferred Stock Preferred Stock, Value, Issued Common stock Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Treasury stock Treasury Stock, Value Total liabilities and stockholders' equity Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Effect of dilutive securities (in shares): Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract] Stock options Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Restricted stock Incremental Common Shares Attributable To Nonvested Restricted Shares Nonvested equity-based payment awards that result in incremental common shares. Dilutive potential shares Weighted Average Number Diluted Shares Outstanding Adjustment Weighted average shares - diluted (in shares) Earnings Per Share, Basic and Diluted [Abstract] Net income per share - diluted (in dollars per share) Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Stock options Employee Stock Option [Member] Restricted Stock [Member] Restricted Stock [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Weighted average number of shares Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Supplemental Cash Flow Information [Abstract] Restrictions on Cash and Cash Equivalents [Table Text Block] Restrictions on Cash and Cash Equivalents [Table Text Block] Interim Financial Statements Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Legal Matters Legal Matters and Contingencies [Text Block] Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] 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 Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Domestic Tax Authority [Member] Domestic Tax Authority [Member] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Total income tax expense (benefit) Provisional charge for re-measurement of U.S. deferred tax assets due to US Tax Reform Provisional charge for re-measurement of U.S. deferred tax assets due to US Tax Reform Provisional charge recorded during Q4 2017 for the remeasurement of U.S. deferred tax assets upon the enactment of Tax Cut and Jobs Act Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Available-for-sale Securities, Income Tax Expense on Change in Unrealized Holding Gain (Loss) Available-for-sale Securities, Income Tax Expense on Change in Unrealized Holding Gain (Loss) Loss Contingencies [Table] Loss Contingencies [Table] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Litigation Case [Axis] Litigation Case [Axis] Litigation Case [Domain] Litigation Case [Domain] Litigation Status [Axis] Litigation Status [Axis] Litigation Status [Domain] Litigation Status [Domain] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Loss Contingencies [Line Items] Loss Contingencies [Line Items] 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, Value Loss Contingency, Damages Sought, Value Schedule of Research and Development Arrangement, Contract to Perform for Others [Table] Schedule of Research and Development Arrangement, Contract to Perform for Others [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Bayer HealthCare LLC [Member] Bayer HealthCare LLC [Member] Bayer HealthCare LLC [Member] EYLEA Collaboration Agreement with Bayer HealthCare LLC [Member] Collaboration agreement with Bayer HealthCare LLC. Ang2 Antibody [Member] Ang2 Antibody [Member] Ang2 Antibody [Member] Collaboration Agreement [Line Items] 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. Deferred Revenue, Additions Deferred Revenue, Additions Net profit (loss) from commercialization of products under collaboration agreement Net profit (loss) from commercialization of products under collaboration agreement Our share of profits/losses related to commercialization of products by our collaborator based on sales outside the United States. Under the terms of our collaboration agreement, we share profits/losses with our collaborator on commercialization of products. Reimbursement of Regeneron research and development expenses Research and Development Arrangement, Contract to Perform for Others, Compensation Earned Contracts Revenue Contracts Revenue Other Collaboration Revenue Revenue Disclosure [Table] Revenue Disclosure [Table] Besse Medical [Member] Besse Medical [Member] Besse Medical [Member] 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. 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. McKesson Corporation [Member] McKesson Corporation [Member] McKesson Corporation [Member] Curascript SD [Member] Curascript SD [Member] Curascript SD [Member] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Customer concentration risk Customer Concentration Risk [Member] Concentration Risk by Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Gross Sales Revenue GrossSalesRevenue [Member] GrossSalesRevenue [Member] Valuation Allowances and Reserves Type [Axis] Valuation Allowances and Reserves Type [Axis] Valuation Allowances and Reserves [Domain] Valuation Allowances and Reserves [Domain] Rebates and Chargebacks 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. Revenue Disclosure [Line Items] Revenues from External Customers and Long-Lived Assets [Line Items] Risks and Uncertainties [Abstract] Risks and Uncertainties [Abstract] Concentration risk, percentage Concentration Risk, Percentage Activity of Sales Related Deductions [Roll Forward] Movement in Valuation Allowances and Reserves [Roll Forward] Balance Valuation Allowances and Reserves, Balance Provision related to current period sales Valuation Allowances and Reserves, Additions for Charges to Other Accounts Credits/payments Valuation Allowances and Reserves, Deductions Schedule of assets measured at fair value on a recurring basis Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block] Restricted Cash Restricted Cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents 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 Capital Lease Obligations Incurred Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Net Income Per Share Earnings Per Share [Text Block] PD-1 PD-1 [Member] Programed Cell Death protein 1, or PD-1 ("REGN2810") Praluent, Kevzara, and Dupixent [Member] Praluent, Kevzara, and Dupixent [Member] [Member] Praluent, Kevzara, and Dupixent [Member] [Member] Collaborative Arrangement [Member] Antibody Collaboration Antibody Collaboration [Member] In November 2007, the Company entered into a global, strategic collaboration (the Antibody Collaboration) with Sanofi to discover, develop, and commercialize fully human monoclonal antibodies. 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. 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. IO Agreement IO Agreement [Member] IO Agreement Immuno-oncology Agreement Immuno-oncology Agreement [Member] Immuno-oncology Agreement Revenue, Remaining Performance Obligation Deferred Revenue From Related Party Deferred Revenue From Related Party Total deferred revenue from related parties Deferred Revenue, Revenue Recognized 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. Reimbursement of Regeneron commercialization-related expenses Reimbursement Revenue Other Revenue from Related Parties 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. 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. 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 Deferred Revenue, Additions Maximum amount of shared development costs Maximum amount of shared development costs The maximum amount of shared development expenses for PD-1. Increase amount of shared development costs Increase amount of shared development costs Increase amount of shared development costs Maximum shares the collaborator could sell Maximum shares the collaborator could sell Maximum shares the collaborator could sell through September 30, 2020. 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 Fair Value Measurements, Recurring and Nonrecurring [Table] 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 [Member] Estimate of Fair Value Measurement [Member] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Measured on a recurring basis Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets, Level 1 to Level 2 Transfers, Amount Fair Value, Assets, Level 1 to Level 2 Transfers, Amount Proceeds from Sale and Maturity of Marketable Securities Other than Temporary Impairment Losses, Investments Other than Temporary Impairment Losses, Investments Payments to Acquire Marketable Securities Marketable securities: Marketable Securities [Abstract] Corporate bonds Financial Instruments, Owned, Corporate Debt, at Fair Value Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value Municipal bonds Municipal Debt Securities, at Carrying Value Commercial Paper Commercial Paper Certificates of Deposit, at Carrying Value Certificates of Deposit, at Carrying Value Marketable Securities, Equity Securities Marketable Securities, Equity Securities Marketable Securities Marketable Securities Securities Owned Not Readily Marketable Securities Owned Not Readily Marketable Collaboration revenue with related party Schedule of Related Party Transactions [Table Text Block] Schedule of Selected Financial Information - Antibody Schedule of Selected Financial Information - Sanofi [Table Text Block] Schedule of selected financial information - Sanofi [Table Text Block] Changes In Deferred Revenue Balance - Antibody Changes In Deferred Revenue Balance [Table Text Block] [Table Text Block] for Changes In Deferred Revenue Balance [Table] Schedule of Selected Financial information - IO Schedule of Selected Financial information - IO [Table Text Block] Schedule of Selected Financial information - IO [Table Text Block] Changes in Deferred Revenue Balance - IO Changes in Deferred Revenue Balance - IO [Table Text Block] Changes in Deferred Revenue Balance - IO Collaboration revenue Collaboration revenue [Table Text Block] Summary of collaboration revenue [Table Text Block] Schedule of Selected Financial Information - Bayer Schedule of Selected Financial Information - Bayer [Table Text Block] Schedule of Selected Financial Information - Bayer [Table Text Block] Changes In Deferred Revenue Balance - Bayer Changes In Deferred Revenue Balance - Bayer [Table Text Block] Changes In Deferred Revenue Balance - Bayer [Table Text Block] Schedule of Selected Financial Information - Teva Schedule of Selected Financial Information - Teva [Table Text Block] Schedule of Selected Financial Information - Teva [Table Text Block] Changes in Deferred Revenue Balance - Teva Changes in Deferred Revenue Balance - Teva [Table Text Block] Changes in Deferred Revenue Balance - Teva [Table Text Block] Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] 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) on Interest Rate Cash Flow Hedge Ineffectiveness Gain (Loss) on Interest Rate Cash Flow Hedge Ineffectiveness Statement of Cash Flows Cash Flow, Supplemental 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 Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Schedule of Inventory, Current Schedule of Inventory, Current [Table Text Block] Marketable Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Product Sales and Concentration Risk [Text Block] Product Sales and Concentration Risk [Text Block] Product Sales and Concentration Risk Disclosure [Text Block] Available-for-sale Securities Available-for-sale Securities [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 Schedule of Unrealized Loss on Investments [Table Text Block]