Share repurchase program, authorized amount Stock Repurchase Program, Authorized Amount Customer [Domain] Customer [Domain] Legal Matters Legal Matters and Contingencies [Text Block] Schedule of Shares Repurchased Class of Treasury Stock [Table Text Block] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Net income Net income Net income - basic and diluted Net Income (Loss) Attributable to Parent Entity Emerging Growth Company Entity Emerging Growth Company Preferred Stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Income Statement Location [Axis] Income Statement Location [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Receivable Type [Axis] Receivable Type [Axis] Entity Address, Address Line One Entity Address, Address Line One Equity securities Equity Securities, FV-NI, Current Royalty percentage to be received on net product sales outside of the United States Royalty Percentage To Be Received On Net Product Sales Outside Of United States Royalty Percentage To Be Received On Net Product Sales Outside Of United States Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Schedule of accounts receivable and deferred revenue information Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Entity Filer Category Entity Filer Category '226 and '992 Patents '226 Patent And '992 Patent [Member] '226 Patent And '992 Patent Other noncurrent assets Other Assets, Noncurrent Net increase (decrease) in cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Stock-based compensation charges APIC, Share-based Payment Arrangement, Increase for Cost Recognition Certificates of deposit Certificates of deposit Certificates of Deposit [Member] Available-for-sale Debt Securities Debt Securities, Available-for-sale [Table Text Block] '487 Patent '487 Patent [Member] '487 Patent [Member] Document Fiscal Year Focus Document Fiscal Year Focus Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Remaining authorized repurchase amount Stock Repurchase Program, Remaining Authorized Repurchase Amount Schedule of Inventory, Current Schedule of Inventory, Current [Table Text Block] Antidilutive weighted average number of shares (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Research and development expense Research and Development Expense [Member] Sales-based milestone earned Sales-Based Milestone Earned [Member] Sales-Based Milestone Earned Unrealized (loss) gain on debt securities OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Award Type [Domain] Award Type [Domain] Share Repurchase Program [Domain] Share Repurchase Program [Domain] McKesson Corporation McKesson Corporation [Member] McKesson Corporation [Member] Evkeeza Evkeeza [Member] Evkeeza ASSETS Assets [Abstract] Marketable Securities, Based on Contractual Maturity Dates Investments Classified by Contractual Maturity Date [Table Text Block] Concentration risk, percentage Concentration Risk, Percentage Preferred Stock, $.01 par value; 30,000,000 shares authorized; issued and outstanding - none Preferred Stock, Value, Issued Entity Address, City or Town Entity Address, City or Town Libtayo LIBTAYO Net Product Sales [Member] LIBTAYO Net Product Sales [Member] Retained Earnings Retained Earnings [Member] Debt Instrument [Axis] Debt Instrument [Axis] (Increase) decrease in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Available-for-sale debt securities: Debt Securities, Available-for-sale [Abstract] Trade accounts receivable Trade Accounts Receivable [Member] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Project [Domain] Project [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. 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] Fair Value and Unrealized Losses of Marketable Securities Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value [Table Text Block] Gains on marketable and other securities, net Marketable Securities, Gain (Loss) Increase in accounts receivable Increase (Decrease) in Accounts Receivable Accrued capital expenditures Capital Expenditures Incurred but Not yet Paid 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 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 Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Entity Interactive Data Current Entity Interactive Data Current Repayment of bridge loan facility Repayments of Short-term Debt Net income per share - basic (in dollars per share) Earnings Per Share, Basic First Sales Milestone Sales Milestone One [Member] Sales Milestone One Pending claims Loss Contingency, Pending Claims, Number U.S. government and government agency obligations U.S. government and government agency obligations U.S. government and government agency obligations US Treasury and Government [Member] Product Sales Revenue from Contract with Customer [Text Block] Document Type Document Type Interest expense Interest Expense, Debt Schedule of product sales Schedule of collaborative revenue Disaggregation of Revenue [Table Text Block] Entity Current Reporting Status Entity Current Reporting Status Percentage of trial costs required to be funded by collaborating party Percentage of Trial Costs Required To Be Funded By Collaborating Party Percentage of Trial Costs Required To Be Funded By Collaborating Party Shares purchase price Investment Owned, at Cost 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. 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 Commercial paper Commercial paper Commercial Paper [Member] 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 Other non-cash items, net Other Noncash Income (Expense) Classification of Investment [Axis] Classification of Investment [Axis] This element represents the general categories of investments, which may be classified as Unrestricted or Restricted. Other operating income Other Operating Income (Expense) [Member] Besse Medical, a subsidiary of AmerisourceBergen Corporation Besse Medical [Member] Besse Medical [Member] Long-term debt Long-term Debt Level 1 Fair Value, Inputs, Level 1 [Member] Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Other liabilities Other Liabilities Document Transition Report Document Transition Report Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] '165 Patent '165 Patent [Member] '165 Patent [Member] Total liabilities and stockholders' equity Liabilities and Equity Pending Litigation Pending Litigation [Member] Investments, Debt and Equity Securities [Abstract] Investments, Debt and Equity Securities [Abstract] 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 Levels Of Twelve Month Sales At Which Sales Milestone Payments Would Be Received Unrealized gain (loss) on cash flow hedges Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax Deferred revenue Contract with Customer, Liability, Current Scenario [Axis] Scenario [Axis] Restricted cash included in Other noncurrent assets Restricted Cash Additional paid-in capital Additional Paid in Capital Invalid claims Loss Contingency, Claims Invalid, Number Loss Contingency, Claims Invalid, Number Concentration Risk [Line Items] Concentration Risk [Line Items] LIABILITIES AND STOCKHOLDERS' EQUITY LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Short-term Debt, Type [Domain] Short-term Debt, Type [Domain] Cost of treasury stock received Total cost of shares received Treasury Stock, Value, Acquired, Cost Method Net Income Per Share Earnings Per Share [Text Block] Sanofi Sanofi [Member] Sanofi [Member] 2019 Share Repurchase Program Share Repurchase Program, 2019 [Member] Share Repurchase Program, 2019 Minimum Minimum [Member] Interim Financial Statements Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Marketable securities Marketable Securities, Current Roche Collaboration Agreement Roche Collaboration Agreement [Member] Roche Collaboration Agreement Schedule of assets measured at fair value on a recurring basis Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block] Selling, general, and administrative Selling, General and Administrative Expense Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Preferred Stock, shares authorized (in shares) Preferred Stock, Shares Authorized Unrealized Gains Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Fair Value - 12 Months or Greater Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer Trading Symbol Trading Symbol Amounts recognized in connection with up-front payments received Amounts recognized in connection with up-front and development milestone payments received Amounts Recognized In Connection With Up-Front Payments [Member] Amounts Recognized In Connection With Up-Front Payments [Member] Deferred tax assets Deferred Income Tax Assets, Net Current liabilities: Liabilities, Current [Abstract] Receivable [Domain] Receivable [Domain] Statement of Cash Flows Cash Flow, Supplemental Disclosures [Text Block] Debt Debt Disclosure [Text Block] Beginning Balance (in shares) Ending Balance (in shares) Shares, Outstanding Senior Unsecured Notes Senior Notes [Member] Reimbursement of research and development expenses Reimbursement of research and development expenses Reimbursement Of Research And Development Expenses [Member] Reimbursement Of Research And Development Expenses [Member] Inventories Inventory Disclosure [Text Block] Reimbursement of commercialization-related expenses Reimbursement Of Commercialization-Related Expenses [Member] Reimbursement Of Commercialization-Related Expenses Common stock Common Stock, Value, Issued Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Total other income (expense) Nonoperating Income (Expense) Customer concentration risk Customer Concentration Risk [Member] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Second Sales Milestone Sales Milestone Two [Member] Sales Milestone Two Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Inventory write-offs and reserves Inventory Write-down January 2021 Share Repurchase Program Share Repurchase Program, January 2021 [Member] Share Repurchase Program, January 2021 Restricted stock awards and restricted stock units Restricted Stock [Member] Teva Teva Pharmaceuticals Collaboration Agreement [Member] Teva Pharmaceuticals Collaboration Agreement [Member] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Document Period End Date Document Period End Date Marketable Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Effect of dilutive securities (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Number of doses Collaborative Arrangement, Number Of Doses Counterparty To Purchase Collaborative Arrangement, Number Of Doses Counterparty To Purchase Costs and expenses, total Costs and Expenses Class of Stock [Axis] Class of Stock [Axis] U.S. Government US Government [Member] US Government Entity Registrant Name Entity Registrant Name Treasury Stock (in shares) Treasury Stock, Shares Work-in-process Inventory, Work in Process, Net of Reserves Capital expenditures Payments to Acquire Productive Assets Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Statements of Comprehensive Income Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Financial Instrument [Axis] Financial Instrument [Axis] Selling, general and administrative expense Selling, General and Administrative Expenses [Member] Revenues Revenue from Contract with Customer, Excluding Assessed Tax Finished goods Inventory, Finished Goods, Net of Reserves Deferred costs Other Inventory, Net of Reserves Stock options Share-based Payment Arrangement, Option [Member] Equity [Abstract] Equity [Abstract] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Bridge Facility Bridge Facility [Member] Bridge Facility Fair Value - Less than 12 Months Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months Common Stock Common Stock Common Stock Common Stock [Member] Income from operations Operating Income (Loss) Cost of goods sold Cost Of Goods Sold [Member] Cost Of Goods Sold Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Maturities after one year through five years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Unrealized Losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Collaboration, License, and Other Agreements Collaborative Arrangement Disclosure [Text Block] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Regeneron's obligation for its share of Sanofi commercial expenses Regeneron's Share Of Commercial Expenses [Member] Regeneron's Share Of Commercial Expenses Non-cash compensation expense Share-based Payment Arrangement, Noncash Expense Sanofi Collaboration Agreement, Antibody Sanofi Collaboration Agreement, Antibody [Member] Sanofi Collaboration Agreement, Antibody [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Cash and Cash Equivalents [Abstract] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Deferred taxes Increase (Decrease) in Deferred Income Taxes Treasury Stock Treasury Stock [Member] Other (expense) income, net Other Nonoperating Income (Expense) Long-term debt fair value Long-term Debt, Fair Value Upfront payment made for collaboration agreement Collaborative Arrangement, Upfront Payment Made Upfront payment made under a collaboration agreement Maximum Maximum [Member] Entity Information [Line Items] Entity Information [Line Items] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Total liabilities Liabilities Raw materials Inventory, Raw Materials, Net of Reserves Legal Entity [Axis] Legal Entity [Axis] EYLEA EYLEA Aflibercept Injection [Member] EYLEA Aflibercept Injection Award Type [Axis] Award Type [Axis] Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Sales Milestones [Axis] Sales Milestones [Axis] Sales Milestones Total stockholders' equity Beginning Balance Ending Balance Stockholders' Equity Attributable to Parent Common Stock, shares issued (in shares) Common Stock, Shares, Issued Preferred Stock, shares issued (in shares) Preferred Stock, Shares Issued Increase in accounts payable, accrued expenses, and other liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Amgen v.s. Regeneron Amgen v.s. Regeneron [Member] Amgen v.s. Regeneron [Member] Summary of Non-Cash Investing and Financing Activities Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Number of ex parte reexamination requests Loss Contingency, Ex Parte Reexamination, Filed, Number Loss Contingency, Ex Parte Reexamination, Filed, Number Repurchases of Common Stock Payments for Repurchase of Common Stock Stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Stockholders' Equity Attributable to Parent [Abstract] Measurement Frequency [Domain] Measurement Frequency [Domain] Debt, principal amount Debt Instrument, Face Amount Unrestricted Unrestricted [Member] Investments whose use is not restricted in whole or in part, by contractual agreements or regulatory requirements. Interest expense Interest Expense Proceeds from bridge loan facility Proceeds from Short-term Debt Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] City Area Code City Area Code Retained earnings Retained Earnings (Accumulated Deficit) Litigation Case [Domain] Litigation Case [Domain] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Restrictions on Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Statements of Operations Income Statement [Abstract] Amendment Flag Amendment Flag Concentration Risk [Table] Concentration Risk [Table] Inventory Disclosure [Abstract] Inventory Disclosure [Abstract] Regeneron's share of profits (losses) in connection with commercialization Share Of Profit (Losses) In Connection With Commercialization [Member] Share Of Profit (Losses) In Connection With Commercialization [Member] Other operating income Other Operating Income Regeneron's obligation for its share of Sanofi research and development expenses Regeneron's obligation for its share of Bayer research and development expenses Regeneron's Share Of Research And Development Expenses [Member] Regeneron's Share Of Research And Development Expenses [Member] Restricted Restricted [Member] Restricted [Member] Income tax expense Income Tax Expense (Benefit) Accounts receivable, net Accounts Receivable, after Allowance for Credit Loss, Current Proceeds from issuance of long-term debt Proceeds from Issuance of Long-term Debt Equity Components [Axis] Equity Components [Axis] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Investment Type [Axis] Investment Type [Axis] Total current assets Assets, Current Concentration Risk Type [Domain] Concentration Risk Type [Domain] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Inventories Total Inventories Inventory, Net Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Entity File Number Entity File Number Repurchases of Common Stock Stock Repurchased During Period, Value 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] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] '741 Patent '741 Patent [Member] '741 Patent [Member] Total adjustments Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities Product and Service [Axis] Product and Service [Axis] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Entity Small Business Entity Small Business Securities owned not readily marketable Equity Securities without Readily Determinable Fair Value, Amount Preferred Stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Maximum agreement payments Maximum Transaction Agreement Payments Maximum Transaction Agreement Payments Equity Component [Domain] Equity Component [Domain] Issuance of Common Stock for equity awards granted under long-term incentive plans (in shares) Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture Repurchases of Common Stock (in shares) Stock Repurchased During Period, Shares Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Cost of collaboration and contract manufacturing Collaboration and Contract Manufacturing [Member] Collaboration and Contract Manufacturing [Member] Marketable securities Marketable Securities, Noncurrent Statement [Line Items] Statement [Line Items] Litigation Case [Axis] Litigation Case [Axis] (Decrease) increase in deferred revenue Increase (Decrease) in Contract with Customer, Liability Remaining performance obligation Revenue, Remaining Performance Obligation, Amount Issuance of Common Stock for equity awards granted under long-term incentive plans Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture Short-term Debt, Type [Axis] Short-term Debt, Type [Axis] Fair Value Total Available-for-sale debt securities Debt Securities, Available-for-sale Counterparty Name [Domain] Counterparty Name [Domain] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Entity Address, State or Province Entity Address, State or Province Purchases of marketable and other securities Payments to Acquire Marketable Securities Finance lease liabilities Finance Lease, Liability, Current 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. Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Level 2 Fair Value, Inputs, Level 2 [Member] Gross product revenue Gross Product Revenue [Member] Gross Sales Revenue [Member] Cumulative catch-up adjustment to revenue, change in estimate of transaction price Contract with Customer, Asset, Cumulative Catch-up Adjustment to Revenue, Modification of Contract Deferred revenue Contract with Customer, Liability, Noncurrent Fair Value - Total Debt Securities, Available-for-sale, Unrealized Loss Position Entity [Domain] Entity [Domain] Amortized Cost Basis Debt Securities, Available-for-sale, Amortized Cost Customer [Axis] Customer [Axis] Number of claims invalidated Gain Contingency, Claims Invalidated, Number Gain Contingency, Claims Invalidated, Number Basic and Diluted Net Income (Loss) Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Entity Shell Company Entity Shell Company Local Phone Number Local Phone Number Scenario, Forecast Forecast [Member] Proceeds from issuance of Common Stock Proceeds from Issuance of Common Stock Total assets Assets Common Stock, shares authorized (in shares) Common Stock, Shares Authorized Percentage of damages company is responsible for Loss Contingency, Percentage Of Damages Responsible For Loss Contingency, Percentage Of Damages Responsible For Geographical [Domain] Geographical [Domain] Research and development Research and Development Expense Product and Service [Domain] Product and Service [Domain] Interest rate Debt Instrument, Interest Rate, Stated Percentage Praluent Agreement Praluent Cross License And Commercialization Agreement [Member] Praluent Cross License And Commercialization Agreement [Member] Research Collaboration and Licensing Arrangements [Table] Research Collaboration and Licensing Arrangements [Table] -- None. No documentation exists for this element. -- Measurement Frequency [Axis] Measurement Frequency [Axis] Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items] Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Litigation Status [Axis] Litigation Status [Axis] Summary of Issued Senior Unsecured Notes Schedule of Debt [Table Text Block] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] 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 Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Entity Tax Identification Number Entity Tax Identification Number Corporate bonds Corporate bonds Corporate bonds Corporate Bond Securities [Member] Geographical [Axis] Geographical [Axis] Accrued expenses and other current liabilities Accrued Liabilities and Other Liabilities Weighted average shares outstanding - basic (in shares) Weighted average shares - basic (in shares) Weighted Average Number of Shares Outstanding, Basic Net income per share - diluted (in dollars per share) Earnings Per Share, Diluted Net product sales Product [Member] Project [Axis] Project [Axis] Outside United States Non-US [Member] Remaining amount of sales milestone payments if total sales achieve specific levels Remaining Amount Of Sales Milestone Payments If Total Sales Achieve Specific Levels Remaining Amount Of Sales Milestone Payments If Total Sales Achieve Specific Levels Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Deferred revenue Contract with Customer, Liability Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities Treasury Stock, at cost; 17,930,390 shares in 2021 and 16,431,520 shares in 2020 Treasury Stock, Value Percentage of royalty payment that can be used to offset litigation proceedings (up to) Percentage Of Royalty Payment That Can Be Offset Percentage Of Royalty Payment That Can Be Offset '631 Patent '631 Patent [Member] '631 Patent Fair Value Measurements Fair Value Disclosures [Text Block] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Depreciation and amortization Depreciation, Depletion and Amortization 2.800% Senior Notes due September 2050 Senior Unsecured Notes Due 2050 [Member] Senior Unsecured Notes Due 2050 Entities [Table] Entities [Table] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Increase in inventories Increase (Decrease) in Inventories Common Stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Other operating expense (income), net Other Operating Income (Expense), Net Financial Instruments [Domain] Financial Instruments [Domain] Casirivimab and imdevimab Casirivimab and imdevimab [Member] Casirivimab and imdevimab Cost of goods, collaboration and contract manufacturing Cost of Goods and Services Sold Revenues: Revenues [Abstract] REGEN-COV REGEN-COV [Member] REGEN-COV Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Other revenue Product and Service, Other [Member] Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table] Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table] Income Statement Location [Domain] Income Statement Location [Domain] Bridge Facility Bridge Loan [Member] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Table] Reimbursement for manufacturing of commercial supplies Reimbursement For Manufacturing Of Commercial Supplies [Member] Reimbursement For Manufacturing Of Commercial Supplies [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Property, plant, and equipment, net Property, Plant and Equipment, Net Intellia Intellia [Member] Intellia Other noncurrent liabilities Other Liabilities, Noncurrent Number of shares repurchased (in shares) Treasury Stock, Shares, Acquired Debt Instrument [Line Items] Debt Instrument [Line Items] Total marketable securities Marketable Securities Earnings Per Share [Abstract] Earnings Per Share [Abstract] Net unrealized gain (loss) on securities Equity Securities, FV-NI, Unrealized Gain (Loss) 1.750% Senior Notes due September 2030 Senior Unsecured Notes Due 2030 [Member] Senior Unsecured Notes Due 2030 Other Transaction Agreement BARDA, Other Transaction Agreement [Member] BARDA, Other Transaction Agreement Document Quarterly Report Document Quarterly Report Unrealized Loss - Total Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss Collaboration revenue Collaboration Revenue [Member] Collaboration Revenue Classification of Investment [Domain] Classification of Investment [Domain] Provides general categories of investments for which information is required or determined to be disclosed. Praluent Praluent Net Product Sales [Member] Praluent Net Product Sales Line of Credit Facility [Table] Line of Credit Facility [Table] 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. Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Libtayo development Libtayo Development [Member] Libtayo Development [Member] Expenses: Costs and Expenses [Abstract] Long-term debt Long-term Debt, Excluding Current Maturities Document Fiscal Period Focus Document Fiscal Period Focus Legal Matters Legal Costs, Policy [Policy Text Block] Number of IPR filed Gain Contingency, Inter Partes Review Filed, Number Gain Contingency, Inter Partes Review Filed, Number Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Sales Milestones [Domain] Sales Milestones [Domain] Sales Milestones [Domain] Investments [Domain] Investments [Domain] Bayer Bayer Collaboration Agreement [Member] Bayer Collaboration Agreement [Member] Marketable securities, realized gain Marketable Securities, Realized Gain Marketable Securities, Realized Gain Counterparty Name [Axis] Counterparty Name [Axis] Sales or maturities of marketable and other securities Proceeds from Sale and Maturity of Marketable Securities Class A Stock Common Class A [Member] Cash, cash equivalents, and restricted cash at beginning of period Cash, cash equivalents, and restricted cash at end of period Total cash, cash equivalents, and restricted cash shown in the Condensed Consolidated Statement of Cash Flows Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Sovereign bonds Sovereign bonds Sovereign Debt Securities [Member] Number of shares sold (in shares) Sale of Stock, Number of Shares Issued in Transaction UNITED STATES UNITED STATES Common Stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Schedules of sales to customers as percentage of total gross product revenue Schedules of Concentration of Risk, by Risk Factor [Table Text Block] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Current assets: Assets, Current [Abstract] Entity Central Index Key Entity Central Index Key Security Exchange Name Security Exchange Name Reduction of Research and development expense Reimbursement Of Research And Development Expense Reimbursement Of Research And Development Expense Weighted average shares outstanding - diluted (in shares) Weighted average shares - diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Dupilumab/REGN3500 Eligible Investments Dupilumab/REGN3500 Eligible Investments [Member] Dupilumab/REGN3500 Eligible Investments [Member] Marketable securities, realized loss Marketable Securities, Realized Loss Marketable Securities, Realized Loss Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax Measured on a recurring basis Fair Value, Recurring [Member] Income Taxes Income Tax Disclosure [Text Block] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Current Fiscal Year End Date Current Fiscal Year End Date Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Antidilutive Securities Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Other income (expense): Nonoperating Income (Expense) [Abstract] Marketable securities, realized gain (loss) Marketable Securities, Realized Gain (Loss) Class of Stock [Line Items] Class of Stock [Line Items] Net cash (used in) provided by investing activities Net Cash Provided by (Used in) Investing Activities Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Total current liabilities Liabilities, Current Payments in connection with Common Stock tendered for employee tax obligations Payment, Tax Withholding, Share-based Payment Arrangement Class of Stock [Domain] Class of Stock [Domain] Litigation Status [Domain] Litigation Status [Domain] Loss Contingencies [Table] Loss Contingencies [Table] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Accounts payable Accounts Payable Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Title of 12(b) Security Title of 12(b) Security Statement [Table] Statement [Table] Asset-backed securities Asset-backed Securities [Member] Statistical Measurement [Axis] Statistical Measurement [Axis] Cover [Abstract] Cover [Abstract] Finance lease liabilities Finance Lease, Liability, Noncurrent Sanofi Collaboration Agreement, Immuno-oncology Sanofi Collaboration Agreement, Immuno-oncology Sanofi Collaboration Agreement, Immuno-oncology Sanofi Collaboration Agreement, Immuno-oncology [Member] Sanofi Collaboration Agreement, Immuno-oncology [Member] Regeneron's obligation for Sanofi's share of Libtayo U.S. gross profits Sanofi's Share of Libtayo U.S. Gross Profits [Member] Sanofi's Share of Libtayo U.S. Gross Profits [Member] Unrealized Loss - Less than 12 months Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Scenario [Domain] Scenario [Domain] 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] Maturities within one year Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Unrealized Loss - 12 Months or Greater Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss