Statistical Measurement [Domain] Statistical Measurement [Domain] Payroll and benefits Payroll And Benefits [Member] Payroll And Benefits Available-for-sale Debt Securities Debt Securities, Available-for-Sale [Table Text Block] Occupancy and other operating costs Occupancy And Other Operating Costs [Member] Occupancy And Other Operating Costs Restricted cash included in Other current assets Restricted Cash, Current Award Timing Predetermined Award Timing Predetermined [Flag] Entity File Number Entity File Number Customer A Customer A [Member] Customer A Additional Paid-in Capital Additional Paid-in Capital [Member] Tabular List, Table Tabular List [Table Text Block] Recently Issued Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Gain Contingencies [Line Items] Gain Contingencies [Line Items] 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 Unrealized Losses Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] 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. Net income per share - basic (in dollars per share) Earnings Per Share, Basic Adjustment to Compensation: Adjustment to Compensation [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Commercial paper Commercial paper Commercial Paper [Member] Increase (decrease) in accounts payable, accrued expenses, and other liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Number of counts submitted Number Of Counts Submitted Number Of Counts Submitted Product Sales Revenue from Contract with Customer [Text Block] Schedule of Stock by Class [Table] Stock, Class of Stock [Table] Schedule of Significant Expenses Schedule of Segment Reporting Information, by Segment [Table Text Block] Inventory Disclosure [Abstract] Inventory Disclosure [Abstract] Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Adjustment to Compensation, Amount Adjustment to Compensation Amount Concentration risk, percentage Concentration Risk, Percentage Stock-based compensation expense Share-Based Payment Arrangement, Noncash Expense Stock options Share-Based Payment Arrangement, Option [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Accounts and Financing Receivables [Table] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Total stockholders' equity Beginning Balance Ending Balance Equity, Attributable to Parent Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-Sale [Table] Insider Trading Policies and Procedures [Line Items] Common Stock, shares authorized (in shares) Common Stock, Shares Authorized Current assets: Assets, Current [Abstract] Total liabilities and stockholders' equity Liabilities and Equity Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] LIABILITIES AND STOCKHOLDERS' EQUITY LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Gain Contingencies [Table] Gain Contingencies [Table] Cover [Abstract] Cover [Abstract] Cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Maximum Maximum [Member] Evkeeza Evkeeza [Member] Evkeeza Maturities after five years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Restricted stock awards and restricted stock units Restricted Stock [Member] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Payments for intangible assets Payments To Acquire Intangible Assets1 Payments To Acquire Intangible Assets1 Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Treasury Stock Treasury Stock, Common [Member] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Pay vs Performance Disclosure [Line Items] Regeneron's share of profits Share Of Profit (Losses) [Member] Share Of Profit (Losses) Libtayo LIBTAYO Net Product Sales [Member] LIBTAYO Net Product Sales [Member] Gain (loss) on foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Entity Shell Company Other noncurrent liabilities Other Liabilities, Noncurrent Legal Matters Legal Costs, Policy [Policy Text Block] 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. Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Summary of Non-Cash Investing and Financing Activities Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Share Repurchase Program, February 2025 Share Repurchase Program, February 2025 [Member] Share Repurchase Program, February 2025 Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Company Selected Measure Amount Company Selected Measure Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent 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 Name Measure Name Maturities within one year Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Class of Stock [Line Items] Class of Stock [Line Items] Document Fiscal Period Focus Document Fiscal Period Focus Accrued contingent consideration in connection with acquisitions Acquisitions, Contingent Consideration Accrued But Not Yet Paid Asset Acquisitions and Business Combination, Contingent Consideration Accrued But Not Yet Paid Award Timing Method Award Timing Method [Text Block] Litigation Case [Domain] Litigation Case [Domain] Award Type [Axis] Award Type [Axis] Deferred revenue Contract with Customer, Liability, Noncurrent Total assets Assets Trading Symbol Trading Symbol Geographical [Domain] Geographical [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 Accrued expenses and other current liabilities Accrued Liabilities and Other Liabilities Entity Address, City or Town Entity Address, City or Town Cash flows from operating activities: Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] 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 Receivable Type [Axis] Receivable Type [Axis] Effect of exchange rate changes on cash, cash equivalents, and restricted cash Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Concentration Risk Type [Axis] Concentration Risk Type [Axis] Inventories Inventory Disclosure [Text Block] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Income Statement Location [Domain] Statement of Income Location, Balance [Domain] Litigation, Damages Type [Axis] Litigation, Damages Type [Axis] Litigation, Damages Type Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Assets, Fair Value Disclosure [Abstract] Assets, Fair Value Disclosure [Abstract] Classification of Investment [Axis] Classification of Investment [Axis] This element represents the general categories of investments, which may be classified as Unrestricted or Restricted. Entity Emerging Growth Company Entity Emerging Growth Company Common stock, dividend, declared (in dollars per share) Common Stock, Dividends, Per Share, Declared Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Compensatory Damages Compensatory Damages [Member] Compensatory Damages Level 2 Fair Value, Inputs, Level 2 [Member] 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. Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Common Stock, shares outstanding (in shares) Beginning Balance (in shares) Ending Balance (in shares) Common Stock, Shares, Outstanding Document Information [Table] Document Information [Table] PEO PEO [Member] Schedule of Product Sales Schedule of Collaborative Revenue Disaggregation of Revenue [Table Text Block] Marketable Securities, Based on Contractual Maturity Dates Investments Classified by Contractual Maturity Date [Table Text Block] U.S. UNITED STATES Changes in assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Retained Earnings Retained Earnings [Member] Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date 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 Statements of Cash Flows Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Statements of Operations Income Statement [Abstract] Income tax expense Income Tax Expense (Benefit) Purchases of marketable and other securities Payments to Acquire Marketable Securities Document Information [Line Items] Document Information [Line Items] Preferred Stock, shares issued (in shares) Preferred Stock, Shares Issued Intangible assets, net Intangible Assets, Net (Excluding Goodwill) Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Product and Service [Domain] Product and Service [Domain] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Customer concentration risk Customer Concentration Risk [Member] Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Indirect research and development expenses: Indirect Expense [Member] Indirect Expense Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] City Area Code City Area Code Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Legal Matters Commitments and Contingencies, Policy [Policy Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Lab supplies and other research and development costs Lab Supplies And Other Research And Development Costs [Member] Lab Supplies And Other Research And Development Costs Schedule of Accounts Receivable and Deferred Revenue Information Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Damages awarded Litigation Settlement, Gain Cash flows from investing activities: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Preferred Stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Subsequent Event Subsequent Event [Member] Reduction of SG&A expense Selling, General and Administrative Expenses [Member] Equity investments Equity Securities, FV-NI Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] PEO Total Compensation Amount PEO Total Compensation Amount EYLEA HD EYLEA HD [Member] EYLEA HD Equity Components [Axis] Equity Components [Axis] Rest Of World Non-US [Member] Reimbursement of commercialization-related expenses Reimbursement Of Commercialization-Related Expenses [Member] Reimbursement Of Commercialization-Related Expenses Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Concentration Risk [Table] Concentration Risk [Table] Trade accounts receivable Trade Accounts Receivable [Member] Net product sales Product [Member] Michael S. Brown, M.D. [Member] Michael S. Brown, M.D. Number of reportable segments Number of Reportable Segments Amortized Cost Basis Debt Securities, Available-for-Sale, Amortized Cost Other Performance Measure, Amount Other Performance Measure, Amount U.S. government and government agency obligations U.S. government and government agency obligations US Treasury and Government [Member] Restrictions on Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Entity Address, State or Province Entity Address, State or Province Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Security, Excluded EPS Calculation [Table] Dividends declared Dividends, Common Stock Total current liabilities Liabilities, Current Individual: Individual [Axis] (R&D expense) Reduction of R&D expense/(R&D expense) Research and Development Expense [Member] Net cash (used in) provided by investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Share Repurchase Program, April 2026 Share Repurchase Program, April 2026 [Member] Share Repurchase Program, April 2026 Document Fiscal Year Focus Document Fiscal Year Focus Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Project [Domain] Project [Domain] Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Entity Interactive Data Current Entity Interactive Data Current Legal Matters Legal Matters and Contingencies [Text Block] Equity [Abstract] Equity [Abstract] Segment Information Segment Reporting Disclosure [Text Block] 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] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Marketable securities Marketable Securities, Noncurrent Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Selling, general, and administrative Selling, General and Administrative Expense Deferred tax assets Deferred Income Tax Assets, Net Repurchases of Common Stock Stock Repurchased During Period, Value Capital expenditures Payments to Acquire Productive Assets Depreciation and amortization Depreciation, Depletion and Amortization Other noncurrent assets Other Assets, Noncurrent Customer [Domain] Customer [Domain] Entity Central Index Key Entity Central Index Key PEO Name PEO Name Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Sanofi Collaboration Agreement, Antibody Sanofi Collaboration Agreement, Antibody [Member] Sanofi Collaboration Agreement, Antibody [Member] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Statements of Comprehensive Income Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Arrangement Duration Trading Arrangement Duration Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Deferred revenue Contract with Customer, Liability, Current Segments [Axis] Segments [Axis] Increase in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Work-in-process Inventory, Work in Process, Net of Reserves Deferred costs Other Inventory, Net of Reserves Exercise Price Award Exercise Price Entity Filer Category Entity Filer Category Local Phone Number Local Phone Number Class of Stock [Domain] Class of Stock [Domain] Kathryn Guarini, Ph.D. [Member] Kathryn Guarini, Ph.D. Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Subsequent Event Type [Axis] Subsequent Event Type [Axis] ASSETS Assets [Abstract] Long-term debt Long-Term Debt, Excluding Current Maturities Underlying Security Market Price Change Underlying Security Market Price Change, Percent Fair Value Measurements Fair Value Disclosures [Text Block] Stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Equity, Attributable to Parent [Abstract] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Entity Address, Address Line One Entity Address, Address Line One Total cost of shares Treasury Stock, Value, Acquired, Cost Method Research and development Research and Development Expense Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] 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 Fair Value as of Grant Date Award Grant Date Fair Value Entity Registrant Name Entity Registrant Name Nature of Expense [Axis] Nature of Expense [Axis] Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table] Earnings Per Share, Diluted, by Common Class, Including Two-Class Method [Table] Total adjustments Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity Effect of dilutive securities (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Total Expenses Costs and Expenses Document Quarterly Report Document Quarterly Report Total Assets, Fair Value Disclosure Long-term debt, fair value Long-Term Debt, Fair Value Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Securities owned not readily marketable Equity Securities without Readily Determinable Fair Value, Amount Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Restatement Determination Date: Restatement Determination Date [Axis] Issuance of Common Stock for equity awards granted under long-term incentive plans Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Non-PEO NEO Non-PEO NEO [Member] Other Proceeds from (Payment for) Other Financing Activity Unrealized Gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Name Trading Arrangement, Individual Name Award Type [Domain] Award Type [Domain] Equity Awards Adjustments Equity Awards Adjustments [Member] Other, net Other Noncash Income (Expense) Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Restricted Restricted [Member] Restricted [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Compensation Amount Outstanding Recovery Compensation Amount Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Certificates of deposit Certificates of deposit Certificates of Deposit [Member] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Share Repurchase Program [Axis] Share Repurchase Program [Axis] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Name Awards Close in Time to MNPI Disclosures, Individual Name Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Revenues: Revenues [Abstract] Customer B Customer B [Member] Customer B Stock-based compensation charges APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Financial Instruments [Domain] Financial Instruments [Domain] Litigation Case [Axis] Litigation Case [Axis] Segments [Domain] Segments [Domain] Income Statement Location [Axis] Statement of Income Location, Balance [Axis] Marketable Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Clinical manufacturing costs Clinical And Manufacturing Costs [Member] Clinical And Manufacturing Costs Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Cost of collaboration and contract manufacturing Collaboration and Contract Manufacturing [Member] Collaboration and Contract Manufacturing [Member] Decrease (increase) in inventories Increase (Decrease) in Inventories Recently Issued Accounting Standards Accounting Standards Update and Change in Accounting Principle [Table Text Block] Inventories Total Inventories Inventory, Net Minimum Minimum [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Company Selected Measure Name Company Selected Measure Name Sovereign bonds Sovereign bonds Sovereign Debt Securities [Member] Preferred Stock, par value $.01 per share; 30.0 shares authorized; shares issued and outstanding - none Preferred Stock, Value, Issued Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Accounts payable Accounts Payable, Current Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] All Executive Categories All Executive Categories [Member] Finished goods Inventory, Finished Goods, Net of Reserves Common stock Common Stock, Value, Issued Gross product revenue Gross Product Revenue [Member] Gross Sales Revenue [Member] Weighted average shares outstanding - diluted (in shares) Weighted average shares - diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Lynozyfic Lynozyfic [Member] Lynozyfic Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Litigation, Damages Type [Domain] Litigation, Damages Type [Domain] Litigation, Damages Type [Domain] Entity Small Business Entity Small Business Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Preferred Stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Document Transition Report Document Transition Report 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 Direct research and development expenses Direct Expense [Member] Direct Expense Schedules of Sales to Customers as Percentage of Total Gross Product Revenue Schedules of Concentration of Risk, by Risk Factor [Table Text Block] Underlying Securities Award Underlying Securities Amount Concentration Risk [Line Items] Concentration Risk [Line Items] Equity Component [Domain] Equity Component [Domain] Document Period End Date Document Period End Date Percentage share of profits to reimburse collaborating party Percentage Of Quarterly Profits Required To Be Paid For Reimbursement Of Development Costs Percentage Of Quarterly Profits Required To Be Paid For Reimbursement Of Development Costs Project [Axis] Project [Axis] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount EYLEA HD And EYLEA EYLEA HD And EYLEA [Member] EYLEA HD And EYLEA Income Taxes Income Tax Disclosure [Text Block] Class A Stock Common Class A [Member] Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Document Type Document Type Level 3 Fair Value, Inputs, Level 3 [Member] Net Income Per Share Earnings Per Share [Text Block] Name Outstanding Recovery, Individual Name Additional paid-in capital Additional Paid in Capital Product and Service [Axis] Product and Service [Axis] Proceeds from issuance of Common Stock Proceeds from Issuance of Common Stock Regeneron vs. Amgen Regeneron vs. Amgen [Member] Regeneron vs. Amgen Revenues Revenue from Contract with Customer, Excluding Assessed Tax All Individuals All Individuals [Member] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Name Forgone Recovery, Individual Name Total current assets Assets, Current Statistical Measurement [Axis] Statistical Measurement [Axis] Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Share repurchase program, authorized amount Share Repurchase Program, Authorized, Amount Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Payments in connection with Common Stock tendered for employee tax obligations Payment, Tax Withholding, Share-Based Payment Arrangement 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] Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Marketable securities Marketable Securities, Current Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Share Repurchase Program [Domain] Share Repurchase Program [Domain] Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Current liabilities: Liabilities, Current [Abstract] Geographical [Axis] Geographical [Axis] Other products Other Products [Member] Other Products Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Level 1 Fair Value, Inputs, Level 1 [Member] Net income per share - diluted (in dollars per share) Earnings Per Share, Diluted Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Accounts receivable, net Accounts Receivable, after Allowance for Credit Loss, Current Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Title of 12(b) Security Title of 12(b) Security Reimbursement of research and development expenses by collaborators Research And Development Expense, Reimbursements Research And Development Expense, Reimbursements Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Treasury stock (in shares) Beginning Balance, treasury (in shares) Ending Balance, treasury (in shares) Treasury Stock, Common, Shares Earnings Per Share [Abstract] Earnings Per Share [Abstract] Total other income (expense) Nonoperating Income (Expense) Investments, Debt and Equity Securities [Abstract] Investments, Debt and Equity Securities [Abstract] Reimbursement of R&D expenses, net of Regeneron's obligation for its share of Bayer R&D expenses Regeneron's Obligation Of Research And Development Expenses, Net of Reimbursement Of Research And Development Expenses [Member] Regeneron's Obligation Of Research And Development Expenses, Net of Reimbursement Of Research And Development Expenses Antidilutive Securities Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Increase in deferred revenue Increase (Decrease) in Contract with Customer, Liability Punitive Damages Punitive Damages [Member] Punitive Damages Equity securities Equity Securities, FV-NI, Noncurrent 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. Number of shares (in shares) Treasury Stock, Shares, Acquired Corporate bonds Corporate bonds Corporate Bond Securities [Member] Reimbursement for manufacturing of commercial supplies Reimbursement for manufacturing of commercial supplies Reimbursement For Manufacturing Of Commercial Supplies [Member] Reimbursement For Manufacturing Of Commercial Supplies [Member] Award Timing Disclosures [Line Items] Schedule of Inventory Schedule of Inventory, Current [Table Text Block] Joseph L. Goldstein, M.D. [Member] Joseph L. Goldstein, M.D. Number of counts ruled in favor of plaintiff Number Of Counts Ruled In Favor Of Plaintiff Number Of Counts Ruled In Favor Of Plaintiff Unrealized (loss) gain on debt securities OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Property, plant, and equipment, net Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization Stockholders' Equity Equity [Text Block] Gains on marketable and other securities, net Marketable and Other Securities, Gain (Loss) Marketable and Other Securities, Gain (Loss) Net income Net income Net income - basic and diluted Net Income (Loss) Attributable to Parent 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. Expiration Date Trading Arrangement Expiration Date Collaboration revenue Collaboration Revenue [Member] Collaboration Revenue Net unrealized gains (losses) recognized on investments still held as of period end date Equity Securities, FV-NI, Unrealized Gain (Loss) 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 Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] 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. Preferred Stock, shares authorized (in shares) Preferred Stock, Shares Authorized Repurchases of Common Stock Payments for Repurchase of Common Stock Adoption Date Trading Arrangement Adoption Date Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Decrease in accounts receivable Increase (Decrease) in Accounts Receivable Entity Current Reporting Status Entity Current Reporting Status Customer [Axis] Customer [Axis] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Income from operations Operating Income (Loss) Retained earnings Retained Earnings (Accumulated Deficit) Schedule of Shares Repurchased Class of Treasury Stock [Table Text Block] Financial Instrument [Axis] Financial Instrument [Axis] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Executive Category: Executive Category [Axis] Bayer Bayer Collaboration Agreement [Member] Bayer Collaboration Agreement [Member] Finance lease liabilities Finance Lease, Liability, Current Research And Development Expense, Type [Axis] Research And Development Expense, Type [Axis] Research And Development Expense, Type Current Fiscal Year End Date Current Fiscal Year End Date Class of Stock [Axis] Class of Stock [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Other income (expense), net Other Nonoperating Income (Expense) Statement [Table] Statement [Table] Adjustments to reconcile net income to net cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Collaboration, License, and Other Agreements Collaborative Arrangement Disclosure [Text Block] Cash flows from financing activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Deferred revenue Contract with Customer, Liability Schedule of Assets Measured at Fair Value On a Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Sales or maturities of marketable and other securities Proceeds from Sale and Maturity of Marketable Securities Finance lease liabilities Finance Lease, Liability, Noncurrent Interim Financial Statements Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Cash and Cash Equivalents [Abstract] Stock options (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount All Adjustments to Compensation All Adjustments to Compensation [Member] Research And Development Expense, Type [Domain] Research And Development Expense, Type [Domain] Research And Development Expense, Type [Domain] Amendment Flag Amendment Flag Treasury Stock, at cost; 34.7 shares in 2026 and 33.7 shares in 2025 Treasury Stock, Common, Value Termination Date Trading Arrangement Termination Date Net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Measure: Measure [Axis] Reportable Segment Reportable Segment [Member] Reportable Segment Raw materials Inventory, Raw Materials, Net of Reserves Receivable [Domain] Receivable [Domain] Weighted average shares outstanding - basic (in shares) Weighted average shares - basic (in shares) Weighted Average Number of Shares Outstanding, Basic Remaining authorized repurchase amount Share Repurchase Program, Remaining Authorized, Amount Statement of Cash Flows Cash Flow, Supplemental Disclosures [Text Block] Cost of goods sold, collaboration and contract manufacturing Cost of Product and Service Sold Basic and Diluted Net Income (Loss) Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Segment Reporting [Abstract] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Other income (expense): Nonoperating Income (Expense) [Abstract] Entity Tax Identification Number Entity Tax Identification Number Expenses: Costs and Expenses [Abstract] Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Common Stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common Stock, shares issued (in shares) Common Stock, Shares, Issued Marion McCourt [Member] Marion McCourt Dividends paid Payments of Dividends Interest expense Interest Expense, Nonoperating Trading Arrangement: Trading Arrangement [Axis] Total Shareholder Return Amount Total Shareholder Return Amount Insider Trading Arrangements [Line Items] Security Exchange Name Security Exchange Name Interim Period, Costs Not Allocable [Domain] Interim Period, Costs Not Allocable [Domain] Other revenue Product and Service, Other [Member] Total liabilities Liabilities Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Accrued capital expenditures Capital Expenditures Incurred but Not yet Paid Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Repurchases of Common Stock (in shares) Stock Repurchased During Period, Shares Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Statement [Line Items] Statement [Line Items] Asset-backed securities Asset-Backed Securities [Member] Acquired in-process research and development Acquired In-Process Research and Development Acquired In-Process Research and Development Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalent Deferred income taxes Increase (Decrease) in Deferred Income Taxes Common Stock Common Stock Common Stock Common Stock [Member] Fair Value Total Available-for-sale debt securities Debt Securities, Available-for-Sale Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Regeneron's obligation for its share of Sanofi R&D expenses, net of reimbursement of R&D expenses Reimbursement Of Research And Development Expenses, Net Of Obligation For Share Of R&D Expenses [Member] Reimbursement Of Research And Development Expenses, Net Of Obligation For Share Of R&D Expenses Net (decrease) increase in cash, cash equivalents, and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation