Payroll and benefits Payroll And Benefits [Member] Payroll And Benefits 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] Occupancy and other operating costs Occupancy And Other Operating Costs [Member] Occupancy And Other Operating Costs Statistical Measurement [Domain] Statistical Measurement [Domain] Remaining authorized repurchase amount Share Repurchase Program, Remaining Authorized, Amount Unrealized Losses Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax ELYEA HD And EYLEA ELYEA HD And EYLEA [Member] ELYEA HD And EYLEA Cover [Abstract] Cover [Abstract] 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 Customer A Customer A [Member] Customer A Legal Matters Legal Costs, Policy [Policy Text Block] Trading Symbol Trading Symbol Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] All Trading Arrangements All Trading Arrangements [Member] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Non-NEOs Non-NEOs [Member] Basic and Diluted Net Income (Loss) Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Common stock, dividend, declared (in dollars per share) Common Stock, Dividends, Per Share, Declared Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [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. Class A Stock Common Class A [Member] Share Repurchase Program, April 2024 Share Repurchase Program, April 2024 [Member] Share Repurchase Program, April 2024 Pay vs Performance Disclosure [Line Items] Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Decrease in accounts receivable Increase (Decrease) in Accounts Receivable Interim Financial Statements Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Fair Value Measurements Fair Value Disclosures [Text Block] Unrealized gain on debt securities OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Award Timing Disclosures [Line Items] Other Performance Measure, Amount Other Performance Measure, Amount Legal Matters Legal Matters and Contingencies [Text Block] Common Stock, shares outstanding (in shares) Beginning Balance (in shares) Ending Balance (in shares) Common Stock, Shares, Outstanding Sales or maturities of marketable and other securities Proceeds from Sale and Maturity of Marketable Securities Other revenue Product and Service, Other [Member] Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Total adjustments Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities Deferred revenue Contract with Customer, Liability, Current U.S. UNITED STATES Other noncurrent assets Other Assets, Noncurrent Entity Tax Identification Number Entity Tax Identification Number Number of shares (in shares) Treasury Stock, Shares, Acquired Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Corporate bonds Corporate bonds Corporate bonds Corporate Bond Securities [Member] Reduction of SG&A expense Selling, General and Administrative Expenses [Member] Receivable Type [Axis] Receivable Type [Axis] Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Treasury Stock Treasury Stock, Common [Member] Evkeeza Evkeeza [Member] Evkeeza Project [Domain] Project [Domain] Equity Components [Axis] Equity Components [Axis] Award Timing Method Award Timing Method [Text Block] Payments for Libtayo intangible asset Payments To Acquire Intangible Assets1 Payments To Acquire Intangible Assets1 Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Fair Value Total Available-for-sale debt securities Debt Securities, Available-for-Sale Measurement Frequency [Axis] Measurement Frequency [Axis] Regeneron's share of profits Share Of Profit (Losses) [Member] Share Of Profit (Losses) Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Insider Trading Policies and Procedures [Line Items] Libtayo LIBTAYO Net Product Sales [Member] LIBTAYO Net Product Sales [Member] Total Expenses Costs and Expenses Receivable [Domain] Receivable [Domain] Adjustment to Compensation, Amount Adjustment to Compensation Amount Compensation Amount Outstanding Recovery Compensation Amount 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] Entity Small Business Entity Small Business Company Selected Measure Amount Company Selected Measure Amount Geographical [Axis] Geographical [Axis] Tabular List, Table Tabular List [Table 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. Level 3 Fair Value, Inputs, Level 3 [Member] Share Repurchase Program, February 2025 Share Repurchase Program, February 2025 [Member] Share Repurchase Program, February 2025 Repurchases of Common Stock Stock Repurchased During Period, Value 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] Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Stock options (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount 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 Number of shareholder derivative complaints filed Number Of Shareholder Derivative Complaints Filed Number Of Shareholder Derivative Complaints Filed Total Debt Securities, Available-for-Sale, Unrealized Loss Position 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 Equivalents, Restricted Cash, and Restricted Cash Equivalents Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Accounts and Financing Receivables [Table] 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 Current assets: Assets, Current [Abstract] Payments in connection with Common Stock tendered for employee tax obligations Payment, Tax Withholding, Share-Based Payment Arrangement Share repurchase program, authorized amount Share Repurchase Program, Authorized, Amount Inventories Inventory Disclosure [Text Block] Treasury stock (in shares) Beginning Balance, treasury (in shares) Ending Balance, treasury (in shares) Treasury Stock, Common, Shares Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Product and Service [Domain] Product and Service [Domain] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-Sale [Table] Stock options Share-Based Payment Arrangement, Option [Member] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Marketable securities Marketable Securities, Current 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 Other Proceeds from (Payments for) Other Financing Activities Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Security, Excluded EPS Calculation [Table] Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Preferred Stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Security Exchange Name Security Exchange Name Marketable Securities, Based on Contractual Maturity Dates Investments Classified by Contractual Maturity Date [Table Text Block] Award Type [Axis] Award Type [Axis] Classification of Investment [Axis] Classification of Investment [Axis] This element represents the general categories of investments, which may be classified as Unrestricted or Restricted. Work-in-process Inventory, Work in Process, Net of Reserves 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. Total liabilities Liabilities Common stock, dividends per share, paid (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Statements of Comprehensive Income Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Common Stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Available-for-sale Debt Securities Debt Securities, Available-for-Sale [Table Text Block] Research and development Research and Development Expense Expiration Date Trading Arrangement Expiration Date Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Total Shareholder Return Amount Total Shareholder Return Amount Common Stock, shares issued (in shares) Common Stock, Shares, Issued Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Concentration risk, percentage Concentration Risk, Percentage Total Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss Schedule of Shares Repurchased Class of Treasury Stock [Table Text Block] Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] (R&D expense) Research and Development Expense [Member] Common Stock, shares authorized (in shares) Common Stock, Shares Authorized Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Weighted average shares outstanding - diluted (in shares) Weighted average shares - diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Total stockholders' equity Beginning Balance Ending Balance Equity, Attributable to Parent Summary of Non-Cash Investing and Financing Activities Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Collaboration, License, and Other Agreements Collaborative Arrangement Disclosure [Text Block] Indirect research and development expenses: Indirect Expense [Member] Indirect Expense Maturities within one year Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Interest expense Interest Expense, Nonoperating Concentration Risk Type [Domain] Concentration Risk Type [Domain] Selling, general, and administrative Selling, General and Administrative Expense Other comprehensive income, net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Measured on a recurring basis Fair Value, Recurring [Member] 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 Accounts receivable, net Accounts Receivable, after Allowance for Credit Loss, Current Net product sales Product [Member] 12 Months or Greater Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Document Fiscal Period Focus Document Fiscal Period Focus All Executive Categories All Executive Categories [Member] Effect of dilutive securities (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] ASSETS Assets [Abstract] Restricted cash included in Other current assets Restricted Cash, Current Document Type Document Type Commercial paper Commercial paper Commercial Paper [Member] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Schedule of Significant Expenses Schedule of Segment Reporting Information, by Segment [Table Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Purchases of marketable and other securities Payments to Acquire Marketable Securities Amortized Cost Basis Debt Securities, Available-for-Sale, Amortized Cost Reimbursement of commercialization-related expenses Reimbursement Of Commercialization-Related Expenses [Member] Reimbursement Of Commercialization-Related Expenses Schedule of Accounts Receivable and Deferred Revenue Information Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Maximum Maximum [Member] Fair Value Debt Securities, Available-for-Sale [Abstract] Deferred revenue Contract with Customer, Liability Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Project [Axis] Project [Axis] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Rest Of World Non-US [Member] Accounts payable Accounts Payable, Current Revenues: Revenues [Abstract] Current Fiscal Year End Date Current Fiscal Year End Date Statistical Measurement [Axis] Statistical Measurement [Axis] PEO Name PEO Name 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 Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Award Type [Domain] Award Type [Domain] Name Outstanding Recovery, Individual Name Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Issuance of Common Stock for equity awards granted under long-term incentive plans (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Antidilutive Securities Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Deferred tax assets Deferred Income Tax Assets, Net Non-PEO NEO Non-PEO NEO [Member] (R&D expense) Research And Development Expenses And Reduction of Research And Development Expense [Member] Research And Development Expenses And Reduction of Research And Development Expense Accrued expenses and other current liabilities Accrued Liabilities and Other Liabilities Additional Paid-in Capital Additional Paid-in Capital [Member] Finance lease liabilities Finance Lease, Liability, Noncurrent Award Timing Predetermined Award Timing Predetermined [Flag] Class of Stock [Line Items] Class of Stock [Line Items] Restricted cash included in Other noncurrent assets Restricted Cash, Noncurrent Recently Issued Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Forecast Forecast [Member] Net income per share - diluted (in dollars per share) Earnings Per Share, Diluted Class of Stock [Axis] Class of Stock [Axis] Interim Period, Costs Not Allocable [Domain] Interim Period, Costs Not Allocable [Domain] Name Measure Name Entity Interactive Data Current Entity Interactive Data Current Increase in deferred revenue Increase (Decrease) in Contract with Customer, Liability Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Preferred Stock, shares issued (in shares) Preferred Stock, Shares Issued Customer [Axis] Customer [Axis] 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] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Asset-backed securities Asset-Backed Securities [Member] Stock-based compensation expense Share-Based Payment Arrangement, Noncash Expense Income tax expense (benefit) Income Tax Expense (Benefit) Other income (expense): Nonoperating Income (Expense) [Abstract] Sanofi Collaboration Agreement, Antibody Sanofi Collaboration Agreement, Antibody [Member] Sanofi Collaboration Agreement, Antibody [Member] Equity investments Equity Securities, FV-NI Revenues Revenue from Contract with Customer, Excluding Assessed Tax Total other income (expense) Nonoperating Income (Expense) Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Net cash provided by (used in) in investing activities Net Cash Provided by (Used in) Investing Activities Income from operations Operating Income (Loss) Number of reportable segments Number of Reportable Segments Total liabilities and stockholders' equity Liabilities and Equity Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] All Adjustments to Compensation All Adjustments to Compensation [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Increase in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Additional paid-in capital Additional Paid in Capital Marketable securities Marketable Securities, Noncurrent Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Dividends paid Payments of Dividends Underlying Security Market Price Change Underlying Security Market Price Change, Percent Scenario [Domain] Scenario [Domain] Individual: Individual [Axis] 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 Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] 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] Inventories Total Inventories Inventory, Net Product and Service [Axis] Product and Service [Axis] Entity Address, State or Province Entity Address, State or Province Statement [Line Items] Statement [Line Items] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Financial Instruments [Domain] Financial Instruments [Domain] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] LIABILITIES AND STOCKHOLDERS' EQUITY LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Minimum Minimum [Member] Restatement Determination Date Restatement Determination Date Adoption Date Trading Arrangement Adoption Date Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Deferred revenue Contract with Customer, Liability, Noncurrent Concentration Risk [Table] Concentration Risk [Table] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Segments [Axis] Segments [Axis] 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] Exercise Price Award Exercise Price Unrealized Losses Debt Securities, Available-for-Sale, Unrealized Loss Position [Abstract] Net Income Per Share Earnings Per Share [Text Block] Arrangement Duration Trading Arrangement Duration Trade accounts receivable Trade Accounts Receivable [Member] Expenses: Costs and Expenses [Abstract] Stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Equity, Attributable to Parent [Abstract] Less than 12 Months Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months Share Repurchase Program, January 2023 Share Repurchase Program, January 2023 [Member] Share Repurchase Program, January 2023 Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Restricted Restricted [Member] Restricted [Member] 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] Inmazeb Inmazeb [Member] Inmazeb Segments [Domain] Segments [Domain] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Recently Issued Accounting Standards Accounting Standards Update and Change in Accounting Principle [Table Text Block] All Individuals All Individuals [Member] PEO PEO [Member] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Name Trading Arrangement, Individual Name Other income (expense), net Other Nonoperating Income (Expense) Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Intangible assets, net Intangible Assets, Net (Excluding Goodwill) Customer B Customer B [Member] Customer B Unrealized Gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Treasury Stock, at cost; 29.7 shares in 2025 and 28.2 shares in 2024 Treasury Stock, Common, Value Schedules of Sales to Customers as Percentage of Total Gross Product Revenue Schedules of Concentration of Risk, by Risk Factor [Table Text Block] Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Clinical manufacturing costs Clinical And Manufacturing Costs [Member] Clinical And Manufacturing Costs Assets, Fair Value Disclosure [Abstract] Assets, Fair Value Disclosure [Abstract] Cost of collaboration and contract manufacturing Collaboration and Contract Manufacturing [Member] Collaboration and Contract Manufacturing [Member] 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] Cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Local Phone Number Local Phone Number Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Repurchases of Common Stock (in shares) Stock Repurchased During Period, Shares Changes in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] PEO Total Compensation Amount PEO Total Compensation Amount Gross product revenue Gross Product Revenue [Member] Gross Sales Revenue [Member] Income Statement Location [Axis] Statement of Income Location, Balance [Axis] Share Repurchase Program [Domain] Share Repurchase Program [Domain] Common Stock Common Stock Common Stock Common Stock [Member] Measure: Measure [Axis] Issuance of Common Stock for equity awards granted under long-term incentive plans Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Preferred Stock, shares authorized (in shares) Preferred Stock, Shares Authorized Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Direct research and development expenses Direct Expense [Member] Direct Expense Entity Emerging Growth Company Entity Emerging Growth Company Segment Reporting [Abstract] 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 Entity Central Index Key Entity Central Index Key Scenario [Axis] Scenario [Axis] 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 Schedule of Inventory Schedule of Inventory, Current [Table Text Block] Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Sovereign bonds Sovereign bonds Sovereign Debt Securities [Member] Stockholders' Equity Equity [Text Block] (Decrease) increase in accounts payable, accrued expenses, and other liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Equity Component [Domain] Equity Component [Domain] Preferred Stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Financial Instrument [Axis] Financial Instrument [Axis] Segment Information Segment Reporting Disclosure [Text Block] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Stock-based compensation charges APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Restricted stock awards and restricted stock units Restricted Stock [Member] Entity Shell Company Entity Shell Company Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Title Trading Arrangement, Individual Title Statement [Table] Statement [Table] Measurement Frequency [Domain] Measurement Frequency [Domain] City Area Code City Area Code Current liabilities: Liabilities, Current [Abstract] Contingent consideration Business Combination, Contingent Consideration, Liability Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Capital expenditures Payments to Acquire Productive Assets Level 1 Fair Value, Inputs, Level 1 [Member] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Total current assets Assets, Current Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Repurchases of Common Stock Payments for Repurchase of Common Stock Document Information [Line Items] Document Information [Line Items] Long-term debt Long-Term Debt, Excluding Current Maturities Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Securities owned not readily marketable Equity Securities without Readily Determinable Fair Value, Amount Income Taxes Income Tax Disclosure [Text Block] Earnings Per Share [Abstract] Earnings Per Share [Abstract] Equity [Abstract] Equity [Abstract] Raw materials Inventory, Raw Materials, Net of Reserves Retained earnings Retained Earnings (Accumulated Deficit) Reimbursement of research and development expenses by collaborators Research And Development Expense, Reimbursements Research And Development Expense, Reimbursements Class of Stock [Domain] Class of Stock [Domain] Increase in inventories Increase (Decrease) in Inventories Net unrealized gains (losses) Equity Securities, FV-NI, Unrealized Gain (Loss) Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Equity Awards Adjustments Equity Awards Adjustments [Member] Net cash (used in) provided by financing activities Net Cash Provided by (Used in) Financing Activities Underlying Securities Award Underlying Securities Amount Marketable Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Regeneron's obligation for its share of Bayer R&D expenses, net of reimbursement of 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 Deferred costs Other Inventory, Net of Reserves Amendment Flag Amendment Flag Long-term debt, fair value Long-Term Debt, Fair Value Entity Registrant Name Entity Registrant Name 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. Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Depreciation and amortization Depreciation, Depletion and Amortization Restrictions on Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] (Loss) gain on foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent ELYEA HD ELYEA HD [Member] ELYEA HD Fair Value as of Grant Date Award Grant Date Fair Value Customer concentration risk Customer Concentration Risk [Member] Statement of Cash Flows Cash Flow, Supplemental Disclosures [Text Block] Level 2 Fair Value, Inputs, Level 2 [Member] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] 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] Geographical [Domain] Geographical [Domain] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Schedule of Product Sales Schedule of Collaborative Revenue Disaggregation of Revenue [Table Text Block] Joseph L. Goldstein, M.D. [Member] Joseph L. Goldstein, M.D. Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date: Restatement Determination Date [Axis] Title of 12(b) Security Title of 12(b) Security Concentration Risk Type [Axis] Concentration Risk Type [Axis] Common stock Common Stock, Value, Issued (Gains) losses on marketable and other securities, net Marketable and Other Securities, Gain (Loss) Marketable and Other Securities, Gain (Loss) 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. Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Collaboration revenue Collaboration Revenue [Member] Collaboration Revenue Equity securities Equity Securities, FV-NI, Noncurrent Certificates of deposit Certificates of deposit Certificates of Deposit [Member] 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] 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 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. Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [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] Concentration Risk [Line Items] Concentration Risk [Line Items] Preferred Stock, par value $.01 per share; 30.0 shares authorized; shares issued and outstanding - none Preferred Stock, Value, Issued Net income per share - basic (in dollars per share) Earnings Per Share, Basic Proceeds from issuance of Common Stock Proceeds from Issuance of Common Stock Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Property, plant, and equipment, net Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization Accrued capital expenditures Capital Expenditures Incurred but Not yet Paid Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Bayer Bayer Collaboration Agreement [Member] Bayer Collaboration Agreement [Member] Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Research And Development Expense, Type [Axis] Research And Development Expense, Type [Axis] Research And Development Expense, Type Fair Value and Unrealized Losses of Marketable Securities Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value [Table Text Block] Schedule of Stock by Class [Table] Stock, Class of Stock [Table] Total current liabilities Liabilities, Current 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] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Total assets Assets Cost of goods sold, collaboration and contract manufacturing Cost of Goods and Services Sold 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] Cash and Cash Equivalents [Abstract] Other noncurrent liabilities Other Liabilities, Noncurrent Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Termination Date Trading Arrangement Termination Date 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] Research And Development Expense, Type [Domain] Research And Development Expense, Type [Domain] Research And Development Expense, Type [Domain] Entity Address, City or Town Entity Address, City or Town 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 Reportable Segment Reportable Segment [Member] Reportable Segment Net income Net income Net income - basic and diluted Net Income (Loss) Attributable to Parent Other operating expense (income), net Other Operating Income (Expense), Net Trading Arrangement: Trading Arrangement [Axis] Investments, Debt and Equity Securities [Abstract] Investments, Debt and Equity Securities [Abstract] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] 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] Entity File Number Entity File Number Liabilities, Fair Value Disclosure [Abstract] Liabilities, Fair Value Disclosure [Abstract] Product Sales Revenue from Contract with Customer [Text Block] Document Fiscal Year Focus Document Fiscal Year Focus Statements of Operations Income Statement [Abstract] Entity Address, Address Line One Entity Address, Address Line One Total cost of shares Treasury Stock, Value, Acquired, Cost Method Effect of exchange rate changes on cash, cash equivalents, and restricted cash Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Continuing Operations Dividends declared Dividends, Common Stock Total assets Assets, Fair Value Disclosure Name Forgone Recovery, Individual Name Document Period End Date Document Period End Date Deferred income taxes Increase (Decrease) in Deferred Income Taxes Finished goods Inventory, Finished Goods, Net of Reserves Other non-cash items, net Other Noncash Income (Expense) Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Insider Trading Arrangements [Line Items] Inventory Disclosure [Abstract] Inventory Disclosure [Abstract] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Adjustment to Compensation: Adjustment to Compensation [Axis] Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Document Transition Report Document Transition Report Document Quarterly Report Document Quarterly Report Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Customer [Domain] Customer [Domain] Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Current Reporting Status Entity Current Reporting Status Retained Earnings Retained Earnings [Member] Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Weighted average shares outstanding - basic (in shares) Weighted average shares - basic (in shares) Weighted Average Number of Shares Outstanding, Basic Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] 12 Months or Greater Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Document Information [Table] Document Information [Table] Nature of Expense [Axis] Nature of Expense [Axis] Acquired in-process research and development Acquired In-Process Research and Development Acquired In-Process Research and Development Share Repurchase Program, April 2024 And Febraury 2025 Share Repurchase Program, April 2024 And Febraury 2025 [Member] Share Repurchase Program, April 2024 And Febraury 2025 Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Executive Category: Executive Category [Axis] Name Awards Close in Time to MNPI Disclosures, Individual Name Less than 12 Months Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Entity Filer Category Entity Filer Category 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 Income Statement Location [Domain] Statement of Income Location, Balance [Domain] Company Selected Measure Name Company Selected Measure Name