Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Trading Arrangement: Trading Arrangement [Axis] Payroll and benefits Payroll And Benefits [Member] Payroll And Benefits Title of 12(b) Security Title of 12(b) Security Occupancy and other operating costs Occupancy And Other Operating Costs [Member] Occupancy And Other Operating Costs Subsequent Event Subsequent Event [Member] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-Sale [Table] Document Fiscal Year Focus Document Fiscal Year Focus Adjustment to Compensation, Amount Adjustment to Compensation Amount Financial Instrument [Axis] Financial Instrument [Axis] Customer A Customer A [Member] Customer A Customer [Axis] Customer [Axis] Segment Reporting [Abstract] Common stock Common Stock, Value, Issued Payments in connection with Common Stock tendered for employee tax obligations Payment, Tax Withholding, Share-Based Payment Arrangement Nature of Expense [Axis] Nature of Expense [Axis] Restatement Determination Date Restatement Determination Date 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. Number of counts submitted Number Of Counts Submitted Number Of Counts Submitted U.S. government and government agency obligations U.S. government and government agency obligations US Treasury and Government [Member] Amendment Flag Amendment Flag Current liabilities: Liabilities, Current [Abstract] Project [Axis] Project [Axis] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Unrealized Losses Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Asset-backed securities Asset-Backed Securities [Member] Available-for-sale Debt Securities Debt Securities, Available-for-Sale [Table Text Block] Deferred income taxes Increase (Decrease) in Deferred Income Taxes Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Entity Address, State or Province Entity Address, State or Province Gain on foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent PEO Total Compensation Amount PEO Total Compensation Amount Common Stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Assets, Fair Value Disclosure [Abstract] Assets, Fair Value Disclosure [Abstract] Cash and Cash Equivalents [Abstract] Intangible assets, net Intangible Asset, Excluding Goodwill, after Accumulated Amortization Share Repurchase Program [Domain] Share Repurchase Program [Domain] Weighted average shares outstanding - basic (in shares) Weighted average shares - basic (in shares) Weighted Average Number of Shares Outstanding, Basic Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Number of reportable segments Number of Reportable Segments Total current liabilities Liabilities, Current Work-in-process Inventory, Work in Process, Net of Reserves 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 Concentration Risk [Table] Concentration Risk [Table] Statements of Comprehensive Income Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Entity Address, City or Town Entity Address, City or Town Summary of Non-Cash Investing and Financing Activities Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Payments for intangible assets Payments To Acquire Intangible Assets1 Payments To Acquire Intangible Assets1 Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Regeneron's share of profits Share Of Profit (Losses) [Member] Share Of Profit (Losses) Document Information [Line Items] Document Information [Line Items] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Libtayo LIBTAYO Net Product Sales [Member] LIBTAYO Net Product Sales [Member] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Net product sales Product [Member] Class of Stock [Axis] Class of Stock [Axis] Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Level 2 Fair Value, Inputs, Level 2 [Member] Receivable [Domain] Receivable [Domain] Other income (expense): Nonoperating Income (Expense) [Abstract] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] 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. U.S. UNITED STATES Subsequent Event Type [Axis] Subsequent Event Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Axis] 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 Recently Issued Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Litigation Case [Axis] Litigation Case [Axis] Accrued capital expenditures Capital Expenditures Incurred but Not yet Paid Increase (decrease) in deferred revenue Increase (Decrease) in Contract with Customer, Liability Schedule of Significant Expenses Segment Reporting [Table Text Block] Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent 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 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 Document Period End Date Document Period End Date Changes in assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Net cash used in investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Preferred Stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Stockholders' Equity Equity [Text Block] Expenses: Costs and Expenses [Abstract] Security Exchange Name Security Exchange Name Treasury Stock, at cost; 36.4 shares in 2026 and 33.7 shares in 2025 Treasury Stock, Common, Value Statement of Cash Flows Cash Flow, Supplemental Disclosures [Text Block] Purchases of marketable and other securities Payments to Acquire Marketable Securities Accumulated other comprehensive (loss) income Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Shell Company Entity Shell Company Litigation, Damages Type [Axis] Litigation, Damages Type [Axis] Litigation, Damages Type Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [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. Net Income Per Share Earnings Per Share [Text Block] Name Outstanding Recovery, Individual Name Earnings Per Share [Abstract] Earnings Per Share [Abstract] Sales or maturities of marketable and other securities Proceeds from Sale and Maturity of Marketable Securities Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Document Fiscal Period Focus Document Fiscal Period Focus Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Total liabilities Liabilities Trading Symbol Trading Symbol Compensatory Damages Compensatory Damages [Member] Compensatory Damages Geographical [Domain] Geographical [Domain] 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] Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Company Selected Measure Name Company Selected Measure Name Restrictions on Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Concentration Risk [Line Items] Concentration Risk [Line Items] Cash flows from operating activities: Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Compensation Amount Outstanding Recovery Compensation Amount Individual: Individual [Axis] Weighted average shares outstanding - diluted (in shares) Weighted average shares - diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Entity Emerging Growth Company Entity Emerging Growth Company Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Property, plant, and equipment, net Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization Commercial paper Commercial paper Commercial Paper [Member] Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Indirect research and development expenses: Indirect Expense [Member] Indirect Expense Award Timing Predetermined Award Timing Predetermined [Flag] Restricted cash included in Other current assets Restricted Cash, Current Treasury Stock Treasury Stock, Common [Member] Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Project [Domain] Project [Domain] Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Stock-based compensation charges APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Level 1 Fair Value, Inputs, Level 1 [Member] Schedules of Sales to Customers as Percentage of Total Gross Product Revenue Schedules of Concentration of Risk, by Risk Factor [Table Text Block] Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [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 Effect of dilutive securities (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements All Executive Categories All Executive Categories [Member] Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Other comprehensive income (loss), net of tax: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Preferred Stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Long-term debt, fair value Long-Term Debt, Fair Value Antidilutive Securities [Axis] Antidilutive Securities [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] EYLEA HD EYLEA HD [Member] EYLEA HD Basic and Diluted Net Income (Loss) Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Reimbursement of commercialization-related expenses Reimbursement Of Commercialization-Related Expenses [Member] Reimbursement Of Commercialization-Related Expenses Segment Information Segment Reporting [Text Block] Marketable Securities Investment in Debt and Equity Securities and Other Trading Assets [Text Block] Expiration Date Trading Arrangement Expiration Date Schedule of Product Sales Schedule of Collaborative Revenue Disaggregation of Revenue [Table Text Block] 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 Income Statement Location [Axis] Location, Statement of Income, Balance [Axis] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Gain Contingencies [Table] Gain Contingencies [Table] Cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Sovereign bonds Sovereign bonds Sovereign Debt Securities [Member] 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] Dividends declared Dividends, Common Stock Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Proceeds from issuance of Common Stock Proceeds from Issuance of Common Stock Common Stock, shares authorized (in shares) Common Stock, Shares Authorized Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Security, Excluded EPS Calculation [Table] Exercise Price Award Exercise Price Cash flows from investing activities: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Segment Reporting [Line Items] Segment Reporting [Line Items] Share repurchase program, authorized amount Share Repurchase Program, Authorized, Amount Share Repurchase Program, April 2026 Share Repurchase Program, April 2026 [Member] Share Repurchase Program, April 2026 Document Quarterly Report Document Quarterly Report Legal Matters Legal Costs, Policy [Policy Text Block] 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] Segments [Domain] Segments [Domain] Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Equity Component [Domain] Equity Component [Domain] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Total Expenses Costs and Expenses Adoption Date Trading Arrangement Adoption Date Total stockholders' equity Beginning Balance Ending Balance Equity, Attributable to Parent Total other income (expense) Nonoperating Income (Expense) ASSETS Assets [Abstract] Title Trading Arrangement, Individual Title Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Amortized Cost Basis Debt Securities, Available-for-Sale, Amortized Cost Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Damages awarded Litigation Settlement, Gain Insider Trading Policies and Procedures [Line Items] Other Proceeds from (Payment for) Other Financing Activity Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Selling, general, and administrative Selling, General and Administrative Expense Sanofi Collaboration Agreement, Antibody Sanofi Collaboration Agreement, Antibody [Member] Sanofi Collaboration Agreement, Antibody [Member] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Stock options (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Antidilutive Securities Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Entity Central Index Key Entity Central Index Key All Adjustments to Compensation All Adjustments to Compensation [Member] Equity [Abstract] Equity [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] Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Legal Matters Legal Matters and Contingencies [Text Block] Statements of Operations Income Statement [Abstract] Stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Equity, Attributable to Parent [Abstract] Document Transition Report Document Transition Report Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Deferred tax assets Deferred Income Tax Assets, Net Finance lease liabilities Finance Lease, Liability, Noncurrent Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] City Area Code City Area Code Restricted stock awards and restricted stock units Restricted Stock [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Document Information [Table] Document Information [Table] All Individuals All Individuals [Member] Dividends paid Payments of Dividends Name Forgone Recovery, Individual Name Finished goods Inventory, Finished Goods, Net of Reserves Legal Matters Commitments and Contingencies, Policy [Policy Text Block] Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Marketable securities Marketable Securities, Noncurrent Statement [Line Items] Statement [Line Items] Total assets Assets Preferred Stock, shares issued (in shares) Preferred Stock, Shares Issued Interest expense Interest Expense, Nonoperating Securities owned not readily marketable Equity Securities without Readily Determinable Fair Value, Amount Unrealized Gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax PEO PEO [Member] Marketable securities Marketable Securities, Current 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 Maturities within one year Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Subsequent Event Type [Domain] Subsequent Event Type [Domain] Retained Earnings Retained Earnings [Member] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Unrealized (loss) gain on debt securities OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Common Stock, shares outstanding (in shares) Beginning Balance (in shares) Ending Balance (in shares) Common Stock, Shares, Outstanding Award Timing Disclosures [Line Items] Net income per share - diluted (in dollars per share) Earnings Per Share, Diluted Entity Current Reporting Status Entity Current Reporting Status Net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Interim Period, Costs Not Allocable [Domain] Interim Period, Costs Not Allocable [Domain] Total Shareholder Return Amount Total Shareholder Return Amount 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 Increase in prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Litigation Case [Domain] Litigation Case [Domain] Restricted Restricted [Member] Restricted [Member] Research and development Research and Development Expense 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] Cash flows from financing activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Revenues Revenue from Contract with Customer, Excluding Assessed Tax Financial Instruments [Domain] Financial Instruments [Domain] Customer B Customer B [Member] Customer B Inventories Inventory Disclosure [Text Block] Repurchases of Common Stock Stock Repurchased During Period, Value Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Underlying Securities Award Underlying Securities Amount Recently Issued Accounting Standards Accounting Standards Update and Change in Accounting Principle [Table Text Block] Product Sales Revenue from Contract with Customer [Text Block] Increase in inventories Increase (Decrease) in Inventories Clinical manufacturing costs Clinical And Manufacturing Costs [Member] Clinical And Manufacturing Costs Cost of collaboration and contract manufacturing Collaboration and Contract Manufacturing [Member] Collaboration and Contract Manufacturing [Member] Segment Reporting [Table] Segment Reporting [Table] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] All Trading Arrangements All Trading Arrangements [Member] Other Performance Measure, Amount Other Performance Measure, Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Income from operations Operating Income (Loss) Current Fiscal Year End Date Current Fiscal Year End Date Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Repurchases of Common Stock (in shares) Stock Repurchased During Period, Shares 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] Common stock, dividend, declared (in dollars per share) Common Stock, Dividends, Per Share, Declared 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] Entity File Number Entity File Number Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Gross product revenue Gross Product Revenue [Member] Gross Sales Revenue [Member] Issuance of Common Stock for equity awards granted under long-term incentive plans Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Marketable Securities, Based on Contractual Maturity Dates Investments Classified by Contractual Maturity Date [Table Text Block] Corporate bonds Corporate bonds Corporate Bond Securities [Member] Lynozyfic Lynozyfic [Member] Lynozyfic Gain Contingencies [Line Items] Gain Contingencies [Line Items] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Common Stock, shares issued (in shares) Common Stock, Shares, Issued Measure: Measure [Axis] Litigation, Damages Type [Domain] Litigation, Damages Type [Domain] Litigation, Damages Type [Domain] Treasury stock (in shares) Beginning Balance, treasury (in shares) Ending Balance, treasury (in shares) Treasury Stock, Common, Shares Total adjustments Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity Equity Components [Axis] Equity Components [Axis] Direct research and development expenses Direct Expense [Member] Direct Expense (Increase) decrease in accounts receivable Increase (Decrease) in Accounts Receivable Product and Service [Domain] Product and Service [Domain] Class of Stock [Line Items] Class of Stock [Line Items] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Class A Stock Common Class A [Member] Entity Interactive Data Current Entity Interactive Data Current Finance lease liabilities Finance Lease, Liability, Current Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] EYLEA HD And EYLEA EYLEA HD And EYLEA [Member] EYLEA HD And EYLEA Entity Small Business Entity Small Business Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Termination Date Trading Arrangement Termination Date Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Other noncurrent assets Other Assets, Noncurrent Document Type Document Type 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] Fair Value as of Grant Date Award Grant Date Fair Value Regeneron vs. Amgen Regeneron vs. Amgen [Member] Regeneron vs. Amgen Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Remaining authorized repurchase amount Share Repurchase Program, Remaining Authorized, Amount Arrangement Duration Trading Arrangement Duration Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Local Phone Number Local Phone Number Deferred revenue Contract with Customer, Liability, Noncurrent Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Increase in accounts payable, accrued expenses, and other liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Executive Category: Executive Category [Axis] Receivable Type [Axis] Receivable Type [Axis] LIABILITIES AND STOCKHOLDERS' EQUITY LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] 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] Inventories Total Inventories Inventory, Net Award Type [Domain] Award Type [Domain] Other products Other Products [Member] Other Products Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Fair Value Measurements Fair Value Disclosures [Text Block] Level 3 Fair Value, Inputs, Level 3 [Member] Number of shares (in shares) Treasury Stock, Shares, Acquired PEO Name PEO Name Geographical [Axis] Geographical [Axis] Accrued expenses and other current liabilities Accrued Liabilities and Other Liabilities Deferred revenue Contract with Customer, Liability Reimbursement of research and development expenses by collaborators Research And Development Expense, Reimbursements Research And Development Expense, Reimbursements Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Entity Tax Identification Number Entity Tax Identification Number Total cost of shares Treasury Stock, Value, Acquired, Cost Method 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 Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code 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 Andrew J. Murphy, Ph.D [Member] Andrew J. Murphy, Ph.D Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Non-NEOs Non-NEOs [Member] 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] Punitive Damages Punitive Damages [Member] Punitive Damages Interim Financial Statements Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Stock-based compensation expense Share-Based Payment Arrangement, Noncash Expense 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. Customer [Domain] Customer [Domain] Schedule of Inventory Schedule of Inventory, Current [Table Text Block] Net income per share - basic (in dollars per share) Earnings Per Share, Basic 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] Repurchases of Common Stock Payments for Repurchase of Common Stock Deferred revenue Contract with Customer, Liability, Current Total current assets Assets, Current Insider Trading Arrangements [Line Items] Long-term debt Long-Term Debt, Excluding Current Maturities Award Type [Axis] Award Type [Axis] Number of counts ruled in favor of plaintiff Number Of Counts Ruled In Favor Of Plaintiff Number Of Counts Ruled In Favor Of Plaintiff Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Accounts receivable, net Accounts Receivable, after Allowance for Credit Loss, Current Schedule of Shares Repurchased Class of Treasury Stock [Table Text Block] Retained earnings Retained Earnings (Accumulated Deficit) Gains on marketable and other securities, net Marketable and Other Securities, Gain (Loss) Marketable and Other Securities, Gain (Loss) Product and Service [Axis] Product and Service [Axis] Equity investments Equity Securities, FV-NI 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. 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] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Common Stock Common Stock Common Stock Common Stock [Member] Fair Value Total Available-for-sale debt securities Debt Securities, Available-for-Sale Collaboration revenue Collaboration Revenue [Member] Collaboration Revenue Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Classification of Investment [Domain] Classification of Investment [Domain] Provides general categories of investments for which information is required or determined to be disclosed. Cover [Abstract] Cover [Abstract] 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. Rest Of World Non-US [Member] Concentration risk, percentage Concentration Risk, Percentage Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Equity Awards Adjustments Equity Awards Adjustments [Member] Collaboration, License, and Other Agreements Collaborative Arrangement Disclosure [Text Block] Total liabilities and stockholders' equity Liabilities and Equity 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] Stock options Share-Based Payment Arrangement, Option [Member] Segments [Axis] Segments [Axis] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Inventory Disclosure [Abstract] Inventory Disclosure [Abstract] Bayer Bayer Collaboration Agreement [Member] Bayer Collaboration Agreement [Member] Tabular List, Table Tabular List [Table Text Block] Additional paid-in capital Additional Paid in Capital Research And Development Expense, Type [Axis] Research And Development Expense, Type [Axis] Research And Development Expense, Type Equity securities Equity Securities, FV-NI, Noncurrent Other income (expense), net Other Nonoperating Income (Expense) Name Awards Close in Time to MNPI Disclosures, Individual Name 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] Preferred Stock, shares authorized (in shares) Preferred Stock, Shares Authorized Preferred Stock, par value $.01 per share; 30.0 shares authorized; shares issued and outstanding - none Preferred Stock, Value, Issued Adjustment to Compensation: Adjustment to Compensation [Axis] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Class of Stock [Domain] Class of Stock [Domain] Research And Development Expense, Type [Domain] Research And Development Expense, Type [Domain] Research And Development Expense, Type [Domain] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Capital expenditures Payments to Acquire Productive Assets Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Trade accounts receivable Trade Accounts Receivable [Member] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Total Assets, Fair Value Disclosure Reportable Segment Reportable Segment [Member] Reportable Segment Name Measure Name Income Taxes Income Tax Disclosure [Text Block] Accounts payable Accounts Payable, Current Pay vs Performance Disclosure [Line Items] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Other, net Other Noncash Income (Expense) Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Additional Paid-in Capital Additional Paid-in Capital [Member] Entity Filer Category Entity Filer Category Deferred costs Other Inventory, Net of Reserves Name Trading Arrangement, Individual Name Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalent Raw materials Inventory, Raw Materials, Net of Reserves Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Company Selected Measure Amount Company Selected Measure Amount Net unrealized gains (losses) recognized on investments still held as of period end date Equity Securities, FV-NI, Unrealized Gain (Loss) Investments, Debt and Equity Securities [Abstract] Investments, Debt and Equity Securities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Issuance of Common Stock for equity awards granted under long-term incentive plans (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Schedule of Stock by Class [Table] Stock, Class of Stock [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Accounts and Financing Receivables [Table] Current assets: Assets, Current [Abstract] Non-PEO NEO Non-PEO NEO [Member] Entity Address, Address Line One Entity Address, Address Line One Income tax expense Income Tax Expense (Benefit) Customer concentration risk Customer Concentration Risk [Member] Cost of goods sold, collaboration and contract manufacturing Cost of Product and Service Sold Award Timing Method Award Timing Method [Text Block] Net decrease 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 Other revenue Product and Service, Other [Member] Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Net income Net income Net income - basic and diluted Net Income (Loss) Attributable to Parent Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Statement [Table] Statement [Table] Restatement Determination Date: Restatement Determination Date [Axis] Certificates of deposit Certificates of deposit Certificates of Deposit [Member] Schedule of Accounts Receivable and Deferred Revenue Information Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Acquired in-process research and development Acquired In-Process Research and Development Acquired In-Process Research and Development Revenues: Revenues [Abstract] 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 Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block]