Document and Entity Information [Abstract] Document Information [Table] Class of Stock [Axis] Class of Stock [Domain] Common Stock [Member] Ordinary Shares Common Class A [Member] Class A ordinary shares Common Class B [Member] Class B ordinary shares Classification of common stock that has different rights than Common Class A1, representing ownership interest in a corporation. Common Class A1 [Member] Class A1 ordinary shares Classification of common stock that has different rights than Common Class B1, representing ownership interest in a corporation. Common Class B1 [Member] Class B1 ordinary shares Document Information [Line Items] Document information Document Type Document Quarterly Report Document Transition Report Document Period End Date Securities Act File Number Entity Registrant Name Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Address, Address Line One Entity Address, City or Town Entity Address, Country Entity Address, Postal Zip Code City Area Code Local Phone Number Title of 12(b) Security Trading Symbol Security Exchange Name Entity Current Reporting Status Entity Interactive Data Current Entity Filer Category Entity Small Business Entity Emerging Growth Company Entity Shell Company Entity Common Stock, Shares Outstanding Current Fiscal Year End Date Document Fiscal Year Focus Document Fiscal Period Focus Entity Central Index Key Amendment Flag CONDENSED CONSOLIDATED BALANCE SHEETS Statement [Table] Statement CONSOLIDATED BALANCE SHEETS CONSOLIDATED STATEMENTS OF CASH FLOWS Assets [Abstract] Assets Assets, Current [Abstract] Current assets: Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents Short-Term Investments Short-term investments Accounts Receivable, after Allowance for Credit Loss, Current Accounts receivable, net Inventory, Net Inventory Commercial product inventory Prepaid Expense and Other Assets, Current Prepaid expenses and other current assets Assets, Current Total current assets Property, Plant and Equipment, Net Property and equipment, net Total property and equipment, net Operating Lease, Right-of-Use Asset Operating lease right-of-use assets Other Assets, Noncurrent Other long-term assets Finite-Lived Intangible Assets, Net Intangible asset, net Net Deferred Income Tax Assets, Net Deferred tax assets Assets Total assets Liabilities and Equity [Abstract] Liabilities and Shareholders' Equity Liabilities, Current [Abstract] Current liabilities: Accounts Payable, Current Accounts payable Carrying value as of the balance sheet date of obligations incurred through that date and payable for collaboration expenses. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Collaboration Expenses, Current Accrued collaboration expenses Accrued Liabilities, Current Accrued expenses Total accrued expenses Operating Lease, Liability, Current Operating lease liabilities Other Liabilities, Current Other current liabilities Liabilities, Current Total current liabilities Liabilities, Noncurrent [Abstract] Non-current liabilities: Contract with Customer, Liability, Noncurrent Balance at End of Period Balance at Beginning of Period Non-current deferred revenue Operating Lease, Liability, Noncurrent Non-current operating lease liabilities Other Liabilities, Noncurrent Other long-term liabilities Liabilities Total liabilities Commitments and Contingencies. Commitments and contingencies (Note 13) Equity, Attributable to Parent [Abstract] Shareholders' equity: Common Stock, Value, Issued Ordinary shares value Additional Paid in Capital Additional paid-in capital Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive loss Retained Earnings (Accumulated Deficit) Accumulated deficit Equity, Attributable to Parent Balance at the end of the period Balance at the beginning of the period Total shareholders' equity Liabilities and Equity Total liabilities and shareholders' equity Common Stock, Par or Stated Value Per Share Ordinary shares, par value (in dollars per share) Common Stock, Shares, Issued Ordinary shares, shares issued (in shares) Common Stock, Shares, Outstanding Balance at the end of the period (in shares) Balance at the beginning of the period (in shares) Ordinary shares, shares outstanding (in shares) CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME Product and Service [Axis] Product and Service [Domain] Product [Member] Product revenue, net Joint operating activities with a collaborator or partner with shared risks and benefits. Collaboration [Member] License and collaboration revenue Product Revenue, Net Revenue: Revenue from Contract with Customer, Excluding Assessed Tax Revenue N/A Cost of Revenue and Operating Expenses [Abstract] Costs and operating expenses: Cost of Goods and Services Sold Cost of goods sold The aggregate costs related to collaboration expenses. Collaboration Expenses Collaboration expenses Research and Development Expense Research and development Selling, General and Administrative Expense Selling, general and administrative Aggregate costs related to goods produced and sold, services rendered, and generally recurring costs associated with normal operations during the period. Includes selling, general and administrative expense. Total Cost of Revenue and Operating Expenses Total operating expenses Operating Income (Loss) Income from operations Other Nonoperating Income Other income, net Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income before income taxes Income Tax Expense (Benefit) Provision for income taxes Provision for income taxes Net income Net income attributable to ordinary shareholders Earnings Per Share, Basic Net income per share attributable to ordinary shareholders, basic Basic net income per share Earnings Per Share, Diluted Net income per share attributable to ordinary shareholders, diluted Diluted net income per share Weighted Average Number of Shares Outstanding, Basic Weighted average ordinary shares outstanding, basic Weighted average ordinary shares outstanding - basic Weighted Average Number of Shares Outstanding, Diluted Weighted average ordinary shares outstanding, diluted Weighted average ordinary shares outstanding - diluted Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Comprehensive income Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent [Abstract] Other comprehensive income (loss) OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Unrealized gain (loss) on short-term investments and currency translation adjustments Unrealized gain (loss) on short-term investments and currency translation adjustments, net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Total other comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Total comprehensive income CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY Equity Components [Axis] Equity Component [Domain] Additional Paid-in Capital [Member] Additional Paid-In Capital AOCI Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) Retained Earnings [Member] Accumulated Deficit Increase (Decrease) in Stockholders' Equity [Roll Forward] Changes in equity Stock Issued During Period, Value, Employee Stock Purchase Plan Issuance of Class A ordinary shares under incentive award plans and employee share purchase plan Stock Issued During Period, Shares, Employee Stock Purchase Plans Issuance of Class A ordinary shares under incentive award plans and employee share purchase plan (in shares) APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Share-based compensation expense CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS Net Cash Provided by (Used in) Operating Activities [Abstract] Cash flows from operating activities: Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities Depreciation, Depletion and Amortization, Nonproduction Depreciation and amortization expense Share-Based Payment Arrangement, Noncash Expense Share-based compensation expense Amount of non-cash lease expense. Noncash Lease Expense Non-cash lease expense Accretion (Amortization) of Discounts and Premiums, Investments Net amortization of premiums and accretion of discounts on short-term investments Gain (Loss) on Disposition of Property Plant Equipment Net gain on disposal of property and equipment Deferred Income Tax Expense (Benefit) Deferred income taxes Non-cash deferred tax benefit Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Prepaid Expense and Other Assets Prepaid expenses and other current assets Increase (Decrease) in Accounts Receivable Accounts receivable, net Increase (Decrease) in Inventories Inventory Increase (Decrease) in Other Noncurrent Assets Other long-term assets Increase (Decrease) in Accounts Payable Accounts payable Increase (Decrease) in Accrued Liabilities Accrued expenses, accrued collaboration expenses and other current liabilities The increase (decrease) during the reporting period in lessee operating lease liabilities. Increase (Decrease) in Operating Lease Liabilities Operating lease liabilities Increase (Decrease) in Other Noncurrent Liabilities Other long-term liabilities Net Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] Cash flows from investing activities: Payments to Acquire Property, Plant, and Equipment Purchases of property and equipment Payments to Acquire Short-Term Investments Purchases of short-term investments Proceeds from Maturities, Prepayments and Calls of Short-Term Investments Proceeds from the maturities of short-term investments Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Cash flows from financing activities: Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Excluding Option Exercised Proceeds from issuance of Class A ordinary shares under incentive award plans and employee share purchase plan Payment, Tax Withholding, Share-Based Payment Arrangement Payments in connection with ordinary shares tendered for employee tax obligations Net Cash Provided by (Used in) Financing Activities Net cash provided by financing activities Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect Net increase in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents Cash and cash equivalents at end of period Cash and cash equivalents at beginning of period Supplemental Cash Flow Elements [Abstract] Supplemental information: Income Taxes Paid, Net Cash paid for income taxes Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Supplemental disclosure of non-cash investing and financing activities: Amount of change in right-of-use asset as a result of new, modified, and terminated leases. Change In Right Of Use Asset, New, Modified, and Terminated Leases Change in right-of-use asset as a result of new, modified, and terminated leases Capital Expenditures Incurred but Not yet Paid Additions to property and equipment included in accrued expenses and other liabilities Nature of the Business and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Nature of the Business and Basis of Presentation Fair Value of Financial Assets and Liabilities Fair Value Disclosures [Text Block] Fair Value of Financial Assets and Liabilities Revenue from Contract with Customer [Text Block] Product Revenue, Net Inventory Inventory Disclosure [Text Block] Inventory Property and Equipment, Net Property, Plant and Equipment Disclosure [Text Block] Property and Equipment, Net Intangible Assets Intangible Assets Disclosure [Text Block] Intangible Assets Accrued Expenses Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block] Accrued Expenses Share-Based Compensation Share-Based Payment Arrangement [Text Block] Share-Based Compensation No definition available. Out-Licensing Agreements The entire disclosure for out-licensing agreements. Out-licensing Agreements Disclosure [Text Block] Out-Licensing Agreements No definition available. License and Acquisition Agreements The entire disclosure for license and acquisition agreements. License and Acquisition Agreements Disclosure [Text Block] License and Acquisition Agreements Net Income per Share Earnings Per Share [Text Block] Net Income per Share Income Taxes Income Tax Disclosure [Text Block] Income Taxes Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Segment Information and Geographic Data Segment Reporting Disclosure [Text Block] Segment Information and Geographic Data Summary of Significant Accounting Policies Disclosure of accounting policy for interim consolidated financial information. Interim Consolidated Financial Information [Policy Text Block] Unaudited Interim Consolidated Financial Information New Accounting Pronouncements, Policy [Policy Text Block] Recently Issued and Adopted Accounting Pronouncements Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of financial assets and liabilities measured at fair value on a recurring basis Investments Classified by Contractual Maturity Date [Table Text Block] Schedule of contractual maturities of short-term investments Debt Securities, Available-for-Sale [Table Text Block] Schedule of short-term investments Disaggregation of Revenue [Table Text Block] Schedule of product revenue, net Tabular disclosure of the balances and activities related to product revenue allowance and reserve categories. Product Revenue Allowance and Reserves [Table Text Block] Schedule of balances and activity of the product revenue allowance and reserve categories Tabular disclosure of the carrying amount as of the balance sheet date of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process, both current and noncurrent. Schedule of Inventory, Current and Noncurrent [Table Text Block] Schedule of inventory Property, Plant and Equipment [Table Text Block] Schedule of property and equipment, net Schedule of Finite-Lived Intangible Assets [Table Text Block] Schedule of intangible assets, net of accumulated amortization, impairment charges, and adjustments Schedule of Accrued Liabilities [Table Text Block] Schedule of accrued expenses Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Share-Based Compensation Tabular disclosure of the changes in outstanding nonvested restricted stock and nonvested performance-based stock units. Nonvested Restricted Stock Shares Activity and Nonvested Performance-Based Units Activity [Table Text Block] Schedule of restricted and performance-based share activity Share-Based Payment Arrangement, Option, Activity [Table Text Block] Schedule of share option activity under the Plans Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Schedule of share-based compensation expense was classified in the consolidated statements of operations and comprehensive income (loss) Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Schedule of contract assets and contract liabilities in connection with license and collaboration agreements Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of basic and diluted net income attributable to ordinary shareholders Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Schedule of anti-dilutive securities excluded from the computation of diluted EPS per share attributable to ordinary shareholders Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of selected financial information with respect to the company's single operating segment Revenue from External Customers by Geographic Areas [Table Text Block] Schedule of total revenue by geographic region of the customer Long-Lived Assets by Geographic Areas [Table Text Block] Schedule of property and equipment, net by geographic region Fair Value, Recurring and Nonrecurring [Table] Measurement Basis [Axis] Portion at Fair Value Measurement [Member] Estimate of Fair Value Measurement [Member] Fair value Measurement Frequency [Axis] Measurement Frequency [Domain] Fair Value, Recurring [Member] Recurring basis Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value, Inputs, Level 1 [Member] Level 1 Fair Value, Inputs, Level 2 [Member] Level 2 Financial Instrument [Axis] Financial Instruments [Domain] Money Market Funds [Member] Money market funds US Treasury Securities [Member] U.S. Treasury Securities Location, Statement of Financial Position, Balance [Axis] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value of Financial Assets and Liabilities Assets, Fair Value Disclosure [Abstract] Assets: Cash and Cash Equivalents, Fair Value Disclosure Cash equivalents Debt Securities, Available-for-Sale, Current Short-term investments Assets, Fair Value Disclosure Assets Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract] Contractual maturities of short-term investments Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Maturities within one year Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Maturities after one year through five years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Fair Value Contractual maturities investments Debt Securities, Available-for-Sale [Abstract] Short-term investments: Debt Securities, Available-for-Sale, Amortized Cost Amortized Cost Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized Gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Gross Unrealized Losses Debt Securities, Available-for-Sale Fair Value Fair Value Measurement Inputs and Valuation Techniques [Abstract] Fair Value, Assets Transfers Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2. Fair Value Assets Level 1 To Level 2 Transfers Amount 1 Fair value of assets transferred from Level 1 to Level 2 Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1. Fair Value Assets Level 2 To Level 1 Transfers Amount 1 Fair value of assets transferred from Level 2 to Level 1 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 Fair value of asset transfer into Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Fair value of asset transfer out of Level 3 Debt Securities, Available-for-Sale, Realized Gain (Loss) Realized gains (losses) on securities Disaggregation of Revenue [Table] Disaggregation of Revenue [Line Items] Product Revenue, Net N/A Contractual Adjustments [Abstract] Contractual Adjustments Amount of reserve established for adjustments to customer contracts. Product Revenue, Reserve for Contractual Adjustments Balance at end of period Balance at beginning of period Expense related to the amount of estimated contractual adjustments. Product Revenue, Provision for Contractual Adjustments Current provisions relating to sales in the current year Amount of adjustments for contractual adjustments relating to prior year sales. Product Revenue Contractual Adjustments Prior Years Sales Adjustments relating to prior years Amount of refunds paid or payments received relating to contractual adjustments. Product Revenue, Refunds On Contractual Adjustments Payments/returns relating to sales in the current year Amount of refunds paid or payments received on prior year sales relating to contractual adjustments. Product Revenue, Contractual Adjustments, Payments and Sales Returns, Prior Year Sales Payments/returns relating to sales in the prior years N/A Government Rebates [Abstract] Government Rebates Amount of reserve established for government rebate program chargebacks. Product Revenue, Reserve for Government Rebates Balance at end of period Balance at beginning of period Expense related to the amount of estimated government rebate chargebacks. Product Revenue, Provision for Government Rebates Current provisions relating to sales in the current year Amount of adjustments for government rebates relating to prior year sales. Product Revenue Government Rebates Adjustments Prior Years Sales Adjustments relating to prior years Amount of refunds paid or payments received relating to government rebate programs. Product Revenue, Refunds and Payments On Government Rebates Payments/returns relating to sales in current year Amount of refunds paid or payments received on prior year sales relating to government rebate programs. Product Revenue, Government Rebates, Payments and Sales Returns, Prior Year Sales Payments/returns relating to sales in the prior years N/A Product Returns [Abstract] Returns Amount of reserve established for estimated returns. Product Revenue, Reserve for Sales Returns Balance at end of period Balance at beginning of period Expense related to the amount of estimated product returns. Product Revenue, Provision for Product Returns Current provisions relating sales in the current year Amount of adjustments for returns relating to prior year sales. Product Revenue Returns Adjustments Prior Year Sales Adjustments relating to prior years Amount of refunds paid relating to product returns related to prior year sales. Product Revenue, Refunds on Product Returns, Prior Year Sales Payments/returns relating to sales in the prior years N/A Product Revenue Allowance and Reserve [Abstract] Total Revenue-related reserves Amount, at balance sheet date, of reserves and allowances netted against product revenue. These reserves and allowances include product returns, customer contractual adjustments and government rebate program chargebacks. Product Revenue, Reserves and Allowances Balance at end of period Balance at beginning of period Revenue-related reserves Expense related to the amount of estimated product revenue reserves and allowances. Product Revenue, Provision for Reserves and Allowances Current provisions relating to sales in the current year Amount of adjustments on prior year sales relating to product reserves and allowances. Product Revenue Adjustments for Reserves and Allowances Prior Year Sales Adjustments relating to prior years Amount of refunds paid or credits granted relating to product reserves and allowances. Product Revenue, Refunds and Credits for Reserves and Allowances Payments/returns relating to sales in the current year Amount of refunds paid or credits granted on prior year sales relating to product reserves and allowances. Product Revenue, Refunds and Credits for Reserves and Allowances, Prior Year Sales Payments/returns relating to sales in the prior years Inventory, Current [Table] Inventory [Line Items] Inventory Inventory, Raw Materials, Net of Reserves Raw materials Inventory, Work in Process, Net of Reserves Semi-finished goods Inventory, Finished Goods, Net of Reserves Finished goods Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed. Inventory, Current and Noncurrent, Net Total inventory Inventory, Noncurrent Other long-term assets Property, Plant and Equipment [Table] Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset [Domain] Equipment commonly used in offices and stores that have no permanent connection to the structure of a building or utilities and equipment used primarily for road transportation. Furniture, Fixtures, And Vehicles [Member] Furniture, fixtures and vehicles Computer Equipment [Member] Computer hardware and software Leasehold Improvements [Member] Leasehold improvements Represents equipment used primarily for lab. Lab Equipment [Member] Lab equipment Construction in Progress [Member] Construction in progress Geographical [Axis] Geographical [Domain] UNITED KINGDOM UK United Kingdom Property, Plant and Equipment [Line Items] Property and Equipment, Net Property, Plant and Equipment, Gross Total property and equipment Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Less: Accumulated depreciation Depreciation Depreciation expense Intangible Asset, Finite-Lived [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Capitalized milestone payment for a specified regulatory milestone. Regulatory Milestone [Member] Regulatory milestone Finite-Lived Intangible Assets [Line Items] Intangible Assets Finite-Lived Intangible Asset, Useful Life Estimated life Finite-Lived Intangible Assets, Gross Cost Intangible asset - Regulatory milestone Finite-Lived Intangible Assets, Accumulated Amortization Accumulated Amortization Amortization of Intangible Assets Amortization expense Employee-related Liabilities, Current Accrued employee compensation and benefits Carrying value as of the balance sheet date of obligations incurred through that date and payable for inventory and manufacturing. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Inventory and Manufacturing, Current Accrued inventory and manufacturing Carrying value as of the balance sheet date of obligations incurred through that date and payable for research and development expenses. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Research and Development Expenses, Current Accrued research and development expenses Accrued Professional Fees, Current Accrued legal, commercial and professional fees Other Accrued Liabilities, Current Other Plan Name [Axis] Plan Name [Domain] Represents information pertaining to 2018 Incentive Award Plan (the "2018 Plan"). Incentive Award Plan 2018 [Member] 2018 Plan Represents information pertaining to 2015 Equity Incentive Plan, as amended (the "2015 Plan"). Equity Incentive Plan 2015 [Member] 2015 Plan Represents information pertaining to 2018 Employee Share Purchase Plan (the "2018 ESPP"). Employee Share Purchase Plan 2018 [Member] 2018 ESPP Options Represents information relating to RSUs, Revenue PSUs, TSR PSUs, and option awards. RSUs, Revenue PSUs, TSR PSUs, and Option Awards [Member] RSUs, revenue PSUs, TSR PSUs, and share options Represents information relating to Development PSUs and performance-based options. Development PSUs and Performance-Based Options [Member] Development PSUs and PSOs Performance Shares [Member] Unvested PSUs Statistical Measurement [Axis] Statistical Measurement [Domain] Maximum [Member] Maximum Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized Additional shares authorized Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant Number of ordinary shares available for future grant Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Outstanding, end of the period Outstanding, beginning of the period Shares outstanding (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Award Requisite Service Period Service period Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross Number of options granted Granted Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Total unrecognized compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Expenses expected to be recognized over a weighted average remaining period Restricted Stock Units (RSUs) [Member] RSUs Unvested RSUs Share instrument which is convertible to stock or an equivalent amount of cash, after a specified period of time. Restricted Stock Units, RSU, Time-Based [Member] Time-based RSUs Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage Vesting percentage Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Granted Weighted average grant date fair values Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Granted PSUs Granted Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Vested PSUs Vested Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Number of shares Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number End of the period Beginning of the period Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Forfeited Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Weighted Average Grant Date Fair Value Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value End of the period Beginning of the period Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Vested Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Forfeited Share-based payment arrangement based on performance granting right, subject to vesting and other restrictions, to purchase or sell certain number of shares at predetermined price for specified period of time. Performance-Based Option [Member] PSOs Performance options to purchase ordinary shares Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] Number of Shares Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Exercised Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period Forfeited Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number Share options exercisable Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested, Number of Shares Share options vested and expected to vest Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Weighted Average Exercise Price Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price Outstanding, end of the period Outstanding, beginning of the period Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Granted Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Exercised Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Forfeited Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price Share options exercisable Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested, Weighted Average Grant Date Fair Value Share options vested and expected to vest Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table] Location, Statement of Income, Balance [Axis] Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Share-Based Compensation Share-Based Payment Arrangement, Expense Share-based compensation expense Collaborative Arrangement and Arrangement Other than Collaborative [Table] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Collaborative Arrangement, Transaction with Party to Collaborative Arrangement [Member] Collaboration Agreements Information pertaining to the territory license for arcalyst. Territory License, Arcalyst [Member] Territory License - ARCALYST Huadong ARCALYST Information pertaining to the worldwide license for vixarelimab. Worldwide License, Vixarelimab [Member] Worldwide License - Vixarelimab Genentech vixarelimab Location, Statement of Financial Position, Activity, Accrual [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] License and Acquisition Agreements Collaborative agreements The amount of upfront payments received. Upfront Payment Received Upfront payments received The amount of initial consideration to which an entity expects to be entitled in exchange for transferring promised goods or services to a customer, excluding amounts collected on behalf of third parties. Contract with Customer, Transaction Price Transaction price The additional amount of initial consideration to which an entity expects to be entitled in exchange for transferring promised goods or services to a customer, excluding amounts collected on behalf of third parties. Contract With Customer, Addition to Transaction Price Addition to transaction price The number of performance obligations in an agreement. Number of Performance Obligations Number of performance obligations in an agreement The amount of payments to be received by the company upon the achievement of specified development, regulatory and sales milestones. Potential Revenue Upon Development, Regulatory, and Sales Milestone Achievement Payments to be received by the company upon the achievement of specified development, regulatory and sales milestones Term of the agreement before expiration. Term of Agreement Term of agreement for royalty payments The notice period upon which the Company can terminate the agreement in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Time Period to Terminate Agreement Notice period to terminate the agreement Change in Contract with Customer, Liability [Abstract] Contract Liabilities: Counterparty Name [Axis] Counterparty Name [Domain] Information pertaining to Regeneron Pharmaceuticals, Inc. Regeneron Pharmaceuticals Inc [Member] Regeneron Arrangement Other than Collaborative [Member] Noncollaborative arrangement Information pertaining to a license agreement. License Agreement [Member] License agreement Represents information pertaining to a clinical supply agreement. Clinical Supply Agreement [Member] Clinical supply agreement The amount of sales profits, after deduction of certain commercialization expenses, shared with the licensor under terms of the agreement. Contractual Obligation, Sales Profit Sharing Profit sharing recognized The period which both parties can terminate the agreement on uncured material breaches, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Time Period to Terminate Agreement by Both Parties Under Uncured Material Breaches Uncured period which causes termination of the agreement, due to insolvency or bankruptcy or for material breach of the agreement by the other party that remains uncured The period which the Company can terminate the agreement under payment-related, breaches in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Time Period to Terminate Agreement Under Payment Related Breaches Notice period to terminate the agreement under payment-related breaches The consecutive suspension of activities period for termination of agreement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Consecutive Suspension of Activities Period to Terminate the Agreement Consecutive suspension of activities period for termination of agreement The notice period to terminate the agreement if products are having safety concerns, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Time Period to Terminate Agreement if the products are determined to have certain safety concerns Notice period to terminate the agreement if products are having safety concerns Information pertaining to other research and discovery related arrangements. Other Research and Discovery Related Arrangements [Member] Other research and discovery related arrangements Earnings Per Share, Basic, by Common Class, Including Two-Class Method [Table] Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Net Income (Loss) Attributable to Parent [Abstract] Numerator: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Denominator: Weighted Average Number of Shares Outstanding, Diluted, Adjustment [Abstract] Effect of dilutive securities Weighted Average Number of Shares Outstanding, Diluted, Adjustment Effect of dilutive securities Antidilutive Security, Excluded EPS Calculation [Table] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Anti-dilutive securities excluded from computation of earnings per share Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Total anti-dilutive shares Disclosure of information pertaining to income taxes. Income Tax Disclosure [Table] Pertaining to jurisdictions outside of Kiniksa US, Kiniksa UK, and Kiniksa Switzerland. Outside Kiniksa US, UK, and Switzerland [Member] Outside Kiniksa US, UK, and Switzerland Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Income Tax Disclosure [Line Items] Deferred Tax Assets, Gross Material deferred tax assets Information pertaining to abiprubart. Abiprubart [Member] Abiprubart No definition available. Manufacturing Commitments Abstract Manufacturing commitments Purchase Commitment, Remaining Minimum Amount Committed Non-cancelable purchase commitments Amount of purchase commitment obligation maturing in the next rolling twelve months following the latest balance sheet. Purchase Commitment, Obligation Due in Next Rolling Twelve Months Amount of purchase commitment obligation due within one year Share-Based Compensation Arrangement by Share-Based Payment Award, Additional General Disclosures [Abstract] Long-term incentive plan The estimated amount of cash award in the event performance goals are achieved. Estimated Cash Award Estimated amount of cash award in the event performance goals are achieved Compensation Expense, Excluding Cost of Good and Service Sold Performance cash award expense Loss Contingency, Estimate [Abstract] Loss contingency Loss Contingency Accrual, Loss (Reversal of Loss) Loss contingency accrual Schedule of Segment Reporting Information, by Segment [Table] Segments [Axis] Segments [Domain] Describes information pertaining to the pharmaceutical operating segment. Pharmaceutical Segment [Member] Pharmaceutical Segment Reporting Information [Line Items] Segment Information and Geographic Data Number of Reportable Segments Number of reportable segments Investment Income, Interest Interest income Information for research and development programs. Research and Development Programs [Axis] Research and development programs. Research and Development Programs [Domain] Information pertaining to Arcalyst. ARCALYST [Member] ARCALYST Information pertaining to KPL-387. KPL-387 [Member] KPL-387 Information pertaining to KPL-1161. KPL-1161 [Member] KPL-1161 Information pertaining to unallocated research and development expense. Unallocated Research and Development [Member] Unallocated research and development expenses Segment Reporting Information, Revenue for Reportable Segment [Abstract] Revenue: Revenues Revenue Research and Development Expense [Abstract] Direct research and development expenses by program: Segment Reporting Information, Additional Information [Abstract] Other significant non-cash items: UNITED STATES United States Pertaining to jurisdictions outside of the United States and the United Kingdom. Outside United States and United Kingdom [Member] Rest of world