Accounting Policies [Abstract] Accounting Policies [Abstract] Accounts Payable and Accrued Liabilities Disclosure [Text Block] Accrued Liabilities Accounts Payable, Current Accounts payable Accrued Bonuses, Current Accrued bonus expense Carrying value as of the balance sheet date of obligations incurred through that date and payable for clinical expenses. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Clinical Expenses Current Accrued clinical expenses Accrued Employee Benefits, Current Accrued employee expenses Carrying value as of the balance sheet date of obligations incurred through that date and payable for lab equipment. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Lab Equipment Expenses Current Accrued lab equipment Carrying value as of the balance sheet date of obligations incurred through that date and payable for legal services received. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Legal Fees Current Accrued legal expenses Accrued Liabilities, Current Accrued liabilities Total accrued liabilities Accrued Liabilities, Current [Abstract] Accrued Liabilities, Current [Abstract] Carrying value as of the balance sheet date of obligations incurred through that date and payable for offering costs. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Offering Costs Current Accrued offering costs 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 Accrued research and development expenses Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive loss Additional area of real estate property leased. Additional Area Of Real Estate Property Leased Additional area of leased office and laboratory space Additional Paid in Capital, Common Stock Additional paid-in-capital Additional research funding commitment amount. Additional Research Funding Commitment Amount Additional research funding obligations Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net loss to net cash used in operating activities: Aggregate clinical trial funding commitment amount. Aggregate Clinical Trial Funding Commitment Amount Clinical trial funding committed amount The minimum amount the entity agreed to spend for research funding under the collaboration agreement. Aggregate Research Funding Commitment Amount Aggregate research funding, committed Period covered by the long-term collaboration agreement research funding commitment. Aggregate Research Funding Commitment Period Aggregate research funding, commitment period Allocated Share-based Compensation Expense Recognized compensation cost Amendment Flag Amendment Flag Amortized Cost and Fair Value Debt Securities [Abstract] Amortized Cost and Fair Value Debt Securities [Abstract] Amortized Cost and Fair Value Debt Securities [Abstract] Amounts capitalized under build to suit leases. Amounts Capitalized Under Build To Suit Leases Capitalized value of build-to-suit property Amounts Capitalized Under Build To Suit Transactions Amounts Capitalized Under Build To Suit Transactions Amounts capitalized under build-to-suit leases Annual base rent after rent abatement. Annual Base Rent After Rent Abatement Base rent after rent abatement Annual base rent increase. Annual Base Rent Increase Increased base rent in the final year Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Anti-dilutive securities excluded from the calculation of diluted net loss per share Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Area of leased office and laboratory space. Area Of Leased Office And Laboratory Space Area of leased office and laboratory space Area of Real Estate Property Area of leased office and laboratory space ARE Seattle Number Sixteen LLC Landlord [Member] A- R- E- Seattle Number Sixteen L- L- C- Landlord [Member] ARE-Seattle No. 16, LLC (Landlord) [Member] Arrangements and Non-arrangement Transactions [Domain] Arrangements and Non-arrangement Transactions [Domain] Assets Total assets Assets [Abstract] ASSETS Assets, Current Total current assets Assets, Current [Abstract] Current assets: Assets, Fair Value Disclosure Total financial assets Assets, Fair Value Disclosure [Abstract] Financial Assets: Available-for-sale Securities Estimated Fair Value, Marketable securities Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized Holding Gains, Marketable securities Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax Gross Unrealized Holding Losses, Marketable securities Available-for-sale Securities, Amortized Cost Basis Amortized Cost, Marketable securities Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Marketable securities, Unrealized Losses, 12 Months or Greater Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss Marketable securities, Unrealized Losses, Total Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value Marketable securities, Fair Value, Total Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Marketable securities, Unrealized Losses, Less than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value Marketable securities, Fair Value, Less than 12 Months Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Marketable securities, Fair Value, 12 Months or Greater Available-for-sale Securities, Current Marketable securities Available-for-sale Securities, Noncurrent Long-term marketable securities Award Type [Axis] Award Type [Axis] Basis of Accounting, Policy [Policy Text Block] Organization and Basis of Presentation Bothell Lease [Member] Bothell Lease [Member] Bothell Lease [Member] Build-to-suit lease obligations that are expected to be paid during the following twelve months or within one business cycle, if longer. Build To Suit Lease Obligation Current Build-to-suit lease obligation Build-to-suit lease obligation current liability The entire disclosure for the entity's build-to-suit lease obligations. Build To Suit Lease Obligation Disclosure [Text Block] Build-to-Suit Lease Obligation Build To Suit Lease Obligation [Line Items] Build To Suit Lease Obligation [Line Items] Build To Suit Lease Obligation [Line Items] Aggregate carrying amount, as of the balance sheet date, of build-to-suit lease obligations expected to be paid after one year (or the normal operating cycle, if longer). Build To Suit Lease Obligation Non Current Build-to-suit lease obligation non-current liability Build-to-suit lease obligation, less current portion Build To Suit Lease Obligation [Table] Build To Suit Lease Obligation [Table] Build To Suit Lease Obligation [Table] Build To Suit Property [Member] Build To Suit Property [Member] Build-to-suit property [Member] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Equity Interest Issued or Issuable, Number of Shares Common stock share issued for acquisition Business Combination Contingent Consideration Earn Out Payments Business Combination Contingent Consideration Earn Out Payments Earn out payments in cash contingent upon the achievement of certain milestones Capital Expenditures Incurred but Not yet Paid Purchases of property and equipment included in accounts payable and accrued liabilities Cash and Cash Equivalents [Abstract] Cash and Cash Equivalents [Abstract] Cash and cash equivalents amortized cost. Cash And Cash Equivalents Amortized Cost Amortized Cost, Cash equivalents Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents at end of period Cash and cash equivalents at beginning of period Cash and cash equivalents Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents, Fair Value Disclosure Estimated Fair Value, Cash equivalents Cash and cash equivalents maturity period. Cash And Cash Equivalents Maturity Period Original maturities of highly liquid investments Cash and Cash Equivalents, Period Increase (Decrease) Net decrease in cash and cash equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Cash and Cash Equivalents Cash, Cash Equivalents, and Marketable Securities [Text Block] Cash Equivalents and Marketable Securities Change in success payment expense (gain). Change In Success Payment Expense Gain Change in success payment expense/gain Class of Stock [Domain] Class of Stock [Domain] Class Shares Purchase Price Class Shares Purchase Price Purchase price of common stock Clinical Research And Development Agreement [Member] Clinical Research And Development Agreement [Member] Clinical Research and Development Agreement [Member] Clinical Trial [Member] Clinical Trial [Member] Clinical Trial [Member] Collaboration agreement aggregate success payments. Collaboration Agreement, Aggregate Success Payments Aggregate success payments Collaboration agreement success payments term. Collaboration Agreement, Success Payments, Term Term of success payments Collaboration agreement term. Collaboration Agreement Term Collaboration agreement, term Collaboration Agreement Upfront Payment Collaboration Agreement Upfront Payment Upfront fee paid Collaborative Agreement Additional Research Funding Period Collaborative Agreement Additional Research Funding Period Research funding additional term Collaborative Agreement Research Funding Period Collaborative Agreement Research Funding Period Research funding term Collaborative Arrangement Disclosure [Text Block] Collaboration Agreements Collaborative Arrangement [Member] Collaborative Arrangement [Member] Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items] Collaborative arrangements milestone payments upon achievement of clinical and regulatory milestones. Collaborative Arrangements Milestone Payments Upon Achievement Of Clinical And Regulatory Milestones Fees and milestone payments upon achievement of clinical, regulatory, and commercial milestones Commercial Paper [Member] Commercial paper [Member] Commitment and contingencies lease term commencement date. Commitment And Contingencies Lease Term Commencement Date Anticipated lease commencement date Commitments and Contingencies Commitments and Contingencies (Note 9) Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Common Stock [Member] Common Stock [Member] Common Stock, Par or Stated Value Per Share Common stock, par value Common Stock, Shares Authorized Common stock, shares authorized Common Stock, Shares, Issued Common stock, shares issued Common Stock, Shares, Outstanding Common stock, shares outstanding Common Stock, Value, Issued Common stock, $0.0001 par value, 495,000,000 shares authorized at March 31, 2015 and December 31, 2014; 82,831,784 and 82,073,647 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Other comprehensive loss: Comprehensive Income, Policy [Policy Text Block] Comprehensive Loss Computer Equipment [Member] Computer equipment and software [Member] Concentration Risk, Credit Risk, Policy [Policy Text Block] Concentrations of Credit Risk and Off-Balance Sheet Risk Construction Payable, Current Accrued construction in progress Consultant [Member] Consultant [Member] Consultant [Member] Conversion of Stock, Amount Converted Carrying value reclassified to common stock and additional paid in capital Convertible Preferred Stock [Member] Convertible Preferred Stock Option [Member] Disclosure of accounting policy for convertible preferred stock options. Convertible Preferred Stock Option Policy [Text Block] Convertible Preferred Stock Option Gain or loss on the remeasurement of convertible preferred stock options. Convertible Preferred Stock Option Remeasurement Gain Loss Loss from remeasurement of fair value of convertible preferred stock options Value of outstanding convertible preferred stock option. Convertible Preferred Stock Option Value Estimated fair value of the convertible preferred stock option Disclosure of accounting policy for convertible preferred stock. Convertible Preferred Stock Policy [Text Block] Convertible Preferred Stock Convertible Preferred Stock, Shares Issued upon Conversion Convertible preferred stock converted into number of common stock Corporate Debt Securities [Member] Corporate debt securities [Member] Cost Method Investments Total investments Cost Method Investments, Policy [Policy Text Block] Other Assets Current Fiscal Year End Date Current Fiscal Year End Date GERMANY Germany [Member] Depreciation, Depletion and Amortization, Nonproduction Depreciation and amortization Description of Lessee Leasing Arrangements, Operating Leases Lease termination description Minimum annual development and commercialization expenses required once certain milestones have been achieved. Development And Commercialization Expenses Development and commercialization expenses Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Stock-Based Compensation Dividends Dividends declared by the board Document And Entity Information [Abstract] Document And Entity Information [Abstract] Document And Entity Information [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Document Fiscal Year Focus Document Fiscal Year Focus Document Period End Date Document Period End Date Document Type Document Type Earnings Per Share [Abstract] Earnings Per Share [Abstract] Earnings Per Share, Basic and Diluted Net loss per share - basic and diluted Net loss per share, basic and diluted Earnings Per Share, Policy [Policy Text Block] Net Loss per Share Attributable to Common Stockholders Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Unrecognized compensation cost, period Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options Unrecognized compensation cost related to non-vested restricted stock Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options Unrecognized compensation cost related to stock options Entity Central Index Key Entity Central Index Key Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Filer Category Entity Filer Category Entity Registrant Name Entity Registrant Name Equipment [Member] Laboratory equipment [Member] Equity [Abstract] Equity [Abstract] Equity Component [Domain] Equity Component [Domain] Estimated fair value of the total success payment liability. Estimated Fair Value Of Success Payment Liability Success payment Estimated fair value of total success payment obligation Fair value of success payment obligations 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 Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Table] Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Table] Asset Class [Domain] Asset Class [Domain] Fair Value Assumptions, Expected Term Expected term (years) Fair Value Assumptions, Expected Volatility Rate Expected volatility Fair Value Assumptions, Risk Free Interest Rate Risk free interest rate Asset Class [Axis] Asset Class [Axis] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Fair Value Disclosures [Text Block] Fair Value Measurements Fair Value, Inputs, Level 1 [Member] Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Level 3 [Member] Sensitivity increase/decrease in stock price used as an input to measure fair value. Fair Value Inputs Stock Price Sensitivity Increase Decrease Stock price increase/decrease percentage Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Summary of Changes in Fair Value of Level 3 Financial Liabilities Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease) Change in fair value of success payments liabilities attributable to the elapsed service period recorded in research and development expense Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value Balance at March 31, 2015 Balance at December 31, 2014 Fair Value of Financial Instruments, Policy [Policy Text Block] Fair Value of Financial Instruments Fate Therapeutics [Member] Fate Therapeutics [Member] Fate Therapeutics [Member] Financial Liabilities Fair Value Disclosure Total financial liabilities Fred Hutchinson Cancer Research Center [Member] Fred Hutchinson Cancer Research Center [Member] Fred Hutchinson Cancer Research Center [Member] General and Administrative Expense General and administrative General and Administrative Expense [Member] General and Administrative Expense [Member] Goodwill, Impairment Loss Impairment losses Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on cash equivalents. Gross Unrealized Holding Gains Cash And Cash Equivalents Gross Unrealized Holding Gains, Cash equivalents Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on cash equivalents. Gross Unrealized Holding Losses Cash And Cash Equivalents Gross Unrealized Holding Losses, Cash equivalents Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Impairment of Long-Lived Assets Income Statement [Abstract] Income Statement [Abstract] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Income Tax, Policy [Policy Text Block] Income Taxes Increase (Decrease) in Accounts Payable Accounts payable Increase (Decrease) in Accrued Liabilities and Other Operating Liabilities Accrued liabilities and other long-term liabilities Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Prepaid Expense and Other Assets Prepaid expenses and other assets Increase (decrease) in success payment liabilities. Increase (Decrease) in Success Payment Liabilities Success payment liabilities Initial annual base rent. Initial Annual Base Rent Base rent for first year Disclosure of accounting policy for the initial public offering. Initial Public Offering [ Policy Text Block] Initial Public Offering Interest Income (Expense), Nonoperating, Net Interest income, net Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] IPO [Member] IPO [Member] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Domain] Lease Arrangement, Type [Domain] Lease Expiration Date Office and laboratory lease expiration date Lease extension term description. Lease Extension Term Description Option to extend term description Leasehold Improvements [Member] Leasehold improvements [Member] Legal Costs, Policy [Policy Text Block] Litigation Expense Legal Fees Litigation Litigation expense for legal reimbursements Lessee Leasing Arrangements, Operating Leases, Term of Contract Initial term of lease Liabilities and Equity Total liabilities and stockholders' equity Liabilities and Equity [Abstract] LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities, Current Total current liabilities Liabilities, Current [Abstract] Current liabilities: Liabilities, Fair Value Disclosure [Abstract] Financial Liabilities: License Agreement Contractual Terms License Agreement Contractual Terms Collaboration and license agreement description License agreement milestone payments upon achievement of clinical and regulatory milestones. License Agreement Milestone Payments Upon Achievement Of Clinical And Regulatory Milestones Milestone payments upon achievement of specified clinical and regulatory milestones The entire disclosure of the entity's license agreements, including a description of the parties involved in the agreement and the terms. License Agreements Disclosure [Text Block] License Agreements Amount of reimbursed litigation expense. Litigation Fees Reimbursements Litigation expense reimbursement Litigation settlement date Litigation Settlement Date Litigation settlement date Long Term Marketable Securities [Member] Long Term Marketable Securities [Member] Long-term marketable securities [Member] Category of Item Purchased [Axis] Category of Item Purchased [Axis] Long-term Purchase Commitment, Category of Item Purchased [Domain] Long-term Purchase Commitment, Category of Item Purchased [Domain] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] Marketable Securities [Member] Marketable Securities [Member] Marketable securities [Member] Marketable Securities, Policy [Policy Text Block] Marketable Securities Maximum [Member] Maximum [Member] License agreement maximum shares for milestone payments upon achievement of clinical and regulatory milestones payable in shares of common stock. Maximum Shares For Milestone Payments Payable In Shares Of Common Stock Maximum shares for milestone payments payable in shares of common stock Memorial Sloan Kettering Cancer Center [Member] Memorial Sloan Kettering Cancer Center [Member] Memorial Sloan Kettering Cancer Center [Member] License agreement milestone payments upon achievement of clinical and regulatory milestones payable in shares of common stock. Milestone Payments Payable In Shares Of Common Stock Milestone payments payable in shares of common stock Milestone payments reimbursement percentage. Milestone Payments Reimbursement Percentage Reimbursement of milestone payment Minimum license maintenance commitment obligation due after year five. Minimum License Maintenance Commitment Obligation Due After Year Five Minimum annual license maintenance payment after year five Minimum license maintenance commitment obligation due in year five. Minimum License Maintenance Commitment Obligation Due In Year Five Minimum annual license maintenance payment in year five Minimum license maintenance commitment obligation due in year four. Minimum License Maintenance Commitment Obligation Due In Year Four Minimum annual license maintenance payment in year four Minimum license maintenance commitment obligation due in year one. Minimum License Maintenance Commitment Obligation Due In Year One Minimum annual license maintenance payment in year one Minimum license maintenance commitment obligation due in year three. Minimum License Maintenance Commitment Obligation Due In Year Three Minimum annual license maintenance payment in year three Minimum license maintenance commitment obligation due in year two. Minimum License Maintenance Commitment Obligation Due In Year Two Minimum annual license maintenance payment in year two Minimum [Member] Minimum [Member] Minimum royalty commitment obligation due after year five. Minimum Royalty Commitment Obligation Due After Year Five Minimum annual royalty payment after year five Minimum royalty commitment obligation due after year two. Minimum Royalty Commitment Obligation Due After Year Two Minimum annual royalty payment after year two Minimum royalty commitment obligation due in year one. Minimum Royalty Commitment Obligation Due In Year One Minimum annual royalty payment in year one Minimum royalty commitment obligation due in year two. Minimum Royalty Commitment Obligation Due In Year Two Minimum annual royalty payment in year two Money Market Funds [Member] Money market funds [Member] Multiple of equity value at issuance used in the calculation of potential success payments. Multiple Of Equity Value At Issuance Multiple of Equity Value at issuance Net Cash Provided by (Used in) Financing Activities, Continuing Operations Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] FINANCING ACTIVITIES Net Cash Provided by (Used in) Investing Activities, Continuing Operations Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] INVESTING ACTIVITIES Net Cash Provided by (Used in) Operating Activities, Continuing Operations Net cash used in operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] OPERATING ACTIVITIES Net Income (Loss) Attributable to Parent Net loss Net loss Notice period for agreement termination. Notice Period For Agreement Termination Notice period for agreement termination Notice period for termination. Notice Period For Termination Notice period for termination Number of clinical studies. Number of Clinical Studies Number of clinical studies Number of common stock shares purchased in connection with license agreement. Number of Common Stock Shares Purchased In Connection With License Agreement Common stock share purchased Number Of Employees Number Of Employees Number of employees Number of operating facilities. Number Of Operating Facilities Number of operating facilities Number of Operating Segments Number of operating segment Number of Reporting Units Number of reportable segment Operating Cash Flows, Direct Method [Abstract] Operating Cash Flows, Direct Method [Abstract] Operating Expenses Total operating expenses Operating Expenses [Abstract] Operating expenses: Operating Income (Loss) Loss from operations Operating lease agreement date. Operating Lease Agreement Date Lease agreement date Operating lease commenced date. Operating Lease Commenced Date Lease commenced date Operating lease commencement date. Operating Lease Commencement Date Operating lease commencement date Operating lease initial term. Operating Lease Initial Term Initial term of lease Operating Leases, Future Minimum Payments Due Total minimum lease payments Operating Leases, Future Minimum Payments Due, Next Twelve Months 2015 Operating Leases, Future Minimum Payments, Due in Five Years 2019 Operating Leases, Future Minimum Payments, Due in Four Years 2018 Operating Leases, Future Minimum Payments, Due in Three Years 2017 Operating Leases, Future Minimum Payments, Due in Two Years 2016 Operating Leases, Future Minimum Payments, Due Thereafter Thereafter Operating Leases, Rent Expense, Net Rent expense Opus Bio [Member] Opus Bio [Member] Opus Bio [Member] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Other Accrued Liabilities, Current Other Other Assets, Noncurrent Other assets Other Commitments [Line Items] Other Commitments [Line Items] Other Commitments [Table] Other Commitments [Table] Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Unrealized gain on marketable securities Other Expenses Other expense Other Liabilities, Noncurrent Other long-term liabilities Other Nonoperating Income (Expense) Other income (expenses) Over-Allotment Option [Member] Underwriters option [Member] Pass through payments owed by counter party. Pass Through Payments Owed By Counter Party Pass-through payments owed by counter party Disclosure of accounting policy for patent costs. Patent Costs Policy [Text Block] Patent Costs Payables and Accruals [Abstract] Payables and Accruals [Abstract] Payment of base rent per square feet. Payment Of Base Rent Per Square Feet Base rent per square foot The cash outflow for payments of build to suit lease obligations. Payments Of Build To Suit Lease Obligation Payments of build-to-suit lease obligation Payments of Stock Issuance Costs Payment of issuance costs related to issuance of common stock Payments to Acquire Available-for-sale Securities Purchases of marketable securities Payments to Acquire Businesses, Gross Cash paid for acquisition Payments to Acquire Other Investments Purchase of cost-method investment Payments to Acquire Property, Plant, and Equipment Purchase of property and equipment Penn Novartis Sublicense Agreement [Member] Penn Novartis Sublicense Agreement [Member] Penn/Novartis Sublicense Agreement [Member] Percentage of escalation of base rent. Percentage Of Escalation Of Base Rent Percentage of increase in annual base rent Percentage reduction on milestone payments. Percentage Reduction On Milestone Payments Percentage of milestone payment reduced Potential success payments based on multiple of equity value at issuance. Potential Success Payments Success payments Preferred Stock, Par or Stated Value Per Share Preferred stock, par value Preferred Stock, Shares Authorized Preferred stock, shares authorized Preferred Stock, Shares Issued Preferred stock, shares issued Preferred Stock, Shares Outstanding Preferred stock, shares outstanding Preferred Stock, Value, Issued Preferred stock, $0.0001 par value; 5,000,000 shares authorized at March 31, 2015 and December 31, 2014; 0 shares issued and outstanding at March 31, 2015 and December 31, 2014 Premises [Member] Premises [Member] New Premises [Member] Prepaid Expense and Other Assets, Current Prepaid expenses and other current assets Proceeds from Issuance Initial Public Offering Aggregate net proceeds received from initial public offering Proceeds from Sale and Maturity of Available-for-sale Securities Sales and maturities of marketable securities Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Estimated Useful Lives Property and equipment, estimated useful lives Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Member] Property, Plant and Equipment [Member] Property, Plant and Equipment, Net Property and equipment, net Property, Plant and Equipment, Policy [Policy Text Block] Property and Equipment, Net Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Useful Life Property and equipment, estimated useful lives Tabular disclosure of the useful lives of major classes of fixed assets. Property Plant And Equipment Useful Life Table [Text Block] Schedule of Estimated Useful Lives of Property and Equipment Property Subject to or Available for Operating Lease, Number of Units Operating lease space, in square feet Range [Axis] Range [Axis] Range Eight [Member] Range Eight [Member] Range Eight [Member] Range Five [Member] Range Five [Member] Range Five [Member] Range Four [Member] Range Four [Member] Range Four [Member] Range [Domain] Range [Domain] Range Nine [Member] Range Nine [Member] Range Nine [Member] Range One [Member] Range One [Member] Range One [Member] Range Seven [Member] Range Seven [Member] Range Seven [Member] Range Six [Member] Range Six [Member] Range Six [Member] Range Three [Member] Range Three [Member] Range Three [Member] Range Two [Member] Range Two [Member] Range Two [Member] Related Party [Domain] Related Party [Domain] Related Party Transactions [Abstract] Related Party Transactions [Abstract] Related Party [Axis] Related Party [Axis] Related Party Transactions Disclosure [Text Block] Related-Party Transactions Research agreement amended expiration date. Research Agreement Amended Expiration Date Sponsored research agreement amended expiration date Research and development annual payment funding under collaboration agreement. Research and Development Annual Payment Funding Under Collaboration Agreement Research funding amount per year Research and Development Arrangement [Member] Research and Development Arrangement [Member] Research and Development Expense Research and development Research and development expenses Research and Development Expense [Member] Research and Development Expense [Member] Research and Development Expense, Policy [Policy Text Block] Research and Development Expense Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Restricted Stock And Restricted Stock Units [Member] Restricted Stock And Restricted Stock Units [Member] Restricted Stock and RSUs [Member] Retained Earnings (Accumulated Deficit) Accumulated deficit Sale of Stock [Domain] Sale of Stock [Domain] Schedule Of Accounting Policies [Line Items] Schedule Of Accounting Policies [Line Items] Schedule Of Accounting Policies [Line Items] Schedule Of Accounting Policies [Table] Schedule Of Accounting Policies [Table] Schedule Of Accounting Policies [Table] Schedule of Accrued Liabilities [Table Text Block] Schedule of Accrued liabilities Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Schedule of Diluted Net Loss Per Share Attributable to Common Stockholders Due to Anti-Dilutive Effect Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Summary of Estimated Fair Value of Cash Equivalents and Marketable Securities Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions [Table] Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions [Table] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Reconciliation of Net Loss to Net Loss Attributable to Common Stockholders Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Summary of Company's Future Minimum Lease Commitments Tabular disclosure of the potential success payments. Schedule Of Potential Success Payments [Table Text Block] Summary of Potential Success Payments, Payable in Cash or Publicly-Traded Equity Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block] Summary of Restricted Stock and RSU Activity Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block] Summary of Stock Option Activity Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Summary of Material Factors Incorporated in Black-Scholes Model in Estimating Fair Value of Options Granted to Employees and Consultants Tabular disclosure of the significant assumptions used during the year to estimate the fair value of success payment liabilities. Schedule Of Success Payment Liabilities Valuation Assumptions [Table Text Block] Assumptions Used to Calculate Estimated Fair Value of Success Payment Liability Schedule of Unrealized Loss on Investments [Table Text Block] Summary of Gross Unrealized Holding Losses and Fair Value for Investments in Unrealized Loss Position Seattle Children's Research Institute [Member] Seattle Childrens Research Institute [Member] Seattle Children's Research Institute [Member] Seattle Lease [Member] Seattle Lease [Member] Seattle lease [Member] Geographical [Domain] Geographical [Domain] Segment Reporting, Policy [Policy Text Block] Segments Selling, General and Administrative Expenses, Policy [Policy Text Block] General and Administrative Expense Series A Convertible Preferred Stock [Member] Series A- Convertible Preferred Stock [Member] Series A convertible preferred stock [Member] Series A- One Convertible Preferred Stock [Member] Series A- One Convertible Preferred Stock [Member] Series A-1 convertible preferred stock [Member] Service Providers [Member] Service Providers [Member] Service Providers [Member] Share-based Compensation Stock-based compensation Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Forfeited, Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Forfeited, Weighted Average Fair Value at Date of Grant per Share Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Granted, Shares 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 Fair Value at Date of Grant per Share Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Unvested shares, Ending balance Unvested shares, Beginning balance Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Unvested shares, Weighted Average Fair Value at Date of Grant per Share, Ending balance Unvested shares, Weighted Average Fair Value at Date of Grant per Share, Beginning balance Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Vested, Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Vested, Weighted Average Fair Value at Date of Grant per Share Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Dividend yield Expected dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Expected life Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum Risk free interest rate, maximum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum Risk free interest rate, minimum Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Aggregate Intrinsic Value, Exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Number of Stock Options, Exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Weighted Average Exercise Price, Exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Weighted Average Remaining Contractual Life, Exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Number of Stock Options, Cancelled Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Number of Stock Options, Granted Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Weighted average grant date fair value of options granted Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Aggregate Intrinsic Value, Outstanding, Ending Balance Aggregate Intrinsic Value, Outstanding, Beginning Balance Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Number of Stock Options, Outstanding, Ending Balance Number of Stock Options, Outstanding, Beginning Balance Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Weighted Average Exercise Price, Outstanding, Ending Balance Weighted Average Exercise Price, Outstanding, Beginning Balance Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Weighted Average Remaining Contractual Life, Outstanding Equity Award [Domain] Equity Award [Domain] Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Weighted Average Exercise Price, Exercised Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Weighted Average Exercise Price, Cancelled Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Weighted Average Exercise Price, Granted Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Stock-Based Compensation Share Price Per share common stock price required for payment Stock price per share Common stock price per share Fair value of common stock Share price sensitivity increase decrease. Share Price Sensitivity Increase Decrease Stock price increase/decrease per share Share price used in calculation of milestone payments payable in shares of common stock. Share Price Used In Milestone Payments Payable In Shares Of Common Stock Calculation Share price used in milestone payments payable in shares of common stock calculation Shares Issued, Price Per Share Issuance of common stock price per share Shares Issued Upon Success Payment Valuation [Member] Shares Issued Upon Success Payment Valuation [Member] Estimated shares issued if success payment valuation occurred [Member] Significant Accounting Policies [Text Block] Significant Accounting Policies Stage Therapeutics GmbH [Member] Stage Therapeutics GmbH [Member] Stage Therapeutics GmbH [Member] Class of Stock [Axis] Class of Stock [Axis] Equity Components [Axis] Equity Components [Axis] Geographical [Axis] Geographical [Axis] Statement [Line Items] Statement [Line Items] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Statement [Table] Statement [Table] St Jude Children Research Hospital [Member] St Jude Children Research Hospital [Member] St. Jude Children's Research Hospital [Member] Stockholders' Equity Attributable to Parent Total stockholders' equity Stockholders' Equity Attributable to Parent [Abstract] Stockholders' equity: Stock Issued During Period, Shares, New Issues Common stock issued, share Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Number of Stock Options, Exercised Equity Option [Member] Options to purchase common stock [Member] Stock Price Decreased to Ten Percentage [Member] Stock Price Decreased to Ten Percentage [Member] Stock Price Decreased to 10% [Member] Stock Price Decreased to Thirty Five Percentage [Member] Stock Price Decreased to Thirty Five Percentage [Member] Stock Price Decreased to 35% [Member] Stock Price Increased to Ten Percentage [Member] Stock Price Increased to Ten Percentage [Member] Stock Price Increased to 10% [Member] Stock Price Increased to Thirty Five Percentage [Member] Stock Price Increased to Thirty Five Percentage [Member] Stock Price Increased to 35% [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Subsequent Event [Member] Subsequent Event [Member] Subsequent Events [Abstract] Subsequent Events [Abstract] Subsequent Events [Text Block] Subsequent Events Subsequent Event [Table] Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Sale of Stock [Axis] Sale of Stock [Axis] Success payment expense (gain). Success Payment Expense Gain Success payment expense gain Success payment expense/gain Success payment liability recorded on the balance sheet. Success Payment Liability Success payment liability balance Estimated fair value of payment liabilities portion attributable to valuation measurement date and associated elapsed service period Success payment liabilities Success Payments Liabilities [Member] Success Payments Liabilities [Member] Fair value of success payments liabilities attributable to the elapsed service period [Member] Disclosure of accounting policy for success payments. Success Payments Policy [Text Block] Success Payments Supplemental Cash Flow Information [Abstract] SUPPLEMENTAL CASH FLOW INFORMATION Text Block [Abstract] Text Block [Abstract] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Trading period used in calculation of milestone payments payable in shares of common stock. Trading Period Used In Milestone Payments Payable In Shares Of Common Stock Calculation Trading period used in milestone payments payable in shares of common stock calculation Trading Symbol Trading Symbol Type of Arrangement and Non-arrangement Transactions [Axis] Type of Arrangement and Non-arrangement Transactions [Axis] Unaudited Interim Financial Information Policy [Text Block] Unaudited Interim Financial Information Policy [Text Block] Unaudited Interim Financial Information Unrecognized Tax Benefits Unrecognized tax benefits Unvested Restricted Stock [Member] Unvested Restricted Stock [Member] Unvested restricted common stock [Member] Upfront license fee. Upfront License Fee Upfront license fee Upfront license fees paid. Upfront License Fees Paid Upfront license fee paid Use of Estimates, Policy [Policy Text Block] Use of Estimates US Government Corporations and Agencies Securities [Member] U.S. government and agency securities [Member] Weighted Average Number of Shares Outstanding, Basic and Diluted Weighted average common shares outstanding, basic and diluted Weighted average number of common shares used in net loss per share - basic and diluted Build To Suit Lease Obligation [Abstract] Build To Suit Lease Obligation [Abstract] Build To Suit Lease Obligation [Abstract]