Carrying value Equity Method Investment, Quoted Market Value Reduction to research and development expense Reduction to Research and Development Expense Reduction to Research and Development Expense Supplemental disclosure: Supplemental Cash Flow Information [Abstract] Founders Founders [Member] Founders [Member] Letter of Credit Letter of Credit [Member] Net Loss Per Share Earnings Per Share, Policy [Policy Text Block] State Current State and Local Tax Expense (Benefit) Restricted stock units, vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Leasehold improvements Leasehold Improvements [Member] Fair Value Hierarchy and NAV Fair Value Hierarchy and NAV [Domain] Net loss Net loss Net loss Net Income (Loss) Attributable to Parent Operating lease right-of-use asset Operating Lease, Right-of-Use Asset Short-term investments Debt Securities, Available-for-sale, Current Net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding 2038-2041 Tax Expiration Years 2038 To 2039 [Member] Tax Expiration Years 2038 To 2039 Income Statement Location Income Statement Location [Axis] Range Statistical Measurement [Domain] Segments Segment Reporting, Policy [Policy Text Block] Security Exchange Name Security Exchange Name Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Pfizer Pfizer Inc [Member] Pfizer Inc. 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Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Payments Commencing January 2019 Payments Commencing January 2019 [Member] Payments Commencing January 2019 Related Party Related Party [Axis] Restricted stock units, vested and expected to vest, weighted average remaining vesting life Share-based Compensation Arrangement By Share-based Payment Awards Other Than Options Vested And Expected To Vest Outstanding Weighted Average Remaining Contractual Term Share-based Compensation Arrangement By Share-based Payment Awards Other Than Options Vested And Expected To Vest Outstanding Weighted Average Remaining Contractual Term Investments, All Other Investments [Abstract] Investments, All Other Investments [Abstract] Property and equipment purchases in accounts payable and accrued and other current liabilities Capital Expenditures Incurred but Not yet Paid 2018 Equity Incentive Plan Two Thousand Eighteen Equity Incentive Plan [Member] 2018 equity incentive plan. 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Notch Therapeutics, Inc. [Member] Notch Therapeutics, Inc. Current liabilities: Liabilities, Current [Abstract] U.S. agency securities US Government Corporations and Agencies Securities [Member] Issuance of common stock, net of issuance costs Stock issued, value Stock Issued During Period, Value, New Issues General and administrative General and Administrative Expense 120 Months Lease Term Lease One, Amended [Member] Lease One, Amended Weighted-average exercise price, exercisable (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Intangibles Deferred Tax Assets, Goodwill and Intangible Assets Stock-Based Compensation Share-based Payment Arrangement [Text Block] Level 3 Fair Value, Inputs, Level 3 [Member] Leases Lessee, Leases [Policy Text Block] Accrued research and development expenses Accrued Research And Development Expense Current Accrued research and development expense, current. 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Common stock, $0.001 par value: 200,000,000 authorized as of December 31, 2021 and December 31, 2020; 142,623,065 and 140,474,305 shares issued and outstanding as of December 31, 2021 and December 31, 2020, respectively Common Stock, Value, Issued Total other income (expense), net Nonoperating Income (Expense) Weighted-average period recognized Period of recognized compensation cost Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Allogene Overland Allogene Overland [Member] Allogene Overland Restricted stock units, weighted average grant date fair value, beginning balance (in dollars per share) Restricted stock units, weighted average grant date fair value, ending balance (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Performance Based Restricted Stock Units Performance Based Restricted Stock Units [Member] Performance Based Restricted Stock Units Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Right of use leased assets Deferred Tax Liabilities Right Of Use Leased Deferred tax liabilities right of use leased assets. 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