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Convertible Preferred Stock and Stockholders' Equity (Deficit) - Additional Information (Details) - USD ($) |  |  |  |  |  |  | 1 Months Ended | 12 Months Ended |
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Feb. 12, 2019 | Sep. 06, 2018 | Jul. 20, 2018 | May 21, 2018 | Jan. 04, 2018 | Dec. 03, 2015 | Mar. 31, 2018 | Jan. 31, 2018 | Nov. 30, 2017 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock in connection with a public offering,net of underwriting discounts,commissions,and offering costs |  |  |  |  |  |  |  |  |  | $ 291,311,000 |  |
Common stock, voting right |  |  |  |  |  |  |  |  |  | one |  |
Shares of common stock, repurchase |  |  |  |  |  |  |  |  |  | 4,648,526 | 7,482,032 | 1,305,421
Founder |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Issuance price per share |  | $ 9.63 |  | $ 2.61 |  |  |  |  |  |  |  |
Sale of shares of common stock |  | 1,795,023 |  | 251,547 |  |  |  |  |  |  |  |
Percentage of fully diluted share capital |  |  |  |  |  |  |  |  |  | 15.00% |  |
Increased in equity capital amount |  |  |  |  |  |  |  |  |  | $ 300,000,000 |  |
Additional shares of restricted stock subject to vesting restrictions |  | 1,795,023 |  | 251,547 |  |  |  |  |  |  |  |
Common Stock |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Sale of shares of common stock |  |  |  |  |  |  |  |  |  | 19,837,500 |  |
Issuance of common stock in connection with a public offering,net of underwriting discounts,commissions,and offering costs |  |  |  |  |  |  |  |  |  | $ 2,000 |  |
Unrestricted shares of common stock were subject to service vesting conditions |  |  |  |  |  |  |  |  |  |  | 4,580,444 |
Founder Shares |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Issuance price per share |  |  |  |  |  | $ 0.0001 |  |  |  |  |  |
Sale of shares of common stock |  |  |  |  |  | 9,160,888 |  |  |  |  |  |
Issuance of common stock in connection with a public offering,net of underwriting discounts,commissions,and offering costs |  |  |  |  |  | $ 4,100 |  |  |  |  |  |
Common Stock vesting percentage |  |  |  |  | 50.00% |  |  |  |  |  |  |
Common stock vesting period |  |  |  |  | 5 years |  |  |  |  |  |  |
Common Stock | Stock Restriction Agreements |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Unrestricted shares of common stock were subject to service vesting conditions |  |  |  |  |  |  |  | 4,580,444 |  |  |  |
Initial Public Offering ("IPO") |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Sale of shares of common stock | 19,837,500 |  |  |  |  |  |  |  |  |  |  |
Series Seed Convertible Preferred Stock | Initial Public Offering ("IPO") | Common Stock |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Conversion of preferred stock into common stock |  |  |  |  |  |  |  |  |  | 30,493,460 |  |
Series Seed Convertible Preferred Stock | AA Biopharma Inc. |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Convertible Preferred Stock Issued |  |  |  |  | 20,000,000 |  |  |  |  |  |  |
Preferred Stock, Conversion Basis |  |  |  |  | On January 4, 2018, the Company issued an aggregate of 20,000,000 shares of Series Seed Convertible Preferred Stock in connection with the merger agreement with AA Biopharma Inc. |  |  |  |  |  |  |
Shares Issuable upon Conversion of Series A Convertible Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Convertible Preferred Stock Issued |  |  |  |  |  |  | 45,714,286 | 45,714,286 |  |  |  |
Issuance price per share |  |  |  |  |  |  | $ 1.75 | $ 1.75 |  |  |  |
Preferred stock, gross proceeds |  |  |  |  |  |  | $ 73,900,000 | $ 73,900,000 |  |  |  |
Conversion of principal amount into preferred stock |  |  |  |  |  |  | $ 6,100,000 | $ 6,100,000 |  |  |  |
Shares Issuable upon Conversion of Series A Convertible Preferred Stock | Initial Public Offering ("IPO") | Common Stock |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Conversion of preferred stock into common stock |  |  |  |  |  |  |  |  |  | 30,493,460 |  |
Series B Convertible Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Convertible Preferred Stock Issued |  |  | 71,506,513 |  |  |  |  |  |  |  |  |
Issuance price per share |  |  | $ 3.2167 |  |  |  |  |  |  |  |  |
Proceeds from issuance of convertible preferred stock, net |  |  | $ 230,000,000 |  |  |  |  |  |  |  |  |
Shares Issuable upon Conversion of Series B Convertible Preferred Stock | Initial Public Offering ("IPO") | Common Stock |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Conversion of preferred stock into common stock |  |  |  |  |  |  |  |  |  | 30,493,460 |  |
Series A Convertible Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Convertible Preferred Stock Issued |  |  |  |  |  |  |  |  |  |  | 42,215,077 |
Proceeds from issuance of convertible preferred stock, net |  |  |  |  |  |  |  |  |  |  | $ 73,491,000 |
Series A Convertible Preferred Stock | Stock Restriction Agreements |  |  |  |  |  |  |  |  |  |  |  |
Stockholders Equity Deficit [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Shares subject to forfeiture |  |  |  |  |  |  |  |  | 1,305,421 |  |  |

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