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Leases - Additional Information (Detail) | 1 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2020 USD ($) ft² | Oct. 31, 2020 USD ($) ft² | May 31, 2019 ft² | Jun. 30, 2018 ft² | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Lessee Lease Description [Line Items] |  |  |  |  |  |  |
Tenant improvement allowance |  |  |  |  | $ 15,700,000 |  |
Amount form letter of credit | $ 1,472,000 |  |  |  | $ 1,472,000 | $ 1,472,000 | $ 1,472,000
Lease expiration year |  |  |  |  | 2029 |  |
Operating lease, renewal period | 10 years |  |  |  | 10 years |  |
Operating lease term |  |  |  |  | The lease expires in 2029 with an option to renew for a period of ten years |  |
Operating sublease, impairment charges |  |  |  |  | $ 238,000 | 1,158,000 |
Rent expense |  |  |  |  |  |  | $ 1,100,000
Weighted average remaining lease term for operating leases | 8 years 2 months 12 days |  |  |  | 8 years 2 months 12 days |  |
Weighted average discount rate for operating leases | 8.50% |  |  |  | 8.50% |  |
Cash paid for amounts included In measurement of lease liabilities |  |  |  |  | $ 6,900,000 | $ 3,200,000 |
Offices and Laboratory Facilities | South San Francisco |  |  |  |  |  |  |
Lessee Lease Description [Line Items] |  |  |  |  |  |  |
Area under lease | ft² | 23,600 |  |  | 105,000 |  |  |
Area under sublease | ft² |  |  | 25,000 |  |  |  |
Sublease expiration month and year |  |  |  |  | 2021-11 |  |
Operating sublease, option to extend |  |  |  |  | The sublessor has the option to extend the Sublease for one additional year subject to the consent of the Company. |  |
Sublease renewal period |  |  | 1 year |  |  |  |
Operating sublease, existence of option to extend |  |  |  |  | true |  |
Ongoing loss over sublease period |  |  |  |  | $ 0 |  |
Offices and Laboratory Facilities | South San Francisco | General and Administrative Expense |  |  |  |  |  |  |
Lessee Lease Description [Line Items] |  |  |  |  |  |  |
Operating sublease, impairment charges |  |  |  |  | $ 1,200,000 |  |
Offices and Laboratory Facilities | South San Francisco |  |  |  |  |  |  |
Lessee Lease Description [Line Items] |  |  |  |  |  |  |
Tenant improvement allowance |  | $ 400,000 |  |  |  |  |
Area of property | ft² |  | 18,700 |  |  |  |  |
Lease, description |  |  |  |  | In October 2020, the Company signed a lease agreement to lease approximately 18,700 square feet of office and laboratory space in Newark, California. The lease term ends on February 6, 2028 with an option to extend for an additional five years. The landlord is obligated to pay for up to $0.4 million of tenant improvements |  |
Lease expiration date |  | Feb. 06, 2028 |  |  |  |  |
Extend for an additional lease term |  | 5 years |  |  |  |  |

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