License, Collaboration and Success Payment Agreements - Narrative (Details)		1 Months Ended		3 Months Ended	12 Months Ended
	Oct. 01, 2022 USD ($)	Jun. 30, 2020 USD ($) $ / shares shares	May 31, 2019 USD ($) $ / shares shares	Dec. 31, 2021 USD ($)	Dec. 31, 2022 USD ($) $ / shares	Dec. 31, 2021 USD ($) $ / shares	Dec. 31, 2020 USD ($) $ / shares	May 19, 2021 USD ($)	Oct. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) $ / shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development expense					$ 159,188,000	$ 138,693,000	$ 182,243,000
Net loss					$ (183,118,000)	$ (250,219,000)	$ (204,472,000)
Net loss per common share, basic (in dollars per share) | $ / shares					$ (0.74)	$ (1.84)	$ (15.69)
Net loss per common share, diluted (in dollars per share) | $ / shares					$ (0.74)	$ (1.84)	$ (15.69)
Impairment of other investments					$ 5,000,000	$ 36,447,000	$ 0
Gain on other investments					2,923,000	0	0
Settled Litigation | Rescission of the PACT Commitment Agreement and the PACT Stock Purchase Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Ownership of fully diluted shares (as a percent)	80.00%
PACT
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Impairment of other investments				$ 36,400,000
Series A Convertible Preferred Stock
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Convertible preferred stock, par value (in dollars per share) | $ / shares									$ 1.83		$ 1.83
PACT
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Gain on other investments	$ 2,900,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Fred Hutch
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Annual license maintenance payments											$ 50,000
Aggregate research payments due											$ 12,000,000
Term of collaborative arrangement for research											6 years
Research and development expense					1,700,000	4,200,000	4,100,000
Potential aggregate success payments					0
Term of success payment agreement											9 years
Trigger period from IPO date											1 year
Trigger period thereafter											2 years
Fair value of potential success payments due				8,500,000	2,500,000	8,500,000
Success payment liability				6,400,000	2,500,000	6,400,000
Success payment (gain) expense					(3,900,000)	1,200,000	4,800,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Fred Hutch | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance											10
Potential aggregate success payments											$ 10,000,000
Per share common stock price required for payment (in dollars per share) | $ / shares											$ 18.29
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Fred Hutch | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance											50
Potential aggregate success payments											$ 200,000,000
Per share common stock price required for payment (in dollars per share) | $ / shares											$ 91.44
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Stanford
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Annual license maintenance payments										$ 50,000
Aggregate research payments due									$ 12,000,000
Term of collaborative arrangement for research									4 years
Research and development expense					3,000,000	3,000,000	800,000
Potential aggregate success payments					0
Term of success payment agreement									9 years
Trigger period from IPO date									1 year
Trigger period thereafter									2 years
Fair value of potential success payments due				9,900,000	3,300,000	9,900,000
Success payment liability				3,100,000	1,900,000	3,100,000
Success payment (gain) expense					(1,200,000)	2,500,000	600,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Stanford | License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Commercial milestone payments due										2,500,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Stanford | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance									10
Potential aggregate success payments									$ 10,000,000
Per share common stock price required for payment (in dollars per share) | $ / shares									$ 18.29
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Stanford | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance									50
Potential aggregate success payments									$ 200,000,000
Per share common stock price required for payment (in dollars per share) | $ / shares									$ 91.44
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Stanford | Maximum | License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments due										3,700,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | GSK
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities				$ 84,700,000	0	84,700,000
Recognized revenue					84,700,000	$ 10,500,000	$ 7,800,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | GSK | Adjustment To Revenue Related To Change In Estimate
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Recognized revenue					83,600,000
Net loss					$ 83,600,000
Net loss per common share, basic (in dollars per share) | $ / shares					$ 0.34
Net loss per common share, diluted (in dollars per share) | $ / shares					$ 0.34
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | GSK | License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities					$ 0					$ 45,000,000
Stock Purchase Agreement portion of transaction price			$ 58,600,000
Transaction price								$ 103,600,000
Recognized revenue					0
Contract assets					$ 0
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | GSK | Series AA Convertible Preferred Stock | License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock sold under Stock Purchase Program (in shares) | shares			30,253,189
Price per share of stock sold under Stock Purchase Program (in dollars per share) | $ / shares			$ 6.78
Fair value per share of stock sold under Stock Purchase Program (in dollars per share) | $ / shares			$ 4.84
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | PACT
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment		$ 50,000,000
Stock purchase agreement, stock purchased (in shares) | shares		17,806,901
Stock purchase agreement, purchase price per share (in dollars per share) | $ / shares		$ 2.81
Stock purchase agreement, fair value per share (in dollars per share) | $ / shares		$ 2.05
Additional purchase price consideration		$ 13,600,000
Total upfront payment paid		63,600,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | PACT | Other Investment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Strategic equity investment		$ 36,400,000