License Agreements - Narrative (Details) - USD ($)		1 Months Ended	12 Months Ended			79 Months Ended
		Jun. 30, 2016	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2022	Oct. 05, 2020
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense	[1]		$ 358,732,000	$ 265,353,000	$ 212,615,000
License Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense						$ 18,800,000
Genentech | Clinical
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments upon achievement of specified clinical and regulatory milestones		$ 37,500,000
Genentech | Regulatory
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments upon achievement of specified clinical and regulatory milestones		102,500,000
Genentech | Commercial
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments upon achievement of specified clinical and regulatory milestones		175,000,000
Genentech | License Agreement | LUMA Study
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Clinical milestone payment obligation responsibility			7,500,000			7,500,000
Genentech | License Agreement | LIGHTHOUSE Study
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Clinical milestone payment obligation responsibility			5,000,000			5,000,000
Genentech | License Agreement | Research and development
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate payments						$ 25,000,000
Genentech | Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense				$ 0	$ 0
Genentech | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments upon achievement of specified clinical and regulatory milestones		$ 315,000,000
Biogen | Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense			$ 6,300,000
Agreed share of commercial profit (loss) percentage							50.00%

[1] Includes expense for cost sharing payments to a related party of $8.2 million for the year ended December 31, 2022 and an offset to expense from related-party cost reimbursements of $6.5 million and $9.3 million for the years ended December 31, 2021 and 2020, respectively.