Basis of Presentation and Significant Accounting Policies - Contract Balances from Contracts with Customers - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Aug. 31, 2022	Feb. 28, 2022	Dec. 31, 2020
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue	$ 53,811	$ 106,005	$ 53,811	$ 106,005	$ 92,068			$ 110,109
Revenue from contract with customer	15,375	9,210	67,615	41,864
Revenue recognized, previously deferred	7,337	3,292	43,961	4,129
License and milestone fees
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer	7,382	$ 2,677	45,247	3,086
Revenue recognized, previously deferred			2,900	200
Hangzhou Zhongmei Huadong Pharmaceutical Co., Ltd | License and milestone fees
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue					28,500
License agreement upfront payment receivable					45,000
Lilly
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
License agreement upfront payment receivable							$ 13,000
Lilly | License and milestone fees
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer			13,800
Lilly | Upfront payment
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue	19,500		19,500
KADCYLA | Royalty revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net proceeds from sale of residual rights to receive royalty payments			12,500
Viridian
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer				2,500	$ 3,000
Viridian | Royalty revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognized, previously deferred				3,700
Viridian | Future Technological Improvements
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognized, previously deferred				$ 200
Novartis
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue	2,800		2,800			$ 2,800
Novartis | License and milestone fees
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer			2,800
Novartis | Future Technological Improvements
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue	$ 800		$ 800