Summary of Significant Accounting Policies - Subsequent Events (Details) - USD ($) $ in Thousands		12 Months Ended
	Feb. 14, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Revenue from contract with customer		$ 69,856	$ 132,299	$ 82,271
Subsequent event | Lilly
Subsequent Event [Line Items]
License agreement upfront payment receivable	$ 13,000
License agreement additional target term	4 years
License agreement, target selection fees and development, regulatory and commercial milestone payments receivable	$ 1,700
Subsequent event | Lilly | Maximum
Subsequent Event [Line Items]
License agreement additional payment receivable	$ 32,500
Upfront payment | CytomX
Subsequent Event [Line Items]
Revenue from contract with customer		$ 7,500		$ 7,500