Collaboration and License Agreements - Schedule of Revenue from Collaboration Agreements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue from collaboration agreements	$ 8,447	$ 5,364	$ 24,933	$ 13,172
Restated Roche Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue from collaboration agreements	1,395	1,762	7,424	3,875
Biogen License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue from collaboration agreements	3,525	642	6,827	1,707
Calico License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue from collaboration agreements	$ 3,527	$ 2,960	$ 10,682	$ 7,590