Revenue from Contracts with Customers - Summary of Collaboration and License Agreement Revenues by Collaborator (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Collaboration and license agreement revenues	$ 277,998	$ 218,447	$ 512,512	$ 413,646
License and Service [Member]
Disaggregation of Revenue [Line Items]
Collaboration and license agreement revenues	6,298	36,130	21,938	80,708
License and Service [Member] | Takeda Collaboration and License Agreement [Member]
Disaggregation of Revenue [Line Items]
Collaboration and license agreement revenues	5,598	28,760	15,913	72,139
License and Service [Member] | Other Collaboration and License Agreement [Member]
Disaggregation of Revenue [Line Items]
Collaboration and license agreement revenues	$ 700	$ 7,370	$ 6,025	$ 8,569