Collaborations - Summary of Changes in Accounts Receivable and Contract Liabilities (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Accounts receivable:
Accounts receivable, Balance at Beginning of Period	$ 4,620	$ 7,547
Accounts receivable, Additions	101,049	7,779
Accounts receivable, Deductions	(101,805)	(11,138)
Accounts receivable, Balance at End of Period	3,864	4,188
Contract liabilities:
Deferred revenue, Balance at Beginning of Period	28,810	55,932
Deferred revenue, Additions	87,477	2,000
Deferred revenue, Deductions	(15,608)	(15,772)
Deferred revenue, Balance at End of Period	$ 100,679	$ 42,160