Schedule of Revenue from Collaborations and Services (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue from collaborations and services	$ 16,235	$ 17,448
Collaborations and services
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue from collaborations and services	8,235	12,372
Collaborations and services | License Agreement | United Therapeutics Corporation
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue from collaborations and services	7,978	7,615
Collaborations and services | Research Agreement | United Therapeutics Corporation
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue from collaborations and services	158	4,658
Collaborations and services | Collaboration and License Agreement | Receptor CLA
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue from collaborations and services	62	62
Collaborations and services | Distribution Agreement | Cipla Distribution Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue from collaborations and services	$ 37	$ 37