Collaboration and License Agreements - Schedule of Performance Obligation Along with Standalone Selling Price and Transaction Price Allocated (Detail) - Everest License Agreement [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Performance Obligations, Transaction Price Allocated	$ 5,000
License and Know-How Transfer [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Performance Obligations, Standalone Selling Price	9,858
Performance Obligations, Transaction Price Allocated	$ 3,553
Performance Obligations, Recognition Method	Fully satisfied; recognized upon delivery of the license
Exclusive Option [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Performance Obligations, Standalone Selling Price	$ 400
Performance Obligations, Transaction Price Allocated	$ 144
Performance Obligations, Recognition Method	Will be recognized upon exercise or expiration of the option
Research and Development Services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Performance Obligations, Standalone Selling Price	$ 3,614
Performance Obligations, Transaction Price Allocated	$ 1,303
Performance Obligations, Recognition Method	Recognized over time as services are delivered through the expected completion date of Q1 2020