Collaborative Research and License Agreement - Additional Information (Detail) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($) PerformanceObligation	Dec. 31, 2017 USD ($)	Oct. 27, 2017 USD ($)
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Proceeds from income tax refunds			$ 1,583
Number of performance obligation | PerformanceObligation		1
Revenue recognized	$ 1,500	$ 4,600
Foreign Tax Authority [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Proceeds from income tax refunds				$ 1,600
BI Agreement [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Initial non-refundable upfront payment				$ 10,000
Additional payments upon potential development and commercial milestones	191,000	191,000
Potential Developmental Milestone	99,000	99,000
Net Sales Milestone	95,000	95,000
BI Agreement [Member] | Over Current Research Term [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Recognition of transaction price	$ 10,300	$ 10,300