Related-Party Transactions - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Mar. 31, 2017	Apr. 30, 2017	Apr. 30, 2016
Related Party Transaction [Line Items]
Percentage of entity's voting stock owned by related party		10.00%
Other Entity [Member]
Related Party Transaction [Line Items]
Committed to make license payment through January 2020	$ 10.3	$ 10.3
Payment for license fees		0.1	$ 0.6
License expenses included in research and development expense		$ 0.8	$ 0.7