Related-Party Transactions - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016
Related Party Transaction [Line Items]
Percentage of entity's voting stock owned by related party		10.00%		10.00%
Committed to make license payment through January 2020				$ 10.5
Other Entity [Member]
Related Party Transaction [Line Items]
Committed to make license payment through January 2020	$ 10.3
Payment for license fees		$ 0.9	$ 0.7	1.0	$ 1.3
License expenses included in research and development expense		$ 0.8	$ 0.7	$ 1.6	$ 1.4