Related-Party Transactions - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2017	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 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				$ 13.7
Other Entity [Member]
Related Party Transaction [Line Items]
Committed to make license payment through January 2020	$ 10.3
Payment for license fees		$ 1.7	$ 0.8	2.7	$ 2.1
License expenses included in research and development expense		$ 0.8	$ 0.8	$ 2.4	$ 2.2