Related-Party Transactions - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Mar. 31, 2017	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Related Party Transaction [Line Items]
Percentage of entity's voting stock owned by related party		10.00%
Committed to make license payment through January 2020		$ 13.9
Other Entity [Member]
Related Party Transaction [Line Items]
Committed to make license payment through January 2020	$ 10.3
Payment for license fees		3.6	$ 2.8	$ 2.8
License amortization expenses included in research and development expense		$ 3.2	$ 2.9	$ 2.7