Deferred Revenue and Performance Obligations - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Revenue From Contracts With Customers [Line Items]
Revenue, remaining performance obligation, recognition period	12 months		12 months
Subscription Services [Member]
Revenue From Contracts With Customers [Line Items]
Recognition of deferred revenue	$ 142.7	$ 113.9	$ 240.4	$ 185.9
Revenue expected to be recognized from remaining performance obligations	439.8		439.8
Revenue expected to recognize from remaining performance obligations over the next 12 months	$ 294.0		$ 294.0