Summary of Business and Significant Accounting Policies - Additional Information (Detail) $ in Millions		3 Months Ended		6 Months Ended
	Feb. 01, 2017 USD ($)	Jul. 31, 2017 USD ($) Customer	Jul. 31, 2016 Customer	Jul. 31, 2017 USD ($) Customer	Jul. 31, 2016 Customer
Accounting Standards Update 2016-09 [Member]
Summary Of Business And Accounting Policies [Line Items]
Net cumulative-effect adjustment on retained earnings	$ 0.7
Accounting Standards Update 2016-09 [Member] | Effect on Provision for Income Taxes [Member]
Summary Of Business And Accounting Policies [Line Items]
Recognition of excess tax benefits		$ 14.8		$ 28.7
Customer concentration risk [Member] | Revenues [Member]
Summary Of Business And Accounting Policies [Line Items]
Number of customers | Customer		0	0	0	0
Minimum [Member]
Summary Of Business And Accounting Policies [Line Items]
Customer payment period				30 days
Maximum [Member]
Summary Of Business And Accounting Policies [Line Items]
Customer payment period				60 days