Equity Incentive Plans - Stock-Based Compensation Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 53,654	$ 36,838	$ 97,609	$ 69,057
Cost of revenue—product
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	720	358	1,328	755
Cost of revenue—support subscription
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	2,929	2,245	5,613	4,019
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	22,232	17,971	43,322	33,559
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	17,269	11,439	31,209	22,065
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 10,504	$ 4,825	$ 16,137	$ 8,659