Equity Incentive Plans - Stock-Based Compensation Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 43,955	$ 32,219
Cost of revenue—product
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	608	397
Cost of revenue—support subscription
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	2,684	1,774
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	21,090	15,588
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	13,940	10,626
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 5,633	$ 3,834