Basis of Presentation and Summary of Significant Accounting Policies - Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Contract Liability
Beginning balance	$ 388,614		$ 374,102
Additions	92,511		167,782
Recognition of deferred revenue	67,878		128,637
Ending balance as of July 31, 2018	413,247		413,247
Product Revenue and Support Subscription Revenue
Contract Liability
Deferred revenue recognized	$ 60,900	$ 44,100	$ 106,200	$ 75,100