Basis of Presentation and Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Balance Sheet) (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Jan. 31, 2018
Assets
Deferred commissions, current	$ 20,122	$ 21,088	[1]
Deferred commissions, non-current	65,922	66,225	[1]
Total deferred commissions		87,313
Liabilities
Deferred revenue, current	199,622	191,229	[1]
Deferred revenue, non-current	188,992	182,873	[1]
Total deferred revenue		374,102
Stockholders' equity
Accumulated deficit	$ (967,891)	(903,587)	[1]
As Previously Reported
Assets
Deferred commissions, current		22,437
Deferred commissions, non-current		20,288
Total deferred commissions		42,725
Liabilities
Deferred revenue, current		209,377
Deferred revenue, non-current		196,632
Total deferred revenue		406,009
Stockholders' equity
Accumulated deficit		(980,082)
Adjustment | Accounting Standards Update 2014-09
Assets
Deferred commissions, current		(1,349)
Deferred commissions, non-current		45,937
Total deferred commissions		44,588
Liabilities
Deferred revenue, current		(18,148)
Deferred revenue, non-current		(13,759)
Total deferred revenue		(31,907)
Stockholders' equity
Accumulated deficit		$ 76,495

[1] *Prior period information has been adjusted to reflect the adoption impact of Accounting Standards Codification 606, Revenue from Contracts with Customers (ASC 606), which we adopted on February 1, 2018.