Summary of Significant Accounting Policies - Additional Information (Details)			12 Months Ended
	Jan. 31, 2018 USD ($) Customer	Jan. 31, 2017 USD ($) Customer	Jan. 31, 2019	Jan. 31, 2018 USD ($) Source Customer	Jan. 31, 2017 USD ($) Customer	Jan. 31, 2016 USD ($) Customer
Significant Accounting Policies [Line Items]
Number of revenue sources | Source				3
Deferred sales commissions costs				$ 26,100,000	$ 20,000,000	$ 21,700,000
Amortization of deferred commissions				$ 21,476,000	18,260,000	15,816,000
Cash and cash equivalents liquid investments original maturity period				90 days
Restricted cash	$ 400,000	$ 26,800,000		$ 400,000	26,800,000
Marketable securities	0	0		0	0
Gross realized gains and losses on marketable securities				0	0	0
Goodwill impairment				0
Costs incurred during the application development stage				0
Advertising costs				$ 32,100,000	28,100,000	$ 28,500,000
Measured tax percentage of likelihood realized upon settlement				50.00%
Excess tax benefits from employee stock option exercises included in net operating loss and research and development tax credit forwards				$ 25,100,000
Accumulated deficit	(1,039,088,000)	(884,128,000)		(1,039,088,000)	(884,128,000)
Deferred commissions	17,589,000	13,771,000		17,589,000	13,771,000
Accounting Standards Update 2016-18
Significant Accounting Policies [Line Items]
Restricted cash	400,000	$ 26,800,000		$ 400,000	$ 26,800,000
Minimum
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives				3 years
Finite-lived intangible assets estimated useful lives				2 years
Minimum | New Commissions Policy | Accounting Standards Update 2014-09 | Effect of Adoption of ASU Topic 606
Significant Accounting Policies [Line Items]
Accumulated deficit	28,000,000			$ 28,000,000
Deferred commissions	28,000,000			28,000,000
Minimum | New Revenue Recognition Policy | Accounting Standards Update 2014-09 | Effect of Adoption of ASU Topic 606
Significant Accounting Policies [Line Items]
Accumulated deficit	9,000,000			9,000,000
Deferred revenue	9,000,000			$ 9,000,000
Maximum
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives				4 years
Finite-lived intangible assets estimated useful lives				7 years
Maximum | New Commissions Policy | Accounting Standards Update 2014-09 | Effect of Adoption of ASU Topic 606
Significant Accounting Policies [Line Items]
Accumulated deficit	30,000,000			$ 30,000,000
Deferred commissions	30,000,000			30,000,000
Maximum | New Revenue Recognition Policy | Accounting Standards Update 2014-09 | Effect of Adoption of ASU Topic 606
Significant Accounting Policies [Line Items]
Accumulated deficit	11,000,000			11,000,000
Deferred revenue	11,000,000			11,000,000
Contract asset	$ 1,000,000			$ 1,000,000
Credit Concentration Risk | Accounts Receivable
Significant Accounting Policies [Line Items]
Number of major customer | Customer	1	2		1	2
Concentration risk percentage				10.00%	10.00%
Customer Concentration Risk | Revenue
Significant Accounting Policies [Line Items]
Number of major customer | Customer	0	0		0	0	0
Concentration risk percentage				10.00%	10.00%	10.00%
Geographic Concentration Risk | Revenue | United States
Significant Accounting Policies [Line Items]
Concentration risk percentage				78.00%	82.00%	82.00%
Geographic Concentration Risk | Property and Equipment | United States
Significant Accounting Policies [Line Items]
Concentration risk percentage	95.00%	99.70%
Scenario, Forecast
Significant Accounting Policies [Line Items]
Customer contracts, expected benefit period			5 years
Data Center Assets
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives				4 years
Data Center Assets | Scenario, Previously Reported
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives				3 years