Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 20,655	$ 15,132
Less accumulated depreciation	(8,115)	(4,106)
Property and equipment, net	12,540	11,026
Depreciation expense	4,000	2,400	$ 1,100
Computers and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,384	3,753
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	7,083	4,204
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 8,188	$ 7,175