Property and Equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 51,355	$ 28,773
Less: accumulated depreciation	(25,155)	(17,696)
Total property and equipment, net	26,200	11,077
Depreciation	7,500	6,200	$ 4,400
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	1,347	719
Office equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	9,966	7,662
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	15,170	13,090
Computer software
Property, Plant and Equipment [Line Items]
Total property and equipment	10,099	6,461
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	13,812	144
Software in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 961	$ 697