Income Taxes - Significant Components of Deferred Income Tax Assets (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019
Deferred Tax Assets, Net [Abstract]
Net operating loss carryforwards	$ 37,507	$ 6,517
Research and development credit carryforwards	5,701	972
Stock-based compensation	4,145	133
Accruals and reserves	11,586	6,856
Deferred revenue	5,234	2,646
Operating lease liabilities	17,716	0
Total deferred tax assets net of valuation allowance	81,889	17,124
Valuation allowance	(36,353)	(877)
Total deferred tax assets net of valuation allowance	45,536	16,247
Deferred Tax Liabilities, Net [Abstract]
Property and equipment	(6,744)	(4,779)
Deferred commissions	(21,156)	(11,468)
Operating right-of-use assets	(16,453)	0
Total deferred tax liabilities	(44,353)	(16,247)
Net deferred tax assets	$ 1,183	$ 0