Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Income Tax Disclosure [Abstract]
Tax at federal statutory rate	$ 142,387	$ 5,536	$ 1,764
State taxes	636	14	67
Foreign rate differential	89	(2,096)	(1,627)
Stock-based compensation	(302,362)	(32,070)	1,662
Permanent items	2,228	1,009	809
Research and development credits	(3,170)	(2,808)	(289)
Tax uncertainties	(607)	1,019	515
Change in valuation allowance	165,869	30,932	(1,438)
Other	648	(479)	(698)
Total provision for income taxes	$ 5,718	$ 1,057	$ 765
Effective tax rate	0.80%	4.00%	9.20%