Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021
Tax Credit Carryforward [Line Items]
Deferred tax assets, valuation allowance	$ 144,678,000	$ 88,015,000
Deferred tax assets, increase in valuation allowance	56,700,000
Unrecognized tax benefits, if recognized, would impact effective income tax rate	0
Unrecognized tax benefits, cumulative interest and penalties	0	0
Unrecognized tax benefits, anticipated significant change over the next 12 months	0
Federal
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards	486,200,000	308,300,000
Tax credit carryforwards, subject to expiration	1,000,000.0
Federal | Research Tax Credit Carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	7,600,000
Federal | Charitable Contribution Carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	25,700,000
State
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards	180,400,000	$ 139,700,000
Tax credit carryforwards, subject to expiration	400,000
State | Research Tax Credit Carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 7,100,000