Leases - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
	Jun. 30, 2020	Jan. 31, 2022	Jan. 31, 2021	Jul. 31, 2020	Jan. 31, 2022	Jan. 31, 2021	Oct. 01, 2021	Apr. 30, 2021	Apr. 01, 2021	Jun. 01, 2020	Mar. 30, 2020
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		$ 469	$ 314		$ 1,400	$ 942
Extension term											6 months
Operating lease right-of-use assets, net		$ 8,418			8,418			$ 8,521
Gain (loss) on termination of lease					$ 0	75
Weighted average remaining lease term (in years)		6 years 10 months 28 days			6 years 10 months 28 days
Weighted average discount rate, percent		5.73%			5.73%
Corporate Headquarters
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		$ 24	24		$ 70	67
Rockville, MD
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		292	290		881	832
Operating lease right-of-use assets, net										$ 3,800	$ 118
Operating lease liability										$ 3,800	$ 125
Incremental rent expense				$ 8
Additional Expansion Premises
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		130	0		390	0
Operating lease right-of-use assets, net									$ 3,300
Operating lease liability									$ 3,300
Rockville, MD New Location
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		0	0		0	43
Operating lease right-of-use assets, net	$ 850
Operating lease liability	926
Gain (loss) on termination of lease	$ 75
Milan, Italy
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		$ 23	$ 0		$ 58	$ 0
Operating lease right-of-use assets, net							$ 205