Leases (Details) - USD ($)			3 Months Ended	12 Months Ended
	Jun. 30, 2020	May 01, 2018	Jul. 31, 2020	Apr. 30, 2020	Apr. 30, 2019	Jun. 01, 2020	Jul. 31, 2019	May 01, 2019
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets, net				$ 2,798,000				$ 3,201,000
Discount rate								7.25%
Weighted average remaining lease term							6 years 10 months 21 days
Weighted average discount rate							7.25%
Operating leases, rent expense				955,000
Operating leases, rent expense					$ 822,000
Gaithersburg, MD
Lessee, Lease, Description [Line Items]
Termination period		7 days
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets, net								$ 3,200,000
Advance rent								900,000
Operating lease, liability								$ 4,100,000
Weighted average remaining lease term								7 years 8 months 5 days
Weighted average discount rate								7.25%
Corporate Headquarters
Lessee, Lease, Description [Line Items]
Operating leases, rent expense				94,000
Operating leases, rent expense					91,000
Rockville, MD
Lessee, Lease, Description [Line Items]
Operating leases, rent expense				604,000
Operating leases, rent expense					604,000
Gaithersburg, MD
Lessee, Lease, Description [Line Items]
Operating leases, rent expense				0
Operating leases, rent expense					41,000
Rockville, MD New Location
Lessee, Lease, Description [Line Items]
Operating leases, rent expense				$ 257,000
Operating leases, rent expense					$ 86,000
Subsequent Event | Rockville, MD
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets, net			$ 118,000			$ 3,800,000
Operating lease, liability			125,000			$ 3,800,000
Operating lease, cost			$ 7,000
Subsequent Event | Rockville, MD New Location
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets, net	$ 850,000
Operating lease, liability	926,000
Gain (loss) on termination of lease	$ 76,000