Property and Equipment - Narrative (Details) - USD ($)	1 Months Ended		3 Months Ended			9 Months Ended		61 Months Ended
	Dec. 31, 2019	Jul. 31, 2018	Jan. 31, 2020	Oct. 31, 2019	Jan. 31, 2019	Jan. 31, 2020	Jan. 31, 2019	Nov. 30, 2019	Jul. 31, 2019	Apr. 30, 2019
Property, Plant and Equipment [Line Items]
Depreciation			$ 184,000		$ 127,000	$ 491,000	$ 353,000
Assets under finance lease			343,000			343,000				$ 366,000
Finance lease costs	$ 231,000	$ 266,000						$ 149,000
Future minimum lease payments remaining	193,000		2,000
Finance leases monthly payments	$ 19,000	$ 11,000
Finance lease, liability				$ 0
Property, plant and equipment, net			3,246,000			3,246,000				$ 2,546,000
Gain on disposal of equipment						52,000	0
Present value of minimum future obligations interest rate	4.75%
Finance lease, depreciation and amortization expense			35,400			35,400
Finance Leased Assets
Property, Plant and Equipment [Line Items]
Depreciation			$ 35,000		$ 37,000	88,000	$ 80,000
Laboratory Equipment
Property, Plant and Equipment [Line Items]
Finance leased assets traded in				235,000
Accumulated depreciation written off				127,000
Traded-in Assets
Property, Plant and Equipment [Line Items]
Reduction in the purchase price				160,000
Property, plant and equipment, net				$ 0					$ 108,000
Gain on disposal of equipment						$ 52,000
Minimum
Property, Plant and Equipment [Line Items]
Useful lives						3 years
Maximum
Property, Plant and Equipment [Line Items]
Useful lives						7 years