Discontinued Operations - Assets and liabilities (Details) - USD ($)	Apr. 30, 2018	Apr. 30, 2017
Balance Sheet
Total current assets	$ 28,349,000	$ 24,930,000
Property and equipment, non-current net		3,258,000
Total current liabilities	9,184,000	9,301,000
Accounts receivable, net of allowance for doubtful accounts of $139 at April 30, 2018 and $187 at April 30, 2017	139	187
EES Business | Discontinued Operations
Balance Sheet
Accounts receivable, net of allowance for doubtful accounts of $139 at April 30, 2018 and $187 at April 30, 2017	6,348,000	5,642,000
Inventories, net	18,716,000	19,168,000
Prepaid expenses and other current assets	185,000	120,000
Property and equipment, current net	3,100,000
Total current assets	28,349,000	24,930,000
Total assets classified as discontinued operations	28,349,000	28,188,000
Property and equipment, non-current net		3,258,000
Total non-current assets classified as discontinued operations		3,258,000
Accounts payable	5,121,000	4,388,000
Wages and related accruals	1,946,000	2,019,000
Customer advances	918,000	1,260,000
Other current liabilities	1,199,000	1,634,000
Total current liabilities	9,184,000	9,301,000
Total liabilities classified as discontinued operations	$ 9,184,000	$ 9,301,000