Fair Value Measurements - (Details) - USD ($)	Apr. 30, 2022	Apr. 30, 2021
Intelligent Systems Group
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration	$ (5,857,000)
Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	24,716,000	$ 36,959,000
Contingently returnable consideration	143,000	479,000
Total	24,859,000	37,438,000
Contingent consideration	(1,084,000)
Total	1,084,000
Recurring basis | Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities	24,716,000	36,959,000
Total	24,716,000	36,959,000
Recurring basis | Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingently returnable consideration	143,000	479,000
Total	143,000	$ 479,000
Contingent consideration	(1,084,000)
Total	$ 1,084,000