Note 13 - Fair Value Measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Apr. 30, 2020	Apr. 30, 2019
Long-term debt	$ 5,439	$ 3,975
Financial and Nonfinancial Liabilities, Fair Value Disclosure	5,439	3,975
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Long-term debt
Financial and Nonfinancial Liabilities, Fair Value Disclosure
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Long-term debt
Financial and Nonfinancial Liabilities, Fair Value Disclosure
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Long-term debt	5,439	3,975
Financial and Nonfinancial Liabilities, Fair Value Disclosure	$ 5,439	$ 3,975