Note 17 - Extension of the Shareholder Rights Plan (Details Textual) - $ / shares	Aug. 02, 2011	Jan. 31, 2022	Apr. 30, 2021
Dividends, Stock, Issued Per Share (in shares)	1
Preferred Share Purchase Right, Exercisable, Percentage of Common Stock Outstanding	15.00%
Preferred Share Purchase Right, Purchase Discount	50.00%
Preferred Stock, Par or Stated Value Per Share (in dollars per share)		$ 5	$ 5
Series C Preferred Stock [Member]
Preferred Stock Purchase Right, Shares Exercisable (in shares)	0.02
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 5.00
Preferred Stock, Purchase Price Per 0.02 Share (in dollars per share)	$ 10