Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jul. 31, 2017	Apr. 30, 2017
Preferred stock, par value (in dollars per share)	$ 5	$ 5
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Supplemental type certificates, accumulated amortization	$ 4,549	$ 4,345
Other assets, accumulated amortization	$ 7,241	$ 6,904
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	65,273,896	65,273,896
Common stock, shares outstanding (in shares)	64,543,550	64,543,550
Preferred Class A [Member]
Preferred stock, liquidation value	$ 100	$ 100
Preferred stock, redemption value	$ 100	$ 100
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Preferred stock, designated classes (in shares)	200,000	200,000
Preferred stock, stated value (in dollars per share)	$ 100	$ 100
Preferred stock, dividend rate	9.80%	9.80%
Preferred Class B [Member]
Preferred stock, liquidation value	$ 1,000	$ 1,000
Preferred stock, redemption value	$ 1,000	$ 1,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Preferred stock, designated classes (in shares)	200,000	200,000
Preferred stock, stated value (in dollars per share)	$ 1,000	$ 1,000
Preferred stock, dividend rate	6.00%	6.00%