CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012
ASSETS
SUPPLEMENTAL TYPE CERTIFICATES net of amortization	$ 2,604	$ 2,500
OTHER ASSETS
Other assets, accumulated amortization	1,213	538
STOCKHOLDERS' EQUITY:
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)	59,619,173	57,907,564
Common stock, shares outstanding (in shares)	59,619,173	57,907,564
Common stock, shares owed but not issued (in shares)	0	278,573
Treasury stock (in shares)	600,000	600,000
Class A [Member]
STOCKHOLDERS' EQUITY:
Preferred stock, par value (in dollars per share)	$ 5	$ 5
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, stated value (in dollars per share)	$ 1,000	$ 1,000
Preferred stock, dividend rate (in hundredths)	9.80%	9.80%
Preferred stock, liquidation preference value (in hundredths)	9.80%	9.80%
Preferred stock, redemption value	100	100
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Class B [Member]
STOCKHOLDERS' EQUITY:
Preferred stock, par value (in dollars per share)	$ 5	$ 5
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, stated value (in dollars per share)	$ 1,000	$ 1,000
Preferred stock, dividend rate (in hundredths)	6.00%	6.00%
Preferred stock, liquidation preference value (in hundredths)	6.00%	6.00%
Preferred stock, redemption value	$ 1,000	$ 1,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Class A and B [Member]
STOCKHOLDERS' EQUITY:
Preferred stock, designated classes (in shares)	200,000	200,000