CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified			9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended
	Jan. 31, 2013	Apr. 30, 2012	Jan. 31, 2013 Class A [Member]	Apr. 30, 2012 Class A [Member]	Jan. 31, 2013 Class B [Member]	Apr. 30, 2012 Class B [Member]	Jan. 31, 2013 Class A and B [Member]	Apr. 30, 2012 Class A and B [Member]
ASSETS
SUPPLEMENTAL TYPE CERTIFICATES net of amortization	$ 2,577	$ 2,500
OTHER ASSETS
Other assets, accumulated amortization	971	538
STOCKHOLDERS' EQUITY:
Preferred stock, par value (in dollars per share)			$ 5	$ 5	$ 5	$ 5
Preferred stock, shares authorized (in shares)			50,000,000	50,000,000	50,000,000	50,000,000
Preferred stock, designated classes (in shares)							200,000	200,000
Preferred stock, stated value (in dollars per share)			$ 1,000	$ 1,000	$ 1,000	$ 1,000
Preferred stock, dividend rate (in hundredths)			9.80%	9.80%	6.00%	6.00%
Preferred stock, liquidation preference value (in hundredths)			9.80%	9.80%	6.00%	6.00%
Preferred stock, redemption value			$ 100	$ 100	$ 1,000	$ 1,000
Preferred stock, shares issued (in shares)			0	0	0	0
Preferred stock, shares outstanding (in shares)			0	0	0	0
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)	58,142,914	57,907,564
Common stock, shares outstanding (in shares)	58,142,914	57,907,564
Common stock, shares owed but not issued (in shares)	278,573	278,573
Treasury stock (in shares)	600,000	600,000