CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified			3 Months Ended
	Jul. 31, 2014	Apr. 30, 2014	Jul. 31, 2014 Class A [Member]	Apr. 30, 2014 Class A [Member]	Jul. 31, 2014 Class B [Member]	Jul. 31, 2013 Class B [Member]	Apr. 30, 2014 Class B [Member]	Jul. 31, 2014 Class A and B [Member]	Apr. 30, 2014 Class A and B [Member]
ASSETS
SUPPLEMENTAL TYPE CERTIFICATES net of amortization	$ 2,849	$ 2,841
OTHER ASSETS
Other assets, accumulated amortization	2,849	2,520
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)			$ 100	$ 100	$ 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)	61,493,092	61,493,092
Common stock, shares outstanding (in shares)	61,493,092	61,493,092
Common stock, shares owed but not issued (in shares)	0	0
Treasury stock (in shares)	600,000	600,000