Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2014	May 31, 2014
Investments
Amortized Cost	$ 80,538	$ 55,538
Unrealized Gains	2,783	1,859
Unrealized Losses	(444)	(2,220)
Fair Value	82,877	55,177
Preferred Stock | Federal Agricultural Mortgage Corporation Series A preferred stock
Investments
Amortized Cost	30,000	30,000
Unrealized Gains	0	0
Unrealized Losses	(444)	(2,220)
Fair Value	29,556	27,780
Preferred Stock | Federal Agricultural Mortgage Corporation Series B Preferred Stock
Investments
Amortized Cost	25,000	25,000
Unrealized Gains	895	500
Unrealized Losses	0	0
Fair Value	25,895	25,500
Preferred Stock | Federal Agricultural Mortgage Corporation Series C Preferred Stock
Investments
Amortized Cost	25,000
Unrealized Gains	287
Unrealized Losses	0
Fair Value	25,287
Common Stock | Federal Agricultural Mortgage Corporation Class A common stock
Investments
Amortized Cost	538	538
Unrealized Gains	1,601	1,359
Unrealized Losses	0	0
Fair Value	$ 2,139	$ 1,897