Preferred Stock Accrued dividends (Details) (USD $)	3 Months Ended		9 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012
Accrued Dividends on preferred stock	$ 483,140	$ 434,264	$ 1,606,166	$ 1,084,023
Accrual of dividends on equity preferred stock	232,979	215,190	682,826	630,690
Dividends on Series B mandatorily redeemable preferred stock deducted from net income	96,781		283,652
Dividends of Series A deduction from net income	$ 14,655		$ 43,374