Earnings Per Share (Details) (USD $)	3 Months Ended		9 Months Ended
	Nov. 30, 2012	Nov. 30, 2011	Nov. 30, 2012	Nov. 30, 2011
Numerator:
Net income for basic and diluted earnings per common share	$ 15,363,680	$ 10,020,918	$ 47,222,557	$ 29,092,140
Denominator:
Denominator for basic earnings per common share-weighted average shares (shares)	25,362,450	25,163,452	25,301,207	25,120,596
Effect of dilutive securities:
Employee and Director stock awards (shares)	240,412	210,832	236,050	219,064
Denominator for diluted earnings per common share (shares)	25,602,862	25,374,284	25,537,257	25,339,660
Earnings per share basic and diluted:
Basic earnings per Common share (usd per share)	$ 0.61	$ 0.40	$ 1.87	$ 1.16
Diluted earnings per common share (usd per share)	$ 0.60	$ 0.39	$ 1.85	$ 1.15