Earnings Per Share (Details) (USD $)	3 Months Ended								12 Months Ended
	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 28, 2014	Feb. 28, 2013	Feb. 29, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stockholders' Equity Note, Stock Split, Conversion Ratio									2
Numerator:
Net income	$ 10,242,000	$ 18,445,000	$ 16,363,000	$ 14,547,000	$ 13,233,000	$ 15,364,000	$ 15,873,000	$ 15,986,000	$ 59,597,048	$ 60,456,206	$ 40,735,796
Denominator:
Denominator for basic earnings per common share-weighted average shares (shares)									25,514,387	25,320,147	25,131,754
Effect of dilutive securities:
Employee and Director stock awards (shares)									179,081	240,447	230,366
Denominator for diluted earnings per common share (shares)									25,693,468	25,560,594	25,362,120
Earnings per share basic and diluted:
Basic earnings per common share (usd per share)	$ 0.42	$ 0.72	$ 0.95	$ 0.27	$ 0.52	$ 0.61	$ 0.63	$ 0.63	$ 2.34	$ 2.39	$ 1.62
Diluted earnings per common share (usd per share)	$ 0.42	$ 0.72	$ 0.94	$ 0.26	$ 0.52	$ 0.60	$ 0.62	$ 0.63	$ 2.32	$ 2.37	$ 1.61
Stock Appreciation Rights (SARs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									113,887