Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2015	Feb. 28, 2017	Feb. 29, 2016	Feb. 28, 2015
Numerator:
Net income	$ 11,584	$ 18,251	$ 10,023	$ 21,063	$ 16,076	$ 23,547	$ 17,243	$ 19,924	$ 60,921	$ 76,790	$ 64,943
Denominator:
Denominator for basic earnings per common share-weighted average shares (shares)									25,965,576	25,800,403	25,675,645
Effect of dilutive securities:
Employee and Director stock awards (shares)									131,910	136,780	102,300
Denominator for diluted earnings per common share (shares)									26,097,486	25,937,183	25,777,945
Earnings per share basic and diluted:
Basic earnings per common share (usd per share)	$ 0.45	$ 0.70	$ 0.39	$ 0.81	$ 0.62	$ 0.91	$ 0.67	$ 0.77	$ 2.35	$ 2.98	$ 2.53
Diluted earnings per common share (usd per share)	$ 0.44	$ 0.70	$ 0.38	$ 0.81	$ 0.62	$ 0.91	$ 0.67	$ 0.77	$ 2.33	$ 2.96	$ 2.52
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											80,683