Quarterly Financial Information, Unaudited (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
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 184,266	$ 228,116	$ 200,790	$ 250,366	$ 207,694	$ 241,596	$ 199,670	$ 240,440	$ 863,538	$ 889,400	$ 819,692
Gross profit	46,803	51,297	42,104	65,128	53,424	61,288	49,702	63,704	205,332	228,118	206,773
Net income	$ 12,270	$ 16,646	$ 10,159	$ 22,189	$ 15,182	$ 22,822	$ 14,866	$ 22,674	$ 61,264	$ 75,544	$ 65,616
Basic earnings per common share (usd per share)	$ 0.47	$ 0.64	$ 0.39	$ 0.86	$ 0.59	$ 0.88	$ 0.58	$ 0.88	$ 2.36	$ 2.93	$ 2.56
Diluted earnings per common share (usd per share)	$ 0.47	$ 0.64	$ 0.39	$ 0.85	$ 0.58	$ 0.88	$ 0.57	$ 0.88	$ 2.35	$ 2.91	$ 2.55