Quarterly Financial Information, Unaudited (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2017	Feb. 28, 2019	Feb. 28, 2018	Feb. 28, 2017
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 202,548	$ 239,516	$ 222,787	$ 262,236	$ 200,660	$ 208,158	$ 196,329	$ 205,283	$ 927,087	$ 810,430	$ 863,538
Gross profit	43,257	49,755	46,904	58,705	38,010	31,117	43,800	47,382	198,621	160,309	205,332
Net income	$ 8,851	$ 15,395	$ 11,244	$ 15,718	$ 23,487	$ (166)	$ 9,786	$ 12,062	$ 51,208	$ 45,169	$ 61,264
Basic earnings per common share (usd per share)	$ 0.34	$ 0.59	$ 0.43	$ 0.60	$ 0.91	$ (0.01)	$ 0.38	$ 0.46	$ 1.97	$ 1.74	$ 2.36
Diluted earnings per common share (usd per share)	$ 0.34	$ 0.59	$ 0.43	$ 0.60	$ 0.90	$ (0.01)	$ 0.38	$ 0.46	$ 1.96	$ 1.73	$ 2.35