Quarterly Financial Information, Unaudited (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
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 181,011,000	$ 197,755,000	$ 189,782,000	$ 183,175,000	$ 140,391,000	$ 149,675,000	$ 153,385,000	$ 127,143,000	$ 751,723,398	$ 570,594,238	$ 469,112,410
Segment operating income	28,955,000	33,169,000	36,978,000	38,746,000	37,992,000	45,003,000	43,312,000	37,866,000
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
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