Condensed Consolidated Statements of Operations (Unaudited) (USD $)	3 Months Ended		6 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Condensed Consolidated Statements of Operations [Abstract]
Net sales	$ 42,039,282	$ 29,353,262	$ 80,974,738	$ 58,575,494
Costs and expenses
Costs of goods sold	37,152,879	25,465,549	71,931,510	51,249,843
General, selling and administrative costs	1,426,427	1,264,251	2,846,246	2,538,721
Total costs and expenses	38,579,306	26,729,800	74,777,756	53,788,564
Interest and other income	(15,250)	(14,000)	(33,122)	(28,027)
Earnings before income taxes	3,475,226	2,637,462	6,230,104	4,814,957
Provision for (benefit from) income taxes:
Current	1,182,993	866,631	2,129,135	1,622,589
Deferred	(22,675)	(13,600)	(45,350)	(27,200)
Total provision for (benefit from) income taxes	1,160,318	853,031	2,083,785	1,595,389
Net earnings	$ 2,314,908	$ 1,784,431	$ 4,146,319	$ 3,219,568
Weighted average number of common shares outstanding:
Basic	6,799,444	6,799,444	6,799,444	6,799,444
Diluted	6,799,444	6,799,444	6,799,444	6,799,444
Net earnings per share:
Basic	$ 0.34	$ 0.26	$ 0.61	$ 0.47
Diluted	$ 0.34	$ 0.26	$ 0.61	$ 0.47
Cash dividends declared per common share	$ 0.13	$ 0.08	$ 0.26	$ 0.12