Condensed Consolidated Statements of Operations (Unaudited) (USD $)	3 Months Ended		9 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010
Condensed Consolidated Statements of Operations [Abstract]
Net sales	$ 36,987,260	$ 31,135,887	$ 117,961,998	$ 89,711,381
Costs and expenses
Costs of goods sold	33,054,379	27,365,134	104,985,889	78,614,977
General, selling and administrative costs	1,244,548	1,160,888	4,090,794	3,699,609
Total costs and expenses	34,298,927	28,526,022	109,076,683	82,314,586
Interest and other income	(15,250)	(15,034)	(48,372)	(43,061)
Earnings before income taxes	2,703,583	2,624,899	8,933,687	7,439,856
Provision for (benefit from) income taxes:
Current	927,008	905,005	3,056,143	2,527,594
Deferred	(22,675)	(13,600)	(68,025)	(40,800)
Total provision for (benefit from) income taxes	904,333	891,405	2,988,118	2,486,794
Net earnings	$ 1,799,250	$ 1,733,494	$ 5,945,569	$ 4,953,062
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	$ 0.26	$ 0.25	$ 0.87	$ 0.73
Diluted	$ 0.26	$ 0.25	$ 0.87	$ 0.73
Cash dividends declared per common share	$ 0.13	$ 0.61	$ 0.39	$ 0.73