Condensed Consolidated Statements of Operations (Unaudited) (USD $)	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Condensed Consolidated Statements of Operations [Abstract]
Net sales	$ 33,334,070	$ 42,039,282	$ 72,768,840	$ 80,974,738
Costs and expenses
Costs of goods sold	29,557,272	37,152,879	64,344,285	71,931,510
General, selling and administrative costs	1,322,549	1,426,427	2,882,384	2,846,246
Total costs and expenses	30,879,821	38,579,306	67,226,669	74,777,756
Interest and other income	(15,527)	(15,250)	(27,734)	(33,122)
Earnings before income taxes	2,469,776	3,475,226	5,569,905	6,230,104
Provision for (benefit from) income taxes:
Current	846,377	1,182,993	1,882,305	2,129,135
Deferred	(20,930)	(22,675)	(48,583)	(45,350)
Total Income tax provision (benefit)	825,447	1,160,318	1,833,722	2,083,785
Net earnings	$ 1,644,329	$ 2,314,908	$ 3,736,183	$ 4,146,319
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	$ 0.24	$ 0.34	$ 0.55	$ 0.61
Diluted	$ 0.24	$ 0.34	$ 0.55	$ 0.61
Cash dividends declared per common share	$ 0.13	$ 0.13	$ 0.26	$ 0.26