Statements of Shareholders Equity (USD $)	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Total
Balance at Mar. 31, 2010	$ 47,006	$ 20,169,924	$ 1,129,726	$ 34,606,638	$ 55,953,294
Balance, shares at Mar. 31, 2010	4,700,583
Exercise of stock options and warrants	756	417,949	0	0	418,705
Exercise of stock options and warrants, shares	75,615
Comprehensive income:
Unrealized (loss) on marketable securities, net of tax	0	0	(69,288)	0	(69,288)
Net income				13,360,945	13,360,945
Comprehensive income					13,291,657
Stock-based compensation	0	76,720	0	0	76,720
Tax benefit of stock-based compensation		230,173			230,173
Balance at Mar. 31, 2011	47,762	20,894,766	1,060,438	47,967,583	69,970,549
Balance, Shares at Mar. 31, 2011	4,776,198
Exercise of stock options and warrants	485	(449)	0	0	36
Exercise of stock options and warrants, shares	48,547
Comprehensive income:
Unrealized (loss) on marketable securities, net of tax	0	0	27,018		27,018
Net income	0	0	0	11,381,095	11,381,095
Comprehensive income					11,408,113
Stock-based compensation		80,160			80,160
Balance at Mar. 31, 2012	48,247	20,974,477	1,087,456	59,348,678	81,458,858
Balance, Shares at Mar. 31, 2012	4,824,745
Exercise of stock options and warrants	377	143,811	0	0	144,188
Exercise of stock options and warrants, shares	37,691
Comprehensive income:
Unrealized (loss) on marketable securities, net of tax	0	0	470,270		470,270
Net income	0	0	0	11,828,838	11,828,838
Comprehensive income					12,299,108
Stock-based compensation		66,720			66,720
Tax benefit of stock-based compensation		15,734			15,734
Balance at Mar. 31, 2013	$ 48,624	$ 21,200,742	$ 1,557,726	$ 71,177,516	$ 93,984,608
Balance, Shares at Mar. 31, 2013	4,862,436