Statements Of Cash Flows (USD $)	6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
OPERATING ACTIVITIES
Net income	$ 7,912,732	$ 5,796,476
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	464,517	380,272
Stock-based compensation	58,960	53,200
Excess tax benefits	(24,288)	0
Deferred income taxes	138,992	28,457
Changes in operating assets and liabilities:
Accounts receivable	(1,346,822)	(509,632)
Inventories	(182,060)	236,147
Prepaid expenses and other assets	(32,252)	63,341
Accounts payable and other current liabilities	10,587	(54,230)
Net cash provided by operating activities	7,000,366	5,994,031
INVESTING ACTIVITIES
Purchases of fixed assets	(27,710)	0
Purchases of marketable securities	(9,280,445)	(11,533,738)
Proceeds from maturities and sales of marketable securities	4,000,000	5,855,000
Net cash used in investing activities	(5,308,155)	(5,678,738)
FINANCING ACTIVITIES
Net proceeds from sale of common stock	302,701	0
Excess tax benefits	24,288	0
Repurchase of common stock	0	(1,263,405)
Net cash provided by financing activities	326,989	(1,263,405)
Increase in cash and cash equivalents	2,019,200	(948,112)
Cash and cash equivalents at beginning of period	1,262,300	2,509,683
Cash and cash equivalents at end of period	3,281,500	1,561,571
Supplemental disclosures of cash flow information:
Cash paid during the period for income taxes	$ 3,760,500	$ 2,838,033