Statements Of Cash Flows (USD $)	9 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
OPERATING ACTIVITIES
Net income	$ 8,573,650	$ 8,719,883
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	601,241	457,937
Stock-based compensation	53,200	66,720
Excess tax benefits	(67,044)	(2,383)
Deferred income taxes	102,118	27,320
Changes in operating assets and liabilities:
Accounts receivable	731,905	63,060
Inventories	306,689	(526,147)
Prepaid expenses and other assets	(262,686)	(173,167)
Accounts payable and accrued expenses	(221,045)	(211,143)
Net cash provided by operating activities	9,818,028	8,422,080
INVESTING ACTIVITIES
Purchases of fixed assets	(33,893)	(1,607,130)
Purchases of marketable securities	(17,879,202)	(17,438,274)
Proceeds from maturities and sales of marketable securities	8,555,000	9,850,000
Net cash used in investing activities	(9,358,095)	(9,195,404)
FINANCING ACTIVITIES
Net proceeds from sale of common stock	188,030	69,428
Excess tax benefits	67,044	2,383
Repurchase of common stock	(1,263,405)	0
Net cash provided by financing activities	(1,008,331)	71,811
Increase in cash and cash equivalents	(548,398)	(701,513)
Cash and cash equivalents at beginning of period	2,509,683	1,544,536
Cash and cash equivalents at end of period	1,961,285	843,023
Supplemental disclosures of cash flow information:
Cash paid during the period for income taxes	$ 4,213,033	$ 4,220,000