Statements Of Cash Flows (USD $)	9 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
OPERATING ACTIVITIES
Net income	$ 10,705,638	$ 8,573,650
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	698,820	601,241
Stock-based compensation	58,960	53,200
Excess tax benefits	(24,288)	(67,044)
Deferred income taxes	141,060	102,118
Changes in operating assets and liabilities:
Accounts receivable	476,495	731,905
Inventories	(478,791)	306,689
Prepaid expenses and other assets	(709,502)	(262,686)
Accounts payable and other current liabilities	(20,142)	(221,045)
Net cash provided by operating activities	10,848,250	9,818,028
INVESTING ACTIVITIES
Purchases of fixed assets	(114,139)	(33,893)
Purchases of marketable securities	(9,136,457)	(17,879,202)
Proceeds from maturities and sales of marketable securities	8,610,000	8,555,000
Net cash used in investing activities	(640,596)	(9,358,095)
FINANCING ACTIVITIES
Net proceeds from sale of common stock	302,701	188,030
Excess tax benefits	24,288	67,044
Repurchase of common stock	0	(1,263,405)
Net cash provided by financing activities	326,989	(1,008,331)
Increase in cash and cash equivalents	10,534,643	(548,398)
Cash and cash equivalents at beginning of period	1,262,300	2,509,683
Cash and cash equivalents at end of period	11,796,943	1,961,285
Supplemental disclosures of cash flow information:
Cash paid during the period for income taxes	$ 5,600,000	$ 4,213,033