Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income	$ 5,968,844	$ 5,401,839
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization	1,084,614	816,113
Stock-based compensation expense	66,952	66,952
Deferred tax expense	218,006	(2,735,645)
Changes in operating assets and liabilities:
Accounts receivable	(852,490)	(1,731,520)
Income tax receivable	204,506	32,404
Prepaid expenses and other current assets	(176,202)	(346,946)
Patent costs	0	(11,215)
Accounts payable and accrued expenses	423,848	(23,568)
Deferred revenue	(637,459)	7,953,439
Net cash provided by operating activities	6,300,619	9,421,853
Cash flows from investing activities:
Maturity of marketable investments	32,855,741	21,703,040
Purchases of marketable investments	(37,669,248)	(28,934,178)
Net cash used in investing activities	(4,813,507)	(7,231,138)
Cash flows from financing activities:
Proceeds from stock option exercises	258,250	177,250
Payments for repurchase of common stock	(478,762)	(692,818)
Excess tax benefits from share-based payment arrangements	0	151,380
Net cash used in financing activities	(220,512)	(364,188)
Increase in cash and cash equivalents	1,266,600	1,826,527
Cash and cash equivalents at beginning of year	4,763,364	5,137,875
Cash and cash equivalents at end of period	6,029,964	6,964,402
Cash paid during the period for:
Interest	0	0
Taxes	$ 2,770,000	$ 5,290,000