Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	$ 10,843,055	$ 8,826,535
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization	150,636	1,369,227
Stock-based compensation expense	260,466	96,314
Deferred tax expense	159,459	82,341
Extinguishment of accrued liabilities	0	(78,138)
Changes in operating assets and liabilities:
Accounts receivable	(210,949)	(1,438,426)
Income tax payable	173,690	(518,513)
Prepaid expenses and other current assets	(365,423)	(213,476)
Patent costs	(92,582)	(79,485)
Accounts payable and accrued expenses	(1,087,775)	177,436
Deferred revenue	0	(139,680)
Net cash provided by operating activities	9,830,577	8,084,135
Cash flows from investing activities:
Maturity of marketable investments	42,451,229	37,279,000
Purchases of marketable investments	(53,104,080)	(40,596,520)
Net cash used in investing activities	(10,652,851)	(3,317,520)
Cash flows from financing activities:
Proceeds from stock option exercises	1,736,946	860,050
Payments for repurchase of common stock	(118,566)	0
Net cash provided by financing activities	1,618,380	860,050
Increase in cash and cash equivalents	796,106	5,626,665
Cash and cash equivalents at beginning of year	13,176,452	7,333,810
Cash and cash equivalents at end of period	13,972,558	12,960,475
Cash paid during the period for:
Interest	0	0
Taxes	$ 1,826,362	$ 2,617,572