Condensed Consolidated Income Statements (unaudited) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues:
Total Revenues	$ 8,852,986	$ 7,850,774	$ 16,982,127	$ 14,940,183
Costs and expenses:
Research and development	161,321	211,796	310,857	407,023
General and administrative	1,728,125	2,043,952	4,635,284	4,113,585
Total Cost and Expenses	1,889,446	2,255,748	4,946,141	4,520,608
Operating income	6,963,540	5,595,026	12,035,986	10,419,575
Other income:
Interest income	517,156	273,746	966,580	491,697
Other income (expense)	0	81,985	0	96,663
Total other income	517,156	355,731	966,580	588,360
Income before income tax expense	7,480,696	5,950,757	13,002,566	11,007,935
Provision for income tax expense	(1,054,236)	(1,102,826)	(2,159,511)	(2,181,400)
Net income	$ 6,426,460	$ 4,847,931	$ 10,843,055	$ 8,826,535
Basic net income per share (in dollars per share)	$ 0.88	$ 0.67	$ 1.49	$ 1.23
Diluted net income per share (in dollars per share)	$ 0.87	$ 0.66	$ 1.48	$ 1.21
Shares used in computation of basic net income per share (in shares)	7,308,268	7,215,057	7,292,663	7,204,040
Shares used in computation of diluted net income per share (in shares)	7,349,696	7,315,276	7,344,008	7,309,325
Royalties [Member]
Revenues:
Total Revenues	$ 8,852,986	$ 7,815,504	$ 16,982,127	$ 14,900,504
Licensing Revenues [Member]
Revenues:
Total Revenues	$ 0	$ 35,270	$ 0	$ 39,679