Consolidated Statements of Income - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue:
Total revenues	$ 32,961,443	$ 27,443,752	$ 26,250,955
Costs and expenses:
Research and development	756,776	1,223,277	1,327,923
General and administrative	8,805,989	8,542,324	7,896,616
Total costs and expenses	9,562,765	9,765,601	9,224,539
Operating income	23,398,678	17,678,151	17,026,416
Other income:
Interest income	1,294,651	636,568	295,783
Other	103,948	51,074	52,805
Total other income	1,398,599	687,642	348,588
Income before income tax	24,797,277	18,365,793	17,375,004
Income tax provision	(4,744,008)	(7,037,527)	(6,002,765)
Net income	$ 20,053,269	$ 11,328,266	$ 11,372,239
Earnings per common share:
Basic (in dollars per share)	$ 2.77	$ 1.58	$ 1.61
Diluted (in dollars per share)	$ 2.73	$ 1.55	$ 1.56
Shares used in calculation of net income per common share:
Basic (in shares)	7,242,212	7,170,701	7,061,404
Diluted (in shares)	7,333,368	7,321,805	7,283,262
Royalties [Member]
Revenue:
Total revenues	$ 32,921,764	$ 27,426,117	$ 25,431,012
Licensing Revenue [Member]
Revenue:
Total revenues	$ 39,679	$ 17,635	$ 819,943