Condensed Consolidated Income Statements (unaudited) - USD ($)	3 Months Ended			6 Months Ended
	Jun. 30, 2018	[1]	Jun. 30, 2017	Jun. 30, 2018	[1]	Jun. 30, 2017
Revenue:
Total Revenues	$ 7,096,409		$ 6,535,516	$ 14,185,818		$ 14,226,135
Costs and expenses:
Research and development	211,796		337,731	407,023		592,512
General and administrative	1,985,212		2,315,283	4,054,845		4,741,000
Total Cost and Expenses	2,197,008		2,653,014	4,461,868		5,333,512
Operating income	4,899,401		3,882,502	9,723,950		8,892,623
Other income:
Interest income	273,746		140,995	491,697		242,748
Other income	81,985		23,423	96,663		25,985
Total other income	355,731		164,418	588,360		268,733
Income before income tax expense	5,255,132		4,046,920	10,312,310		9,161,356
Provision for income tax expense	(954,465)		(1,422,829)	(2,033,039)		(3,192,512)
Net income	$ 4,300,667		$ 2,624,091	$ 8,279,271		$ 5,968,844
Basic net income per share (in dollars per share)	$ 0.60		$ 0.37	$ 1.15		$ 0.83
Diluted net income per share (in dollars per share)	$ 0.59		$ 0.36	$ 1.13		$ 0.81
Shares used in computation of basic net income per share (in shares)	7,215,057		7,170,223	7,204,040		7,167,251
Shares used in computation of diluted net income per share (in shares)	7,315,276		7,329,118	7,309,325		7,330,875
Royalties [Member]
Revenue:
Total Revenues	$ 7,061,139		$ 6,531,107	$ 14,146,139		$ 14,217,317
Licensing Revenues [Member]
Revenue:
Total Revenues	$ 35,270		$ 4,409	$ 39,679		$ 8,818

[1] As of January 1, 2018, the Company adopted the requirements of ASC 606 using the modified retrospective adoption method, and as a result, there is a lack of comparability of certain amounts to the prior periods presented. See Note 2 for additional discussion.