Investments - Short term invesmtments (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Notes to Financial Statements
Short-term U.S. treasury bills	$ 0	$ 1,148,395
Certificates of deposit	200,000	200,000
Commercial paper	0	499,383
Total short-term investments	$ 200,000	$ 1,847,778