Investments - Short term invesmtments (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Notes to Financial Statements
Short-term U.S. treasury bills	$ 1,174,217	$ 0
U.S. treasury money market fund	6,673,261	8,542,292
Certificates of deposit	200,000	1,098,000
Short-term bonds	999,877	0
Commercial paper	998,570	0
Bank money market accounts	3,032,827	562,548
Bank savings accounts	1,763	1,763
Total short-term investments	$ 13,080,515	$ 10,204,603