Investments - Short term invesmtments (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Notes to Financial Statements
Short-term U.S. treasury bills	$ 1,848,938	$ 0
U.S. treasury money market fund	1,038,729	8,542,292
Certificates of deposit	350,000	1,098,000
Short-term bonds	999,725	0
Bank money market accounts	853,619	562,548
Bank savings accounts	1,763	1,763
Total short-term investments	$ 5,092,774	$ 10,204,603