Investments - Short term invesmtments (Details) - USD ($)	Jun. 30, 2016	Dec. 31, 2015
Notes to Financial Statements
Short-term U.S. treasury bills	$ 0	$ 9,987,804
U.S. treasury money market fund	5,063,582	3,357,841
Certificates of deposit	948,000	1,346,000
Bank money market accounts	945,496	947,395
Bank savings accounts	1,763	1,763
Total short-term investments	$ 6,958,841	$ 15,640,803